Antioxidant, antimicrobial, and photocatalytic activity of green synthesized ZnO-NPs from Myrica esculenta fruits extract

Abstract

• Novel synthesis of zinc oxide nanoparticles (ZnO-NPs) using an aqueous extract of Myrica esculenta fruits. • ZnO-NPs exhibits very high concentration of surface chemisorbed species. • Excellent antimicrobial activity against B. subtilis, S. aureus, and R. necatrix than E. coli, P. aeruginosa, and F. oxysporum . • ZnO-NPs show good photocatalytic activity for the degradation of methylene blue dye. The present report aims to synthesize the zinc oxide nanoparticles (ZnO NPs) employing Myrica esculenta fruits aqueous extract as a reducing and/or capping agent. Different techniques viz., X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), and ultraviolet–visible spectroscopy (UV–vis), were used to characterize the formation of ZnO NPs. The results revealed the formation of thin pellets-like ZnO NPs with an average crystallite size of 31.67 nm. Further, the aqueous extract of fruits and fabricated ZnO NPs were investigated for their antimicrobial [disc diffusion assay, poisoned food technique, and Minimum Inhibitory Concentration (MIC) assay], antioxidant [2,2-diphenyl-1-picrylhydrazyl (DPPH), and Ferric ion reducing antioxidant power (FRAP) assays], and photocatalytic activities. The study showed that ZnO NPs have higher antimicrobial activity (MIC- Bacillus subtilis : 0.031 mg/mL, Staphylococcus aureus : 0.062 mg/mL, Fusarium oxysporum : 0.250 mg/mL, and 0.125 mg/mL for Pseudomonas aeruginosa, Escherichia coli , Rosellinia necatrix ) as compared to pure fruits’ aqueous extract. Additionally, they also showed strong antioxidant activity (IC 50 -DPPH: 182.63 ± 3.21 µg/mL; FRAP: 129.44 µM Ferric sulphate (FeSO 4 ) equivalents). The XPS analysis revealed that a high percentage of surface chemisorbed species could be accountable for the excellent biological activities of ZnO NPs. Furthermore, photocatalytic activity showed 91% photodegradation of methylene blue dye in 180 min. Due to their excellent biological potential and photocatalytic activity, these synthesized nanoparticles can be used in various biomedical applications.