Synthesis of silver nanoparticles using coffee senna (Senna occidentalis) stem extract and its antimicrobial evaluation

Abstract

This research was carried out to synthesize silver nanoparticles (AgNPs) using the stem extract of Sennaoccidentalis Linn (Coffee senna) and testing its antimicrobial activity. In this study, the crushed stem of Sennaoccidentalis Linn was subjected to sequential extraction by increasing polarity index of solvents (hexane, ethyl acetate, methanol and water). The water extract gave the highest percentage yield of extract in the sequential extraction. The AgNPs were characterized and tested for their antimicrobial activity using the methanol and water extracts. UV-visible spectrophotometer and Fourier Transform Infrared (FTIR) Spectrometer were used to analyse the AgNPs. Colour changes were observed for each extract indicating AgNPs formation. The UV-VIS spectra showed peaks at 440nm, 440nm, 620nm, 620nm for the hexane, ethyl acetate, methanol and water extracts of the synthesized AgNPs respectively. The FTIR analysis indicated the presence of active functional groups for the methanol and water extracts. The synthesized AgNPs for the methanol and water extracts showed antimicrobial activity against all the test organisms used (Klebsiellapneumoniae, Shigellaspp, E. Coli, Salmonella typhi, and S. Aureus), however, hexane and ethyl acetate crude extracts prove positive for only E.coli, while water crude extract showed negative for all the test organisms. The crude extracts and the synthesized AgNPs showed medium zone of inhibition, with only the methanol AgNPs showing a higher zone of inhibition than the control for S. aureus. The synthesized nanoparticles via biological method is safe and can be used to modify and improve the efficacy of drugs through drug discovery.