Dendrobium heyneanum Lindl. and Coelogyne mossiae Rolfe, two critically conserved orchid species from the Western Ghats of India, remain among the least studied members of the Orchidaceae family due to their limited availability. In the present study, silver nanoparticles (AgNPs) were synthesized using aqueous extracts from in vitro-raised plants of D. heyneanum and C. mossiae, designated as DHSNP and CMSNP, respectively. The phyto-synthesized AgNPs were characterized using UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Dynamic light scattering (DLS), and Scanning electron microscopy (SEM). DHSNP and CMSNP exhibited UV peaks at 402 nm and 416 nm, respectively. FT-IR analysis identified functional groups such as alcohols, primary amines, aliphatic amines, and alkynes, while XRD confirmed their crystalline, Face-centered cubic structure. SEM revealed clustered particles with multiple-crystalline morphology. The phyto-synthesized AgNPs demonstrated notable antibacterial activity against Staphylococcus aureus (MTCC-7443), Bacillus subtilis (MTCC-7164) and Pseudomonas aeruginosa (MTCC-1688), with the highest zones of inhibition recorded against P. aeruginosa (27.59 mm for DHSNP and 26.00 mm for CMSNP). Both the phyto-synthesized AgNPs also exhibited promising antioxidant effects in the DPPH, Hydroxyl radical, Nitric oxide, and ABTS Scavenging assays. Furthermore, DHSNP reduced the cell viability of Human Glioblastoma U87-MG cells to 54.06%, whereas CMSNP reduced the viability of Human Melanoma SK-MEL-2 cells to 9.05%, accompanied by dose-dependent induction of apoptosis. Overall, the study demonstrates the antibacterial, antioxidant and anticancer activities of phyto-synthesized AgNPs from in vitro-raised D. heyneanum and C. mossiae, while establishing a sustainable approach for harnessing the pharmaceutical potential of unexplored orchid taxa.
Keywords: Antibacterial screening; Coelogyne mossiae; Dendrobium heyneanum; Orchid; SK-MEL-2 cells; Silver nanoparticles; U87-MG cell line.
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