Biosensors for the enantioselective analysis of S-enalapril and S-ramipril

S-Enalapril, and S-ramipril are angiotensin-converting enzyme (ACE) inhibitors which are used for treatment of hypertension. Due to the fact that only the S enantiomer possesses the ACE inhibiting activity, it is necessary to develop an enantioselective analytical method for its discrimination from the less active R-enantiomer. An amperometric biosensor, based on L-amino acid oxidase, was developed and proved reliable for the analysis of the S-enantiomer of these ACE inhibitors. The working range of the biosensor for S-enalapril assay (A) is 0.4-120 mumol/L, and for S-ramipril assay (B) is 0.2-100 mumol/L, with a limit of detection of 163 nmol/L (A) and 107 nmol/L (B), respectively. It is of interest to mention that the biosensors demonstrated enantioselectivity versus D-proline (1.4 x 10(-3) mol/L(A), 5.3 x 10(-3) mol/L(B) and also the selectivity versus the polyvinylpyrolidone (3.0 x 10(-3) mol/L(A), 3.2 x 10(-3) mol/L(B), respectively. The working pH ranges are: 6.8-7.4 (A), and 6.2-7.0 (B), respectively. The RSD < 1% assured by using the amperometric biosensors for S enantiomers assay in raw materials, in tablet formulations, and their suitability for the analysis of these drug enantiomers.