Green Synthesis of Zinc Oxide Nanoparticles Using Salvia officinalis Leaf Extract and Their Photocatalytic and Antifungal Activities

SIMPLE SUMMARY: Herein, we examined the facile synthesis of ZnONPs using aqueous extract of Salvia officinalis without any additional stabilizing/capping agents. When compared to chemically synthesized nanoparticles, green chemistry-based synthesis using medicinal plants has less harmful effects. The photocatalytic degradation of methyl orange under UV light irradiation was performed with 92.47% degradation efficiency, and the reaction rate constant (k(app)) was found to be 0.02134 min(−1). In addition, the antifungal activity of biofabricated ZnONPs was determined against Candida albicans isolates by standard protocols of broth microdilution and disc diffusion assay. Phytofabricated ZnONPs using S. officinalis were found to be more effective against drug-resistant Candida albicans isolates and have efficient photocatalytic properties. ABSTRACT: The facile bio-fabrication of zinc oxide (ZnO) nanoparticles (NPs) is described in this study using an aqueous leaf extract of Salvia officinalis L. as an efficient stabilizing/capping agent. Biosynthesis of nanomaterials using phytochemicals present in the plants has received great attention and is gaining significant importance as a possible alternative to the conventional chemical methods. The properties of the bio-fabricated ZnONPs were examined by different techniques, such as UV-visible spectroscopy, X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric/differential scanning calorimetry analysis (TGA/DTG). The photocatalytic activity of ZnONPs was investigated against methyl orange (MO) under UV light irradiation. Under optimum experimental conditions, ZnONPs exhibited 92.47% degradation of MO. Furthermore, the antifungal activity of bio-fabricated ZnONPs was determined against different clinical Candida albicans isolates following standard protocols of broth microdilution and disc diffusion assay. The susceptibility assay revealed that ZnONPs inhibit the growth of all the tested fungal isolates at varying levels with MIC values ranging from 7.81 to 1.95 µg/mL. Insight mechanisms of antifungal action appeared to be originated via inhibition of ergosterol biosynthesis and the disruption of membrane integrity. Thus, it was postulated that bio-fabricated ZnONPs have sustainable applications in developing novel antifungal agents with multiple drug targets. In addition, ZnONPs show efficient photocatalytic efficiency without any significant catalytic loss after the catalyst was recycled and reused multiple times.