Green Synthesised Silver Nanoparticle From <i>Cotoneaster horizontalis</i> , In Vitro and In Silico Antibacterial Properties

Antimicrobial resistance is becoming an epidemic and a leading cause of death worldwide. The search for drugs in nature has recently become more important, as natural molecules are more likely to be suitable for use as drugs. This study aimed to compare the antibacterial properties of the methanol extract of Cotoneaster horizontalis and its silver nanoparticles (AgNPs). The presence of metabolites was established using gas chromatography-tandem mass spectrometry (GC-MS/MS) and liquid chromatography (LC)-ESI-MS/MS. FT-IR, x-ray diffraction (XRD), FE-SEM and FE-SEM-EDAX were used to characterise the structure of the AgNPs. Identified molecules were docked in sortase-A (protein data bank [PDB] ID: 1T2P) of Staphylococcus aureus. Chlorogenic acid, isoquercitrin, hesperidin, quercetin-3-d-xyloside, rutin and vanillic acid were from the methanolic extract, whereas five fatty acids were identified from the hexane extract. The antibacterial activity was found to be dose dependent: 80 mg/mL for the extract and 10, 20, 40 and 80 mg/mL for Ag NPs on all studied bacterial strains. Amoxicillin (25 µg), tetracycline (30 µg) and gentamicin (10 µg) were used as standards. The docking scores demonstrated that major molecules inhibited sortase-A, and PASS analysis corroborated these results, suggesting membrane integrity antagonist as mechanism of antibacterial action. This study demonstrates that AgNPs synthesised from methanolic extract of C. horizontalis were more antibacterial than the methanol extract in vitro.