Introduction

Arthropods are extremely dangerous vectors of pathogens and of humans and animals [1]. Malaria remains one of the major public health problems, which ultimately cause death if not diagnosed and treated initially [2, 3]. Mosquitoes (Diptera: Culicidae) represent a key threat for millions of people worldwide, vectoring important diseases, including malaria, dengue, Zika virus, yellow fever, Japanese encephalitis, St. Louis encephalitis, and filariasis [4]. The protozoan parasite Plasmodium falciparum is responsible of dangerous form of malaria that is transmitted by Anopheles mosquitoes during their blood feeding activity [5]. A dramatic revival of malaria is going on due to the increasing resistance of vectors to insecticides [6]. Moreover, the resistance to classical antimalarial drugs, such as chloroquine (CQ), atovaquone, sulphadoxine and pyrimethamine and the problem of recrudescence of artemisinin stresses, underlined the importance to develop new and effective antimalarial drugs, affordable also in developing countries [7, 8]. People living in regions with endemic mosquito-borne diseases should synergize these strategies with the reduction or removal of Culicidae breeding sites, as well as with mosquitocidal treatments using chemical or microbiological ovicides, larvicides and pupicides [9].

The lung cancer is a leading cause of death worldwide, it has a dismal prognosis related in part to the lack of routine screening, late stage presentation and at best, modest effects of systemic therapy. Smoking remains one of the major risks leading to lung cancer, but a gradual increase of adenocarcinoma in non-smokers, especially women, has been reported. Among the 85% adenocarcinoma, the most common type of lung cancer in both men and women under the age of 60, is registered in most developed countries including United States, Europe and Asia [10].

Natural product plays a significant role in drug discovery and development, especially an active agent against malaria, cancer and infectious diseases [11]. The difficulty of creating efficient vaccines and/or curative drugs underlines the urgent need for new antimalarial and anticancer tools. In India, herbal medicines represent an important part of culture and traditions. Apart from their cultural significance, traditional medicines are accessible and affordable by the majority of the Indian population. India has great plant biodiversity potential and many plants are used in traditional medicine systems [12].

Nanotechnology has revolutionized a number of aspects of human life. In particular, silver nanoparticles (Ag NPs) have received enormous attention because of their wide range of applications in biology, i.e. genomics, biosensors, immunoassays, treatment of photothermolysis of cancer cells and tumors, targeted delivery of drugs and, and optical bio-imaging of cells and tissues [13, 14]. The nanoparticle size, shape and surface morphology play a pivotal role in controlling the physical, chemical, optical, and electronic properties of these nanomaterials [15].

In past decades, biosynthesis of metal nanoparticles emerged to develop clean, nontoxic chemicals, environmentally benign solvents and renewable materials [16] and hence, the focus turned towards “green chemistry” and bioprocesses. Inspiration from nature comes through yeast, fungi, bacteria and plant extracts for the controlled synthesis of biocompatible metal nanoparticles [17].

A recent pharmacological study revealed that β-caryophyllene isolated from the leaves of M. koenigii exhibited promising antimalarial activity against chloroquine-sensitive strain of Plasmodium falciparum (3D7) and Plasmodium berghei (NK65) and low cytotoxic against HeLa cell line [18]. Several biological activities were attributed to β-caryophyllene, such as anticancer activity against amelanotic melanoma C32 and human breast adenocarcinoma MCF-7 cell lines [19], cytotoxic and anti-oxidative activities against several tumour cell lines [20] and effective antimicrobial activity on Bacillus subtilis and Escherichia coli [21]. The chloroform extract of leaves exhibited profound and exclusive lactate dehydrogenase inhibitory activity against CQ-sensitive (NE) and CQ-resistant (MRC-2) strains of P. falciparum and P. vivax [22]. The aqueous extract of this plant can be mixed with an aqueous solution of metal ions, which were rapidly reduced. Among the advantages of plant-mediated nanosynthesis, should be pointed out that botanical-based methods do not require costly laboratory maintenance procedures, at variance with other green reducing routes relying to bacteria or fungi [23].

Currently, a growing number of plant-borne compounds have been proposed for efficient and rapid extracellular synthesis of metal nanoparticles, which showed excellent antiplasmodial potential, as well as mosquitocidal properties, even in field conditions [24]. In this framework, starting from the connection between mosquito biting activity and the spread of cancer in USA, as well as from the analogies at the physiological level among cancer pathology and mosquito-borne diseases, this research focused on green-synthesized nanoparticles effective on both mosquito-borne diseases and cancer. Indeed, to combat mosquito-borne diseases and cancer outbreaks, a growing number of nanodrugs, including those synthesized using natural products, have been investigated separately against the cancer cells, mosquito vectors, and mosquito-borne diseases (i.e. mainly against Plasmodium spp. [25]).

The present study focused on the synthesis of Ag NPs using β-caryophyllene isolated from the leaves of M. koenigii at ambient conditions. The secondary hydroxyl and carbonyl groups of β-caryophyllene reduced metal ions in the absence of photo-activation. The shape of the nanoparticle can be modulated by varying the amount of β-caryophyllene in the reaction medium. This approach is a simple, cost-effective, led to nano-products stable for a long time effective against both malaria parasites and difference cancer cells.

Materials and Methods

Materials

Silver nitrate (Ag NO3) was obtained from Sigma-Aldrich Mumbai and all the glassware was sterilized with acids. Deionized water was used for all the experiments. A chloroquine-sensitive P. falciparum (3D7) obtained from the National Institute of Malaria Research (NIMR), Delhi, India was used to assess the in vitro antimalarial activity. Human lung cancer (A549) and HeLa cell lines were obtained from National Centre for Cell Sciences (NCCS), Pune, India.

Synthesis of Silver Nanoparticles Using β-Caryophyllene

The identification and isolation of β-caryophyllene were carried out folloing the methods by Kamaraj et al. [18]. β-caryophyllene (1.5 × 10−2 M) and AgNO3 (2 × 10−3 M) stock solutions were prepared using deionized triple distilled water and the subsequent dilutions were made from this stock solution. A series volume (0.013–0.032 ml) of β-caryophyllene was added in 1 ml of 2 × 10−3 M aqueous AgNO3 solution and the final volume was adjusted to 5 ml with water at room temperature. The time of addition of β-caryophyllene into the metal ion solution was considered as the start of the reaction. Under continuous stirring conditions, after 10 min, the light color of the AgNO3 solution turned pale yellow to brown color indicates the formation of Ag NPs, which remain stable for more than a month without any changes in the absorption spectrum.

Characterizations of Synthesized Silver Nanoparticles

Biophysical characterization of the Ag NPs was carried out using UV–visible spectroscopy. Millipore water was used as blank. The bio-reduction of the Ag+ ions in solutions was monitored by periodic sampling of aliquots (0.5 ml) of the aqueous component after 20 times dilution and measuring the UV–Vis spectra of the solution. UV–Vis spectra of these aliquots were monitored as a function of time of reaction on Shimadzu 1601 spectrophotometer in 300–700 nm range operated at a resolution of 1 nm. Furthermore, the reaction mixture was subjected to centrifugation at 60,000×g for 40 min; the resulting pellet was dissolved in deionized water and filtered through a Millipore filter (0.45 μm). An aliquot of this filtrate containing Ag NPs was used for scanning electron microscopic (SEM) analysis, TEM measurement by placing a drop of the nanoparticle bearing different sizes on copper-grid precoated formvar films, followed by solvent evaporation under vacuum. Fourier transform infrared (FTIR), and X-ray diffraction (XRD). For the electron microscopic studies, 25 μl of the sample was sputter coated on copper stub and the images of nanoparticles were observed under scanning electron microscope (SEM JEOL, Model JFC-1600), with magnification ranging from 20× to approximately 30,000×, spatial resolution of 50–100 nm. For FTIR measurements, the Ag NPs powder was prepared by centrifuging the synthesized Ag NPs suspension at 10,000 rpm for 15 min. The solid residue containing Ag NPs was dispersed in sterile deionized water for three times to remove the unattached biological impurities. The pure residue was then dried perfectly in an oven overnight at 70 °C. The powder obtained was subjected to FTIR measurements carried out on a Perkin–Elmer Spectrum at a resolution of 4 cm−1 in KBr pellets. The purified powders obtained after 4 h of interaction under laboratory conditions was subjected to X-ray diffraction analysis (PANalytical-XPERT PRO diffractometer system, Eindhoven, Netherlands) and the target was Cu Kα with a wavelength of 1.54060 Å. The generator was operated at 40 kV and with a 30 mA current. The scanning range was selected between 10° and 90°. The atomic composition of nanoparticles was confirmed by energy dispersive X-ray spectroscopy (EDX) coupled with transmission electron microscopy (TEM). The EDX and TEM analyses of samples were carried out by the Indian Institute of Technology Madras (IITM), Chennai, Tamil Nadu.

In Vitro Cytotoxic Activity

Cytotoxicity of nanoparticles on cancer cell line A549 and HeLa cells was determined by MTT assay [26]. Cells (1 × 105/well) were plated in 100 μl of medium/well in 96-well plates (Costar Corning, Rochester, NY). After 48 h incubation, the cell reaches 80% confluence. Then, the cells were incubated with various concentrations of the samples in 0.1% DMSO for 48 h at 37 °C. After incubation, the samples were removed and washed with phosphate buffered saline (pH 7.4), 20 µl/well of 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-tetrazolium bromide cells (MTT) and 5 mg/ml of phosphate buffered saline solution was added. After 4 h incubation, 0.04 M HCl/isopropanol were added. Viable cells were determined by the absorbance at 570 nm. Measurements were done three times, and the concentration required for 50% inhibition of viability (IC50) was determined graphically. To investigate the potential effects of Ag NPs on cell proliferation and the cells were exposed to 6.3–100 µg/ml for 48 h. The, we measured cell proliferation with a microplate reader (Bio-Rad, Richmond, CA), using wells without sample containing cells as blanks. All experiments were performed in triplicate. The effect of the samples on the proliferation of lung cancer cells was expressed as the percentage (%) of cell viability, using the following formula:

$$ {\text{Cell}}\;{\text{viability}}\;(\% )\; = \;{\text{A}}549\;{\text{of}}\;{\text{treated}}\;{\text{cells}}/{\text{A}}549\;{\text{of}}\;{\text{control}}\;{\text{cells}} \times 100\% . $$

50% inhibitory concentration (IC50) of the drug was determined by analysis of dose response curves.

In Vitro Anti-Plasmodial Activity

Following the method by Trager and Jensen [28] and Murugan et al. [27], CQ-sensitive strain 3D7 of P. falciparum were reared and used in in vitro blood stage culture to test the anti-malarial efficacy of β-caryophyllene and Ag nanoparticles.

Control and stock solutions of CQ were prepared in water (milli-Q grade); the M. koenigii, β-caryophyllene and Ag nanoparticles were prepared in dimethyl sulfoxide (DMSO). All stocks were diluted with culture medium to achieve the required concentrations (in all cases except CQ, the final solution contained 0.4% DMSO (which was found to be non-toxic to the parasite). Then, CQ, β-caryophyllene and Ag nanoparticles were placed in 96-well flat-bottom tissue culture-grade plates [29].

In the in vitro assays, the synthesized Ag NPs were dissolved in 0.5 ml of sterile distilled water to give a stock concentration of 100 µg/ml. CQ-stock concentrations (50 µg/ml) was used as positive controls, while 0.4% DMSO was used as the negative control. From these stock solutions, a tenfold dilution was made with RPMI 1640 medium (without bicarbonate). 100 μl aliquots of diluted extract dispensed into 96-well plates obtained 6.3, 12.5, 25, 50 and 100 μg/ml as final concentrations against P. falciparum (3D7) as per the procedure followed by Smilkstein et al. [30]. 50 μl of RPMI 1640 medium plus sodium bicarbonate and serum A+ as complete serum were aliquoted into all the wells. 25 μl of infected red cells of each isolate were separately added. The starting parasitemia was between 2.5 and 5.0%. However, the negative controls were maintained without the nanoparticles. After this, the plates were covered, shaken gently and incubated in desiccators at 37 °C for 24–48 h. After incubation, the content of both the controls and tested wells were harvested, and the deposited red cells were transferred to a slide to form thick film. The film was dried and stained with Giemsa, and the parasites were assessed for growth. The numbers of schizonts with three or more nuclei out of 200 asexual parasites were noted. A graph of percent inhibition of parasite growth against the concentration of the nanoparticles, compounds and the standard agents were also plotted, and the IC50 values were determined. CQ (Sigma–Aldrich) and AgNO3 (Sigma–Aldrich) were used as standards, and infected and uninfected erythrocytes were added as positive and negative controls, respectively.

Data Analysis

One-way analysis of variance (ANOVA) followed by Tukey’s HSD test were used to analyze biological data using JMP 11. P = 0.05 was used as threshold to assess significant differences among means. In addition, IC50 values were estimated from dose–response curves, both on human cancer cell lines and Plasmodium parasites [31].

Results

Here, β-caryophyllene was selected for synthesis of Ag NPs because this molecule has sites for photosynthesis and high availability of H+ ions to reduce AgNO3 to metallic nanosilver. UV–Vis spectra of Ag NPs were recorded during the reaction of aqueous AgNO3 (2 × 10−3 M) with 0.028 ml of β-caryophyllene extract over various time intervals. After the addition of β-caryophyllene (0.028 ml) to aqueous AgNO3, the solution changed from pale yellow to brown, indicating the formation of Ag NPs.

We observed the appearance of a strong surface plasmon resonance at about 420 nm after 10 min from the reaction, which increased in intensity as a function of time of reaction and it gained a maximum at 60 min of incubation (Fig. 1). Figure 2a depicts the FTIR spectrum of β-caryophyllene with peaks indicating stretching of various functional groups at 3066.82 (C–H stretch; aromatics), 2949.16 (C–H stretch; alkanes), 2926.01 (O–H stretch; carboxylic acids), 2856.58 (C–H stretch; alkanes), 2713.84 (H–C=O: C–H stretch; aldehydes), 1666.50 (–C=C– stretch; alkenes), 1633.71 (N–H bend; primary amines), 1448.54 (C–C stretch (in-ring); aromatics), 1382.96 (S=O sulfate; miscellaneous), 1367.53 (C–H rock; alkanes), 1276.88 (C–N stretch; aromatic amines), 1228.66 (C–O stretch; alcohols, carboxylic acids, esters, ethers), 1182.36 (C–H wag (–CH2X); alkyl halides), 1105.21 (C–F stretch; alkyl halides), 985.62 (=C–H bend; alkenes), 885.33 and 875.68 (C–H “oop”; aromatics), 812.05 (=C–H bend; alkenes), 642.30 (C–Cl stretch; alkyl halides) and 543.93 cm−1 (C–Br stretch; alkyl halides). Likewise, Fig. 2b revealed the characteristic functional group in the Ag nanoparticle suspension at 3407.98 (O–H stretch, H-bonded; alcohols, phenols), 2928.96 (C–H stretch; alkanes), 1621.46 (N–H bend; primary amines), 1406.50 (C–C stretch (in-ring); aromatics), 1332.61 (C–N stretch; aromatic amines), 1273.01 (C–H wag (–CH2X); alkyl halides), 1073.78 (C–N stretch; aliphatic amines), 856.90 (C–Cl stretch; alkyl halides), 675.85 (C–H “oop”; aromatics) and 615.01 cm−1 (C–Br stretch; alkyl halides). The dry powder of the Ag NPs was used for XRD analysis. The control β-caryophyllene extract as well as the AgNO3 did not show any characteristic peaks. The diffracted intensities were recorded from 10° to 90° at 2θ angles. The results of XRD analysis (Fig. 3) showed five strong intense peaks at 2θ values of 28.79, 38.26°, 44.45°, 64.58° and 77.49° which were indexed to the planes (1 1 0), (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes of a face centered cubic (fcc) structure of Ag NPs. The target was Cu Kα with a wavelength of 1.54060 Å. The XRD pattern indicates that the Ag NPs had a cubic structure. The observed peak broadening and noise were probably related to the effect of nano-sized particles and the presence of various crystalline natures. Overall, the results showed that Ag+ were reduced by β-caryophyllene.

Fig. 1
figure 1

UV-visible spectra of β-caryophyllene synthesized Ag nanoparticles over various time intervals

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Fig. 2
figure 2

a FTIR spectrum of β-caryophyllene and b β-caryophyllene synthesized Ag nanoparticles

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Fig. 3
figure 3

XRD pattern of β-caryophyllene synthesized Ag nanoparticles

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SEM micrographs of synthesized nanoparticles showed granular, spherical structures both at lower and higher magnification (Fig. 4a–c). The EDX provides information on the chemical analysis of the composition at specific locations (spot EDX). Peaks were found between 1.741 and 5.430 keV confirming the presence of Ag; the amount of atomic and weight percentage was 41.02 and 85.34%. Figure 4d represents the profile of the spot EDX analysis that was obtained by focusing on Ag NPs. Figure 5a shows representative TEM images and the corresponding size of the Ag NPs synthesized using β-caryophyllene. It has been confirmed that the Ag NPs mostly exist in the spherical and granular with low-density dispersion and the average size is about 29.42 nm. Figure 5b shows selected-area electron diffraction (SAED) pattern of one of the Ag NPs, which clearly shows that it is single crystalline. The pattern was obtained by aligning the electron beam perpendicular to the triangular facet of the nano-plate.

Fig. 4
figure 4

SEM images of β-caryophyllene synthesized Ag nanoparticles: a–c lower (×5000) and higher (×15000) magnification, d EDX showing the chemical composition

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Fig. 5
figure 5

a TEM of β-caryophyllene synthesized Ag nanoparticles obtained by the reduction of AgNO3 (2 × 10−3 M) salt with β-caryophyllene (0.028 mL), b SAED pattern of β-caryophyllene synthesized Ag nanoparticles

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Figure 6a, b shows that the M. koenigii, β-caryophyllene and Ag NPs treated on lung cancer cell line (A549) and HeLa cell line with different concentrations using MTT assay. The Ag NPs showed maximum cell viability on HeLa cells (86.40%), whereas the minimum viability was observed in A549 lung cancer cells (6.42%), when tested at 100 µg/ml). Furthermore, β-caryophyllene and Ag NPs exhibited promising anticancer activity on human lung cancer cell line (A549) with growth inhibition values ranging from about 22 to 9 µg/ml, for the three preparations tested at 100 µg/ml (Fig. 7a), with statistically significant differences among treatments on A549 cells (P < 0.05). Figure 7b shows the cytotoxicity of leaf ethyl acetate extract of M. koenigii, purified compound β-caryophyllene and synthesized Ag NPs on HeLa cells. There were no significant differences between the tested samples and the tested concentrations (M. koenigii, β-caryophyllene and Ag NPs) observed in the HeLA cells (P > 0.05). Figure 8 represents in vitro parasite inhibitions of β-caryophyllene and synthesized Ag NPs against CQ-sensitive 3D7 strain of P. falciparum. We observe statistically significant between the tested samples and control groups of 3D7 strain of P. falciparum (P < 0.05). The extract of M. koenigii, β-caryophyllene and Ag NPs exhibited promising activity with IC50 values of 22.55 ± 0.14, 18.97 ± 0.09 and 9.39 ± 0.08 on A549 cancer cell line, 118.4 ± 0.26, 274.7 ± 0.24 and 594.9 ± 0.21 µg/mL on HeLa cells and 6.25 ± 1.50, 9.06 ± 0.04 and 2.34 ± 0.07 on 3D7 strain of P. falciparum, respectively (Table 1). Selectivity indices (HeLa/3D7 (TC50/IC50) values of 18.94, 30.32 and 254.33 µg/ml were observed for M. koenigii, β-caryophyllene and Ag NPs, respectively. Hence, the tested samples suggesting a good safety margin on 3D7 strain of P. falciparum.

Fig. 6
figure 6

a Cytotoxicity of β-caryophyllene and β-caryophyllene synthesized Ag nanoparticles on lung cancer cells (A549). b Cytotoxicity of ethyl acetate leaf extract of Murraya koenigii, β-caryophyllene and β-caryophyllene synthesized Ag nanoparticles on HeLa cells. Same letters above each column indicate no significant differences (P > 0.05) among treatments. T-bars represent standard errors

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Fig. 7
figure 7

In vitro anticancer activity of β-caryophyllene synthesized Ag nanoparticles tested at different concentrations on a human lung cancer (A549) cells, and b HeLa cells after 48 h of exposure

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Fig. 8
figure 8

Parasite growth inhibitions of β-caryophyllene and β-caryophyllene synthesized Ag nanoparticles on CQ-sensitive 3D7 strain of Plasmodium falciparum. Different letters indicates significant differences among columns (P < 0.05). T-bars represent standard errors

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Table 1 Antimalarial and cytotoxic activity of Murraya koenigii extract, β-caryophyllene and Ag nanoparticles
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Discussion

Nanomedicine is facing a number of key challenges, which mostly deal with the paucity of effective preventive and curative tools against mosquito-borne diseases and cancer [32]. Medicinal plants have proved to be a boon against malaria and cancer therapy in many traditional medicines and current ethnopharmacology. β-caryophyllene isolated from the ethyl acetate extract of M. koenigii, exhibited promising activity against CQ-sensitive (3D7) strain of P. falciparum, whereas low cytotoxic effect was found in HeLa cells [18]. When the AgNO3 solution reacts with β-caryophyllene aqueous extract, a color change to brown color was detected within a short time span, just 10 min. This rapid bio reduction of Ag NPs was due to the excitations of ions and color intensity of the solutions. The UV–visible spectrum showed a strong plasmon resonance peak at 420 nm with maximum absorption that was in agreement with the earlier report using other ethnomedicinal plant species, such as Phyllanthus niruri [33] and Moringa oleifera [34]. Bio-reduction of the Ag+ could be linked with the metabolic processes utilizing nitrate by reducing nitrate to nitrite and ammonium [35]. FTIR spectrum of synthesized Ag NPs showed the presence of different functional groups i.e. alkane, methylene, alkene, amine, and carboxylic acid, which have been previously reported as reducing agents in the bio-reduction process [36, 37]. Presently, the FTIR spectrum results are correlated with the earlier reports of Gole et al. [38], which showed that proteins are capable of binding to nanoparticles (NPs) through free amine groups or cysteine residues in the proteins and electrostatic attraction of negatively charged carboxylate groups were present. Similarly, Sastry et al. [39] reported that the functional groups –C–O–C–, –C–O– and –C–C– are derived from heterocyclic compounds like proteins, which are present in fungal extract, and are the capping ligands of green-synthesized metallic nanoparticles [40]. The peaks at 1027–1092 cm−1 correspond to the C single bond N stretching vibration of aliphatic amines or alcohols and/or phenols, pointing out the presence of polyphenols in the plant extract [41]. The absorbance peaks at 802 cm−1, represents C single bond H vibration in the aromatic ring, which may indicate the involvement of free catechins [42]. The peaks indicate that the carbonyl group formed and this residue “capped” the Ag NPs in order to prevent agglomeration and thereby stabilizes the medium [43].

The X-ray diffraction pattern of pure silver ions showed peaks at 2θ values of 07.9°, 11.4°, 17.8°, 30.38°, 44°, and 23.22°, 27.88°, and 32.18° [44, 45]. Earlier reports supported the results of the present study, which revealed the characteristic peaks corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) Bragg reflection index of silver. Therefore, X-ray diffraction results also suggest that crystallization of bioorganic phase occurred in the surface of Ag NPs. Shape and size were confirmed by SEM and TEM, showing that most of Ag NPs were spherical in shape and well dispersed. The average size of the observed Ag NPs was 29.42 nm suggesting that these particles are highly stable. However, Ahmad and Kidwai [46] also reported the production of 5–200 nm sized Ag NPs, while bigger silver particles (449–491 nm) has been observed by Sanghi and Verma [47]. The EDX confirmed the presence of elemental Ag by the sharp peaks at 3–4 keV, which is typical of the absorption of metallic Ag NPs.

The β-caryophyllene synthesized AgNPs exhibited promising activity against P. falciparum (3D7) with IC50 value of 2.34 ± 0.07 μg/ml. Recently, Murugan et al. [27] have synthesized Ag NPs using Azadirachta indica seed kernel extract. These NPs evaluated against CQ-resistant and CQ-sensitive strains of P. falciparum showed moderate activity with IC50 of 82.41 and 86.12 μg/ml. Also, Murugan et al. [48] have reported that spongeweed, Codium tomentosum, fabricated Ag NPs showed antiplasmodial activity against CQ-resistant and CQ-sensitive strains of P. falciparum with IC50 values of 72.45 and 76.08 μg/ml. Whereas, Panneerselvam et al. [49] have reported that fern, Pteridium aquilinum, fabricated Ag NPs exhibited moderate activity against CQ-resistant and CQ-sensitive strains of P. falciparum with IC50 of 78.12 and 88.34 μg/ml. Compared with the previous reports, the present results about β-caryophyllene mediated Ag NPs showed promising activity on CQ-sensitive strains of P. falciparum. The small sized NPs disrupt the function of the parasite membrane (such as permeability and respiration) by attaching on its surface and subsequently, penetrating into the cell, causing further damage by interacting with the DNA of P. falciparum. Notably, green fabricated metal nanoparticles showed antiplasmodial properties which often encompasses the effectiveness of currently marked drugs for malaria treatment (e.g. CQ), with no resistant strain currently reported [50]. Furthermore, green synthesized nanoparticles have been also proposed as growth inhibitors against dengue virus (serotype DEN-2), with moderate cytotoxicity rates [51].

Recently, it has been highlighted that basic epidemiological knowledge on the relationships occurring between mosquito vector activity and the spread of cancer is needed, as well as detailed information about the ability of Culicidae to transfer viruses or tumor cells among hosts over time [52]. The control of mosquitoes and mosquito-borne diseases is facing the paucity of effective preventive and/or curative tools against malaria, arboviruses and cancer [53], as well as the urgent request of effective mosquitocides [50]. On the other hand, limited information is available about nanoformulates synthesized using natural products showing multi-potency against the above mentioned public health concerns, which still represent major challenges in the fields of nanobiotechnology, parasitology and entomology [52, 53].

Here, the cytotoxic activity of Ag NPs against lung cancer cells exhibited IC50 of 9.39 ± 0.08 µg/ml. Similarly, Du et al. [54] have reported that benzoin gum (Styrax benzoin) fabricated Ag NPs showed promising anticancer activity against Raw 264.7 (non-cancerous), HeLa (human cervical cancer) and A549 (human lung cancer), with % cell viability of 56.4 ± 5.7, 40.5 ± 5.3 and 44.8 ± 2.4%, respectively. Aceituno et al. [55] have reported that the Dendropanax morbifera fabricated Ag NPs showed good anticancer activity against human lung cancer A549 and HepG2 cell lines when tested at 50 μg/ml. In agreement with Palaniappan et al. [56], Cymodocea serrulata-synthesized Ag NPs showed potential cytotoxicity against human lung cancer A549 cells (LD50 = 100 μg/ml). At variance, the activity on HeLa cells was rather scarce. Therefore, the present β-caryophyllene fabricated Ag NPs could represent a valuable bioresource to generate reliable and eco-friendly Ag NPs for cancer therapy.

Concerning the mechanisms of actions, Morones et al. [57] have reported that the Ag NPs were preferentially bound and localized on the membrane of bacterial cells. In addition, the pitting of the cell membranes by Ag NPs causes an increase in permeability and resulted final cell death [58,59,60,61,62,63]. In the present study, exact parasite death effect of Ag NPs is still indistinct, suggesting three different possible mechanisms of action. First, Ag ions connecting to the cell membrane and causing plasmolysis (cytoplasm of parasite separated from parasites cell wall), reducing the parasites cell membrane synthesis. Second, Ag NPs might strongly inter-related with sulphur/phosphorus containing compounds present inside (DNA, proteins) and outside (membrane proteins) of the parasite cells, disturbing respiratory chain reaction, cell division, and finally leading to cell death. Third, Ag NPs release Ag ions that penetrate into the cell wall, causing condensation of DNA damage and affecting the protein synthesis. Ag NPs could easily reach the nuclear material of parasites by their unique size and greater surface area. Figure 9 shows the mode of entry of Ag NPs and their interactions with the parasite metabolism. The green synthetic strategy using phytochemicals as reducing agents has received considerable attention since it is inexpensive and uses a simple reaction process. Most importantly, the use of phytochemicals instead of noxious chemicals fulfills global sustainability initiatives, and the resulting nanoparticles are environmentally benign, biocompatible and renewable. Examples of phytochemicals utilized for the green synthesis of Ag NPs include starch, apiin (apigenin-7-apiosyl-glucoside), chlorogenic acid, saponin, curcumin, caffeic acid and resveratrol. The NPs synthesized using plants and its derivatives are the vast resources that are predominantly used in day-to-day life. Plant compound-mediated NPs have specific properties such as controlled monodispersity, high stability, faster rate of synthesis and non-laborious process (see also [64]).

Fig. 9
figure 9

Schematic representation of the mode of action of β-caryophyllene synthesized Ag nanoparticles against the malaria parasite Plasmodium falciparum

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Conclusions

Overall, the present investigation shows that β-caryophyllene isolated from M. koenigii can be used as an effective, reducing agent for the synthesis of antimalarial and anticancer Ag NPs. This biological reduction of metal would be advantageous for the development of clean, cost effective, nontoxic, and environmentally acceptable metal nanoparticles. Ag NPs are hydrophilic in nature, disperse uniformly in water, highly stable, and had significant biological activities against P. falciparum and human lung cancer cells (A549). Ag NPs present excellent opportunities for the design of next-generation, multimodal antimalarial and anticancer treatment strategies involving biotherapy, drug delivery, gene therapy, and cell cycle regulation. Together, these biomedical properties of Ag NPs could emerge as a selective and potent biological agent in future pharmacology.