Evaluation of the Antimicrobial Activity of Biogenic Silver Nanoparticles from Aqueous Extracts of the Tuber and Leaves of Ruellia tuberosa (L.) and Leonotis nepetifolia (L.)

Objective: The biogenic silver nanoparticles have gained significant attention in the 21st century due to their promising antimicrobial properties and potential applications across various fields. Methods: The biogenic silver nanoparticles were synthesized from aqueous tuber and leaf extracts of R. tuberosa and L. nepetifolia. The in vitro antimicrobial activity of the biogenic AgNPs (RtAgNPs and LnAgNPs) was studied against four bacteria (both gram-positive and gram-negative) and two fungi: B. subtilis, S. aureus, E. coli, P. aeruginosa, A. brasiliensis, and C. albicans. Results: The diameter of the inhibitory zone ranged from 11.66 to 13.66 mm for both RtAgNPs and LnAgNPs against bacteria and fungi at a 20 µg/mL concentration, except for C. albicans. The MIC of RtAgNPs and LnAgNPs was observed at 2.5 µg/mL for bacteria and 5 µg/mL for A. brasiliensis. Conclusion: The biogenic silver nanoparticles (RtAgNPs and LnAgNPs) showed moderate activity compared to the standards, but their activity was statistically significant (P < 0.001) when compared to the respective ethanolic tuber and leaf extracts, as well as synthetic silver nanoparticles (SNPs).