Characterization of retinoyl beta-glucuronide as a minor metabolite of retinoic acid in bile.

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Abstract
Several metabolites detected in the bile of rats given radioactive retinoic acid were separated by liquid/gel partition chromatography and purified by high-pressure liquid chromatography. One of these metabolites was sensitive to .beta.-D-glucuronidase, yielding both 13-cis- and all-trans-retinoic acid. It had the characteristic UV absorption spectrum of retinoic acid esters. Trimethylsilyl ether and acetyl derivatives of the methylated metabolite were prepared and examined by mass spectrometry. The resulting mass spectra established the structure to be retinoyl .beta.-glucuronide. Retinoyl glucuronide was rapidly excreted into the bile; the excretion was complete by 12 h after the administration of retinoic acid. At this time the metabolite represented 12% of bile radioactivity (10% of dose). The existence of retinoyl glucuronide was confirmed but it represents only one of several retinoic acid metabolites in bile.