Inhibition effects of the classical pathway complement of isolated compounds from Quercus glauca

Species of the Quercus species is an evergreen broadleaf tree found not only in Korea but also in China, Taiwan, and Japan. Quercus species is the most commonly occurring plant among the 50 native species of the family Fagaceae in Korea, China, and Taiwan. Quercus species have been used for diarrhea, dysentery, dermatitis, and hemorrhagia in Korean folk medicine. The present study evaluated the anticomplement effect of constituents from Quercus species (Fagaceae) in classical pathway complement system. We have evaluated leaves of five species of the Quercus genus with regard to its anticomplement activity and have identified its active principles following activity-guided isolation. Bioactivity-guided fractionation of the 80% methanol extracts of the stem barks of Quercus glauca Thunberg has led to the isolation of galloyl derivatives, displaying high anticomplement activity. Four galloyl derivatives isolated from the leaves of Q. glauca, namely 6′-O-galloyl salidroside (1), methyl gallate (2), 1,2,3,6-tetragalloylglucose (3), and 1,2,6-trigalloylglucose (4). 1, 2, 3 and 4 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC50) values of 224 μM, 362.4 μM, 32.3 μM, and 138.3 μM. Among the compounds tested, 3 showed the most potent anticomplement activity (IC50, 32.3 μM). This is the first report of the isolation and anticomplement activity from Q. glauca.