Galloyl, caffeoyl and hexahydroxydiphenoyl esters of dihydrochalcone glucosides from Balanophora tobiracola

Seven galloyl, caffeoyl and (S)-hexahydroxydiphenoyl (HHDP) esters of dihydrochalcone glucosides were isolated from Balanophora tobiracola; based on spectroscopic and chemical evidence, their structures were determined to be 6"-O-galloyl-, 3",4"-di-O-galloyl-, 4",6"-di-O-galloyl-, 4",6"-O-(S)-HHDP-, 3"-O-galloyl-4",6"-O-(S)-HHDP-, 3"-O-caffeoyl-4",6"-O-(S)-HHDP-3-hydroxyphloretin 4'-O-beta-D-glucosides and 3"-O-galloyl-4",6"-O-(S)-HHDP-phloretin 4'-O-beta-D-glucoside, respectively. By contrast, these compounds were not found in the taxonomically related B. japonica. The 3"-galloyl-4",6"-HHDP esters of the dihydrochalcone glucosides showed strong inhibitory activities against alpha-glucosidase. Four known compounds were also isolated namely, (+/-)-eriodictyol 7-O-beta-D-glucoside, 1-O-caffeoyl-3-O-galloyl-beta-D-glucose, phloretin 4'-O-beta-D-glucoside, and 3-hydroxyphloretin 4'-O-beta-D-glucoside. (c) 2004 Elsevier Ltd. All rights reserved.