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 ring 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 of the six-membered hemiacetal ring of the rearranged cholestanes was shown to be almost a boat-form by molecular mechanics and molecular dynamics calculation 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 those of the clinically applied anticancer agents, etoposide and methotrexate. (C) 1999 Elsevier Science Ltd. All rights reserved.