Inhibition of influenza virus infection by pine cone antitumor substances.

The anti-influenza virus activity of polysaccharides and other high molecular weight fractions from pine cone extract (PCE) of Pinus parviflora Sieb. et Zucc. was investigated. None of the fractions affected the growth of MDCK cells. The acidic PCE substances markedly suppressed the growth of the influenza virus in MDCK cells. Significant inhibition of both the viral protein synthesis in infected cells and virion-associated RNA-dependent RNA polymerase activity was observed with these acidic fractions. Although amantadine inhibited virus plaque formation as effectively as PCE fractions, it was less effective in inhibiting the RNA polymerase activity. These results suggest that PCE, which has been shown to contain antitumor substance(s), also contains anti-influenza virus substance(s).