Green Synthesis and Characterization of Zinc Oxide Nanoparticles Biosynthesized from Butea monosperma Flowers and Glycyrrhiza glabra Roots and their Antioxidant and Antibacterial Properties

Antimicrobial resistance is one of the principal global health problems, and it is imperative to develop new drugs to reduce the spread of antimicrobial-resistant microorganisms. The flower extract of Butea monosperma and the root extract of Glycyrrhiza glabra are used to green synthesize zinc oxide nanoparticles (ZnO-NPs) using zinc acetate dihydrate. We characterized the biosynthesized ZnO-NPs using various techniques. The UV–visible spectra of ZnO-NPs using flower extract of B. monosperma and root extract of G. glabra were observed at 276 and 261 nm, respectively. Fourier transform infrared spectroscopy (FT-IR) analysis depicted different functional groups. The size of the biosynthesized ZnO-NPs was calculated at 19.72 nm. Moreover, scanning electron microscopy (SEM) analysis showed that ZnO-NPs synthesized from flower extracts of B. monosperma were agglomerated in rod-shaped clusters. The nanoparticles synthesized from G. glabra were dispersed and semi-spherical in shape. The most pronounced increases in antioxidant activity against 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic) acid [ABTS] were detected at the high concentrations of ZnO-NPs (800 µg/ml) biosynthesized from B. monosperma (48.8%) and G. glabra (38.8%). Antibiotics revealed smaller inhibition zones, while the higher concentrations of ZnO-NPs (800 µg/ml) biosynthesized from B. monosperma and G. glabra displayed strong antibacterial activity against Bacillus subtilis, Escherichia coli, and Klebsiella pneumoniae. The results indicated that the ZnO-NPs synthesized using B. monosperma and G. glabra extracts demonstrated significant antibacterial and antioxidant properties. This green synthesis approach highlights plant-mediated ZnO-NPs potential as effective agents for biomedical applications and offers an eco-friendly alternative to conventional chemical synthesis methods.