QUANTITATION OF INO]-3-PHENYLPROPIONYLAMINO)PROPIONYLAMINO)BUTYRIC ACID ISOPROPYL ESTER (CP-80,794), A RENIN INHIBITOR, AND ITS HYDROLYTIC CLEAVAGE METABOLITE 2-[(MORPHOLINE-4-CARBONYL)AMINO]-3-PHENYLPROPIONICACID (CP-84,364) IN DOG AND HUMAN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Simple and precise high-performance liquid chromatographic (HPLC) assa ys were developed and validated for the determination of a renin inhib itor (RI), -2-hydroxy-3-(3-methylsulfanyl-2-{2-[(morpholine-4 ino]-3-p henylpropionylamino}propionylamino)butyric acid isopropyl ester (CP-80 ,794, I), and its hydrolytic cleavage metabolite, 2-[(morpholine-4-car bonyl)amino]-3-phenylpropionic acid (CP-84,364, II) in dog and human p lasma. The internal standard for I, CP-83,092 (III, a carbon-substitut ed derivative of I) and analyte were extracted by liquid-liquid extrac tion using n-butyl chloride, cleaved to form a fragment containing a p rimary amine, and subsequently fluorescently derivatized for measureme nt by HPLC. Samples were analyzed by reversed-phase HPLC using a Water s C-18 column with fluorescence detection at 390 nm excitation/440 nm emission. The quantitation limit of I was 10 ng/ml and the calibration curve was linear over the range of 0.01-1.0 mu g/ml (r(2)>0.99). In d og and human plasma, intra- and inter-assay precision ranged from 2.3 to 16% and 3.0 to 18%, respectively, The average recoveries were simil ar (greater than or equal to 63%) for both I and III and the upper lim it of quantification of I can be as high as 4 mu g/ml. The internal st andard for II, CP-96,452 (IV, a methoxy derivative of II) and analyte were extracted by anion-exchange solid-phase extraction and subsequent liquid-liquid extraction using methyl tert.-butyl ether. Samples were analyzed by reversed-phase HPLC using a Waters C-18 column with ultra violet detection at 214 nm. The quantitation limit of II was 20 ng/ml and the calibration curve was linear over the range of 0.02-2.0 mu g/m l (r(2)>0.99). In dog and human plasma, intra- and inter-assay precisi on ranged from 2.6 to 13.0% and 1.8 to 20.0%, respectively. The averag e recoveries were similar (greater than or equal to 75%) for both II a nd IV and the upper limit of quantification of II can be as high as 20 mu g/ml. The methods described have been successfully applied to the quantification of I and II in about 5000 dog and human plasma samples over a 2 year period. (C) 1997 Published by Elsevier Science B.V.