Biosynthesis and Characterization of Zinc Oxide Nanoparticles Using Monoon longifolium Leaf Extract and Evaluation of Their Antimicrobial and Antioxidant Activities

Abstract

The present investigation reports the ecofriendly fabrication of zinc oxide nanoparticles (ZnO NPs) employing the aqueous leaf extract of Monoon longifolium (M. longifolium). The biosynthesized ZnO NPs were systematically characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), thermogravimetric/differential thermal analysis (TGA/DTA), and scanning electron microscopy (SEM). Synthesis conditions, namely extract volume (10-50 mL), precursor concentration (1 mM zinc nitrate), reaction duration (1 h), heating time (15 min), and temperature (60 °C), were methodically optimized to enhance nanoparticle yield. The resulting ZnO NPs demonstrated potent antibacterial efficacy against Staphylococcus aureus (zone of inhibition: 22 ± 0.57 mm) and Escherichia coli (19 ± 1.00 mm), alongside notable antifungal activity against Candida albicans (21 ± 0.16 mm), all determined via the agar-well diffusion method. Minimum inhibitory concentrations (MIC) were established at 6.25 µg/mL and 12.5 µg/mL against S. aureus and E. coli, respectively, while the minimum fungicidal concentration (MFC) against Candida albicans was 25 µg/mL. Antioxidant assessment via the DPPH radical scavenging assay yielded an IC₅₀ of 12.5 µg/mL, with scavenging activity ranging from 32% to 78% across tested concentrations. Collectively, these findings affirm the considerable potential of the green-fabricated ZnO NPs as multifunctional agents for antimicrobial and antioxidant applications.

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