Biochemical composition, antimicrobial and antibiofilm activities of Syntrichia ruralis (Hedw.) F.Weber & D.Moh extracts against some resistant bacteria

This study investigates the biochemical composition, antimicrobial, and antibiofilm properties of Syntrichia ruralis (Hedw.) F.Weber & D.Moh extracts obtained using ethanol, methanol, n-hexane and distilled water solvents. Disk diffusion assays demonstrated selective antimicrobial activity against specific bacterial and fungal strains, including Staphylococcus epidermidis, Klebsiella pneumoniae, Candida glabrata, and Proteus vulgaris. The MIC value for S. epidermidis was notably low (155 µg/mL) with the methanol extract, while other strains exhibited MIC values exceeding 10,000 µg/mL. Antibiofilm assays revealed significant inhibitory effects, particularly against foodborne Listeria innocua and clinical Escherichia coli isolates, with inhibition rates ranging from 57% to 87%, comparable to commercial disinfectant Halamid. In contrast, biofilm formation was enhanced in Listeria monocytogenes upon exposure to the extracts. The ethanol extract showed limited antioxidant activity in the DPPH assay (30.69% at 1000 µg/mL), with an EC₅₀ of 1743.47 µg/mL. GC-MS analysis identified a total of 50 compounds in all extracts. Palmitic acid, neophytadiene, vitamin E, and triterpenoids such as β-amyrin acetate were predominant in ethanol extract, while methanol and n-hexane extracts contained long-chain alkanes, sterols, and fatty acid derivatives. The presence of these compounds may underlie the observed biological effects. This study represents the first comprehensive report on the antimicrobial, antibiofilm and antioxidant activities of S. ruralis and highlights its potential as a source of bioactive metabolites, especially for targeting biofilm-associated infections.