[A new bibenzyl derivative from stems of Dendrobium officinale]

Eleven compounds were isolated from the 95% ethanol extract of the stems of Dendrobium officinale after water extraction by various modern chromatographic techniques, such as silica gel column chromatography(CC), octadecyl-silica(ODS) CC, Sephadex LH-20 CC, preparative thin layer chromatography(PTLC) and preparative high performance liquid chromatography(PHPLC). According to spectroscopic analyses(MS, 1D-NMR, 2D-NMR) combined with optical rotation data and calculated electronic circular dichroism(ECD), their structures were identified as dendrocandin Y(1), 4,4'-dihydroxybibenzyl(2), 3-hydroxy-4',5-dimethoxybibenzyl(3), 3,3'-dihydroxy-5-methoxybibenzyl(4), 3-hydroxy-3',4',5-trimethoxybibenzyl(5), crepidatin(6), alternariol(7), 4-hydroxy-3-methoxypropiophenone(8), 3-hydroxy-4,5-dimethoxypropiophenone(9), auriculatum A(10) and hyperalcohol(11). Among them, compound 1 was a new bibenzyl derivative; compounds 2 and 7-11 have not been previously reported from Dendrobium plants; compound 6 was reported from D.officinale for the first time. Compounds 3-6 exhibited potent antioxidant activity with IC_(50) values of 3.11-9.05 μmol·L~(-1) in ABTS radical scavenging assay. Compound 4 showed significant inhibitory effect on α-glucosidase, with IC_(50) value of 17.42 μmol·L~(-1), indicating that it boasted hypoglycemic activity.