Determination of apovincaminic acid in biological samples by high-performance liquid chromatography

A method is described for measuring the concentrations of apovincaminic acid and vincaminic acid (internal standard) in blood plasma and urine by high-performance liquid chromatography using ion pair extraction. The main metabolite of vinpocetine, apovincaminic acid, and vincaminic acid were extracted from 1 ml of plasma and urine into chloroform as an ion pair using tetrabutylammonium hydroxide as counter ion. Analysis was carried out on a reversed-phase column of RP-8 with acetonitrile-0.0075 M phosphate buffer (28:72) at pH 3.5 as mobile phase. The eluted derivatives were detected by UV absorption at 254 nm. The sensitivity of the method is 20 ng/ml for AVA in plasma and urine samples. The relative recovery of these compounds added to plasma was about 50%.