Assay of retinoids in biological samples by reverse-phase high-pressure liquid chromatography

A separation procedure for retinoids based on reversephase high-pressure liquid chromatography with solvent mixtures of acetonitrile and water is described. The method may be applied to the screening of synthetic retinoids, which have potential for use in the prevention of cancer. It is easily adapted to a variety of biological samples and can be applied to other conventional retinoid assays in liver and plasma, detecting as little as 1 nmol retinyl esters and less than 0.3 nmol retinol per g tissue. The one-step chromatography results in separation and simultaneous determination of many of the synthetic retinoids and all of the natural retinoids, including the retinyl esters that are separated into their major fatty acid components. The method has been applied to the analysis of retinoid levels in the liver and intestine of vitamin A-deficient hamsters following a p.o. dose (0.5 mg/day for 2 days) of retinyl acetate or of a synthetic vitamin A analog and is predictive of the degree to which various synthetic retinoids can be converted to retinol and stored in the liver as retinyl esters. Because of its speed, excellent recoveries, and high resolution, the method offers significant advantages over previous, more lengthy procedures.