Isolation and structural characterization of eight new resin glycosides, calyhedins XVI–XXIII, from the rhizomes of Calystegia hederacea

Abstract

Biological effects attributed to resin glycosides, including cytotoxicity against cancer cells and antibacterial, multidrug resistance-modulating, and antiviral activities have been documented. Penta-glycosides composed of calysolic acid A or calyhedic acid A, which are glycosidic acid components of the crude resin glycoside fraction of Calystegia hederacea, have not yet been isolated from this plant. In this study, eight new resin glycosides, termed calyhedins XVI (1)–XXIII (8), were isolated from the rhizomes of C. hederacea. Compounds 1–8 are penta- or hexa-glycosides with macrolactone structures, and their sugar moieties are partially acylated by five organic acids, including 2S-methylbutyric, (E)-2-methylbut-2-enoic, and 2R-methyl-3R-hydroxybutyric acids. Compounds 1–5 are the first identified macrocyclic resin glycosides with five monosaccharides obtained from this plant, and 2 and 4 are the first to be characterized as containing calyhedic acid A as the glycosidic acid component. Compounds 1–8 were of the four following macrolactone types: one with a 22-membered ring (5), another with a 23-membered ring (6–8), the third with a 27-membered ring (1, 3), and the fourth with a 28-membered ring (2, 4). Compounds 2–8 exhibited cytotoxic activity against HL-60 human promyelocytic leukemia cells comparable to that of the positive control, cisplatin.