Harnessing Asystasia gangetica Flower Extract and Green Synthesized Zinc Oxide Nanoparticles for Combating Multidrug‐Resistant Pathogens

Abstract This study investigates the green synthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous extract from Asystasia gangetica ( A. gangetica ) flowers, emphasizing an eco‐friendly and sustainable approach. The synthesized ZnO NPs were characterized using XRD, SEM‐EDS, FT‐IR, and UV–visible spectroscopy. The A. gangetica extract and the ZnO NPs were further evaluated for their antibacterial activity. Characterization of the synthesized nanoparticles using XRD, SEM‐EDS, FT‐IR, and UV–vis, provided useful insights into ZnO NPs' purity, particle size, morphological structure, and high stability. The structure was found to be highly crystalline with an average crystallite size of 17–44 nm in diameter. ZnO photocatalyst had a significant absorption peak at 362 nm, which corresponds to an energy band gap of 3.43 eV, as determined by UV–vis spectral analysis. The ZnO NPs and aqueous extract exhibited significant antibacterial properties against multiple pathogens, with ZnO NPs showing superior efficacy, and statistically significant ( p < 0.001) antibacterial activity when compared to both, the extract and the standard antibiotic, ampicillin. The antibacterial assay revealed that A. gangetica ZnO NPs (100 µg/mL) exhibited enhanced activity with inhibition zones ranging from 5 ± 0.1 mm to 6 ± 0.3 mm, compared to the aqueous extract which ranged from 2 ± 0.02 mm to 5 ± 0.21 mm. Although the standard antibiotic ampicillin (25 µg/mL) showed the highest activity (10 ± 0.18 mm to 12 ± 0.31 mm), the ZnO NPs demonstrated notable antibacterial potential, especially against B. subtilis , P. aeruginosa , and S. aureus . This research serves as a stepping stone for future studies, encouraging the utilization of green synthesis methods for the creation of functional nanoparticles with antibacterial potential against multidrug resistant bacteria. Further studies are warranted to establish the safety, efficiency, and mechanism of action of the ZnO NPs.