Study On The Preparation Of Epo A,B And Microbial Transformation

Epothilones, a new class of macrolides originally isolated from the soil bacterium Sorangium cellulosum, represent a new class of naturally occurring microtubule depolymerization inhibitors. Epothilones have great potential for the treatment of cancer. Although structural distinct, the mechanism of epothilones is similar to the anticancer drug paclitaxel (Taxol), involving induction of tubulin polymerization and stabilization of microtubule assembly. They showed dramatically potency against multiple drug resistant (MDR) tumor cell lines even resistant to Taxol. Moreover, epothilones are more stable and water-soluable than Taxol. Ixabepilone, one of epothilones, has been approved by FDA, for treatment of colon carcinoma, breast cancer, cancer of kidney and ovarian cancer in 2007. In our work, fermentation and isolation of epothilone A and B were studied. fed-batch broth of 250L fermenter was adsorbed using adsorber resin. The adsorber resin was extracted with isopropyl alcohol and ethyl acetate. Epothilone A and B were separated by chromatography on a Sephadex LH-20 column and C18 reversed-phase column. structures of epothilone A and B were confirmed by NMR.Epoehilone B has been tested in clinical trial, however, epothilone A has not been developed because of its lower activity. There is a little research work on epothilone A up to now.In our study, epothilone A was biotransformed with microorganism to obtain four compounds.At first, 11 strains were screened to biotransform epothilone A, 3 of which displayed positive results and one strain, Aspergillus niger AS 3.739, was selected for further biotansformation work. As a result, four products were obtained and their structures were confirmed by 1D, 2D-NMR and FAB-MS to be: 12R,15R-epoxidated epothilone A, 12R,15S-epoxidated epothilone A , Trans-12,13-hydrolized epothilone A and Cis-12, 13-hydrolized epothilone A.Four biotransformed products were tested for inhibiting the growth of tumor cells. The maxium ratio of 12R, 15R-epoxidated epothilone A to MCF cells is 82.76% and IC50 at 5.68μg/mL. 12R, 15S-epoxidated epothilone A inhibits MCF cells at maxium ratio 69.37% with IC50 9.88μg/mL. The maxium ratio of WYL-III-39A to MCF cells is about 64.31% and IC50 9.88μg/mL. WYL-III-39B inhibits MCF cells at a maxium ratio of 84.37% with IC50 2.52μg/mL. Our study made some foundations to produce and isolate epothilone A,B. Transforming epothilone A with microorganism generated some candidates for future study.