Introduction

Cosmetic regulations vary globally, with the European Union defining cosmetics as substances intended for external human body parts, including the epidermis and mucous membranes, for cleansing, perfuming, or altering appearance [1]. Under the Federal Food, Drug, and Cosmetic Act, regulations in Japan and the United States likewise serve these functions. In recent years, the cosmetic industry has experienced exponential growth, driven by the growing middle-class demographics in emerging economies, making it a highly profitable sector worldwide. Estimates suggest that each woman spends around $15,000 on cosmetics throughout her lifetime [2]. In 2016, the European cosmetics market held a value of €77 billion (wholesale rate), with the United States and Brazil, following closely behind [3]. This economic boom highlights the industry's reliance on innovation for product development, driven by marketing demands and the need to replace banned or unpopular substances.

Cosmetics primarily target the skin and hair, vital components of an individual’s physical appearance. The skin serves as a natural defence shield and sensory receptor. Its multi-layered structure (Fig. 1a), including the epidermis, dermis, and hypodermis, is crucial in maintaining health and appearance [4]. Skin aging, marked by dermal degradation and collagen loss, is a key focus of anti-aging research, emphasizing collagen synthesis stimulation and antioxidant protection against oxidative stress. Hair, organized into follicular units (Fig. 1b), comprises three main layers: the medulla, cortex, and cuticle. The cortex, rich in keratin, provides structural integrity and moisture retention, while the cuticle's smoothness contributes to hair's shiny appearance [5]. Understanding these structures guides cosmetic formulation development, aimed at preserving and enhancing skin and hair health, meeting consumer demands for effective anti-aging and hair care solutions.

Fig. 1
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Schematic illustration depicting the anatomy of a Skin and b Hair follicle (The image template used in this figure was obtained from BioRender)

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Many cosmetic products today are formulated with artificial ingredients, often resulting in expensive final products with adverse effects on human well-being [6]. A notable shift in consumer preferences towards health-beneficial and eco-friendly options in cosmetics has prompted a significant move towards natural ingredients, reflecting a broader inclination towards products that are natural, simple, and ethically sourced [7]. The rising popularity of natural cosmetics is underpinned by a growing environmental and societal consciousness, as consumers recognize the sustainability and ethical considerations inherent in such products [8]. The rise of cosmeceuticals, blending cosmetics with pharmaceuticals, emphasizes skincare products providing therapeutic benefits beyond superficial enhancement [9]. Integrating scientific research and clinical validation, cosmeceuticals enhance appearance and promote skin health and wellness.

Against this dynamic backdrop of increasing demand for skincare products with proven therapeutic benefits, recently algae have become a significant player in the cosmeceutical sphere. Algae, which are photosynthetic organisms, exhibit a wide and diverse variety of species from microscopic single-celled organisms to large, multicellular seaweeds (Fig. 2). Thriving in diverse aquatic environments including oceans, rivers, and lakes, they contribute significantly to global oxygen production and play an essential role as primary producers in aquatic ecosystems. Dating back as long as 14,000 years BP and with written reports from 600 AD, evidence supports the long historical path of human macroalgae consumption [10]. Algae's prominence in the cosmetic industry stems from its rich bioactive compound and diverse metabolites with significant potential for skincare applications. They are particularly valued for their polysaccharides, polyunsaturated fatty acids, vitamins, minerals, antioxidants, and pigments, among other constituents, which contribute to their extensive therapeutic properties [11]. These metabolites can help the skin retain moisture, boost blood flow, and promote cellular renewal, addressing various skincare concerns such as anti-senescence, antioxidant shielding, moisturization, and anti-inflammatory properties [12]. As consumers increasingly prioritize natural and sustainable beauty solutions, the utilization of algae-derived ingredients in cosmetics aligns with these preferences.

Fig. 2
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Schematic illustration of diverse algae species (Created with BioRender)

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Macroalgae consists of a substantial reservoir of cosmetic viscosifiers, hygroscopic compounds, and free radical scavengers. Their cultivation on seashores at a large scale offers an attractive and sustainable ingredient option with minimal ecological footprint and cost-effectiveness [13]. Due to their fast and steady growth, their bioactive compound synthesis can be controlled, primarily influenced by nutrient availability and exposure to stress conditions like excess light [2, 14]. From a regulatory standpoint, macroalgae are classified as vegetal extracts, enjoying lenient restrictions for cosmetic applications.

Altogether, the exploration and ongoing use of algae presents an encouraging direction for meeting the evolving needs of various industries. In this lieu, the current review focuses in depth on algae's beneficial bio compounds and their diverse applications in cosmetics, highlighting its current applications, challenges, and prospects. Moving forward, continued research and innovation in this field will undoubtedly pave the way for novel and effective cosmetic formulations, further cementing the pivotal role of algae in the cosmetics industry.

Algae: nature's cosmetic powerhouse: marine seaweed in the spotlight

Marine algae, the most plentiful resource in the ocean, are invaluable reservoirs of functional metabolites such as mineral salts, polyphenols, amino acids, lipids, peptides, proteins, and polysaccharides. Marine macroalgae fall into four categories [15] depending on their pigments. Marine algae exhibit remarkable adaptability to environmental changes by producing stress-tolerant substances, such as organic osmolytes which act like an antioxidant. Additionally, they form specialized spores called aplanospores in response to desiccation, entering dormancy until conditions improve [16]. Additionally, they assimilate inorganic ions to maintain extracellular ion equilibrium and produce organic osmolytes to shield against desiccation and ultraviolet radiation. Their rich array of secondary metabolites further aids in adaptation and survival in harsh environments [17].

Astaxanthin-rich aplanospores inhibit cell photooxidation [18]. Algae exposed to ultraviolet radiation synthesize UV-screening compounds like mycosporine-like amino acids (MAA) that function as free radical’s scavengers and regulate osmotic levels. Algae subjected to intense solar radiation and depleted nitrogen levels, such as Dunaliella are known to produce more carotene. Marine algae are recognized for being rich in essential nutrients, phlorotannins, pigments, and sulfated polysaccharides. For centuries, the therapeutic potential of these algae has been recognized, particularly for treating skin conditions, demonstrating their value beyond mere nutrition. Numerous studies have elucidated the anti-inflammatory, antioxidant, antidiabetic, antihypertensive, antitumor, and anti-allergic properties of metabolites from brown algae. Moreover, they play a vital role in the inhibition of hyaluronidase enzyme, neuroprotective functions, conditions related to bone health, and the activity of inhibiting MMPs [19]. The rapid growth in incorporating marine algae into environmental and industrial natural product manufacturing reflects their superior biological value, innovative cultivation techniques, and cost-effectiveness compared to synthetic alternatives. As a result, the protective capabilities of these compounds against UV radiation make them potential candidates for cosmetic applications. For example, algae, naturally exposed to oxidative stress, possess defence mechanisms that shield them from reactive oxygen species (ROS) and free radicals. This natural resilience highlights their increasing competitiveness in the market [20].

Overall, the burgeoning interest in algae within the cosmetic industry is fueled by their rich biochemical compounds, which offer a plethora of benefits for skincare. These compounds, including polysaccharides, peptides, antioxidants, and essential fatty acids, provide moisturization, antioxidant protection, and soothing properties, and promote skin firmness and elasticity. Moreover, their natural and sustainable sourcing aligns with consumer preferences for eco-friendly ingredients. As a result, algae-derived ingredients are gaining prominence in skincare formulations, promising effective and environmentally conscious solutions for maintaining healthy and radiant skin [7, 21, 22].

Diatoms and their therapeutic role in cosmeceuticals applications

Diatoms have been acknowledged as crucial organisms of the aquatic ecosystem for over two centuries and thrive in nearly every aquatic habitat, from rivers and oceans to streams [23]. The unique attribute of diatoms lies in their silica-rich cell walls, known as frustules. These frustules, often referred to as "sea jewels," exhibit structural coloration due to photonic nanostructures. Diatoms comprise unique metabolic pathways and possess diverse and essential bioactive compounds with utilization in food, cosmetics, medicine, pharmaceuticals, bioremediation, and nanotechnology (Fig. 3). The pigments of diatoms play a significant role in photoprotection because of their antioxidant capabilities [24]. Polyunsaturated fatty acids such as eicosapentaenoic acid (EPA), docosapentaenoic acid (DHA), myristic acid, palmitic acid, and palmitoleic acid are abundant in diatoms, providing crucial membrane support and serving as energy reservoirs. Phenolic compounds from diatoms, on the other hand, serve as natural sources of antioxidative chemicals with notable health benefits, effectively safeguarding against diseases induced by oxidative stress. This intricate balance of biochemical compounds underscores the remarkable adaptability and resilience of diatoms in aquatic environments [25, 26]. Utilizing diatom biomass for improving polluted water systems involves its capacity to address both nutrient enrichment and heavy metal contamination [27].

Fig. 3
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Schematic illustration of high-value compounds from diatoms and their properties [34]

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In the realm of cosmetical applications, diatom metabolites offer promising potential. Their diverse array of proteins and complex polysaccharides plays a significant role in various skin-related ailments. Studies suggest that compounds like EPA and other polyunsaturated fatty acids combat Gram-positive bacteria by disrupting cell membranes, interfering with cellular processes, generating reactive oxygen species, and modulating gene expression, ultimately leading to bacterial death [28]. Additionally, diatom metabolite contains antioxidants such as carotenoids, fucoxanthin, and polyphenols which lend themselves to a range of medical and pharmacological purposes, including cosmetical formulations aimed at enhancing skin health and vitality.

Pigments serve a multifaceted role in cosmetical products, beyond adding color. They contribute to adjust skin tone, camouflage imperfections, and create a radiant complexion [29]. Diatoms possess properties that counter inflammation, cancer development, angiogenesis, obesity, oxidative stress, and neurodegeneration due to their pigment composition, acting as a barrier against damaging UV radiation [28]. Diatoms contain natural pigments such as chlorophyll a, chlorophyll c, fucoxanthin (Fx), and photoprotective pigments including -carotene, diadinoxanthin (Ddx), diatoxanthin (Dtx), zeaxanthin (Zx), antheraxanthin (Ax), and violaxanthin (Vx). Isopentenyl pyrophosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP) are isoprenoid precursor molecules responsible for carotenoid synthesis [30]. In fibroblasts, fucoxanthin emerges as a vital defender against reactive oxygen species (ROS) generated by UV exposure. UV radiation triggers intricate photochemical reactions within skin cells, initiating a cascade of events. Fucoxanthin reinforces cell viability and mitigates cellular damage, indicating its role in shielding the skin from UV radiation and environmental stressors. Scientific investigations have corroborated fucoxanthin's efficacy in reducing cyclooxygenase-2, prostaglandin-E receptors, and other enzymatic activities. Its ability to counteract UV-induced epidermal hypertrophy, a precursor to wrinkles and skin ailments, underscores its importance in skin protection. Therefore, integrating fucoxanthin into cosmetics and sunscreens presents a promising approach to safeguarding the skin against premature aging caused by UV exposure [31].

Diatoms produce phenolic chemicals, which are secondary metabolites. Phenolics are commonly made to protect cells from UV irradiation and infections. The chemical structure of phenolic compounds has been linked to antioxidant, skin-protecting, antibacterial, antihemolytic, and anti-inflammatory properties. Polyphenols are renowned for their antioxidative properties, attributed to their ability to scavenge free radicals and chelate metals. Conversely, isoflavones, lignans, stilbene resveratrol, and other phytoestrogens exhibit antibacterial properties [32, 33]. Flavonoids, classified as polyphenols, exhibit antioxidative characteristics and can induce the up-regulation of defense mechanisms in reaction to light-induced stress. These compounds are distributed across diverse organelles, including the chloroplast, where they fulfil a crucial function in photoprotection. For example, Skeletonema marinoi is a diatom that produces flavonoids with ABTS scavenging activity when exposed to aberrant light. This could support flavonoids' ability to shield cells from light stress by acting as photoprotectors [33].

Seaweed and derived polysaccharides

Seaweed, also referred to as macroalgae, constitutes a significant group of aquatic photosynthetic organisms within the domain of Eukaryota. They are found in the Plantae kingdom, encompassing green and red algae, as well as in the Chromista kingdom, which includes brown algae [56,57,58,59]. In general, seaweed presents numerous merits for various applications, including its abundance of essential nutrients, versatility in culinary and industrial uses, and its role in environmental conservation through carbon sequestration and habitat provision (Fig. 4).

Fig. 4
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Schematic illustration: Key Advantages and Unique Structural/Functional Traits of Marine-Derived Seaweed Polysaccharide [62]

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Seaweeds' remarkable biochemical diversity positions them as prime candidates for studying an extensive array of physiologically active components, offering a wide spectrum of physiological and biochemical features that are often rare or absent in other taxonomic groups [56]. Compared to terrestrial plants and animal-based foods, seaweed boasts high levels of health-promoting compounds and materials such as dietary fiber, omega-3 fatty acids, essential amino acids, and vitamins A, B, C, and E, all of which play pivotal roles in the development of cosmeceutical products [60, 61]. Respectively, green, red, and brown macroalgae contain specific fatty acids such as alpha-linolenic acid (ω3 C18:3), eicosapentaenoic acid (EPA, ω3 C20:5), and arachidonic acid (ω6 C20:4). Their lipid profile is predominantly composed of two polyunsaturated fatty acids (PUFAs), omega-3 and omega-6 acids, known for their preventive roles against cardiovascular diseases, osteoarthritis, and diabetes. Macroalgae are also rich reservoirs of several essential minerals, including iodine, calcium, iron, copper, and magnesium [62]. Macroalgae are prolific producers of polysaccharides, widely used as hydrocolloids across various industries. In addition to their mineral content, macroalgae are abundant in micronutrients such as vitamins B3, B9, B12, C, and E, along with antioxidants like polyphenols, especially phlorotannins, which can constitute up to 15% of the dry matter. In response to stressors like UV radiation or salinity, seaweeds produce primary metabolites for normal cellular functions and secondary metabolites [61]. Primary metabolites include polysaccharides, proteins, amino acids, and fatty acids, while secondary metabolites encompass pigments, phenolic compounds, sterols, vitamins, and more [7]. These naturally occurring bioactive compounds and metabolites found in seaweeds have a history of safe usage in folk medicine to address various ailments.

Polysaccharides, colloquially known as sugars, play a beneficial role in cosmetical formulations, particularly in the creation of hydrogels or hydrocolloids. These complex molecules possess the ability to immobilize water within insoluble polymers, resulting in a profound moisturizing effect [63]. In the realm of cosmetics, polysaccharides are broadly categorized as functional and active groups. To ensure the product's structural integrity and longevity, functional polysaccharides are crucial in formulation technology and stabilization processes. Conversely, active polysaccharides showcase remarkable properties that directly boost the efficacy of cosmetic products as moisturization and antioxidant capabilities [64]. The versatile role of polysaccharides in cosmetics is underscored by their dual classification, highlighting their importance both as structural elements and active ingredients in skincare formulations. Recently, there has been growing interest in seaweed-derived polysaccharides, which boast unique structural and functional attributes. These polysaccharides from seaweed are garnering attention due to their biologically adaptable, biocompatible, biodegradable, renewable, and non-toxic properties. Researchers are increasingly exploring their potential in developing effective, efficient, and controlled drug delivery platforms that cater to patient needs across different age groups. Seaweed polysaccharides offer numerous beneficial biological functions, such as antioxidative, anticarcinogenic, antiviral, targeted drug delivery, wound healing, and anti-inflammatory properties. This renewed focus on seaweed polysaccharides opens promising avenues for innovation in skincare and pharmaceutical industries [65, 66]. Additionally, it has surfaced as a highly efficient substance for controlling drug delivery and engineering tissue systems, owing to its significant retention capabilities, customizable active components, swelling, and colloidal features. The polysaccharides derived from macroalgae have been extensively employed for their impressive skin-preserving benefits, including anti-aging, brightening, hydrating, UV protection, antioxidative, and anti-inflammatory properties [67]. Additionally, their unique physicochemical characteristics, particularly their ability to form hydrogels, make them valuable additives in cosmetical formulations [64]. These polysaccharides serve versatile roles in skincare products, acting as emulsifiers, stabilizers, and viscosity-controlling agents, thereby enhancing both the efficacy and stability of the final product [68]. This multifunctional nature underscores the immense potential of macroalgae-derived polysaccharides in advancing cosmetical formulations for improved skincare outcomes.

Seaweed-derived bioactive polysaccharides exhibit properties that combat photoaging, inflammation, oxidation, and cance. For example, a sulfated polysaccharide (fucoidan) found in brown seaweeds such as Undaria pinnatifida (wakame) and Fucus vesiculosus (bladderwrack), has demonstrated potent anti-photoaging properties. Studies have shown that fucoidan can inhibit the activity of matrix metalloproteinases (MMPs), enzymes that degrade collagen and elastin fibres in the skin, thereby averting premature aging induced by exposure to UV radiation [69]. Additionally, the red seaweed-derived carrageenan, like Chondrus crispus (Irish moss), demonstrates powerful antioxidant and anti-inflammatory attributes. Carrageenan has been found to reduce skin inflammation and alleviate symptoms of conditions like eczema and psoriasis. Additionally, its antioxidant activity helps to remove free radicals, safeguarding skin cells against oxidative harm and premature aging. Sargachromanol E, a bioactive molecule isolated from the Sargassum horneri, improved ROS scavenging activity and reduced oxidative alteration of cell membranes in UV-exposed human dermal fibroblasts [70]. Li et al. used various in-vitro bioassays on epidermal keratinocytes and dermal fibroblasts to assess the efficacy of S. glaucescens extracts in cosmetics. Through a 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging experiment, the extract's antioxidant activity was confirmed by reducing the formation of H2O2-induced ROS in dermal fibroblasts [71].

Comprehensive knowledge about phenolic and atypical phenolic compounds in seaweed is highly valuable for cosmetic applications. By understanding these compounds, targeted skincare formulations can be developed, leveraging their antioxidant, anti-inflammatory, and photoprotective properties. This optimization enhances the effectiveness of cosmetic products in promoting skin health and vitality. Details about essential compounds concerning seaweed having significance in cosmetical industries are as follows:

  1. 1.

    Phenolic Compounds: They represent a significant group of secondary metabolites found in seaweeds, offering a distinctive array of chemical compounds valuable for cosmetic applications due to their varied biological effects. This category encompasses water-soluble compounds characterized by a hydroxyl group linked to an aromatic hydrocarbon group. Polyphenols, a subset of phenols, further diversify into various compounds like terpenoids, flavonoids, phlorotannins, bromophenols, and mycosporine-like amino acids. Their classification as simple phenolic compounds or polyphenols hinges on the number of substituents they possess. Essentially, these compounds present in seaweeds offer a rich source of natural ingredients with potential benefits ranging from antioxidative properties to UV protection, contributing to the multifaceted landscape of cosmetic formulations [72].

    • Phlorotannins: a class of polyphenolic compounds found in brown algae (Phaeophyceae). These compounds are characterized by their structural units derived from phloroglucinol, which is a phenolic compound [73]. From a biosynthetic standpoint, the oligomeric form, phloroglucinol—only found in brown seaweed—is produced in the Golgi apparatus via the acetate-malonate pathway. They have received a lot of attention. Antioxidant, anti-inflammatory, anticancer, antiallergic, hyaluronidase inhibitory, and matrix metalloproteinase inhibitor properties can be counted among their clinical and cosmeceutical potential. Furthermore, as previously discussed, they exhibit activity for UV protection and ionizing radiation protection [74]. Phlorotannins like phloroeckol and tetrameric phloroglucinol are found in Macrocystis pyrifera which exhibit anti-diabetic and antioxidant properties. By combating oxidative stress and inflammation, they help prevent skin aging, promoting a youthful complexion. Additionally, their anti-diabetic effects offer systemic benefits, contributing to overall skin health [11]. Phlorotannins are not exclusive to brown macroalgae; they are also found in other groups of macroalgae, for example, Corallina pilulifera, a red macroalgae species. This alga is rich in phenolic compounds and phlorotannins, showcasing the ability to inhibit MMP overexpression induced by UV exposure [75, 76]. Preventing this inhibition is crucial to avoid premature collagen degradation, the formation of wrinkles, and the development of cancer cells, highlighting the potential photoprotective properties of phlorotannins from red macroalgae.

    • Flavonoids: These compounds are characterized by a heterocyclic oxygen molecule linked to two aromatic rings. These rings can vary in their levels of hydrogenation, contributing to the diverse chemical structures and properties observed within the flavonoid group. Catechins and other flavonoids, such as rutin, quercetin, and hesperidin, are extensively found in terrestrial plants. Still, catechins and other flavonoids, such as rutin, quercetin, and hesperidin, have been detected in species (for example Undaria pinnatifida) from all three major families of seaweed [76]. Because these chemicals are powerful antioxidants, they usually protect plants from environmental stress. Antiallergic, anticarcinogenic, antiviral, and anti-inflammatory effects are all found in flavonoids. Flavonoids are crucial in cosmetics because they protect our skin from UV radiation and give a high antioxidant defense [77].

    • Phenolic terpenoids: They are a subclass of natural compounds that combine the structural features of phenolic compounds and terpenoids. Terpenoids are derived from isoprene units and are widely distributed in nature, while phenolic compounds contain a hydroxyl group attached to an aromatic ring. Phenolic terpenoids thus possess both the aromatic ring structure of phenolic compounds and the isoprene-based backbone characteristic of terpenoids. These compounds are abundant in various natural sources, including plants, fungi, and some marine organisms like macroalgae [78]. They are high in antioxidants and are responsible for the vibrant hues found in many fruits, vegetables, and flowers. Because these chemicals are powerful antioxidants, they usually protect plants from environmental stress. Antiallergic, anticarcinogenic, antiviral, and anti-inflammatory effects are all found in flavonoids. An example of macroalgae containing phenolic terpenoids is Sargassum muticum, commonly known as Japanese wireweed or sargassum [79]. This brown seaweed species is rich in various phenolic terpenoids, including carotenoids and phytosterols. Carotenoids contribute to the seaweed's characteristic brown colour and have been studied for their antioxidant properties as they can aid in shielding the skin from oxidative harm caused by UV radiation. Phytosterols found in Sargassum muticum help maintain skin barrier function and promote hydration, making them beneficial for skincare applications. Incorporating extracts of Sargassum muticum into cosmeceutical formulations may offer potential benefits for skin health and protection [80].

    • Mycosporine-like aminoacids (MAA): These compounds are a class of small water-soluble compounds especially found in marine algae. They act as UV-absorbing molecules posing minimal molecular weight found in the cytoplasm of cells. Most of these chemicals are produced by the Shikimate pathway, where a cyclohexenone or cyclohexenimine ring is linked to amino acid substituents in their chemical structure. The bonds formed between the ring and the substituents determine the broadband absorption of various wavelengths [81]. In cosmetics, MAAs have a vital role in photoprotection and skincare because they absorb UV light and dissipate the absorbed energy as heat, effectively averting UV-induced damage to the skin. One example of an algae species containing MAAs is Porphyra umbilicalis, commonly known as nori [82]. Nori is a red alga widely used in Asian cuisine, particularly in the production of sushi. It contains significant levels of MAAs, including porphyra-334 and shinorine. These MAAs contribute to nori's natural ability to protect itself from UV radiation in its marine environment [81]. In cosmetical formulations, extracts derived from Porphyra umbilicalis can be incorporated into sunscreens, moisturizers, and other skincare products to provide enhanced UV protection and prevent photoaging of the skin. By harnessing the photoprotective properties of MAAs from algae like nori, cosmeceutical products can offer effective defence against the harmful effects of sun exposure while promoting healthy and radiant skin.

  2. 2.

    Non-Typical Phenolic Compound: Non-typical phenolic compounds refer to a diverse group of organic compounds that possess phenolic structures but may have unique characteristics or chemical properties compared to typical phenolic compounds. While traditional phenolic compounds have one or more hydroxyl groups (–OH) attached in their aromatic ring, non-typical phenolic compounds may have variations in their chemical structure or functionalities. The presence of a non-typical phenolic component was reported in some seaweed species. Lignin, a polymerized hydroxycinnamyl alcohol, was discovered in the red seaweed Calliarthron cheilosporioides, challenging the previous assumption that it was exclusive to vascular plants. Phenylpropanoid derivatives, such as colpols and tichocarpols, are present in brown and red seaweed, including Colpomenia sinuosa and Tichocarpus crinitus [65, 83].

    • Polysaccharides: Seaweeds harbour a variety of polysaccharides with documented biological activities, which can be incorporated into cosmeceutical products such as moisturizers and antioxidants. These polysaccharides, composed of repeating units of monosaccharides such as glucose, fructose, or galactose, serve crucial roles in living organisms as both energy storage molecules and structural components. They are large carbohydrate molecules formed by glycosidic bonds linking multiple monosaccharide units together, making them polymers with diverse functionalities in biological systems [7]. Macroalgal hydrocolloids, also known as phycocolloids, represent essential compounds for industrial commercialization. These structural polysaccharides derived from seaweed typically yield colloidal solutions, which exhibit properties midway between a solution and a suspension. Consequently, polysaccharides find versatile applications across industries, including cosmetics, where they serve as thickeners, gelling agents, and stabilizers for suspensions and emulsions [84]. Some of the common polysaccharides are:

    • Agar: Also referred to as agar–agar, is a gelatinous hydrocolloid derived from certain species of red algae, particularly from the genera Gelidium, Gracilaria, and Pterocladia [85]. It is utilized as an emulsifier and stabilizer in creams, controlling moisture levels in cosmetics like hand lotions, liquid soap, deodorants, foundations, exfoliants, cleansers, shaving creams, facial moisturizers/lotions, acne, and anti-ageing treatments. This polysaccharide, composed of a heterogeneous mixture of agarose and agaropectin, serves as a structural carbohydrate in the cell wall and intercellular gaps [86]. In cosmetics, agar is valued for its gelling, thickening, and moisturizing properties. It is incorporated into skincare products, hair care products, and cosmetics to improve texture, stability, and hydration [87].

    • Alginic acid: This linear copolymer, found in several brown seaweeds, has 14 glycosidic linkages linking D-mannuronic acid and L-guluronic acid, including Ascophyllum, Durvillaea, Ecklonia, Laminaria, Lessonia, Macrocystis, Saccharina, Sargassum, and Turbinaria [88]. In the manufacture of hand jellies and lotions, ointment bases, pomades, and other hair preparations, greaseless creams, dentifrices, and other cosmetic items, alginates are frequently used as thickeners, protective colloids, or emulsion stabilizers due to their chelating capabilities [89]. This polysaccharide can also play a role in the development of skin protection to prevent occupational dermatitis. Creams containing these components generate flexible films with improved skin adherence, making them ideal for multifacet cosmetics applications [90].

    • Carrageenin: A linear sulfated polysaccharide extracted from red seaweed, carrageenin is also known as carrageenan. It is a pure polysaccharide derived from various species of red seaweed belonging to multiple families within the Gigartinales order, commonly referred to as Carragenophytes [91]. Seaweeds rarely synthesize this perfect carrageenan; instead, they opt for hybrid forms. Carrageenan can be extracted from a variety of red seaweeds, including Betaphycus gelatinum, Chondrus crispus, Eucheuma denticulatum, Sarcopeltis skottsbergii (formerly Gigartina skottsbergii), Kappaphycus alvarezii, Hypnea musciformis, Mastocarpus stellatus, Mazzaella laminarioides, and carrageenan is found in many everyday cosmetic items, including toothpaste, hair wash products, lotions, medications, sun blockers, shaving creams, deodorant sticks, sprays, and foams [92]. Given the claimed excellent safety, effectiveness, biocompatibility, and the fact that they are biodegradable and non-toxic, these are compelling justifications for their use. Yet, further research is necessary to ascertain the genuine effectiveness of carrageenan [91].

    • Porphyrans: These compounds are composed of repeating units of galactose molecules linked together with the sulfate group found in certain species of red seaweed, particularly in the genera Porphyra and Pyropia. It is a complex carbohydrate composed of repeating units of galactose and 3,6-anhydrogalactose, with sulfate groups attached to some of the sugar residues. Porphyran's application for skin whitening, anti-inflammatory, pain reliever, and antiulcer bioactivities has been highlighted in studies, making it attractive for cosmeceutical applications [93].

    • Laminaran: It exists in soluble and insoluble forms and is known as laminarin or leucosin. A cold solution of the first form dissolves in water, while a hot solution dissolves only in water. This polysaccharide is mostly found in seaweeds of the Phaeophyceae (brown algae) class, such as Laminaria and Saccharina, and in smaller amounts in Ascophyllum, Fucus, Sargassum, and Undaria. Anti-tumour, anti-inflammatory, anti-coagulant, anti-viral, and antioxidant properties of laminarans are being investigated [73]. Laminaran's linear structure consists of (1,3)-glucose in the backbone molecule, which branches outwards at a branching point (1,6). This -glucan typically has a molecular mass ranging from 2.9 to 3.3 kDa and contains approximately 50–69 percent d-glucose, along with around 1.3 percent d-mannitol. The proportion of (1,3) glucose to (1,6) glucose varies significantly among algae, and their molecular mass is also affected by the degree of polymerization. The extraction length and solvent used significantly impact the molecular weight of laminaran, with a longer extraction technique resulting in a higher molecular weight [94]. Overall, laminarin is a versatile ingredient in cosmetics, offering multiple potential benefits for the skin. Its moisturizing, antioxidant, anti-inflammatory, and skin barrier-enhancing properties make it a valuable addition to skincare formulations.

    • Fucoidan: It is a hydrocolloid that is mainly composed of α-l-fucopyranose residue. The binding and branching forms of these sulfated polysaccharides and their monomeric makeup can play an important role in modifying their biological capabilities. It is found in various species of brown seaweed, such as kelp, bladderwrack, and wakame. Moon et al. [95] showed that when the skin is subjected to UVB (ultraviolet B) radiation, fucoidan can enhance procollagen type I synthesis while inhibiting metalloproteinase matrix expression. Fucoidan, extracted from edible seaweed through boiling in water for 20–40 min, exhibits potential medicinal properties, suggesting its utility in preventing skin photoaging. When consumed, it appears to mitigate inflammatory responses and accelerate tissue repair post-wounding or surgical trauma. Consequently, it's recommended for a range of conditions such as muscle and joint injuries, falls, bruising, cuts, and surgery. These sulfated polysaccharides are increasingly recognized for their multifaceted bioactivities, including anti-coagulant, anti-thrombotic, anti-inflammatory, UV radiation skin protection, tyrosinase inhibition, antitumoral, antibacterial, anti-obesity, anti-diabetic, antioxidative, and antihyperlipidemic effects. Fucoidans also function as tyrosinase inhibitors, potentially aiding in reducing skin pigmentation. Furthermore, fucoidan exhibits protective effects on hair and skin by scavenging free radicals, reducing inflammation, addressing wrinkles, alleviating allergies, and mitigating sensitive skin reactions. This polysaccharide additionally contributes to hair health by promoting growth, strength, cleanliness, and gloss [7, 96]. In cosmetic formulations, fucoidan is used as moisturizers, serums, and masks to provide hydration, anti-aging benefits, soothing effects, and skin-brightening properties.

    • Ulvan: It is a sulfated polysaccharide present in green seaweeds, especially species within the Ulva genus, and can constitute between 8 and 29% of the algae's dry weight. The formation of ulvan gel is a complex process marked by the formation of spherical ulvan structures in the presence of boric acid and calcium ions. (Fig. 5) This phenomenon is pivotal in the gelation of ulvan, where the interaction between ulvan molecules, boric acid, and calcium ions leads to gel network formation [97]. The intricate interplay between these components facilitates the development of stable ulvan gels, which find applications in various fields due to their unique properties and versatility. Moreover, ulvans have moisturizing, anticancer, antioxidative, and antitumor effects and are now used as a clouding and flavouring agent in beverages and a stabilizer in cosmetics due to their mentioned properties [98]. Ulvan's antioxidant properties have piqued interest in the cosmetic industry, as in vitro studies have demonstrated its ability to shield against hydrogen peroxide-induced oxidative stress. With its moisturizing attributes attributed to glucuronic acid and the cell proliferation and collagen synthesis capacities associated with rhamnosyl residues, ulvan emerges as an attractive raw material for the cosmetics industry [99].

  3. 3.

    Pigments: Pigments are substances that impart color to materials by selectively absorbing and reflecting certain wavelengths of light. In biological systems, pigments are molecules that absorb light energy for various purposes, such as photosynthesis, photoprotection, and visual signalling [100]. Pigments are accountable for the diverse spectrum of colors visible in living organisms, spanning plants, animals, and microorganisms. Additionally, they play a vital role in safeguarding human health and preventing diseases. Seaweed encompasses an array of pigments contributing to its varied hues, spanning from green to red and brown. These pigments fulfil diverse roles within seaweed, including facilitating photosynthesis, absorbing light, and shielding against harmful UV radiation. Examples of seaweed pigments comprise chlorophylls, carotenoids, and phycobilins.

    • Chlorophylls are pigments found in any seaweed species, regardless of colour. Chloroplasts contain this pigment, which gives plants their green color. One potential benefit of chlorophyll in cosmetics is its antioxidant activity. Pollution and UV radiation, among other environmental factors, can cause oxidative stress on the skin. Chlorophyll protects the skin as an antioxidant. By neutralizing free radicals, chlorophyll can help prevent premature aging and maintain skin health [101]. Additionally, chlorophyll has been suggested to have detoxifying properties, which may help purify the skin and reduce the appearance of blemishes and imperfections. Multiple studies suggest that chlorophyll can aid in the removal of toxins and impurities from the skin, promoting a clearer complexion [102]. Moreover, chlorophyll's natural green color can be used in cosmetics to provide a vibrant and natural hue to skincare products. Green formulations are often associated with freshness and vitality, enhancing the visual appeal of cosmetics. Chlorophylls also have deodorizing and antimicrobial properties. Overall, chlorophylls are an appealing raw material for the cosmetic industry because of their antioxidant activity and potential to enhance tissue formation [103].

    • Carotenoids are lipophilic isoprenoid compounds containing astaxanthin, fucoxanthin, loraxanthin, lutein, violaxanthin, and zeaxanthin. By modulating gene expression triggered by UVA radiation, these pigments can protect the skin and eyes from photooxidation and prevent eye disease in humans. They include xanthophylls such as astaxanthin, fucoxanthin, loraxanthin, lutein, violaxanthin, and zeaxanthin, along with carotenes like β-carotene. These compounds exhibit various bioactive qualities, encompassing anti-inflammatory, antioxidant, and antitumoral capabilities, making them valuable for natural dye application [104].

  4. 4.

    Lipids: They are the "building blocks" of all living cells, along with proteins and carbohydrates, comprising one of the three major nutritional categories. They're a diverse category of lipophilic chemical molecules found in animals, microbes, and plants. Lipids are a class of chemical substances that have a lipophilic property as a typical characteristic. Seaweed lipids have emerged as valuable ingredients in the cosmetics industry, offering a range of benefits for skin health and beauty. Extracted from seaweed species rich in essential fatty acids, these lipids provide a natural source of omega-3 and omega-6 fatty acids, along with other bioactive compounds like sterols, phospholipids, and glycolipids [105]. One of their key roles lies in moisturization, as they help replenish the skin's lipid barrier, retaining moisture and promoting hydration. Additionally, seaweed lipids exhibit anti-inflammatory properties, making them effective in soothing irritated skin conditions. Their antioxidant activity further protects the skin from environmental stressors, contributing to anti-aging effects and preventing damage caused by free radicals. Moreover, these lipids support skin barrier repair, enhancing the skin's resilience and protecting it from external aggressors [105]. As a result, seaweed lipids are increasingly incorporated into cosmetics formulations, including moisturizers, serums, and facial oils, offering a natural and effective solution for nourished, protected, and rejuvenated skin. Conversely, research has focused on the anti-allergic, antioxidant, and anti-inflammatory properties of algal fatty acids. Additionally, lipids serve to safeguard the skin against moisture loss by functioning as emollients, which soften the skin [106].

  5. 5.

    Proteins, Peptides, and Amino Acids: One or more amino acid chains form the structure of proteins, which are biological macromolecules. They are found in all living species and are involved in nearly all cellular processes, performing various bodily activities, including DNA replication, trigger response, and molecular transport. Certain seaweed species like Porphyra tenera, commonly known as nori, contain proteins with exceptional moisturizing properties [107]. These proteins can help improve skin hydration by enhancing the skin's natural moisture-retaining abilities, resulting in softer, smoother, and more supple skin. Furthermore, the bioactive peptides found in seaweed proteins have been shown to have anti-inflammatory and skin-soothing effects, making them beneficial for calming irritated or sensitive skin Seaweed proteins can be used as hair and body moisturizers. Amino acids are commonly used as a hydrating agent in cosmetics since several are components of human skin's natural moisturizing factor (NMF) [7, 42, 107].

Fig. 5
figure 5

Ulvan extraction, characterization, and versatile applications [97]

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Clean and washed seaweed refers to seaweed that has undergone a thorough cleaning and washing process to remove impurities, contaminants, and excess salt [108] (Fig. 6). Ensuring the purity and safety of seaweed through processing is crucial for its diverse applications in industries like food, pharmaceuticals, and cosmetics. The cleaning process involves the removal of debris, sand, and other foreign materials from the harvested seaweed. This is typically done by rinsing the seaweed multiple times in clean water to ensure that all impurities are eliminated. After cleaning, the seaweed undergoes washing to eliminate any remaining contaminants and reduce the salt content. Washing helps ensure that the seaweed meets quality standards and is free from pollutants or harmful substances that may be present in the seawater [109]. Once cleaned and washed, the seaweed may be dried using methods such as air drying, sun drying, or mechanical drying. Drying helps preserve the seaweed's shelf life and facilitates storage and transportation. Overall, clean and washed seaweed is a purified and sanitized product that can be further processed into various forms, such as seaweed flour or carrageenan [110]. This ensures that the seaweed maintains its nutritional content, functional properties, and potential health benefits while meeting stringent quality and safety standards.

Fig. 6
figure 6

Process flow for producing seaweed flour and carrageenan from clean and washed seaweed

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Altogether, the remarkable compounds and metabolites found in seaweed make it an ideal ingredient for cosmetics. These compounds possess antioxidant, anti-inflammatory, and moisturizing properties, making seaweed a valuable addition to cosmetic formulations aimed at enhancing skin health and appearance. Moreover, the sustainable sourcing of seaweed aligns with the increasing consumer demand for eco-friendly beauty products, further solidifying its status as a preferred ingredient in the cosmetic industry.

Extraction techniques for marine natural products from microalga

Algal cell walls are structurally diverse and complex, containing Matrix Associated Proteins (MAPs) along with polysaccharides. An amorphous matrix is enclosed within a fibrous skeleton. The polysaccharides within them are both linear and branching, forming the primary structural components, with combinations of both neutral and acidic polysaccharides. Hot water extraction, a widely used and convenient method, is commonly employed to extract polysaccharides from algae [111]. However, this method presents limitations, including time-intensive procedures, high-temperature requirements, and suboptimal extraction efficiency. Extraction protocols frequently employ a methanol/chloroform/water mixture to overcome these challenges and eliminate interfering compounds such as low molecular weight chemicals, lipids, and pigmented materials from algal samples [112]. Enhanced extraction efficiency of marine algae polysaccharides (MAPs) has been achieved through novel techniques including microwave, ultrasonic, and enzyme-assisted methods. Microwave-assisted extraction has gained prominence for its effectiveness in extracting polysaccharides from marine algae. Parameters such as microwave power, irradiation period, solid-to-liquid ratio, and temperature can be optimized utilizing the response surface methodology to enhance extraction efficiency [113]. In comparison to the conventional method, microwave-assisted extraction offers several advantages, including reduced extraction time, lower energy consumption, and decreased costs, coupled with higher extraction efficiency [112]. Tsubaki et al. discovered that varying microwave processing temperatures influenced the molecular weights and viscosity of extracted polysaccharides. As temperature increased, viscosity decreased due to polysaccharide breakdown. The study also examined the impact of microwave parameters on polysaccharide breakdown percentages, sulfate content, monosaccharide composition, and molecular weights during extraction [114].

Ultrasonic-assisted extraction, increasingly popular for obtaining polysaccharides from marine algae, utilizes ultrasound waves to create cavitation effects. These waves break cell walls, facilitating the release of water-soluble polysaccharides [115]. Kadam et al. demonstrated that ultrasonic-assisted extraction of laminarin from brown seaweeds resulted in higher yields compared to conventional water extraction. Additionally, enzyme-assisted extraction has attracted interest due to its ability to disrupt cell walls and release intracellular polysaccharides by breaking down complex molecules [116]. Commercially available enzymes like viscozyme, cellucast, termamyl, ultraflo, carragenanase, agarase, amyloglucosidase, xylanase, kojizyme, protamex, neutrase, flavourzyme, and alcalase are commonly utilized in enzyme-assisted extraction procedures [117, 118]. Hardouin et al. found that endo-protease treatments significantly increased the extraction yields of sulfated polysaccharides from algal samples [119]. Supercritical fluid extraction and ionic liquids extraction have emerged as viable, environmentally friendly, and high-yielding polysaccharide extraction procedures from algal cell walls.

Understanding the intricate mechanisms by which algae-derived compounds interact with skin cells, potentially offering a diverse array of cosmeceutical benefits such as hydration, anti-aging effects, and skin rejuvenation is of paramount importance (Fig. 7) This knowledge can guide the development of innovative skincare formulations harnessing the therapeutic properties of algae extracts, paving the way for effective and sustainable cosmetic solutions tailored to enhance skin health and appearance.

Fig. 7
figure 7

Flowchart depicting the application of algae extract on skin layers, including epidermis, dermis, and fibroblasts, along with its cosmeceutical applications

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Potential applications of macroalgae and microalgae in anti-aging, photoprotection, and skin whitening.

Algae, both macro and micro, possess superior bioactive compounds like antioxidants, polysaccharides, and pigments, offering natural anti-aging, photoprotective, and skin-whitening effects in skincare. Their inclusion in formulations can rejuvenate skin, protect against UV damage (Table 1) and promote a brighter complexion.

Table 1 Comprehensive overview of algae species, their bioactive compounds, beneficial properties, and promising applications for enhanced skincare and well-being
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Active ingredients for moisturizing care

Maintaining adequate skin hydration is crucial for overall skin health. Lipids including ceramides, fatty acids, and cholesterol, are commonly used in skincare to replenish the skin's lipid barrier, preventing moisture loss, and promoting hydration. Microalgae of the genus Nannochloropsis are of interest due to chemicals that prevent water loss to the skin [120]. Polysaccharides, fatty acids (sophorolipids, rhamnolipids, and mannosylerythritol), and proteins produced by marine organism have moisturizing characteristics and are commonly employed in their high linolenic acid concentration. Furthermore, seaweeds high in serine, such as Undaria pinnatifida and Thalassiosira microalgae, are of great interest as they can hydrate and relax the skin [42].

Active ingredients to prevent skin aging

Extracellular matrix breakdown is closely linked to skin aging in both the epidermal and dermal layers. Intrinsic (genetic) factors are the most important, but environmental influences are equally crucial. UV radiation, whether natural or in a tanning bed, smoking, and weather (for example, wind exposure) are all major contributors in the latter group. Carotenoids are one of the most important active principles in anti-aging ingredients. The major carotenoid produced by the halotolerant microalga Dunaliella salina is -carotene, which can yield more than 10% of its dry weight in -carotene [121]. Carotene is also employed as a provitamin A in anti-aging products [122]. Astaxanthin's extraordinary antioxidant capacity, which is superior to that of -tocopherol, is also used in anti-aging treatment. An aqueous extract of the brown alga Macrocystis pyrifera of the Laminariaceae family is available in the market. Syndecan-4, another key extracellular matrix protein, may similarly be stimulated by M. pyrifera extract. The aging process causes wrinkles in the skin by reducing skin thickness, elasticity, and curling of elastic fibers in the skin [120]. Matrix metalloproteinase (MMP) inhibitors have the potential to be used as an anti-wrinkle cosmetic. Wrinkles form because of significant collagen breakdown by MMPs over time [123]. Minerals found in seawater are also recognized to have health benefits [122].

Active ingredients for topical photoprotection

Operating as a chemical and physical barrier, the skin comprises three layers: epidermis, dermis, and hypodermis. Various environmental elements, such as chemicals, ultraviolet (UV), and pollution, can harm the skin Photo-aging, also known as dermatoheliosis, is caused by UVA (400 nm 320 nm) and UVB (320 nm 290 nm) induced skin damage (Fig. 8) [124, 125]. Long-term and short-term impacts on the skin may emerge from prolonged human exposure to UV radiation. The effects are beneficial in the short term. The key ones are the positive effects on mood, vitamin D induction, and rapid skin pigmentation, as well as the negative effects on skin thickness, actinic erythema, and tanning. Photo-induced skin aging and photo-carcinogenesis linked to ultraviolet radiation-induced immunosuppression are all long-term detrimental impacts. Algal metabolites, particularly those derived from marine algae like mycosporine-like amino acids (MAAs), astaxanthin, carotenoids, scytonemin, phlorotannins, and polysaccharides, serve essential functions in shielding against UV radiation [126]. MAAs found in marine and terrestrial algae absorb UV photons and thus prevent direct exposure of UV rays to skin cells which reduces the risk of DNA damage. This mechanism was demonstrated in the cytotoxicity study involving extracts from red algae Hydropuntia cornea and Gracilariopsis longissimi [127]. Phlorotannins are polyphenolic compounds predominantly found in brown algae, such as Ascophyllum nodosum and Ecklonia cava. These compounds exhibit strong antioxidant properties, effectively neutralizing ROS induced by UV-B radiation which helps to preserve the integrity of the extracellular matrix and protects against UV-induced damage to the skin. Additionally, phlorotannins reduce the expression of matrix metalloproteinases in dermal fibroblast cells of the skin [128]. Astaxanthin is a carotenoid pigment found in algae such as Haematococcus pluvialis. It possesses potent antioxidant properties, scavenging ROS generated by UV radiation. Astaxanthin protects cellular components, including lipids, proteins, and DNA, from oxidative damage, thereby promoting skin health and reducing the signs of aging caused by UV exposure. Sulfated polysaccharides found in red algae like Porphyra yezoensis and Gracilaria sp., can form protective films on the skin surface, thus acting as physical barriers against UV radiation.

Fig. 8
figure 8

Schematic representation illustrating the intricate entry of ultraviolet (UV) rays into the skin with the subsequent initiation of photochemical processes within skin cells

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Active ingredients with skin whitening properties

Whitening cosmetics are in high demand for the treatment of lentigo, pregnancy masks, residual hyperpigmentation, and hyperpigmentation caused by drug poisoning. In recent years, research has concentrated on the development of novel skin-whitening chemicals generated from marine microorganisms. Among these, zeaxanthin [129], which may be found in Nannochloropsis oculata extract, appears to be of particular interest. A Chlorella extract offered by the business Codif would also reduce skin pigmentation by more than 10% in the skin whitening area. Through its anti-tyrosinase activity, 7-phloroeckol, a phlorotannin isolated from E. cava brown seaweed, has been recommended as a skin-whitening agent [130].

Leading companies in the algal pigments market

In recent years, the algal pigments market has surged as companies recognize their potential. This trend reflects a broader shift in cosmetics towards sustainable sourcing. Algal pigments, prized for their vibrant colors and bioactive properties, show promise in skin care. However, the market remains niche due to cultivation complexities and limited formulations. Yet, investing in algal pigments offers advantages, aligning with consumer preferences for eco-friendly products. As research progresses, the market is primed for growth, offering a sustainable path forward for cosmetics. The leading companies in this realm are:

  1. 1.

    Earthrise Nutritionals, LLC

    Earthrise Nutritionals, formerly Proteus Corporation, has been a pioneer in Spirulina production since 1976. Through a strategic partnership with Dainippon Ink and Chemicals (DIC) in 1981, Earthrise became the world's largest Spirulina producer. Today, as part of DIC, Earthrise remains an industry leader, distributing quality Spirulina and products to over 20 countries worldwide.

  2. 2.

    Cyanotech Corporation

    Cyanotech is committed to advancing holistic health through Hawaiian microalgae. Their mission revolves around offering top-notch microalgae products for health and human nutrition, all while prioritizing sustainability and environmental awareness. Their premier offering, BioAstin® Hawaiian Astaxanthin®, derived from natural microalgae Haematococcus pluvialis, is renowned for its exceptional antioxidant properties. Cultivated in the pristine environment of Hawaii's Kailua-Kona Coast, Cyanotech ensures a pure and GMO-free process, harnessing the island's abundant sunlight, clean air, and lava-filtered aquifer water. Astaxanthin, celebrated as nature's potent antioxidant, is extensively studied for its broad health benefits.

  3. 3.

    BlueBioTech Int. GmbH

    BlueBioTech International GmbH (BBT) is a leading producer and distributor of natural food supplements, specializing in microalgae-based products. Founded in 2000 by Dr. Peter Hartig, the company cultivates Spirulina platensis and Haematococcus pluvialis in its company-owned algae farms in China and Tenerife.

  4. 4.

    Zhejiang Binmei Biotechnology Co., Ltd.

    Zhejiang Binmei Biotechnology Co., Ltd, established in 2013, is a reputable supplier specializing in phycocyanin. With a primary focus on manufacturing high-quality blue Spirulina and Spirulina powder, the company has gained recognition for its products exported to the USA, Europe, Japan, and various other countries. Binmei distinguishes itself as a leading blue Spirulina manufacturer, extracting the pigment from Spirulina (blue-green algae) using a solvent-free water-based process.

  5. 5.

    Bluetec Naturals Co., Ltd.

    In 1998, the company established a pure natural farm for cultivating Spirulina and Chlorella in China. Situated near China's largest Salt Lake, the farm benefits from access to high-quality natural minerals essential for the cultivation of Spirulina and Chlorella.

  6. 6.

    Algatechnologies Ltd.

    Algatech, founded in 1998 at Kibbutz Ketura, specializes in cultivating four key microalgae species: Haematococcus pluvialis, Phaeodactylum tricornutum, Porphyridium cruentum, and Nannochloropsis. Situated in the Arava desert between the Dead Sea and the Red Sea, their production facility benefits from ideal climate conditions and pristine surroundings. Algatech's innovative approach harnesses the potential of these microalgae to promote health and ecological benefits.

  7. 7.

    E.I.D.—Parry (India) Limited

    Headquartered in Chennai, India, EID is a leading player in the Sweeteners and Nutraceuticals sector. Part of the Murugappa Group, the company is renowned for its organic Spirulina and microalgal products sold under the brand 'Parrys Spirulina'. With three major international certifications, these products are distributed in over 41 countries worldwide.

  8. 8.

    Tianjin Norland Biotech Co., Ltd

    It is a leading microalgae product manufacturer in China. With over 15 years of expertise and a professional team, they specialize in Spirulina, Chlorella, and Haematococcus pluvialis production. Operating vast algae cultivation farms and a cutting-edge processing plant in Erdos, northern China, they produce over 1100 tons of high-quality microalgae products annually. Additionally, they offer green food ingredients like Wheat Grass Powder and Barley Grass Powder.

  9. 9.

    AstaReal AB

    AstaReal, headquartered in Toyama, Japan, stands as a pioneering force in the realm of natural astaxanthin production. As the first company globally to successfully culture Haematococcus pluvialis algae commercially for astaxanthin extraction, AstaReal has set a benchmark for innovation in the industry. With over two decades of experience and a commitment to research and development, AstaReal continues to lead the way in harnessing the potential of natural astaxanthin for human consumption.

Challenges and and Prospects

Quality control and standardization play pivotal roles in ensuring the safety, efficacy, and quality of cosmetic products and their raw materials. As consumers increasingly prioritize product integrity, stringent quality control measures must be implemented throughout the manufacturing process. Given that certain algae serve as high-value cosmetic raw materials, it is imperative to conduct comprehensive testing for heavy metals such as arsenic, mercury, lead, and cadmium, as well as pesticides like organochlorine, allergens, toxins, and other chemical contaminants in algal samples. Additionally, it is essential to consider the potential phototoxic adverse effects of certain medications during cosmetic production. Phytophotodermatitis, induced by phototoxic substances or photoallergens activated upon skin contact and exposure to light, underscores the importance of thorough quality control measures. Many of these substances generate singlet oxygen and other reactive oxygen species (ROS), necessitating rigorous assessment to ensure product safety and efficacy [139]. Consumers often lack awareness that natural-based cosmetics consist of a intricate mixture of natural raw materials and chemical compounds, some of which may pose risks to human health. Cyanotoxins, a metabolite formed from algae, are toxic to immunological and brain cells; yet they could be employed as insecticides in agriculture [140]. Aplysiatoxin, debromoaplysiatoxin, lingbyatoxin, and lipopolysaharide endotoxin are examples of algal toxins that can accumulate in the body of animals. As a result, a clinical trial is required to determine the chemicals' safety and efficacy in humans [141]. Overall, ensuring compliance with regulatory standards, such as those set by the FDA and EU Cosmetics Regulation, requires comprehensive safety assessments, including toxicity studies, allergenicity testing, and stability testing under various conditions.

Algae cultivation faces challenges related to maintaining optimal growth conditions, which directly influence the yield and quality of bioactive compounds. Moreover, difficulties in extracting bioactive compounds from algae encompass a spectrum of technical, biological, and economic hurdles. Some of the most common challenges are summarised below [142,143,144,145].

  • Complexity of Algal Biomass: Extracting bioactive compounds from algae is a complex task due to the intricate composition of algal biomass. Algae contain a pool of rich bioactive compounds enclosed within rigid cell walls composed of polysaccharides, proteins, and other macromolecules. These cell walls act as formidable barriers, hindering the extraction process. Traditional extraction methods often struggle to efficiently disrupt algal cell walls or recover target compounds. Hence, there is a pressing need to explore alternative techniques such as ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, or enzymatic hydrolysis.

  • High Moisture Content and Extraction Efficiency: Algal biomass typically possesses a high moisture content, posing challenges to extraction efficiency. The presence of excess water can impede the solubility of target compounds in extraction solvents and reduce extraction yields. Traditional solvent extraction methods relying on organic solvents may be less effective in such conditions and pose environmental concerns and energy inefficiencies.

  • Variability in Biochemical Composition: Algal species exhibit significant variability in their biochemical composition, posing challenges in developing universal extraction protocols. Each species may contain different levels of specific bioactive compounds, necessitating tailored extraction methods to maximize yield and purity. Understanding and accounting for this variability is crucial for optimizing extraction processes and ensuring consistent product quality across different algae species.

  • Environmental Regulation of Metabolism: In a laboratory setting, environmental factors such as temperature, light, and nutrient availability critically regulate microalgae metabolism and biosynthesis pathways. These factors intricately influence the production of desired bioactive compounds in algae. For instance, certain bioactive compounds in algae, like enzymes and pigments, are sensitive to heat and light, leading to degradation during extraction. To address this challenge, extraction techniques that minimize exposure, such as cold extraction or extraction under inert atmospheres, are preferred to preserve compound integrity and bioactivity.

  • Formulation Challenges in Cosmeceutical Applications: Incorporating microalgae-derived compounds into cosmeceutical formulations poses challenges related to stability, compatibility, and sensory attributes. Ensuring the desired texture, appearance, and shelf-life stability while preserving bioactivity necessitates careful formulation design and testing. Formulators must consider ingredient compatibility, emulsion stability, and potential interactions with other components. Advanced analytical techniques like high-performance liquid chromatography (HPLC) and mass spectrometry (MS) monitor compound stability and degradation pathways, ensuring product efficacy and safety.

  • Consumer Education and Market Acceptance: Educating consumers about the advantages and safety of cosmeceuticals derived from algae is a significant yet often overlooked challenge. Promoting understanding and acceptance of these products is essential to encourage their use. Overcoming misconceptions and addressing concerns regarding algae sourcing, extraction methods, and potential allergenicity requires transparent communication and evidence-based marketing strategies. Consumer perception studies and market research play a pivotal role in understanding consumer preferences and shaping product development and marketing initiatives in the algae-based cosmeceutical industry. By providing accurate information and emphasizing the efficacy and safety of algae-derived cosmeceuticals, manufacturers can build trust with consumers and drive market acceptance of these innovative products.

Overall, addressing these challenges necessitates collaborative research efforts integrating knowledge from diverse fields including marine biology, biotechnology, cosmetics science, and engineering. Interdisciplinary approaches combining advanced cultivation technologies, innovative extraction techniques, and formulation optimization strategies are essential to harnessing the full potential of microalgae in cosmeceutical applications. Furthermore, academic-industry partnerships play a critical role in bridging the gap between fundamental research and commercial product development, facilitating the translation of scientific discoveries into marketable cosmeceutical products that meet consumer expectations for efficacy, safety, and sustainability in the rapidly evolving landscape of skincare innovation.

Algal biorefinery envisages the utilizing natural marine resources in cosmetics as algae-derived chemicals offer promise for innovative cosmetic formulations. Algae produce diverse bioactive compounds, making them desirable for cosmetics. Diatoms, for instance, yield fucoxanthin and polyphenols [23, 24, 27, 42]. Seaweed extracts are favoured as natural substitutes for synthetics in cosmetics, though monitoring seaweed biochemical profiles remains a challenge. Advances in seaweed cultivation and extraction methods can lead to enhanced applications of seaweed polysaccharides like carrageenan and fucoidans as potential materials for novel biomedical cues [57]. Many cosmetics with algae or algal extracts exist, but their specific bio compounds and mechanisms are often undisclosed. Further research on stability, compatibility, and toxicity is crucial to realize algae's full potential in industrial cosmetic production.

Conclusion

The cosmetic industry is undergoing a transformative shift towards sustainability and natural ingredients, driven by evolving consumer preferences for eco-friendly products with minimal environmental impact. In this context, algae emerge as a promising resource due to their abundant availability, diversity and more importantly its rich reservoir of metabolites. Polysaccharides, pigments, and phenolic compounds extracted from algae offer diverse cosmetic benefits, including moisturizing, antioxidant, and photoprotective properties. Brown and red macroalgae offer a treasure trove of diverse chemical compounds, making them prime candidates for discovering new bioactive ingredients in cosmetics. These compounds hold promise for a wide range of skincare products, from sunscreens to anti-aging creams and skin-brightening treatments. Despite current use primarily as thickeners or gelling agents, macroalgae compounds remain largely untapped in the cosmetics industry, signalling ample room for innovation and further research. Integrating macroalgae into circular economy models can not only enhance sustainability but also ensure a renewable and eco-conscious source of bioactive compounds for future cosmetic formulations.