Novel multitasking gold nanoparticles biosynthesized using Cassia fistula with potential biomedical applications

Gold nanoparticles (AuNPs) have garnered significant attention for their expanding biomedical applications. This study reports the green synthesis of gold nanoparticles (CFL-AuNPs) using aqueous Cassia fistula leaf extract (CFLE) and evaluates their antifungal, anti-obesity, anti-diabetic, and anti-ulcer activities. CFL-AuNPs were characterized by UV–visible spectroscopy, Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX), and Fourier Transform Infrared (FTIR). The nanoparticles formed a stable wine-red colloid with a maximum absorption peak at 560 nm, were nearly spherical, and measured 10–50 nm in size. FTIR spectra indicated the involvement of phenolic –OH, alkane –CH, aromatic –C–C, and nitro –N–O groups in nanoparticle formation. CFL-AuNPs exhibited significant antifungal activity, inhibiting foodborne Aspergillus flavus (50.70%), A. fumigatus (47.73%), A. niger (44.29%), and Fusarium solani (47.65%). They also exhibited strong lipase inhibition (88.93%), closely matching Orlistat (89.46%), suggesting anti-obesity potential and moderate α-glucosidase inhibition (42.93%) indicating possible anti-diabetic relevance. Notably, CFL-AuNPs showed high H⁺/K⁺-ATPase inhibition (84.60%), outperforming acetaminophen (73.89%) and demonstrating promising anti-ulcer activity. Overall, these findings revealed a multitasking biological profile, supporting potential applications of CFL-AuNPs as a nano-preservative and therapeutic candidate for metabolic and gastrointestinal disorders. To the best of our knowledge, this study is among the first reports of H⁺/K⁺-ATPase inhibition by gold nanoparticles synthesized via plant extract, thereby contributing novel insights to the field of plant-mediated nanoparticle research.