Green Synthesis of ZnO Nanoparticles Using Delonix elata & Gynura cusimbua Leaf Extracts and Evaluating Their In-vitro Antibacterial Properties

With an increasing focus on the application of nanoparticles in the field of research, this study aims to evaluate the in-vitro antibacterial properties of chemically and green synthesized zinc oxide nanoparticles (ZnO NPs) from two plant sources Delonix elata and Gynura cusimbua. The bioactive compounds present in the leaf extracts were utilized to stabilize the nanoparticles. UV-Visible spectrophotometry (UV-Vis), X-ray diffraction (XRD), and Scanning electron microscopy (SEM) were used to elucidate the optical and structural properties of the synthesized ZnO NPs. The in-vitro antibacterial potential of ZnO NPs were evaluated by Agar Disc Diffusion Assay against two pathogenic bacterial strains: Bacillus cereus, a gram-positive animal pathogen and Pseudomonas syringae, a gram-negative plant pathogen, making it a well-rounded approach. The UV–visible spectrum was measured in 250 – 400 nm range and the crystallite structure was analyzed via XRD. SEM-EDS (Energy-Dispersive X-ray Spectroscopy) analysis confirmed the nanostructures with partial nanoflakes and aggregates for all three samples of the synthesized ZnO NPs. The D. elata ZnO NPs showed relatively greater antimicrobial activity against both the bacterial strains than that of G. cusimbua ZnO NPs. Consequently, plant-based NPs may be an excellent strategy for developing versatile and environmentally friendly biomedical products. They have an added advantage due to their pre-existing medicinal properties, which make them a more suitable alternative to the broadly used chemically synthesized nanoparticles. KEY WORDS: Delonix elata, Gynura cusimbua, Zinc oxide Nanoparticle, antimicrobial activity, Bacillus cereus, Pseudomonas syringae.