Three new biphenyls, 4,7,8-trimethoxy-2,3-methylenedioxydibenzofuran(1), 7-hydroxy-4,8-dimethoxy-2,3-methylenedioxydibenzofuran(2), and 30,5-dimethoxy-3,4-methylenedioxybiphenyl(3), along with eighteen known compounds(4–21) were isolated from the aerial part of Ribes takare D. Don. Their structures were elucidated on the basis of spectroscopic data. Compound 1 and compound 2 showed mild a-glucosidase inhibitory activity.
Eight new 9,10-anthraquinones(1-8)including three acetonide derivatives of 3-hydroxy-2-hydroxymethyl-9,10-anthraquinones(68)were isolated from an ethanol extract of the roots of Knoxia valeriamoides.On the basis of chemical transformation reactions of the co-occurring 14 and 15 combined with HPLC-DAD-ESI-MS analysis of the extracts,the previously and newly isolated 2-methoxymethy-and 2-ethoxymethyl-9,10-anthraquinones(4,5,and 9-13),as well as the 3-hydroxy-2-hydroxymethyl-9,10-anthraquinone acetonide derivatives(68),were shown to be solvolytic artifacts.In the in vitro assays,compound 4 was active to protect hepatocyte(WB-F344)damage.
