Green synthesis of silver nanoparticles using Malachra alceifolia (wild okra) for wastewater treatment and biomedical applications with molecular docking approach.

The current investigation focused on the green synthesis of silver nanoparticles (Ag NPs) using Malachra alceifolia (Ma) (the common name is wild okra) leaf extract. The morphological, structural, and optical properties of the synthesized Ma-Ag NPs were characterized by various techniques. The absorption spectral studies (UV-vis and FTIR) confirm the formation of Ma-Ag NPs and their band gap was calculated as 2.1 eV with the help of Tauc's equation. The XRD study gives information about the crystalline nature and FCC structure. The SEM analysis estimates the particle size as 10-55 nm and the average size as 28 nm with a spherical shape. Furthermore, biological studies such as antibacterial activity was performed by the broth dilution method whereas antioxidant was studied through the DPPH radical scavenging technique. To compare the antibacterial activity between Gram-positive and Gram-negative pathogens, the highest bacterial growth of inhibition was observed for Pseudomonas aeruginosa than Staphylococcus aureus when increasing the concentration of the plant extract and Ma-Ag NPs. The scavenging activity of DPPH for both leaf extract and synthesized Ma-Ag NPs was represented in a dose-dependent manner (0.1-1.0 mg/mL), Ma-Ag NPs have shown a significant scavenging activity ranging from 39 to 54% with an average IC value of 0.87 ± 0.08. Furthermore, a molecular docking study was performed to confirm the binding interaction outline between the bioactive molecule methyl commate A, Ma-Ag NPs, and proteins such as Aminotransferase and Tyrosyl-tRNA synthetase active sites. The highest interaction tendency was observed between the Aminotransferase and methyl commate A with a binding energy of - 7.79 kcal/mol. The high electronegative oxygen of the ligand interacts with H-N- of Lys98 (-O--H-N-) through the formation of hydrogen bond by 3.53A° distance. In addition, the photocatalytic efficiency of Ma-Ag NPs was studied with methylene blue dye degradation under sunlight irradiation at different time intervals. The attained photocatalytic degradation efficiency was 98.3% after 120 min.