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KMID : 0545120110210060582
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Journal of Microbiology and Biotechnology
2011 Volume.21 No. 6 p.582 ~ p.589
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Stereoselective Biotransformation of Timosaponin A-III by Saccharomyces cerevisiae
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Yong-Mei Hu
Zhi-Ling Yu
Wang-Fun Fong
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Abstract
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Bioconversion of timosaponin A-III (TA-III), one of the major steroidal saponins isolated from the rhizomes of Anemarrhenae asphodeloides Bunge (Liliaceae), was investigated in Saccharomyces cerevisiae. Five bioconversion products, denoted compounds 2-6, were obtained. Biotransformation metabolite 2 was a stereoisomer of TAIII with a specific isotype F-ring and β-ranged CH3-21, which rarely occurs in nature. The structure of 2 was elucidated by extensive spectroscopic analysis (H-H COSY, HSQC, HMBC), as well as by high-resolution mass spectral analysis. The growth inhibitory activity of compounds 1-6 was assayed against four human cancer cell lines, HepG2, H-1299, HT-29, and HCT-116. Compounds 1 and 2 obviously inhibited the growth of the four types of cancer cells with IC50 values being less than 19 μM. A structure-activity relationship is discussed, and the spirostane-ring F in compounds 1 and 2 appears to be the critical bioactive moiety for the cell growth inhibitory property.
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KEYWORD
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Steroidal saponins, Timosaponin A-III, Biotransformation, Saccharomyces cerevisiae, growth inhibitory effect
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