Antioxidant, Antibacterial, and Antivirulence Activities of a Bioactive Fraction from Lycopus lucidus Against Porphyromonas gingivalis

Porphyromonas gingivalis (Pg) is a keystone periodontal pathogen associated with biofilm formation and gingipain-mediated virulence. This study evaluated the antioxidant, antibacterial, antibiofilm, and antivirulence activities of a hexane extract of Lycopus lucidus (LLH) and its eight chromatographic fractions (H1–H8). Antioxidant activity was assessed using DPPH and ABTS radical-scavenging assays, whereas antibacterial activity, biofilm formation, and virulence-associated gene expression were evaluated using corresponding in vitro assays. LLH exhibited antioxidant and antibacterial activities, while H4 showed the strongest overall biological activity among the fractions. The DPPH IC50 values of LLH and H4 were 98.33 ± 2.05 and 60.67 ± 3.09 µg/mL, respectively, and the corresponding ABTS IC50 values were 89.24 ± 1.67 and 28.15 ± 1.21 µg/mL, respectively. H4 also showed greater inhibition of biofilm formation than LLH and more pronounced downregulation of several virulence-associated genes. LC–MS/MS analysis tentatively identified α-cyperone as a constituent of H4. Overall, chromatographic fractionation of LLH yielded H4 with enhanced biological activity across several measured endpoints, including radical-scavenging, antibacterial, and antibiofilm effects, together with more pronounced suppression of several virulence-associated genes. However, the contribution of α-cyperone or other individual constituents to these effects remains to be established.