Atypical regioselective biohydrolysis on steroidal oxiranes by Aspergillus niger whole cells: some stereochemical features.

5,6-Epoxycholestan-3beta-ol derivatives were hydrolyzed in a diastereoconvergent manner by growing and resting cells of several strains of Aspergillus niger, particularly A. niger ATCC 11394. These strains displayed opposite regioselectivity toward each isomer in an alpha and beta epoxide mixture, thus, the nucleophilic attack took place at the less substituted and the most substituted carbon atom on each diasteromer, respectively.

Interactions between calcium entry blocking drugs and carbonic anhydrase.

The interactions between some of the most common calcium entry blocker drugs (CEB) and the enzyme carbonic anhydrase (CA) are studied in the present work by an electroanalytical approach. The study comprises drugs belonging to the classes of phenylalkylamines, dihydropyridines, benzothiazepines and piperazines. The evaluation of the potential inhibitory power towards CA was performed either by measuring the speed of CO2 diffusion taking place from a buffered solution of NaHCO3, or by monitoring the metabolic activity of yeast cells.