Hong_2026_J.Microbiol.Biotechnol_36_e2510052

Acne vulgaris is a prevalent inflammatory skin disorder mediated by Cutibacterium acnes, a key etiological factor. In this study, the anti-acne properties of the ethyl acetate fraction of Quercus salicina Blume (QsB-EE) against C. acnes were investigated. The QsB-EE fraction was separated into subfractions (E1-E6) using preparative HPLC. Antimicrobial and anti-virulence activities were evaluated via bacterial growth, biofilm, and lipase activity assays. Virulence gene expression was assessed using qRT-PCR, and bioactive compounds were identified by LC-MS/MS. The QsB-EE demonstrated significant antimicrobial (MIC 125 microg/ml) and strong anti-virulence effects. The E1 fraction was the most potent, exhibiting the lowest MIC (16 microg/ml), highest biofilm inhibition (86.19% at 1,000 microg/ml), and highest lipase inhibition (93.72% at 10 microg/ml). In addition, mechanistic studies confirmed that E1 significantly downregulated the expression of key virulence genes: ppa0149 (biofilm), gehA (lipase), and hyl (hyaluronidase). LC-MS/MS identified (+)-catechin as the major compound in E1, alongside kaempferol and quercetin in E5. Although further in vivo studies are warranted to evaluate the therapeutic efficacy, our findings suggest that QsB-EE possesses promising anti-acne potential by targeting C. acnes virulence factors through the active compounds concentrated in the E1 fraction.