Bioinspired silver nanoparticles from Barleria lawii leaf extract: phytochemical-mediated synthesis, characterization, and multifunctional properties.

Plant-mediated synthesis of silver nanoparticles (AgNPs) represents an emerging bioinspired strategy for generating multifunctional nanomaterials by exploiting natural phytochemicals as reducing and stabilizing agents. In this study, Barleria lawii leaf extract was utilized for the first time as a biological platform for the synthesis of silver nanoparticles (Bl-AgNPs). Phytochemical analysis revealed substantial phenolic and flavonoid contents (28.4 mg GAE/g and 18.1 mg QE/g, respectively), supporting their role in Ag⁺ reduction and nanoparticle stabilization. Under optimized conditions (10 mM AgNO₃, extract-to-precursor ratio of 1:2, pH 8, and 60 °C), stable spherical Bl-AgNPs were obtained, exhibiting a characteristic surface plasmon resonance band at 422.5 nm. XRD analysis confirmed face-centered cubic crystallinity with an average crystallite size of 27.60 ± 6.57 nm, while TEM revealed spherical particles with an average size of 22.1 ± 6.5 nm. DLS gave a hydrodynamic diameter of 121.8 nm, and zeta potential measurements indicated good colloidal stability (- 31.2 mV). The synthesized Bl-AgNPs demonstrated enhanced antioxidant activity (DPPH IC50 = 17.24 µg/mL), broad-spectrum antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus altitudinis (inhibition zones of 30.5, 25.5, and 26.5 mm, respectively, at 500 µg/mL), and increased cytotoxicity against MCF-7 breast cancer cells (IC50 = 12.95 µg/mL) compared with the crude extract (IC50 = 40.57 µg/mL). Additionally, Bl-AgNPs exhibited efficient catalytic performance in NaBH4-mediated reduction of 4-nitrophenol and methylene blue, following pseudo-first-order kinetics. Overall, this study highlights B. lawii as an underexplored phytochemical resource for the bioinspired generation of stable and multifunctional silver nanoparticles, demonstrating the potential of plant-derived metabolites in developing biologically active nanomaterials.