Merremins A–G, Resin Glycosides from Merremia hederacea with Multidrug Resistance Reversal Activity

Five new pentasaccharide resin glycosides, named merremins A–E (1–5), two new pentasaccharide resin glycoside methyl esters, named merremins F and G (6, 7), and four known resin glycosides, murucoidin IV, murucoidin V, stoloniferin IV, and murucoidin XVII, were obtained from the aerial parts of Merremia hederacea. This is the first report of resin glycosides obtained from M. hederacea. In addition, the new compounds can be divided into three types: those possessing an 18-membered ring (1–4), compound 5 with a 20-membered ring, and those with an acyclic core (6, 7). Furthermore, the different types of resin glycosides were evaluated for their multidrug resistance reversal activities. Compounds 1, 5, 6, and murucoidin V were noncytotoxic and enhanced the cytotoxicity of vinblastine by 2.3–142.5-fold at 25 μM. Compound 5 and murucoidin V, with 20-membered rings, were more active than compound 1, with an 18-membered ring.