Abstract
Abstract Cinobufotalin ( 1 ), a major bioactive bufadienolide, has the potential anti-cancer activity. In the present paper, a scaled-up biotransformation of 1 by Aspergillus niger AS 3.739 and Alternaria alternate AS 3.4578 was performed for improving its biological activities and water-solubility. Seven metabolites were prepared in the biotransformation process of 1 , and their structures were elucidated as 9 α -hydroxycinobufotalin ( 2 ), 3-oxo-cinobufotalin ( 3 ), 5 β -hydroxy-3-epi-deacetyl-cinobufagin ( 4 ), 5 β -hydroxy-deacetylcinobufagin ( 5 ), 3-acetoxy-cinobufotalin ( 6 ), 5 β ,15 β ,16 α -trihydroxyl-17 β H-bufalin ( 7 ) and norbufadienolide A ( 8 ), on the basis of extensive spectral data including 2D NMR and MS spectroscopy. Among them, metabolites 2 , 7 and 8 are novel, and metabolite 8 possessed a novel chemical skeleton of bufadienolide in nature. The highly stereo- and region-specific dehydrogenation of 1 by A. niger AS 3.739 were observed. While, A. alternate AS 3.4578 could catalyze a novel rearrangement reaction, hydroxylation and acetylation in biotransformation process of 1 . In addition, the transformed products ( 2 – 8 ) exhibited the significant antiproliferative activities against human cervical carcinoma (Hela) and human breast cancer (MCF-7) cell lines.
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