Calcidiol 25-hydroxyvitamin

Zierold, C., H.M. Darwish, and H.E DeLuca (1994). Identification of a vitamin D-response element in the rat calcidiol (25-hydroxyvitamin D3) 24-hydroxylase gene. Proc. Natl. Acad. Sci. USA 91, 900-902. 

Vitamin D3 is converted to 1,25-dihydroxyvitamin D3 by a series of two hydroxyl a tion reactions. The 25-hydjroxylation, which occurs first, is catalyzed by an enzyme of the liver. The subsequent conversion of 25 hydroxyvitamin Dj to 1,25-dihydroxyvitamin Dj i.s catalyzed by an enzyme of the kidney The enzyme that catalyzes this latter step is called "1-hydroxylase" in this text. Figure 9.50 indicates the positions of the 1-carbon and 25-carbon of the steroid ring. Vitamin Dean also be converted to 24,25-dihydroxyvitamin Dj, as well as a number of other metabolites. Although there is much interest in the possible physiological value of these compounds, they seem generally to be inactive catabolites of the vitamin. 1,25-Di-hydroxyvitamin Dj is also call calcitrol. 25-Hydroxyvitamm Dg is also called calcidiol. 

Hydroxyvitamin D3 26,23-lactone (calcidiol lactone, 1045), another metabolite of vitamin D3, has also been synthesized by a coupling methodology applied to steroidal ade-... 

Vitamin D2 is a straightforward choice as an internal standard for vitamin D3, whereas 5,6-trans-calcidiol has been used in an LC assay of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3. 

---