RAPID SYNTHESIS OF SILVER NANOPARTICLES USING AQUEOUS LEAF EXTRACT OF ACHYRANTHES ASPERA AND STUDY OF THEIR ANTIMICROBIAL AND FREE RADICAL SCAVENGING ACTIVITIES

Objective: To study the biosynthesis of silver nanoparticles (AgNPs) using the aqueous leaf extract of Achyranthes aspera and check the antimicrobial and free radical scavenging activity of the biosynthesized AgNPsMethods: 20 ml of aqueous leaf extract of A. aspera was added to 80 ml of 2 mM silver nitrate and the reaction solution was heated at 55-60 °C for 20 min and incubated. Biosynthesized AgNPs were characterized by different spectroscopic measurements including UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction pattern (XRD), Transmission electron microscopy (TEM) and Dynamic light scattering (DLS). Antimicrobial activity of AgNPs was checked against Staphylococcus aureus, Bacillus subtilis (Gram+ve bacteria), Klebsiella pneumonia, Pseudomonas aeruginosa (Gram-ve bacteria), Aspergillus niger, Candida albicans and Candida nonalbicans (Human pathogenic fungi) by employing disc diffusion method. The free radical scavenging activity of AgNPs was checked against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Hydrogen peroxide (H2O2) radicals. Results: After 1 h of incubation, the light yellow color of the reaction solution was turned to dark brown. UV-Vis spectra showed the absorption peak at 445 nm and confirmed the synthesis of AgNPs. FTIR spectra revealed the functional groups plausibly involved in the biosynthesis and stabilization of AgNPs. XRD pattern revealed that the synthesized AgNPs were crystalline in nature with face-centered cubic (FCC) phase. TEM revealed that the synthesized AgNPs were spherical in shape with 20-40 nm in size. DLS analysis revealed that the average size of AgNPs was 24.5 nm. Biosynthesized AgNPs were highly stable due to their high negative zeta potential value of-28.1 mV. AgNPs showed effective antimicrobial activity against S. aureus (16.4 mm), B. subtilis (14.5 mm), K. pneumonia (13.2 mm), P. aeruginosa (12.4 mm), A. niger (12.2 mm), C. albicans (11.5 mm) and C. nonalbicans (11.8 mm). AgNPs showed effective free radical scavenging activity with IC50 values of 77.73 and 90.53 µg/ml respectively against DPPH and H2O2 radicals.Conclusion: Successful and rapid synthesis of AgNPs was achieved using aqueous leaf extract of A. aspera. Biosynthesized AgNPs were proved to be excellent antimicrobial agents and free radical scavengers.Keywords: Achyranthes aspera, Silver nanoparticles, TEM, DLS, Antimicrobial and Radical scavenging activit