DETERMINATION OF MDL-74,405, A SYNTHETIC ANALOG OF ALPHA-TOCOPHEROL, IN DOG PLASMA AND HEART-TISSUE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

A high-performance liquid chromatographic (HPLC) procedure with electrochemical detection was developed to analyze MDL 74,405 (I), the (-)-(S)-enantiomer of an alpha-tocopherol analogue, in dog plasma and heart tissue after infusion (0.3 mg/kg/h). The sample preparation involved the addition of an internal standard to either the dog plasma and heart tissue prior to protein precipitation. After centrifugation, the resulting supernatant was directly analyzed by HPLC with a Zorbax Rx C-8 column and a mobile phase of acetonitrile-0.04 M potassium phosphate, pH 7.0 (70:30, v/v). The concentration of I found was ca. 100 ng/ml in plasma and ca. 3 mu g/g in heart tissue. A chiral separation with an Ultron ES-OVM column and a mobile phase of methanol-0.025 M potassium phosphate, pH 6.5 (17:83, v/v) was also used to investigate the enantiomeric conversion of I. Preliminary results of a probe study indicated that I is not inverted to the (+)-(R)-enantiomer in vivo.