Green Synthesis and Characterization of Silver Nanoparticles Using Lespedeza juncea Extract: An Insight Into Its Antibacterial, Antifungal, and Enzyme Inhibitory Potential.

Herein, we adapted a quick, cost-effective, and environmentally friendly biological method for the synthesis of Ag-NPs using silver nitrate solution as a precursor, and the aqueous leaf extract of Lespedeza juncea (Chinese lespedeza) was exploited to synthesize Ag-NPs. Various physiochemical characterization techniques were used to characterize the nanoparticles. The UV spectrum revealed a resonance absorption peak at 428 nm, indicating successful synthesis of the nanoparticles. The EDX results indicated the presence of Ag, C, O, and Cl elements in biosynthesized Ag-NPs with elemental compositions of 53.93%, 32.34%, 12.49%, and 1.23%, respectively. The XRD analysis displayed the crystalline nature of the nanoparticles with a face-centered cubic lattice. The FTIR spectrum confirmed the involvement of plant-based biological compounds as reducing and capping agents. TEM revealed quasi-spherical Ag-NPs of 50 nm or smaller in size. An insight into its biological activities reveals significant antimicrobial activities against Staphylococcus aureus (14.1 ± 0.76 mm), Pseudomonas aeruginosa (11.50 ± 0.40 mm), Escherichia coli (16 ± 0.95 mm), and the fungal strains, viz. Candida albicans (14 ± 0.80 mm), Aspergillus flavus (16.50 ± 0.50 mm), Aspergillus niger (17 ± 0.86 mm) and afflicted 75% mortality to Caenorhabditis elegans. Furthermore, the Ag-NPs were found to be potent inhibitors of the enzymes tyrosinase, urease, acetylcholinesterase, and butyrylcholinesterase with IC50 values of 14.3 ± 0.2, 19.5 ± 1.1, 9.3 ± 1.3, and 32.65 ± 1.9 μg/mL, respectively. The overall outcome of the study suggests that L. juncea mediated synthesized Ag-NPs hold the potential to be employed as a promising tool for their antibacterial, antifungal, nematocidal, and for a variety of enzymes inhibitory activities.