Vachellia nilotica Mediated Biosynthesis of Zinc Oxide Nanoparticles, Efficacy and Safety Evaluation

Abstract

Biogenic synthesis of nanoplatforms from metallic salts using secondary metabolites from plant extracts provides an ecofriendly, easily scalable one pot fabrication of novel biomaterials. Among the nanomaterials that can be obtained through green synthesis, ZnONPs have shown considerable potential in the management of symptoms of cancer which is a worldwide scourge.  Vachellia nilotica a widespread plant native to Southern Africa has been used as a natural remedy for various health conditions including cancer in traditional African and Asian medicinal practices. Thus, the main objective of this work was to investigate the phytoconstituents of Vachellia nilotica and their capacity to mediate in the biosynthesis of ZnONPs as bio reduction, capping and stabilising agents. The obtained nanostructures were characterised by Transmission electron microscopy (TEM), UV -Vis spectrometry as well as Dynamic light scattering (DLS). The toxicity of the lyophilised leaf extract was also investigated using OECD TG 425 in Sprague Dawley rats. The anti-inflammatory activity was investigated using the egg albumin assay with diclofenac as a standard. The anti oxidancy potential was evaluated using the DPPH scavenging assay. Metabolomics studies confirmed the presence of numerous secondary metabolites including polyphenols which can mediate in biosynthesis of ZnONPs. UV-Vis spectra showing absorbance around 370nm confirmed the nanoparticles’ identity. The morphology of the nanostructures was observed to be mostly spherical by TEM and DLS estimated the particle size as ranging between 20 and 50nm. In the anti-inflammatory tests the ZnONPs demonstrated 67.1% protein denaturation inhibition (vs. 78.8% for diclofenac at 100 100 mg/mL). Acute toxicity studies showed no adverse effects at 2000 mg/kg. Based on the foregoing it was concluded that the biogenic synthesis of ZnONPs from the polyphenolic lyophilized leaf extracts of V nilotica was feasible, safe and could potentially offer an opportunity to combine anti-cancer metallic oxides and pharmacologically active plant extracts in novel, effective ecofriendly dosage forms for use in the management of familiar end points of cancer symptoms.