Novel quercetin glucosides from Helminthostachys zeylanica root and acceleratory activity of melanin biosynthesis.

Two novel quercetin glucosides, namely 4'-O-β-D-glucopyranosyl-quercetin-3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranoside (compound 1) and 4'-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-quercetin-3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranoside (compound 2), were isolated from Helminthostachys zeylanica root 50 % EtOH extract. Structural analysis of isolated compounds was achieved mainly by 600 MHz and 800 MHz NMR, UPLC-TOFMS and GC-MS. Of the two quercetin glucosides, compound 1 showed a high melanogenic acceleratory effect, 2.7 times higher than control, at 10 μM concentration in murine B16 melanoma cells, with no cytotoxic effect.