Green synthesis of antimicrobial silver nanoparticles using fruit extract of Glycosmis pentaphylla and its theoretical explanations

The present study reports a novel, one-pot, cost-effective, green synthesis route of silver nanoparticles (AgNPs) from the fruit epicarp extract of Glycosmis pentaphylla (FGP). The UV–Vis spectroscopy (UV-Vis), dynamic light scattering (DLS), and transmission electron microscopy (TEM) studies confirmed that the synthesis produces stable, monodispersed AgNPs with an average size of 17 nm. Fourier transform infrared spectroscopy (FTIR) studies suggested that the carbonyl group of the different compounds of FGP made significant interaction with AgNPs. With this indication, a theoretical simulation using density functional theory (DFT) was performed, which established that among the different compounds of FGP, arborine was mainly responsible for the stabilization of AgNPs with a binding energy of 58.45 kJ/mol. Synthesized AgNPs showed strong antifungal (against Alternaria alternata, Colletotrichum lindemuthianum, Fusarium moniliforme, and Candida glabrata) and antibacterial (against Bacillus subtilis, Streptococcus mutans, Escherichia coli, and Salmonella enterica serovar Typhimurium) activity. Synthesized AgNPs showed the highest antifungal activity against Fusarium moniliforme and the highest antibacterial activity against Salmonella enterica serovar Typhimurium. A remarkable synergistic activity of AgNPs was observed with fungicide Bavistin (∼25% increased activity against Alternaria alternata) and antibiotic Streptomycin (∼33.3% increased activity against Bacillus subtilis), which indicated that AgNPs could be applied to control crop and human pathogens with a lower dose of synthetic antimicrobial compounds (e.g., Bavistin, Streptomycin, etc.). Hence, green synthesized AgNPs by this method can be a blessing for crop productivity and hospital management as an effective alternative to conventional fungicides and antibiotics, respectively.