| [ Summary ] |
Vitamin D generates more than 40 daughter metabolites in the vitamin D endocrine system. At this time, 1alpha,25(OH)2D3 recognized to be the sole metabolite possessing clinical significance and usefulness in the development of therapeutic agents, although all metabolites have not been tested. However, a novel metabolite of 1alpha,25(OH)2D3, 1alpha,25(OH)2-3-epi-D3, has recently been identified, in which the orientation of the hydroxyl group at the C-3 position of the A-ring changed from natural (beta) to epi (alpha). Interestingly, 3-epimerization can be observed in common with not only natural vitamin D metabolites, but also synthetic vitamin D analogs. In addition, it was found that the 3-epimers were capable of exhibiting significant apoptosis-inducing activity in cancer cells. Although the biological significance of 3-epimerization has not yet been clarified, further research may provide useful information concerning the development of vitamin D analogs. |