STUDIES ON THE ISOMERIZATION OF VITAMIN D AND RELATED COMPOUNDS WITH ACIDIC REAGENTS

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Abstract
The determination of vitamin D2 isomers in mixtures was investigated in order to use in kinetic experiments on their isomerization with acidic reagents. Vitamin D2, pre-D2, 5, 6-trans-D2, iso-D2, T2 and iso-T2, thought to exist in the reaction mixtures, were chosen as standard compounds of vitamin D2 isomers. When a mixture of the standard compounds was ap-plied to the GLC using OV-17 as a stationary phase after trimethylsily-lation, the separation of vitamin D2 from pre-D2 and of T2 from iso-T2 were impossible while the two groups and the other compounds were separated one another (Both vitamin D2 and pre-D2 were quantitatively isomerized into the thermal cyclized compounds “pyro- and isopyro-D2” in the same manner.). Therefore, it was possible to determine the compounds by the GLC when the coexistences of vitamin D2 with pre-D2 and of T2 with iso-T2 were simultaneously unidentified, whereas pre-treatment was thought necessary to separate them when their coexistence was identified. When a mixture of the standard compounds was applied to the TLC using Kieselgel GF254 as an adsorbent and benzene-acetone (95:5) as a developing solvent, vitamin D2 from pre-D2 and T2 from iso-T2 were separated each other. From these results, a method based on the TLC and GLC was proposed for the determination of vitamin D2 isomers in mixtures.

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