[Heterocyclic compounds and phenolic glycosides from flowers of Dendrobium officinale]

Eight heterocyclic compounds and twelve phenolic glycosides were separated from the water extract of Dendrobium officinale flowers through chromatographic techniques, such as Diaion HP-20 macroporous adsorption resin column chromatography(CC), silica gel CC, ODS CC, Sephadex LH-20 CC, and preparative high performance liquid chromatography(PHPLC). According to the spectroscopic analyses(MS, ~1H-NMR, and ~(13)C-NMR) and optical rotation data, the compounds were identified as dendrofurfural A(1), 2'-deoxyadenosine(2), 4-[2-formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl] butanoic acid(3), 4-[2-formyl-5-(methoxymethyl)-1H-pyrrol-1-yl] butanoic acid(4), 1-(2-hydroxyethyl)-5-(methoxymethyl)-1H-pyrrole-2-carbaldehyde(5), 5-(methoxymethyl)-1H-pyrrole-2-carbaldehyde(6), methyl 5-(hydroxymethyl)-furan-2-carboxylate(7),(S)-5-hydroxymethyl-5H-furan-2-one(8), 2-methoxyphenyl-1-O-β-D-glucopyranoside(9), arbutin(10), isotachioside(11), 2,6-dimethoxy-4-hydroxyphenol-1-O-β-D-glucopyranoside(12), orcinol glucoside(13), tachioside(14), gastrodin(15), 4-O-β-D-glucopyranosylvanillyl alcohol(16), 2,6-dimethoxy-4-hydroxymethylphenol-1-O-β-D-glucopyranoside(17), icariside D_2(18), 4-formylphenyl-β-D-glucopyranoside(19), and vanillin-4-O-β-D-glucopyranoside(20). Among them, compound 1 is a new furfural benzyl alcohol condensate, with the skeleton first found in Dendrobium. Compounds 2-9, 11, 13, and 19 are reported from Dendrobium for the first time, and compounds 14 and 18 are reported for the first time from D. officinale. Compounds 11 and 14 showed moderate DPPH radical scavenging capacity, and compounds 11-14 demonstrated potent ABTS radical scavenging capacity, possessing antioxidant activity.