BIOGENIC SYNTHESIS AND CHARACTERIZATION OF ZnO AND CuO NANOPARTICLES FROM Entada abyssinica AND Warburgia ugandensis LEAF EXTRACTS FOR ANTI-BACTERIAL APPLICATIONS

Abstract

In this study, biosynthesis, structural characterizations, optical and bactericidal properties of copper oxide and zinc oxide nanoparticles have been documented. Copper oxide (CuO) and zinc oxide (ZnO) nanoparticles were prepared using Entada abyssinica (EA) and Warburgia ugandensis (WU) leaf extracts. EA and WU possessed various biomolecules identified in GC-MS and FT-IR analysis which acted as reducing, capping and stabilizing agents in the synthesis of ZnO and CuO nanoparticles. The two-plant species had total phenolic contents, total flavonoid contents and total tannins contents obtained by optical means in the range of 19-58 mg/g, 940-1400 mg/g and 0.6-4.9 mg/g of the acid equivalents, respectively. The total percentage contents of saponins and alkaloids were in the range of 0.94-1.33 % and 1.27-1.42 % respectively. The green route synthesized CuO and ZnO nanoparticles were characterized using UV-VIS (Ultra-Violet Visible Spectroscopy), FTIR (Fourier Transform Infra-red) spectroscopy and X-ray Diffraction (XRD) instrumental methods. The visual observation of color changes during synthesis, the maximum SPR (Surface Plasmon Resonance) peaks observed in the UV-VIS spectra at varied synthesis parameters and the well-developed FT-IR peaks of functional groups responsible for the formation of the nanoparticles confirmed fabrication of nanoscale materials. Time and pH variations were the experimental control parameters. The XRD calculation of average particles sizes confirmed that the synthesized CuO and ZnO NPs were within the nanoscale range. The evaluation of the anti-microbial activities of the biosynthesized nanoparticles against Escherichia coli and Staphylococcus aureus bacteria was significant since p-value was less than 0.05. In comparison with other test samples against the two bacterial strains selected, the copper oxide nanoparticles synthesized from EA leaf extracts had higher zones of inhibition of 12.0±1.0 mm against Staphylococcus aureus pathogen. The lowest inhibition was shown by CuO NPs synthesized using Warburgia ugandensis leaf extracts against Escherichia coli (7.3±0.6 mm). The research can therefore contribute to the use and documentations of several locally available plants in Kenya in the synthesis of beneficial CuO and ZnO nanoparticles in the treatment of various illnesses.