57 Ipomoea orizabensis根およびI. muricata種子の樹脂配糖体の単離と構造  [in Japanese] 57 ISOLATION AND STRUCTURES OF THE RESIN GLYCOSIDES OF IPOMOEA ORIZABENSIS (ROOTS) AND I. MURICATA (SEEDS)  [in Japanese]

The so-called "resin glycosides" are well known as the purgative ingredients, which are characteristic of some crude drugs, such as Pharbitidis Semen and Jalapae Tuber, originated from the Convolvulaceae plants. They have been regarded as the complex glycolipids (mw: 10,000〜) composed of a number of the repeating unit which is an oligoglycoside of a long chain hydroxy-fatty acid (glycosidic acid) having several organic acids attached at the sugar moiety. Because of their supposed high molecular weights, complex structures, and others, the chemical studies have so far been confined to the characterizations of organic acids and glycosidic acids afforded by alkaline hydrolysis. We have recently succeeded, for the first time, in isolation of the intact and pure resin glycosides, that is, five (Mb-1〜Mb-5) from the seeds of I. muricata and four (Oc-1 Oc-4) from the root tubers of I. orizabensis, with the aid of successive various kinds of column chromatographies and finally of the high resolution preparative HPLC (theoretical plates N: 10,000-50,000). Their FD-, negative FAB-MS and ^<13>C-NMR spectra suggested all of them were composed of organic acids and one mole of glycosidic acid (Mb-acid, Oc-acid) in which the carboxy group is combined with a hydroxy group of the sugar moiety. Both the sites of acylation and the kinds of acyl groups were determined by 400MHz ^1H- and COSY-NMR, but the correlation of them failed even by NOESY and PRFT methods. Subsequently, the resin glycosides were respectively subjected to mild alkaline hydrolysis, and almost all the partially deacylated and the acyl-migrated derivatives were isolated and characterized by ^1H-NMR. On the basis of all the above data, the structures of nine resin glycosides were fully clarified. It is noted that all the resin glycosides isolated in this study are, contrary to the presumption, the monomers and that any oligomer was not obtained.