Au Nanoparticles, Green Synthesized by Plants of Bignoniaceae Family: Antioxidant Powerhouses with DNA Damage Mitigation Activity.

The synthesis of nanoparticles using plant extracts has become a green approach for developing modern drugs. This study focuses on synthesizing gold nanoparticles (Au NPs) using methanolic leaf (L) and bark (B) extracts from four Bignoniaceae species with a focus on their antioxidant properties. The formation of these nanoparticles was confirmed using UV-Vis spectroscopy, while their size, shape, and morphological characteristics were analyzed through multiple analytical methods. Among four plants, leaf and bark extracts of Kigelia africana (sausage tree) were found most effective in synthesizing the stable Au NPs (KA-Au NPs), which displayed unique hexagonal, rhomboid, and triangular shapes with an average size of 24-28 nm, as observed in TEM. In addition, the presence of plant-based phytochemicals bound to the nanoparticle surfaces was confirmed through FT-IR studies. Among the synthesized NPs, KA-Au NPs demonstrated higher antioxidant activity in both DPPH and nitric oxide radical scavenging assays, with the lowest IC₅₀ values. Cytotoxicity analysis using the MTT assay indicated that KA-Au NPs are non-toxic. Furthermore, the KA-Au NPs exhibited significant antioxidant properties by effectively mitigating H₂O₂-induced DNA damage, as evidenced by gel electrophoresis and comet assays. This study also illustrated the mechanistic insights into the DNA-protective effects of KA-Au NPs by evaluating binding interactions between NPs and calf-thymus DNA and confirmed the NPs' ability to scavenge intracellular reactive oxygen species (ROS). Overall, the present research highlights the potential of K. africana-mediated Au NPs for developing safe and effective therapeutic agents, leveraging their unique chemical properties and biocompatibility for applications in nanomedicine.