Green route synthesis of silver nanoparticles driven by Cassia fistula flower extract: characterization, antioxidant, antibacterial, anticancer, and photocatalytic assessment

Cassia fistula L. is essential in various traditional medicine applications, ubiquitously silver nanoparticle (AgNP) synthesis using Cassia flower extracts. Notable results have reported the economic feasibility, biocompatibility, non-toxicity, and eco-friendly prospects from medicinal perspectives. The formation of AgNPs was validated through ultraviolet–visible absorbance of the surface resonance band at 408 nm. Fourier transform infrared spectroscopy revealed the inherent phytochemicals that serve as reductants and stabilizers for AgNPs. X-ray powder diffraction spectra showed crystallinity with a face-centered cubic phase and strongly agreed with the JCPDS file 04–0783. The electron microscopic observations show spherical AgNPs with crystallite size at 50 to 100 nm and the elemental composition was revealed using EDAX analysis. Dynamic light scattering study showed a mean particle size of 58.77 nm and a surface potential zeta of − 24.0 mV, indicating their robustness and adaptability. The AgNPs quenched unstable cationic free radicals on DPPH (60.34%), ABTs (67.79%), and nitric oxide (64.15%), depending on concentration correlatedness. Staphylococcus aureus exhibited a considerable zone of inhibition (16.2 mm), followed by Escherichia coli (11.8 mm) at 250 µg/mL. The lowest MIC and MBC were exhibited against S. aureus, followed by E. coli. FE-SEM analysis revealed that AgNPs triggered structural pathological cellular damage in tested bacterial pathogens. Prominent cytotoxic effects (26.26 µg/mL) against breast carcinoma cells. Fluorescent labeling established apoptosis and necrosis patterns in the treated cells. AgNPs showed photocatalytic efficiency in degrading methylene blue (83.82%) and crystal violet (65.14%) dyes. Hence, the plant-mediated AgNPs show bioactive potentials and environmental implications for future sustainable applicability.