Comparative Antiviral Activity of Three Scrophularia Species(S. buergeriana, S. takesimensis, and S. koraiensis) Against Influenza A Virus in MDCK Cells

Background: Species of the genus Scrophularia have been traditionally used in East Asian medicine for anti-inflammatory and detoxifying purposes. However, comparative antiviral activity among different Scrophularia species remains insufficiently characterized. Methods and Results: Extracts of S. buergeriana, S. takesimensis, and S. koraiensis were evaluated for cytotoxicity, antiviral activity against influenza A virus (A/PR/8/34, H1N1), and neuraminidase (NA) inhibitory effects. MDCK cells were used for cytotoxicity and cytopathic effect (CPE) reduction assays. Zanamivir was used as a positive control. All three extracts showed minimal cytotoxicity (> 93.40% cell viability) across concentrations of 3.13-300.00 ㎍/mL. In antiviral ￿assays, all extracts inhibited viral replication in a dose-dependent manner. Among them, S. buergeriana showed the highest activity, reducing CPE by 22.36% at 200 ㎍/mL. In contrast, NA inhibition was generally weak; S. takesimensis showed the highest inhibition (16.38% at 300 ㎍/mL), whereas S. buergeriana showed no significant activity. Conclusions: These results suggest that Scrophularia extracts exert antiviral effects through mechanisms other than NA inhibition, potentially involving intracellular viral replication pathways.