26. The Research on Biotransformation Pathway of Digitoxin by Aspergillus ochraceus and the Analysis of Products Activity

In order to analyze the biotransformation pathway of digitoxin by Aspergillus ochraceus Rn405, a product—digitoxigenin was used as the substrate to biotransform. The substrate consumption and product synthesis were monitored by HPLC during the bioconversion process. The preliminary results were as follows: Firstly, hydrolysis reaction happened and digitoxin was converted into digitoxigenin; then, with extension of the reaction time, the hydroxyl group was introduced to the C-11 of digitoxigenin by the role of hydroxylase and another product named 11α-hydroxydigitoxigenin was generated in a large amount. The influences of these two products on myocardial apoptosis and their antineoplastic activities were further analyzed. It was found that compared with the substrate digitoxin and reference substance digoxin, the apoptosis effects of digitoxigenin and 11α-hydroxydigitoxigenin on rat myocardial cells remarkably decreased; but no obvious antineoplastic activities on the four tumor cells, including human breast cancer cell MCF-7, rat breast cancer cell 4T1, human cervical cancer cell Hela, and rat melanoma cell B-16 were observed.