Integrated in Vitro and in Silico Investigation of Antimicrobial, Anti-biofilm, and Quorum-Sensing Inhibitory Activities of Allium atroviolaceum Bulb Extract.

The growing burden of antimicrobial resistance (AMR) and the persistence of biofilm-associated and quorum-sensing-mediated infections represent major public health challenges, highlighting the need for new anti-infective agents from natural sources. In this context, Allium atroviolaceum is recognized for its culinary and medicinal uses, remains relatively underexplored with respect to its anti-virulence potential, despite biological activities previously attributed to its organosulfur and phenolic constituents. In this study, ethanolic Allium atroviolaceum bulb extract (EAABE) was investigated for its antimicrobial, antibiofilm, and anti-quorum sensing (QS) activities. HR-LCMS analysis tentatively annotated 19 metabolites, including organic acids, phenolics, triterpenoids, fatty acids, glycosides, alkaloids, sphingolipids, steroid derivatives, and peptide-type compounds. EAABE demonstrated moderate antibacterial effects, with inhibition zones ranging from 6.00 to 7.33 mm and MIC values between 0.292 and 2.343 mg/mL. In contrast, a relatively enhanced antifungal activity was observed, with inhibition zones of 12.67-15.00 mm and MIC values of 0.292-0.585 mg/mL. The extract also inhibited biofilm formation in a dose-dependent manner, achieving up to a 56.91% reduction, while swarming motility was reduced by up to 64.13%. In addition, EAABE significantly attenuated QS-regulated virulence traits in a concentration-dependent manner. Violacein production was reduced by 67-86% at concentrations of 250-1000 µg/mL, whereas swarming motility was inhibited by 29 to 64% at 50-100 µg/mL. Similarly, pyocyanin production and extracellular proteases activity were reduced by 67-90% and 29-46%, respectively, across the concentration range of 250-1000 µg/mL. Molecular docking analysis predicted favorable binding affinities for several tentatively annotated metabolites, ranging from - 7.9 to - 12.4 kcal/mol, with Gravelliferone, Americine, and (2'S)-Deoxymyxol 2'-α-L-fucoside as compounds with favorable predicted binding affinities toward the selected targets. These interactions were further supported by 100 ns molecular dynamics simulations. ADMET predictions and DFT calculations provided further insights into the physicochemical, predicted pharmacokinetic, and electronic properties of the tentatively annotated metabolites. Overall, the findings indicate that EAABE exhibits promising in vitro antimicrobial and anti-virulence activities; however, further isolation of individual constituents, experimental validation, and mechanistic investigations are needed to clarify the specific contribution of each metabolite to the observed effects.