Antioxidant and Anti-Inflammatory Phenolic Glycosides from Clematis tashiroi.
From the 95% EtOH extract of dried aerial parts of Clematis tashiroi, eight new and four known phenolic (caffeic acid, coumaric acid, ferrulic acid) glycosides were isolated and characterized. The structures of the new isolates (clematisides A-H) were elucidated by spectroscopic data interpretation as trans-4-O-(6-O-trans-caffeoyl-β-D- glucopyranosyl)-9-O-β-D-glucopyranosyl caffeic acid (1), trans-4-O-(6-O-trans-feruloyl-β-D-glucopyranosyll)-9-O-β-D-glucopyranosyl caffeic acid (2), trans-4-O-(6-O-trans-p-coumaroyl-β-D-glucopyranosyl)-9-O-β-D-glucopyranosyl caffeic acid (3), trans-4-O-(6-O-trans-caffeoyl-β-D-glucopyranosyl)-9-O-β-D-glucopyranosyl p-coumaric acid (4), trans-3-O-(6-O-trans-caffeoyl-β-D-glucopyranosyl)-9-O-β-D-glucopyranosyl caffeic acid (5), trans-3-O-(6-O-trans-p-coumaroyl-β-D-glucopyranosyl)-9-O-β-D-glucopyranosyl caffeic acid (6), 6-(3',4'-dihydroxystyryl)-2-pyrone-4-O-(6-O-trans-caffeoyl)-β-D-glucopyranoside (7), and 6-(3',4'-dihydroxystyryl)-2-pyrone-4-O-{6-O-[4-O-(6-O-trans-caffeoyl)-β-D-glucopyranosyl]-trans-caffeoyl}-β-D-glucopyranoside (8), respectively. In a DPPH radical-scavenging test, compounds 1, 7, and 8 showed more potent antioxidant activity than that of the positive control, vitamin E. In addition, compound 7 also showed inhibitory activity in an antinitric oxide release assay.