Chemical constituents from Chinese Yam (Dioscorea opposita Thunb.) peel

Nineteen compounds were isolated from the dichloromethane portion of the ethanol extract of Chinese Yam (Dioscorea opposita Thunb.) peel, using various chromatographic techniques including: silica gel column chromatography, medium-pressure liquid chromatography, Sephadex LH-20 gel column chromatography, and preparative high-performance liquid chromatography. Based on the physicochemical properties and spectral data, their structures were determined as follows: six phenanthrenes: 7′-hydroxybleformin E (1), 1,7-dihydroxy-5-methoxy-9,10-dihydrophenanthrene (2), 6-methoxycoelonin (3), 6-hydroxy-2,4,7-trimethoxyphenanthrene (4), 2,7-dihydroxy-4,6-dimethoxyphenanthrene (5), 5,7-dimethoxy-2,3-phenanthrenediol (6); three bibenzyls: dihydropinosylvin (7), 2′,3-dihydroxy-5-methoxybibenzyl (8), demethyl batatasin Ⅳ (9); eight diarylheptanoids: 1,7-bis(4-hydroxyphenyl)-1,5-epoxy-3-hydroxyheptane (10), engelheptanoxide C (11), diosniponol A (12), (+)-hannokinol (13), (3S,5S)-3,5-dihydroxy-1-(4-hydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)heptane (14), (3S,5S)-3,5-dihydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)heptane (15), hexahydrocurcumin (16), (5S)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)-3-heptanone (17); other compounds: one alkaloid, feruloyltyramine (18), and one fatty acid, octadecadienoic acid-2,3-dihydroxypropyl ester (19). Compound 1 is a new compound, whereas the ¹H NMR and ¹³C NMR spectral signals of 2 were fully attributed. compounds 2, 11, 16-19 were isolated from the Dioscoreaceae family for the first time, while compounds 3, 6, and 12 were the first to be reported from D. opposita. Among these, thirteen compounds showed differential inhibitory activities against α-glucosidase.