Flavonol Glycosides from Muehlenbeckia platyclada and Their Anti-inflammatory Activity

A new flavonol, morin-3-O-alpha-rhamnopyranoside (1), along with four known flavonols, kaempferol 3-O-alpha-rhamnopyranoside (2), kaempferol 3-O-beta-glucopyranoside (3), quercetin 3-O-alpha-rhamnopyranoside (4) and (+)-catechin (5), were isolated from the methanolic extract of Muehlenbeckia platyclada. The structures of these compounds were determined on the basis of chemical and spectroscopic evidence, as well as acid hydrolysis of the original glycoside. Isolates were evaluated for inhibition of generation of superoxide anion, and inhibition of release of neutrophil elastase. Compound 2 showed moderate inhibition of superoxide anion generation with an IC50 value of 6.11 +/- 0.86 mu g/ml; 1, 3 and 5 inhibited neutrophil elastase release with IC50 values of 3.82 +/- 0.80, 8.61 +/- 1.38 and 4.37 +/- 0.72 mu g/ml, respectively, and were 15-fold more potent than phenylmethylsulfonyl fluoride (PMSF), the positive control, in this anti-inflammatory assay.