Phytogenic synthesis of zinc oxide nanoparticles using extract of Vachellia erioloba seed and their anticancer and antioxidant activity

Biosynthesized nanomaterials, with sizes in nanometric dimensions, have gained great attention in various fields including biotechnology, medicine, and agriculture. Their synthesis via green resources is a facile, pollutant-free, environmentally friendly, and low-cost method. Herein, non-toxic phyto-mediated ZnO nanoparticles (ZnO NPs) were prepared successfully by using aqueous seed extract of Vachellia erioloba. The functional groups present in V. erioloba seed extract and the synthesized NPs were analysed using Fourier transform infrared (FTIR) spectroscopy. Major peaks were identified in the IR spectrum of the plant extract at 3277, 1632, and 1035 cm(-1) which were indicative of the presence of hydroxyl and carboxylic acid groups. The IR spectrum of the nanoparticles present bands that are confirmatory of the presence of Zn-O bond around 674 cm(-1). Formation of ZnO NPs was confirmed by various techniques including UV-visible absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction. Hexagonal phase and highly crystalline ZnO NPs of spherical morphology were obtained with an average particle size of 17.92 and 21.14 nm for the ZnO NPs prepared using 20 and 30 mL of the plant extract and denoted as ZnO (20) and ZnO (30) respectively. Biological studies showed that ZnO (20) exhibited higher anticancer activity against HEK 293 cells, while ZnO (30) revealed significantly higher anticancer activity against HeLa cells. ZnO (30) also showed a higher free radical scavenging activity compared to ZnO (20). However, the potency of ascorbic acid used as the reference/standard antioxidant agent was higher than the synthesized ZnO NPs. These results agree with other studies that green routes to NPs are more effective for the generation of metal oxide NPs with enhanced biological activity. Therefore, the nanoparticles are safe and stable potential alternatives to synthetic chemicals currently used in pharmaceutical and biomedical industries.