3-O-Methylquercetin glucosides from Ophioglossum pedunculosum and inhibition of lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages.

The three new 3-O-methylquercetin glucosides 1–3, together with three known congeners and 3-O-methylquercetin, were isolated from the fern Ophioglossum pedunculosum (quercetin=2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one). The new compounds were identified on the basis of spectroscopic analysis as 5′-isoprenyl-3-O-methylquercetin 4′,7-di-β-D-glucopyranoside (1), 3-O-methylquercetin 4′-β-D-glucopyranoside 7-[O-β-D-glucopyranosyl-(12)-β-D-glucopyranoside] (2), and 3-O-methylquercetin 7-[O-β-D-glucopyranosyl-(12)-β-D-glucopyranoside] (3). The effect of the isolated compounds on lipopolysaccharide (LPS)-induced NO production was evaluated. The inhibitory activity of 3-O-methylquercetin derivatives decreased markedly with the increasing number of glucosyl groups in the structures.