Green synthesis of Nonea lutea-mediated gold nanoparticles with multifunctional biomedical and environmental applications

Green synthesis provides an environmentally friendly approach for producing gold nanoparticles (AuNPs) using biological resources. Despite the reported medicinal potential of Nonea lutea , its use for AuNPs synthesis remains largely unexplored. Therefore, this study aimed to synthesize N. lutea -mediated AuNPs (N@AuNPs) and evaluate their physicochemical, biological, and catalytic properties. N@AuNPs were synthesized using a methanolic extract of N. lutea aerial parts and characterized by UV–Vis, FE-SEM, XRD, FT-IR, EDX, TEM, and zeta potential analyses. Their antioxidant, catalytic, antibacterial, antileishmanial, and α -glucosidase inhibitory activities were evaluated. Caffeic acid, epicatechin, and p -coumaric acid were identified in the methanolic extract by HPLC based on comparing the retention times with the corresponding authentic standards. The formation of N@AuNPs was indicated by a surface plasmon resonance peak at 540 nm. TEM revealed predominantly spherical nanoparticles with an average size of 6.614 ± 2.686 nm, while the zeta potential was − 57.8 mV. XRD analysis further demonstrated the presence of crystalline metallic gold, with a crystallite size of 8.13 nm. N@AuNPs showed DPPH scavenging activity with an IC₅₀ of 108.47 ± 4.26 μg/mL and catalytic reduction efficiencies of 89.05%, 77.83%, and 96.48% for methyl orange, 4-nitrophenol, and rhodamine B, respectively. Antibacterial activity was strain-dependent, with MICs of 12.5–100 μg/mL. N@AuNPs also exhibited antileishmanial and α -glucosidase inhibitory activities. Overall, N. lutea -mediated synthesis yielded crystalline, predominantly spherical AuNPs with antioxidant, catalytic, antibacterial, antileishmanial, and α -glucosidase inhibitory activities.