Sustainable synthesis of nickel oxide nanoparticles using Abrus precatorius seed extract: Antioxidant and antibacterial potential

Nickel oxide nanoparticles (NiO NPs) were synthesized via a green route using Abrus precatorius seed extract as a natural reducing and stabilizing agent. The produced NiO NPs were physicochemical characterized using ultraviolet–visible (UV-vis) spectroscopy, revealing the characteristic absorbance peak at 320 nm. SEM revealed nanoparticles with nearly spherical to polyhedral morphologies and a tendency to agglomerate, typical of green synthesis . Energy-Dispersive X-ray Spectroscopy (EDX) confirmed Ni (55.76 wt%) and O (32.75 wt%) as the major elements, validating the formation of NiO. Dynamic light scattering (DLS) analysis showed an average particle size of 166.9 nm with a Poly Dispersity Index (PDI) of 0.340, indicating moderate uniformity. Thermogravimetric analysis (TGA) showed ∼20–25% weight loss due to organic decomposition, confirming the thermal stability and purity of the calcined NiO NPs. In vitro antioxidant assays indicated that NiO NPs exhibited dose-dependent activity; however, their scavenging efficiency at 250 μg/mL (49.3%) was lower than that of ascorbic acid (AA) (70.6%). Antimicrobial evaluation using agar well diffusion showed stronger inhibition against Bacillus subtilis and Escherichia coli than against Aspergillus flavus , Klebsiella pneumoniae , and Staphylococcus aureus , with activity increasing dose-dependently up to 200 μg/mL. The findings highlight that A. precatorius seed extract not only enables eco-friendly synthesis but also enhances the biological functionality of NiO NPs, supporting their potential as antimicrobial agents and pharmaceutical candidates, particularly against antibiotic-resistant pathogens. • Study focuses on biosynthesizing NiO NPs using A. precatorius seed extract. • Plant extract-based green synthesis presents a sustainable and cost-efficient method. • Synthesized NPs showed irregular morphology and average size of 93.5–128.9 nm. • UV-Vis and FT-IR confirmed formation and phytochemical capping of NiO NPs. • NiO NPs exhibited dose-dependent antioxidant and antimicrobial activities. • The NPs show potential for alternative therapeutic use against resistant pathogens.