Cholestane rhamnosides from the bulbs of Ornithogalum saundersiae

Phytochemical examination of the bulbs of Ornithogalum saundersiae yielded six cholestane rhamnosides, two of which had previously been isolated from the same plant material. However, detailed spectroscopic analysis of the ag lycone led us to revise the configuration of the C-ll hydroxyl group of the latter two and reassign their structures as; (22S)cholest-5-ene-3 beta,11 alpha,16 beta,22-tetrol 16-O-alpha-L-rhamnopyranoside and (22S)-cholesta-5, 24-diene-3 beta, 11 alpha,16 beta,22-tetrol 16-Q-alpha-L-rhamnopyranoside, respectively. The other four are new naturally occurring constituents and t heir structures were determined to be (22S)-cholest-5-ene-3 beta,11 alpha,1 6 beta,22-tetrol 16-O-(2,3-di-O-acetyl-alpha-L-rhamnopyranoside), (22S)-cho lest-5-enq-3 beta,11 alpha,16 beta,22-tetrol 16-O-{2-O-acetyl-3-O-(3,4,5-tr imetboxybenzyol)-alpha-L-rhamnopyanoside}, (22S)-cholest-5-ene-3 beta, 11 a lpha,16 beta,22-tetro 16-O-{2-O-acetyl-3-O-(p-methaxybenzoyl)-alpha-L-rhamn opyranoside}, and (22S)-cholesta-5,24-diene-3 beta,11 alpha,16 beta,22-tetr ol 16-O-(2,3-di-O-acetyl-alpha-L-rhamnopyranoside), respectively. The isola ted compounds were evaluated for their cytostatic activity against leukemia HL-60 cells. (C) 1999 Elsevier Science Ltd. All rights reserved.