Antiviral activity of Chongkukjang extracts against influenza A virus in vitro and in vivo

Background Chongkukjang is a traditional Korean fermented product prepared from soybeans and reported to have multiple biological functions, including antidiabetic, antiinflammatory, and neuroprotective effects. Influenza is a respiratory disease caused by influenza viruses and continues to be a worldwide threat with a high potential to cause pandemics. Besides vaccination, only two classes of drugs are available for antiviral treatment against these pathogens. Methods We tested the inhibitory activity of an ethyl acetate extract from Chongkukjang toward influenza A virus neuraminidase. Results All 10 compounds extracted from Chongkukjang showed neuraminidase inhibitory activity. Extracts A3 and A8, with high neuraminidase content, had the best inhibitory activities. The in vivo antiinfluenza virus activities of the ethyl acetate, A3, and A8 extracts as well as commercially available genistein were evaluated using H1N1 (A/NWS/33) to test mice survivability after virus challenge. The Chongkukjang extracts did not reduce mortality, but the A3 and A8 extracts delayed the median time to death after influenza A virus infection of mice. Conclusion Our results suggest that the Chongkukjang extracts may have potential as a therapeutic agent to treat influenza virus infection.