Hepatoprotective, superoxide scavenging, and antioxidative activities of aromatic constituents from the bark of Betula platyphylla var. japonica

The 50% aqueous methanolic extract from the bark of Betula platyphylla Sukatchiev var. japonica (Miq.) Hara was found to show potent inhibitory activity on the liver-injury induced by CCl4 or d-galactosamine (d-GalN)/lipopolysaccharide as well as O2 scavenging and antioxidative activities. From the 50% aqueous methanolic extract, two new diarylheptanoids named betulaplatosides Ia (1) and Ib (2) and a new arylbutanoid named betulaplatoside II (3) were isolated together with seventeen known aromatic constituents. 1, 2, and two known diarylheptanoids [(5S)-5-hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone 5-O-β-d-apiofurano-syl-(1→6)-β-d-glucopyranoside (6) and aceroside VIII (7)] showed protective activity against-d-GalN-induced cytotoxicity in primary cultured rat hepatocytes. Furthermore, several aromatic constituents exhibited potent O2-scavenging and antioxidative activities.