Modified bile acids and androstanes-Novel promising inhibitors of human cytochrome P450 17A1

Discovery of the potential of cholesterol-lowering human CYP7 enzymes as biocatalysts for the production of C7 hydroxylated steroids

Steroidal C7 alcohols and their esters are perspective agents in drug discovery. In addition, hydroxylation at C7 position could allow further modification of steroidal moiety. Such transformation is performed easily by the enzymes. Human steroid 7α-hydroxylases CYP7A1 and CYP7B1 are key enzymes taking part in the biotransformation of cholestanes, androstanes, pregnanes. In the article, we are focusing on the results of in vitro screening of a library of modified steroids toward CYP7 enzymes. A couple of compounds were found to express the affinity for binding to the enzymes, comparable with corresponding values for CYP7 natural ligands. Among them are 17-substituted androstane derivatives with N-containing pyridine ring and enone derivative of lithocholic acid, which bound by human CYP7A1, and D-seco and C16 oxime androstanes, which were identified as novel CYP7B1 ligands. Screening results revealed that both enzymes bind with high affinity a well-known drug abiraterone: in the case of CYP7A1 substrate-like binding mode was detected, with the formation of monohydroxylated product, while in case of CYP7B1 inhibitor-like binding was observed. Since CYP7 enzymes convert some of the studied compounds into their 7-hydroxy derivatives, potential of these enzymes as perspective regio- and stereoselective biocatalysts for obtaining C7 hydroxylated steroids could be assumed.

Feasibility study of separation and purification of bile acid derivatives by HPLC on C18 and F5 columns

Organic synthesis could be very demanding, usually due to difficulties related to the separation of main reaction products from by-products. Steroidal compounds could have similar lipophilicity, which is mostly based on the lipophilicity of the steroidal core. This causes many problems during purification, i.e. in obtaining a pure single steroidal compound. In this research, a group of bile acid derivatives were subjected to HPLC analysis using four experimental systems, which presented combinations of C18 and F5 columns with methanol-water and acetonitrile-water as mobile phases. Retention parameters and retention order of the compounds were established and indicated that all experimental systems could be applicable in order to separate and/or purify some individual compounds or a mixture of a few compounds. However, the only experimental system that could separate a mixture of all investigated derivatives proved to be a C18 column with acetonitrile-water as a mobile phase. Since complex interactions between F5 column and the analytes exist, molecular surface polarity (MSP) was tested as a lipophilicity parameter, and also compared with logP using multivariate statistics. Retention parameters obtained on F5 column were used as descriptors, both with MSP and with logP, concluding that logP has shown to be a better lipophilicity descriptor.