[en] One of the two major photoproducts resulting from the irradiation of 5-ethylorotate in neutral aqueous medium has been identified as an unusual cyclobutane photodimer formed from the 5.6 bond of the parent 5-ethylorotate and the exocyclic C-5-C⁸ bond of 5-ethylidenehydroorotate the initial photoproduct of 5-ethylorotate. Irradiation at 254 nm in neutral aqueous medium causes the heterodimer to photodissociate to the two parent monomers with a quantum yield of 0.28. The heterodimer also hydrolyzes to the parent monomers in aqueous base at room temperature or by heating in the solid state. A scheme for the major photochemical transformation of 5-ethylorotate is presented. (author)

[en] Studies were carried out to develop a simple, rapid and accurate HPLC method for the simultaneous determination of Orotic Acid and Folic Acid in pharmaceutical formulation. The separation was done on ODS column by the application of isocratic reversed-phase liquid chromatographic technique. Mobile phase consisted of 800 ml phosphate buffer pH 7.2 and 70 ml methanol. The method was successfully used for the determination of these drugs in the presence of additives and excipients, which were normally encountered in pharmaceutical formulations. The proposed method of analysis was applied for the individual analysis of both these constituents in their pure forms and found equally effective. (author)

[en] The method is presented of universally labelled (U-¹⁴C)-orotic acid of a mole activity higher than 250 mCi/mMole. The Claisen condensation with (1,2-¹⁴C)-oxalic acid ethylester and (1,2-¹⁴C)-acetic acid ethylester having mole activities higher than 50 mCi/milliatom ¹⁴C results in the sodium salt of (U-¹⁴C)-oxalacetic acid ethylester. When reacted with S-methyl-(¹⁴C)-isothiouronium iodide (having an activity higher than 50 mCi/mMole), the substance yields S-methyl-(U-¹⁴C)-2-thioorotic acid ethylester whose hydrolysis in an acid medium results in (U-¹⁴C)-orotic acid. The (U-¹⁴C)-orotic acid can easily be separated from the reaction mixture in the form of precipitate which chemically and radiochemically is almost pure. When an inactive oxalic acid ethylester is used for synthesis, (2,4,5-¹⁴C)-orotic acid of a mole activity higher than 150 mCi/mMole can be prepared using the procedure described. (B.S.)

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[en] Administration of α-1,2,3,4,5,6-hexachlorocyclohexane (α-HCH) to rats decreased the utilization of [2-¹⁴C]orotic acid for the synthesis of liver cytidine nucleotides. The specific radioactivities of uridine components of the acid-soluble pool and rRNA increased during the first hours of treatment with the drug. Later on the specific radioactivities of uridine nucleotides remained unchanged, while those of cytidine components decreased gradually. Administration of hydrocortisone increased the incorporation of labelled orotic acid into rRNA cytidylic acid

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[en] A description of the synthesis of ¹⁴C-6 orotic acid starting from ¹⁴C-1 sodium acetate and passing via ¹⁴C-1 ethyl acetate; the overall radioactive yield is 47 per cent. Specific activity: 3 mc/mM. Reprint of a paper published in Bulletin de la Societe Chimique de France, no. 2653, 4. quarter 1959, p. 1798-1799