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Isolation, Quantification, and Biosynthetic Origin of Orotic Acid in Milk¹

Department of Food Science, The Pennsylvania State University, University Park 16802

ABSTRACT

The most frequently used methods for estimating orotic acid in milk have been variations of a colorimetric procedure. Assay here involves the isolation of orotic acid by dialysis and anion exchange and silicic acid chromatography. This is followed by the silylation of the purified orotic acid and its quantification by gas-liquid chromatography. This technique was compared with a colorimetric method on various milk samples and the results by the two methods were similar. Both confirmed the high orotic acid content of bovine milk. Orotic acid was less in commercial cultured buttermilk and goat milk and not detectable in human milk.

The ability to isolate orotic acid in essentially pure form made it possible to study its biosynthesis in vivo. Intramammary infusion of carbon-14 uniformly labeled aspartic acid, a precursor, confirmed in vitro studies (8) indicating that orotic acid in milk originates almost exclusively in mammary cells.

¹ Authorized for publication July 18, 1977 as paper no. 5338 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

² Fatih University, Tripoli, Libya.