Green Synthesis of Silver Nanoparticles Using Grewia optiva Leaf Aqueous Extract and Isolated Compounds as Reducing Agent and Their Biological Activities

Abstract

In this study, an attempt was made to synthesize silver nanoparticles (Ag-NPs) using Grewia optiva leaf extract and isolated compounds. The bioreductant capacity of Grewia optiva leaf extract for the synthesis of Ag-NPs was assessed using various confirmatory techniques like thermogravimetric analysis (TGA), particle size analysis (PSA), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy. The presence of various bioactive compounds in leaf aqueous extract was confirmed through HPLC analysis, and 8 compounds were identified among the different peaks present in the chromatogram. Biopotencies like antioxidant, antibacterial, and effect on hair growth were determined for extract and NPs. Antioxidant capacities were assessed through standard ABTS and DPPH methods. The antibacterial potential was evaluated in terms of zone of inhibition, minimum bactericidal concentration, and minimum inhibitory concentration of the Ag-NPs and the leaf extract against selected strains of bacteria, whereas the effect on growth of rabbit hair was studied through topical treatment for a specific period of time. Better antibacterial and DPPH and ABTS free radical inhibition was observed for the formulated Ag-NPs as compared to leaf extract. The previously isolated eight compounds from this plant’s chloroform and ethyl acetate extracts were also tested for their bioreductant capacities. Out of them, the highest amount of precipitates was obtained with compound VII ((2,5-dihydroxyphenyl)-3 ${}^{\prime }$ ,6 ${}^{\prime }$ ,8 ${}^{\prime }$ -trihydroxyl-4H-chromen-4 ${}^{\prime }$ -one). The study implies that the biogenically engineered nanoscale particles could have promising biological activities in comparison to parental extract and they need to be investigated further as potential therapeutic agents to be used as antibacterial and antioxidant agents and for hair growth enhancement.