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

Two novel quercetin glucosides, namely 4'-O-beta-d-glucopyranosyl-quercetin-3-O-beta-d-glucopyranosyl-(1 -> 4)-beta-d-glucopyranoside (compound 1) and 4'-O-beta-d-glucopyranosyl-(1 -> 2)-beta-d-glucopyranosyl-quercetin-3-O-beta-d-glucopyranosyl-(1 -> 4)-beta-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 mu M concentration in murine B16 melanoma cells, with no cytotoxic effect.