Evaluation of in vitro antiviral activity in methanol extracts against in fl uenza virus type A from Korean medicinal plants.

Methanol extracts from 101 Korean medicinal plants were tested for inhibitory activity against influenza virus type A by means of a modified haemagglutination inhibition (HI) test. MM-57, MM-72, MM-104 and MM-110, four of 101 extracts tested exhibited strong anti-influenza virus type A activity at concentration ranges of 0.78-6.25 mg/mL, 0.78-3.13 mg/mL, 0.78-1.56 mg/mL and 0.0975-0.39 mg/mL, respectively. The extracts MM-57, MM-72 and MM-110 showed very strong anti-influenza virus type A activity in the range 1.56-6.25 mg/mL, 1.56-3.13 mg/mL and 195-390 micro g/mL, respectively. The four methanol extracts were weakly cytotoxic to red blood cells. These results demonstrated that four methanol extracts of Korean medicinal plants exhibit strong anti-influenza virus type A activity, and weak cytotoxic effects. They may inhibit attachment of the virus to the cell and may therefore be used for prophylaxis.