Keywords

17.1 Introduction

The kingdom Fungi is a diverse group of decomposers which majorly includes moulds, yeasts and mushrooms. Mushrooms are found worldwide and are also known to be the earliest form of fungi to mankind (Okhuoya et al. 2010). Generally, they are the fruiting bodies of macroscopic filamentous fungi which are usually known for high nutritional as well as medicinal properties. There are several evidences in history which shows that mushrooms have been consumed by mankind since a long back in the form of food or medicine. The ancient civilizations of Greek, Romans, Egyptians, Japanese, Chinese and Mexicans prized mushrooms for their medicinal properties and consumed them as dietary supplement or medicinal food (Agrawal and Dhanasekaran 2019; Chang and Zhao 2002; Guzmán 2015; Hobbs 2002). According to Greeks, mushrooms are the source of strength for soldiers in battle, whereas Romans believed them as “God’s food” and Chinese consider them as a health food or a medicine of life. Many researchers have studied and documented that mushrooms are the reservoir of variety of nutraceuticals, nutriceuticals and bioactive compounds . During the last few decades, consumption and cultivation of mushrooms increased continuously as nutritional resource. Internationally, China is the biggest producer of mushrooms, whereas Agaricus bisporus is highly cultivated mushroom species followed by Pleurotus spp. , and Flammulina velutipes (Valverde et al. 2015). Mushrooms are important inclusions for human diet as they contain significant amount of proximate constituents, prominent amount of minerals, proteins, vitamins and low fat contents along with several medicinally important active components (Kalač 2013; Isabel CFR Ferreira and Heleno 2017; Beelman et al. 2019). Different species of mushrooms are recognized to possess different medicinal properties like anti-tumor, neuroprotective, anti-oxidant, anti-hypoglycemic, anti-cancer, anti-bacterial, immunomodulatory, anti-inflammatory, anti-viral, anti-atherosclerotic properties, etc. (Wani et al. 2010; Thatoi and Singdevsachan 2014; Kim et al. 2008; Khatun et al. 2012; Gaglarirmak 2011; Elkhateeb et al. 2019; Cohen et al. 2014). The chapter presents an overview of the research on the nutraceutical, mineral, proximate constituents and bioactive component from beneficial mushrooms.

17.2 Proximate Analysis and Mineral Composition

The proximate composition including moisture content, crude fat content, ash content, carbohydrate content, total sugar content and energy value are given in Table 17.1. Many reports have been documented the proximate composition of edible and wild mushrooms. The water content of mushroom varies greatly, as their fruiting body get influenced by the type of species, growth and climatic condition, collection strategy and storage measures. The moisture content of mushrooms have been recorded from a range of 2.71 to 93.25 g/100 g dry weight. The lowest and highest moisture content has been recorded in Astraeus hygrometricus and Pholita microsporeo, respectively (Meng et al. 2019; Pavithra et al. 2018). Few species such as Agaricus albertii, Termitomyces clypeatus, Russula delica, Hygrophorus chrysodon and Suillus variegates have also showed high moisture content. The ash content generally estimates the mineral content and the value usually varies between 2.80 and 33.10 g/100 g dry weight for different mushrooms. The lowest and highest ash content has been assessed in Ganoderma lucidum and Lycoperdon umbrinum (Pereira et al. 2012; Stajic et al. 2013). While, the content of crude fat ranges between 0.18 and 17.52 g/100 g dry weight in Bovista aestivalis and Amanita princeps (Pereira et al. 2012; Srikram and Supapvanich 2017).

Table 17.1 Nutraceutical and proximate profiling of few selected species of mushrooms from different regions

Carbohydrates are the major composition of mushrooms; they are basically present in the form of glycoproteins or polysaccharides. The highest and lowest carbohydrate content has been detected in Boletus edulis (81.00 g/100 g dry weight) and Lepista inversa (10.35 g/100 g dry weight), while some heterogeneity has also observed between species (Leal et al. 2013). The energy value for mushrooms ranges between 269 and 413.46 kcal/100 g dry weight in Lycoperdon umbrinum and Craterellus cornucopioides (Beluhan and Ranogajec 2011; Pereira et al. 2012). The two major forms of sugar detected in mushrooms are mannitol and trehalose. Basically, mannitol contributes in growth and firmness of fruiting body and can vary from species to species, it is abundantly present in wild mushrooms (Kalač 2009). In wild mushrooms, mannitol ranges between 11.03 and 43.34 g/100 g dry weight, the lowest and highest values has been observed in Lyophyllum decastes and Clavariadelphus truncates, whereas in cultivated species the highest amount of mannitol has detected in Agaricus bisporus (64.15 g/100 g dry weight) and the lowest amount has detected in Lentinula edodes (49.51 g/100 g dry weight), respectively (Pereira et al. 2012; Reis et al. 2012). Trehalose, found profusely from a range of 14.21 to 25.57 g/100 g dry weight in Pleurotus eryngii and Chlorophyllum rhacodes, respectively, however in cultivated mushrooms the value of trehalose has detected to be 72.82, 42.82 and 60.51 g/100 g dry weight, the lowest and highest has been recorded in Pleurotus eryngii, Coprinus comatus and Cortinarius praestans, respectively (Pereira et al. 2012; Reis et al. 2012; Vaz et al. 2011). Other than mannitol and trehalose, low content of other sugars like sucrose, fructose, mannose, and arabinose has also been detected in mushrooms.

Mushrooms (wild or cultivated), are capable of accumulating micro and macro minerals in their fruiting bodies to perform several functions. The trace mineral contents for different species of mushrooms are given in Table 17.2. Few minerals like, Iron (Fe), Phosphorus (P) and Potassium (K) are abundantly present in mushroom fruiting bodies (Wang et al. 2014). The other minerals detected in mushrooms includes Calcium (Ca), Magnesium (Mg), Sodium (Na), Manganese (Mn) and Copper (Cu). The mineral content in the fruiting body depends on the type of species or on the substrate on which they are cultivated. The highest and lowest potassium content has been detected in Macrocybe gigantea and Volvopluteus gloiocephalus from a range of 1300 to 46,926 μg/g dry weight (Heleno et al. 2015a). While, the highest and lowest phosphorus content has been estimated in Lentinus cladopus and Stropharia rugosoannulata from 1005 to 7290 μg/g dry weight, respectively (Liu et al. 2012b; Mallikarjuna et al. 2012). For other elements like Mg, Cu, Mn, Fe and Zn, a huge variation in values have been reported, ranging from 88 to 2289, 1.53 to 88.8, 0.03 to 103.9, 0.02 to 6762 and 0.94 to118.84 μg/g dry weight, respectively. Along with beneficial minerals some toxic minerals like, Chromium (Cr), Lead (Pb), Cadmium (Cd) and Arsenic (As) have also been detected in fruiting bodies. These toxic elements are absent or very less in the cultivated species of mushrooms (Mallikarjuna et al. 2012).

Table 17.2 Trace elements in few selected mushrooms from different regions

17.3 Nutritional and Nutraceutical Potential of Mushrooms

Nutraceuticals and nutriceuticals are considered as food or a part of diet that have therapeutic and health benefits, which helps in fighting against several diseases. They may vary from herbal products to dietary supplements, isolated nutrients, genetically engineered/designer food and processed food products like beverages, cereals and soups. There are several examples of nutritive nutraceuticals/functional food ingredients like proteins, peptides, keto acids, amino acids, polyunsaturated fatty acids (PUFA), vitamins, minerals and antioxidants (Barros et al. 2008). Mushrooms are extremely nutritious with low fat content and high protein, essential amino acid, mineral and vitamin content (Agrahar-Murugkar and Subbulakshmi 2005). Studies showed that around 35 different species of edible mushrooms are cultivated commercially, however almost 200 species of wild mushrooms are used for their medicinal properties (Beulah et al. 2013). Recently, researchers gain interests in exploring mushrooms as a functional food, as a reservoir for development of potent therapeutic products and as a rich nutraceuticals, responsible for their anti-oxidant, anti-microbial and anti-tumor properties (Barros et al. 2007; Çağlarırmak 2007; Elmastas et al. 2007; Gupta et al. 2018; Ribeiro et al. 2007; Salihović et al. 2019). Several researchers, have documented the therapeutic potential of nutraceutical compounds isolated from mushrooms in cure and prevention of fatal diseases like cancer, hypertension, diabetes, heart diseases and cerebral stroke (Pardeshi and Pardeshi 2009; Wasser and Weis 1999). The investigation of therapeutic and nutraceutical potential of mushrooms gives an idea that they can be future food, which provides high quality protein and minerals (Barreira et al. 2014; Cheung 2013; El Enshasy and Hatti-Kaul 2013; Heleno et al. 2015a; Khatua et al. 2013; Kumar 2015; Ruthes et al. 2016; Singh et al. 2016; Tel-Cayan et al. 2017).

17.3.1 Proteins and Peptides

Proteins are one of the major macronutrients found in a quality food. In the last few decades, researchers have studied the importance of protein, essential amino acids, peptides and their significance for nutrition and health. Particularly, the biological functions of several dietary or bioactive proteins & peptides have been studied in more detail (Walther and Sieber 2011). Proteins and peptides are substantial bioactive nutraceuticals in mushrooms which possess numerous health benefits, like improving the digestion and absorption of nutrients, enhancing immune activity and regulating enzymatic activity (Valverde et al. 2015). The protein and peptides commonly found in mushrooms are ribosome inactivating proteins (RIPs), lectins, laccases, fungal immunomodulatory proteins (FIPs), and ribonucleases (Ko et al. 1995; Munoz et al. 1997; Xu et al. 2011). Among these proteins, lectins are glycoproteins or non-immune proteins have the property of cell agglutination and binds with the carbohydrates of cell surface. It was reported that the lectins isolated from Clitocybe nebularis, Pholiota adiposa, Narcissus tazetta, Xylaria hypoxylon, Russula lepida, Russula delica and Hericium erinaceum possess anti-proliferative, immunomodulatory, anti-viral, anti-microbial and anti-tumor activities (Li et al. 2010; Liu et al. 2006; Ooi et al. 2010; Singh et al. 2015; Zhang et al. 2010).

Mushrooms FIPs has been extracted from Ganoderma lucidium, Ganoderma microsporum, Flammulina velutipes, Volvariella volvacea, Antrodia camphorate, etc., and reported with immunomodulatory activity (Xu et al. 2011). They also prevent the invasion and metastasis of tumour cells and therefore can be used as adjuvants for treating tumour (Lin et al. 2010). Bioactive protein “RIPs” belongs to enzyme class and has been extracted from several mushroom species including Pleurotus tuberregium, Flammulina velutipes, Lyophyllum shimeiji, Calvatia caelata, and Hypsizigus marmoreus (Lam and Ng 2001; Lin et al. 2010; Ng et al. 2003; Wang and Ng 2001a, b, 2006). They are capable to inactivate the ribosomes by removing one or more adenosine from rRNA and also they help in inhibiting the HIV-1 reverse transcriptase activity and fungal proliferation (Puri et al. 2012). Like RIPs, laccases also belong to the enzyme category, and are considered as a promising candidate in the field of industry and biotechnology. They are majorly isolated from Pleurotus eryngii, Pleurotus ostreatus, Tricholoma mongolicum and Clitocybe maxima, and reported for anti-viral and anti-proliferative activity (M EL-Fakharany et al. 2010; Wang and Ng 2006; Zhang et al. 2010). They are known as Green tool/green catalyst in the field of biotechnology and have immense applications in the field of medicine, food, cosmetics, etc. (Agrawal et al. 2018). Ribonucleases, another bioactive protein isolated from mushroom has been documented for their antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Pseudomonas fluorescens (Alves et al. 2013).

According to Rathore and co-workers (Rathore et al. 2017), the highest content of crude protein has observed in Auricularia auricular (360 g/kg dry weight), followed by Pleurotus ostreatus (284 g/kg dry weight) and Lentinus edodes (228 g/kg dry weight). The protein content from beneficial mushrooms in the past few years are shown in Table 17.1. The higher content of protein have been determined in Agaricus subrufescens (50.40 g/100 g dry weight), followed by Russula cyanoxantha (49.20 g/100 g dry weight), Craterellus cornucopioides (47.21 g/100 g dry weight), Pleurotus geesteranu (39.80 g/100 g dry weight), Pleurotus ostreatus (28.40 g/100 g dry weight), and Laccaria amethystea (29.84 g/100 g dry weight) (Beluhan and Ranogajec 2011; Ikon et al. 2019; Liu et al. 2019, 2012b; Srikram and Supapvanich 2017), whereas the lowest protein content have been reported in Pleurotus eryngii (2.09 g/100 g dry weight), followed by Helvella lacunose (4.40 g/100 g dry weight), Boletus regius (5.22 g/100 g dry weight), Amanita curtipes (6.40 g/100 g dry weight) and Clitocybe subconnexa (7.42 g/100 g dry weight), respectively (Fernandes et al. 2015; Heleno et al. 2015b; Leal et al. 2013; Reis et al. 2014). The research findings could confirm the anti-tumor, anti-viral and anti-inflammatory activities of proteins isolated from mushrooms (Chatterjee et al. 2017; Lin et al. 2010).

17.3.2 Amino Acids and Vitamins

The essential amino acids are vital for humans as they are not synthesized by the body, therefore they are obtained from the food. Mushrooms are ideal source of essential amino acids (Kıvrak et al. 2014). They contain all essential amino acid along with few non-essential amino acid (Manzi et al. 1999). Free amino acid are leading components of functionally active compounds, contributing for the unique flavors of mushroom (Kalač 2009; Kıvrak et al. 2014). Research findings showed the presence of 18 free amino acids in mushrooms which includes lysine, leucine, isoleucine, tryptophan, threonine, valine, methionine, histidine and phenylalanine from the class of essential amino acids and glycine, tyrosine, arginine, serine, aspartate, alanine, cysteine, glutamate and proline from non-essential amino acid group. The content of major amino acids detected in beneficial mushrooms are shown in Table 17.3. Boletus edulis, Clavulina rugosa, Lepista nuda, Cantharellus tubaeformis, Leucopaxillus giganteus, Hydnum repandum, Russula rosea and Tricholoma saponaceum showed highest (18 known amino acids) diversity of amino acids, whereas Inonotus obliquus showed the least (2 known amino acids) diversity of amino acids (Ayaz et al. 2011). Usually, the number of amino acids in mushroom varies between 14 and 18. Mushrooms, also known as a rich source of vitamins especially riboflavin (B2), niacin (B3), folates (B9) and traces of vitamin A, B1, B5, B12, C, D, and E in mushrooms (Anderson and Fellers 1942; Bernaś et al. 2006; Cardwell et al. 2018; Jaworska et al. 2014).

Table 17.3 Amino acids in different species of mushrooms

17.4 Bioactive Components

Polysaccharides are one of the most common but potent compounds extracted from mushrooms. All the polysaccharides present in mushrooms possess b-linked glucose backbone but vary from species to species on the basis of pattern and degree of branching. Most common monosaccharides found in mushrooms are glucose, fructose, xylose, galactose, mannose, trehalose, arabinose, mannitol and rhamnose (Valverde et al. 2015). The few types of polysaccharides detected in mushrooms are homopolysaccharides, heteropolysaccharides (heteroploysaccharides grifloan and lentinan), b-glucans type polysaccharides and Glucan-protein complex, respectively (Lakhanpal 2014). Polysaccharides isolated from mushrooms are well studied for their health benefits and also utilized to develop functional foods.

Lentinan, erothionine, ganoderan, pleuran, calocyban, schizophyllan and agaritine, proteoglycans are well studied polysaccharides, which are derived from Lentinus edodes, Ganoderma lucidium, Pleurotus species, Calocybe indica, Schizophyllum commune and Agaricus blazei, respectively (Badalyan 2014; Kim et al. 2005; Villares et al. 2012). These polysaccharides has been reported with anti-oxidant, anti-tumor, immunomodulatory, anti-viral, anti-inflammatory, anti-fatigue and anti-carcinogenic activities (Jeong et al. 2012; Kim et al. 2005; Liu et al. 2015; Ma et al. 2014; Meng et al. 2016; Rathore et al. 2017). Few polysaccharides have also been discussed in the proximate analysis and mineral content section.

During last few decades researchers are more concerned about oxidative damage because the risk of oxidative species, including free radicals is increasing constantly, resulting from unhealthy habits and pollution exposure. A free radical is known as any unstable molecule which are very reactive and cause oxidative stress to body, resulting in growth of several fatal diseases like cancer, neurodegenerative disease, cardiovascular disease, etc., (Carocho and Ferreira 2013; Gutteridge and Halliwell 2000). An anti-oxidant can stabilize these free radicals and help in preventing the diseases caused by oxidative stress (Carocho and Ferreira 2013; Ferreira et al. 2009, 2015; Painuli et al. 2018, Painuli and Kumar 2016, Semwal and Painuli 2019; Stajic et al. 2013). Although, human body can prevent oxidative stress by endogenous antioxidant defense mechanism, we can also obtain anti-oxidants by inclusion of healthy food in our diet (Ferreira et al. 2009).

In this view, mushrooms are considered to be a rich source of anti-oxidants and have been extensively studied for their antioxidant properties. The antioxidants reported in mushrooms are phenolic acids, tocopherols, terpenes, carotenoids, steroids and ascorbic acid (Ferreira et al. 2009, 2015; Stajic et al. 2013). Alkaloid is one of the important class of phenolic compounds. They possess immense therapeutic properties and have been used from a long back for curing diseases. In past few years mushrooms are reported with significant content of alkaloids, which are further studied for their bioactivity. Astraeus odoratus, Flammulina velutipes, Ganoderma sinense, Hericium erinaceum, Macrolepiotaneo mastoidea, Pseudobaeospora pyrifera are examples of such mushrooms which possess alkaloids with anti-tubercular activity, cytotoxic activity, anti-cholinesterase and anti-mycobacterial activity (Arpha et al. 2012; Kim et al. 2012; Liu et al. 2010; Rhee et al. 2001; Song et al. 2009).

Terpenoids are hydrocarbon formed by the combination of different isoprene units. They are reported for various medicinal and therapeutic activities like anti-malarial, anti-cancer, anti-viral, anti-microbial, anti-inflammatory and anti-cholinesterase (Arpha et al. 2012; Kim et al. 2013; Lee et al. 2011; Liu 1995; Mann et al. 1994; Mothana et al. 2003; Shibata et al. 1998; Wang et al. 2012, 2013a, b). The major terpenoid isolated from mushroom is lanostane, a triterpenes well studied for its anti-cancer activities (Arpha et al. 2012; Kim et al. 2013; Wang et al. 2012, 2013a, b). Ganoderic, lucidenic, ganodermic, ganolucidic, ganoderols, applanoxidic acids and lucidones are terpenoids isolated from Ganoderma lucidium which are reported for anticancer treatments (Li et al. 2005). Terpenoids isolated from mushrooms have also been observed to their anti-mycobacterial and anti-candidal activities (Öztürk et al. 2015).

Steroid is an organic compound, resulting from the characteristic arrangement of four cycloalkane rings that are linked with each other. They play an important role in biological systems and are responsible for cell functioning. Steroids have been isolated from different species of mushrooms including Tomophagus cattienensis, Fomes fomentarius, Ganoderma lucidum, Hypsizigus marmoreus and Sarcodon joedes, respectively (Hien et al. 2013; Liu et al. 2013; Seo et al. 2009; Zang et al. 2013). Steroids isolated from the mushrooms have anti-microbial, cytotoxic, anti-tubercular, anti-complement and anti-viral activities (Itoh et al. 2008; Liu et al. 2013; Niedermeyer et al. 2005; Seo et al. 2009).

Phenolic compounds are the largest group of phytochemicals which are well known for their interesting pharmacological activities. Flavonoids, coumarins, anthocyanin, catechins and phenolic acid, etc., are few examples of phenolic compound. The rich source of these compounds are vegetables, fruits, herbs, seeds, juices, etc. Several mushrooms including Albatrellus caeruleoporus, Boletus pseudocalopus, Cortinarius purpurascens, Ganoderma colossum, Ganoderma pfeifferi, Ganoderma fornicatum, and Tricholoma oriruben have been reported with biologically active phenolic compounds (Awadh Ali et al. 2003; Bai et al. 2013; El Dine et al. 2009; Kawagishi et al. 2004; Mothana et al. 2000; Niu et al. 2006; Quang et al. 2006; Song et al. 2009; Venkateswarlu et al. 2002; Yousfi et al. 2009). Current report on antioxidant activity of wild-growing (Agaricus campestris, Boletus edulis, Cantharellus cibarius, Macrolepiota procera, Pleurotus ostreatus, Russula alutacea, and Russula vesca) and cultivated (Agaricus bisporus, Pleurotus ostreatus) mushrooms suggests them as a rich source of phenolics and flavonoids (Buruleanu et al. 2018). The pharmacological activities reported in phenolic compound of mushrooms are anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial activities, etc., (Öztürk et al. 2015). Different biological activities of different compounds isolated from mushrooms are presented in Table 17.4.

Table 17.4 Biological activities of few beneficial mushrooms from different regions

17.5 Conclusion

Presently, the global production of cultivated mushrooms has exceeded ten million tons and is continuously increasing, with China being the largest producer. More than 2000 mushroom species are safe and eatable. Further, mushrooms can help in boosting the economic growth in a society. Worldwide, both cultivated and wild species of mushrooms are consumed as they possess distinctive and unique taste, texture and smell along with low calorific values and high fibre content. They synthesize active compounds with broad spectrum of biological activities. In vitro studies, clinical trials and animal studies validated the traditional knowledge and indicated the immense potential of mushroom-derived compounds and products, for the suppression and treatment of various diseases. The present chapter covers the information on proximate content, proteins, vitamins, minerals, bioactive compounds and potential benefits of medicinal mushrooms. Mushrooms can be consumed as tonics, medicines, nutritional products, etc. and can be used as cosmetics and natural bio-control agents. In view of promising outcomes, additional efforts are required to explore the ability of mushrooms as functional food along with the therapeutic potential. The major tasks comprise the understanding of clinical trials, development of mushroom derived products with standardized protocols, and their sustainable production under appropriate environment.