Resin glycosides from the seeds of Ipomoea muricata and their multidrug resistance reversal activities.

Resin glycosides represent an important chemotaxonomic marker of the Convolvulaceae family and possess multidrug resistance (MDR) reversal activity. In our recent study, nine previously undescribed resin glycosides, Calonyctins B-J, were isolated from the seeds of Ipomoea muricata. Their structures with the absolute configuration were established on the basis of comprehensive spectroscopic analysis and chemical methods. Among these, Calonyctins F-I possessed a skeleton in which the aglycone moiety and the oligosaccharide core were linked by a 3-hydroxy-2-methylbutanoic acid moiety to form a 25-membered macrocyclic structure. Calonyctins E, J, and muricatic acid C methyl ester were non-cytotoxic but enhanced the cytotoxicity of vincristine by 2.5-407.1 fold at 25 μM in KB/VCR cells. Calonyctin E was the most active one.