Radical scavenging and antioxidant properties of green zinc oxide nanoparticles from Anacardium occidentale leaves

Abstract

Nanotechnology has become a focal point of interest on the road to disease intervention due to its vast applications in biomedicine and biotechnology. In this study, we evaluated the antioxidant properties of zinc oxide nanoparticles (ZnONPs) synthesised from Anacardium occidentale leaf extracts. The ZnONPs were characterised using UV-Visible and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDX), transmission electron microscopy (TEM) and gas chromatography-flame ionisation detection (GC-FID). Maximum UV-Vis spectra absorption revealed a prominent peak at 364–365 nm. The FTIR showed characteristic peaks at 3202 cm^-1, with the O-H functional vibration of carboxylic acids, and 1197 cm^-1, confirming the C-O stretch of alcohols. The absorption band of Zn tetrahedral coordination and Zn-O occurred at 869 cm^-1 and 731–820 cm^-1, respectively. The ZnONPs particle size was 17.19 nm while SEM-EDX revealed the crystalline nature and elemental compositions of the ZnONPs. TEM showed particle size distribution to be within 10–29 nm, while GC-FID revealed the presence of flavonoids, alkaloids and polyphenolic compounds. ZnONPs exhibited high antioxidant properties using 2,2-diphenyl-1-picrylhydrazyl, 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic, nitric oxide, thiobarbituric acid reactive substances, and ferric reducing antioxidant potential. Our findings show that A. occidentale leaves are a promising source of bioreductants for green synthesis, while the robust antioxidant properties exhibited by the ZnONPs are favourable in biomedical applications.

Significance:

This study shows a simple, cost-effective and eco-friendly approach for the synthesis of zinc oxide nanoparticles (ZnONPs) for therapeutic purposes. The utilisation of Anacardium occidentale leaves as a source of reducing agents for the capping and stabilisation processes makes it robust as plants are rich in bioactive compounds that possess a high therapeutic index. Antioxidant property assessment showed high scavenging activities for DPPH, ABTS and nitric oxide. Meanwhile, the ferric-reducing antioxidant power and the lipid peroxidation quenching properties exhibited by the ZnONPs would be favourable in controlling inflammation, with efficient permeation of the nanoparticles into targeted regions.