Green synthesis of Characterized Bio-functionalized ZnO Nanoparticles from Terminalia catappa (Almond) Methanol Leaf Extract and their Potential Antioxidant and Antibacterial Properties

Abstract

Synthesis of zinc oxide nanoparticles (ZnO-NPs) using plants has been suggested to have biological applications. ZnO-NPs were synthesized using Terminalia catappa (Almond) methanol leaf extract and Zn(CH3COO)2.6H2O as precursors. UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared (FTIR) were used to characterize the ZnO-nanoparticles. The antioxidant, GC-MS, and antibacterial activities were determined using standard methods. The phytochemical screening of the extract shows that it contains alkaloids, flavonoids, tannins, saponins, etc. The GC-MS analysis of the Almond extract indicated the presence of 12 different compounds, with the 9, 17-Octadecadienal-Z being the most abundant. The UV–vis analysis has absorption peaks at 370 nm; SEM shows a quasi-spherical-like shape, while EDX indicates that the ZnO-NPs contain oxygen (54.93%) and zinc (36.14%). The optical energy band gap of 3.353 eV was obtained. The average crystallite size of the ZnO-NPs was 53.46 nm with a dislocation density of 0.000349899 (nm)-2. FTIR spectrum revealed the presence of organic moieties serving as reducing and capping agents. The extract and the ZnO-NPs have antioxidant scavenging activity. The extract and tetracycline exhibited a moderate and strong antibacterial response against Klebsiella pneumonia, Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, while the nanoparticles exhibited a weak and moderate response. The MIC and MBC values of the extract against the bacteria strains ranged from 12.50 to 25, and 25 to 50 mg/mL, respectively. The study supports the plant's traditional uses for treating infections and other diseases.