Inactivation Effect of Tea Leaf Catechins on Human Type-A Influenza Virus.

Abstract

The effects of catechins obtained from the hot water extract of green tea leaves on two human type-A influenza virus strains of Aichi/2/68 and PR/8/34 were studied. In this study, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin gallate (EGCg), the crude catechins containing these catechins and (+)-catechin were used. Consequently it was observed that catechins used in this study had an inhibitory effect on the hemolytic activity to red blood cells induced by these two type-A virus strains under acidic conditions (pH 5.1 or 5.4) although they did not have an influence on the agglutination activity to red blood cells induced by the same virus strains. After incubation of (-)-ECg and (-)-EGCg with A/Aichi/2/68 virus, MDCK cells, virus-sensitive cells, were infected with the virus and the ability of virus proliferation was measured in terms of an index of the agglutination activity of the virus to red blood cells. The used two catechins, (-)-ECg and (-)-EGCg, inhibited the virus proliferation at concentrations of 100μg/ml and 50μg/ml, respectively. Furthermore, at a concentration of 2.0 mg/ml these two catechins were found to inhibit the activity of neuraminidase on the surface of the virus membrane by 71.3% and 60.8%, respectively. From the above-mentioned results, it is considered that among the catechins contained in green tea leaves, such two catechins as (-)-ECg and (-)-EGCg inhibit the activity of neuraminidase present on the surface of human influenza virus in order to block the invasion of the influenza virus into virus-sensitive cells.