ABSTRACT
New findings on vitamin D metabolites and their significant biological activities inspired synthetic organic chemists a great deal and the many compounds synthesized allowed to attain more precise understanding on the mechanism of function of vitamin D hormone. To be emphasized is that the structure, regulation, and molecular function of the receptor of vitamin D hormone has shed light on the similarity in biochemical as well as signal transduction systems to other steroidal hormones and retinoic acid. This development may significantly influence the area of the structure-biological activity relationship. Some 50 metabolites of vitamin D3 and vitamin D2 have now been isolated and identified. Most of these have been isolated from in vitro incubation systems, kidney perfusions, and cell cultures. To date any unique biological properties have not been shown to most of these metabolites, which are derived from the metabolic transformations on the side chain and are apparently associated with the inactivation or breakdown of the parental metabolites.
