Novel cholestane glycosides from the bulbs of Ornithogalum saundersiae and their cytostatic activity on leukemia HL-60 and MOLT-4 cells

Two novel 24(23-->22)abeo-cholestane glycosides with a six-membered hemiacetal ring system and a five-membered acetal ring system (2, 3), designated as saundersioside A and B, respectively, together with a new 16,23-epoxy-5 beta-cholestane glycoside (1) were isolated from the bulbs of Ornithogalum saundersiae. Their structures were determined by detailed analysis of the H-1 and C-13 NMR spectra, including various two-dimensional spectroscopy, and acid-catalyzed hydrolysis. The conformations of the 16,23-epoxy moiety of 1 and the six-membered hemiacetal moiety of 2 and 3 were studied through molecular mechanics and molecular dynamics calculation methods. Compound 3 bearing a p-methoxybenzoyl group at the saccharide part showed potent cytostatic activity on leukemia HL-60 and MOLT-4 cells, and the effect to HL-60 cells was revealed to be mediated partially through induction of apoptosis by cell morphology and DNA fragmentation. (C) 1997 Elsevier Science Ltd.