Antibacterial and seed germination activities of biosynthesized zinc oxide nanoparticles using aqueous leaf and fruit extract of Annona reticulata

Abstract

In the present work, the zinc oxide nanoparticles were synthesized using an environmentally friendly green synthesis method utilizing Annona reticulata leaf and fruit extracts and compared with the ZnO prepared by the chemical route method. The Rietveld refinement X-ray diffraction (XRD) pattern revealed the formation of wurtzite-structured ZnO. The presence of abundant hydroxyl functional groups with Zn-O stretching vibrations was corroborated using Fourier Transform Infrared (FTIR) spectroscopic analysis. The particle size distribution and the morphological analysis were inferred through the Field emission scanning electron microscopic (FESEM) images. The antibacterial potential of the prepared ZnO NPs was evaluated against pathogenic strains of Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli. Based on the zone of inhibition, the fruit-derived ZnO NPs showed higher antibacterial activity, followed by leaf-derived and chemically synthesized nanoparticles. Notably, fruit-derived ZnO NPs exhibited an almost equal zone of inhibition of 21.1 mm at 100 µg and a greater zone of inhibition of 16.9 mm at 50 µg against Klebsiella pneumoniae compared to antibiotic streptomycin. Finally, the germination of Vigna radiata seeds under the influence of ZnO NPs demonstrated that the nanoparticles favoured seed germination at a lower concentration of 2.5 mg. The highest seed germination was observed in green synthesized ZnO NPs (26 cm), with both leaf and fruit-derived nanoparticles exhibiting almost similar impacts on seed germination. The findings indicate that Annona reticulata-derived ZnO NPs could be utilized as potential antibacterial agents.