title: An optimized fluoroenzymatic assay for the determination of angiotensin converting enzyme inhibitors in biological fluids.
abstract: An easy, analytically sound fluoroenzymatic assay for angiotensin converting enzyme (ACE) inhibitors is described. Drug samples and standards are extracted with methanol and evaporated to dryness. Drug residues are then incubated with the substrate N-benzyloxycarbonyl-phenyllanyl-l-histidyl-leucine and human plasma ACE at 37 degrees C, pH 7.65, for 1 h. Fluorescence of the o-phthaldialdehyde derivatized product is measured at wavelengths of 365 nm (excitation) and 490 nm (emission). A computer program converts fluorescence to percent of ACE activity inhibited and correlates this percent inhibition with drug concentration. The ester prodrug enalapril (MK-421) was measurable at levels of a 1 ng ml(-1) in serum after base hydrolysis to enalaprilat. Lowest reliable detection limits for enalaprilat (MK-422) and lisinopril (MK-521) in serum were 0.7 ng ml(-1). This method is easily adapted to most other ACE inhibitors, is well suited to automation and avoids the use of radioactivity.
authors.affiliation: Division of Clinical Pharmacology, Department of Medicine, Jefferson Medical College, Philadelphia, PA 19107, USA.
authors.forename: K
authors.initials: K
authors.lastname: Shepley
authors.forename: M L
authors.initials: ML
authors.lastname: Rocci
authors.forename: H
authors.initials: H
authors.lastname: Patrick
authors.forename: P
authors.initials: P
authors.lastname: Mojaverian