Green synthesis of silver nanoparticles (AgNPs) using Alstonia scholaris extract: Evaluation of their antioxidant, enzyme inhibitory, antimicrobial, and antimutagenic activities through in vitro and in silico studies

Abstract Alstonia scholaris is used as a traditional medicine for the treatment of various human and livestock diseases as it contains diverse types of biologically active compounds. In the current study silver nanoparticles (AgNPs) were synthesized by an eco-friendly method using Alstonia scholaris leaf extract (aqueous and methanolic). The synthesized nanoparticles (NPs) were characterized by UV-visible spectroscopy, Fourier transform infrared (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM). Green synthesized AgNPs were evaluated for their antioxidant, enzyme inhibition, antimicrobial, and antimutagenic potential. The AgNPs exhibited efficient antioxidant activities and considerable enzyme inhibition potential against α-amylase, and butyrylcholinesterase (BChE) enzymes. Meth-AgNPs showed strong antioxidant activity and high enzyme inhibitory effect as compared to Aq. AgNPs. Both AgNPs demonstrated significant antimicrobial activity. Synthesized AgNPs did not show any antimutagenic activity while Meth. AgNPs have demonstrated lower toxicities than previously reported AgNPs. Plant extracts are complex and contain several phytochemicals, which participate in the reduction and capping of AgNPs. Thus, despite the popularity of plant extract-mediated synthesis of AgNPs, the exact mechanism is still unclear. Here, we have used molecular simulation to reveal the interaction of phytochemicals and AgNP. Molecular dynamics simulation trajectory analysis showed that all phytochemicals- AgNP complexes reach an equilibrium within 100 ns. In addition, molecular docking experiments were performed to understand the mechanism of enzyme inhibition. The data from molecular simulation and dynamic support the capping of phytochemicals on the surface of AgNPs and is also responsible for the antioxidant, enzyme inhibition, and lower toxicity of AgNPs.