Green Synthesis and Antibacterial Evaluation of Silver Nanoparticles using Senna surattensis Extracts

Green synthesis of silver nanoparticles (AgNPs) using plant extracts is among the simplest, most convenient, economical, and environmentally friendly approaches, as it reduces the use of toxic chemicals. This study aimed to biosynthesize AgNPs using Senna surattensis and to evaluate both the plant extracts and the resulting nanoparticles as antibacterial agents. Aqueous extracts were prepared using three methods, and AgNPs were produced by adding silver nitrate to these extracts. Ultraviolet–visible (UV–Vis) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and gas chromatography–mass spectrometry (GC–MS) were employed to characterize the nanoparticles. The antibacterial activity of the extracts and AgNPs against various Gram-positive and Gram-negative bacteria isolated from hospital wastewater was assessed at three concentrations: 25, 35, and 50 mg/mL. The largest inhibition zone for the plant extracts alone was 25 mm against Kocuria rosea using the Soxhlet acetone extract at 50 mg/mL, whereas the smallest was 12 mm against Pseudomonas aeruginosa and Serratia marcescens using the cold-soak extract and the Soxhlet aqueous extract at 35 and 25 mg/mL, respectively. Additionally, the cold-soaked extract, the 50 °C hot-soaked extract, and the Soxhlet water extract showed no activity at 25 and 35 mg/mL. For AgNPs derived from S. surattensis extracts, the highest inhibition zone was 26 mm against P. aeruginosa using AgNPs from the Soxhlet aqueous extract at 50 mg/mL, while the lowest was 14 mm against Escherichia coli using AgNPs from the Soxhlet aqueous extract at 35 mg/mL. These findings indicate that AgNPs biosynthesized from S. surattensis extracts are promising antibacterial agents and may serve as viable alternatives to conventional antibiotics.