Inhibition of the Growth of Bacteria and Synergism of Ag and ZnO: Calendulla Officinalis Mediated Green Approach Towards Ag-ZnO Nanoparticles and Impact of Altitude

Appraisal of changes in plant functional behavior due to altitudinal gradients have proved its utility for munificent congregation of communities and their rejoinder to universal and restricted ecological drivers. The accessibility of an ample range of nanostructures and its ability to strappingly defy microorganisms make ZnO a superlative material for antimicrobial impending and biotechnology. The current research endeavor demonstrates the upshot of altitudinal variations in phytochemicals, & antimicrobial and antioxidant activities of Ag nanoparticles (AgNPs) and Ag doped ZnO (Ag-ZnO) nanostructures synthesized in the presence of the floral extract of C. officinalis. The aforementioned plant was collected from three diverse altitudes in Himachal Pradesh, (India). Silver (Ag), Zinc oxide (ZnO), and Ag-ZnO NPs were synthesized in the presence of the floral extract of C. officinalis collected from the Shimla (2104masl), Mandi (1235masl) and Kangra (733masl) hills in the Himalayas. Structural, morphological, and vital ocular properties of the same were inspected. Among Ag NPs, the ones from the Kangra floral extract revealed the maximum inhibition zone (20.83±1.20) against S. aureus, whereas ZnO demonstrated the maximum activity (23.65±1.59) against K. pneumonia . Results also indicated that lower ranges favor the increased potential of antimicrobial activity in floral extracts and synthesized AgNPs from among all the altitudinal ranges. Synergistic effects of Ag doped ZnO NPs and streptomycin showed amplified efficacies as signified by the enlarged zones of inhibition in comparison to their individual effects. The ensuing exertion provided a plausible scheme to develop nanostructures with enviable properties, possessing promising prospect in antimicrobial activity