Antibacterial Compounds from Oak,Quercus acutaThunb.

An ethanol extract of Quercus acuta trunk showed antibacterial activity against both gram-positive and gram-negative bacteria. The extract was sequentially partitioned with n-hexane, chloroform, ethyl acetate and water, and the highest activity was observed in the ethyl acetate fraction. Two active compounds isolated from the ethyl acetate fraction were 4,5-di-O-galloyl ( + )-protoquercitol and 3,5-di-O-galloyl protoquercitol, of which the former was the major active constituent. Gallic acid was also isolated from the same fraction, but it was not active.