Possible involvement of lignin structure in anti-influenza virus activity.

Commercial lignins suppressed the growth of influenza A virus infecting MDCK cells, and the RNA-dependent RNA synthesis, as efficiently as the high-molecular weight fractions extracted from pine cone of Pinus parviflora Sieb. et Zucc. The anti-influenza A virus activity of both pine cone extract and commercial alkali-lignin was considerably reduced by treatment with sodium chlorite, but was not affected by sulfuric acid or trifluoroacetic acid. The degraded components of lignin, various synthesized polyphenols unrelated to lignin, and natural and chemically modified glucans, were not appreciably inhibitory. The data suggest that the polymerized phenolic structure of lignified materials is responsible for the anti-influenza A virus activity.