Antiviral Effects of Maoto, a Traditional Herbal Medicine, Against Murine Hepatitis Virus‐1: In Vitro and In Vivo Studies

Aim To evaluate the in vitro antiviral effects of maoto and its constituent herbs against murine hepatitis virus‐1 (MHV‐1). We also evaluate the antiviral effects of maoto on MHV‐1 in vitro and in vivo experimental infection models. Methods DBT cells were infected with MHV‐1, and the antiviral effects of maoto were evaluated by immunofluorescent staining and by measuring the viral RNA level, viral titer, and viral protein expression. Additionally, experimental murine infection was done to assess the viral titer and histopathological changes in the lung and liver of mice at day 5. Results Treatment of DBT cells with maoto resulted in a dose‐dependent reduction in the MHV‐1 viral RNA levels, with a 50% inhibitory concentration (IC 50 ) of 34.54 μg/mL and a 50% cytotoxic concentration (CC 50 ) of 118.2 μg/mL. Among the four constituent herbs, Ephedra Herba (EH) and Cinnamomi Cortex (CC) exhibited particularly potent antiviral effects, with Selectivity Index (SI) values of 7.02 and 21.93, respectively. Time‐course analysis revealed a significant decrease in the viral RNA level as early as three hours post‐infection, showing that maoto acts in an early phase of infection. In vivo, maoto‐treated mice exhibited a decreased viral titer, accompanied by reduced inflammatory cell infiltration in the lung and liver. Conclusion Maoto demonstrated antiviral activity against MHV‐1. Among the constituent herbs of maoto, Ephedra Herba and Cinnamomi Cortex exhibited significantly higher antiviral activity than the other components. Trial Registration #390351 (Nihon Bioresearch Inc.