Saundersiosides C-H, rearranged cholestane glycosides from the bulbs of Ornithogalum saundersiae and their cytostatic activity on HL-60 cells

Six novel rearranged cholestane glycosides with a six-membered hemiacetal r ing system, designated as saundersiosides C-H, were isolated from the bulbs of Ornithogalum saundersiae. Their structures were determined on the basis of spectroscopic analysis and the result of hydrolysis. The conformation o f the six-membered hemiacetal ring of the rearranged cholestanes was shown to be almost a boat-form by molecular mechanics and molecular dynamics calc ulation studies. Among the isolated compounds, saundersioside E, F, G and H with an aromatic acid ester group at the glycoside moiety were found to be highly cytostatic to human leukemia HL-60 cells, showing IC50 values of 0. 021, 0.019, 0.063 and 0.052 mu M, respectively, which are as potent as thos e of the clinically applied anticancer agents, etoposide and methotrexate. (C) 1999 Elsevier Science Ltd. All rights reserved.