Abstract
The microbial transformation of a cytotoxic bufadienolide, bufotalin (1), was carried out. Three transformed products from 1 by Alternaria alternata were isolated. Their structures were characterized as 3-keto-bufotalin (2), 12β-hydroxyl-bufotalin (3), and 3-keto-12β-hydroxyl-bufotalin (4) based on the extensive NMR studies. Among them, 3 and 4 were new compounds with strong in vitro cytotoxic activities against HeLa cells.
Acknowledgements
We thank the Youth Foundation (30701088) by National Natural Science Foundation of China and PHR (IHLB) for financial support.