Effect of silymarin on Helicobacter pylori growth and adhesion: in vitro and in silico evaluation

Abstract

Helicobacter pylori is one of the main risk factors for gastric diseases and gastric cancer due to its ability to colonize the gastric mucosa, induce chronic inflammation, and express virulence adhesins involved in bacterial persistence. Silymarin, a flavonolignan complex extracted from Silybum marianum , exhibits antioxidant, anti-inflammatory, and antimicrobial properties, suggesting potential therapeutic application against H. pylori . This study aimed to evaluate the antibacterial, anti-adhesive, anti-inflammatory, cytotoxic, and in silico interaction profiles of silymarin against H. pylori and its main adhesins BabA, SabA, and HopQ. The antibacterial activity was evaluated by broth microdilution for determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Morphological alterations were analyzed by scanning electron microscopy (SEM). Cytotoxicity was assessed by MTT assay using AGS gastric adenocarcinoma cells and RAW 264.7 macrophages. TNF-α, IL-6, and nitric oxide (NO) production were quantified in stimulated macrophages. Anti-adhesive activity was determined using FITC-labeled H. pylori adhesion assays in AGS cells. Molecular docking and physicochemical predictions were performed for the major flavonolignans present in silymarin. Silymarin exhibited MIC and MBC values of 128 μg mL −1 against H. pylori ATCC 43504, with 90.46% growth inhibition. SEM demonstrated bacterial deformation and coccoid-like morphology after treatment. Silymarin reduced TNF-α, IL-6, and NO production by 80.82%, 76.24%, and 97.50%, respectively. In adhesion assays, silymarin inhibited bacterial attachment by 25.87% ± 3.50%. Molecular docking demonstrated favorable interactions between flavonolignans and H. pylori adhesins. Isosilybinin A showed the highest affinity for BabA (fitness score = 57.75), establishing hydrogen bonds with CYS189 and SER244. Isosilychristin presented the best interaction with SabA (fitness score = 74.79), interacting with LYS152 and GLN159, while silychristin demonstrated the highest affinity for HopQ (fitness score = 66.42), interacting with SER135, ILE130, and ILE242. Silymarin demonstrated significant antibacterial, anti-inflammatory, and anti-adhesive activities against H. pylori ATCC 43504, supporting its potential as a multifunctional natural therapeutic candidate for the management of H. pylori -associated gastric diseases.