title: 23,25-Dihydroxyvitamin D3: a natural precursor in the biosynthesis of 25-hydroxyvitamin D3-26,23-lactone.
abstract: To elucidate the biosynthesis of 25-hydroxyvitamin D3-26,23-lactone, two known metabolites of 25-hydroxyvitamin D3--23,25-dihydroxyvitamin D3 and 25,26-dihydroxyvitamin D3--were incubated individually with kidney homogenate prepared from vitamin D-supplemented chickens, a preparation known to produce the lactone from 25-hydroxyvitamin D3. The 25-hydroxyvitamin D3-26,23-lactone produced in vitro was then separated, purified, identified, and quantitated by consecutive straight-phase and reverse-phase high-performance liquid chromatography. 23,25-Dihydroxyvitamin D3 is a far better substrate for production of 25-hydroxyvitamin D3-26,23-lactone than is 25,26-dihydroxyvitamin D3. Production of lactone is highly selective for the natural 23(S)-hydroxy-23,25-dihydroxyvitamin D3 while both epimers of 25,26-dihydroxyvitamin D3 resulted in small amounts of product comigrating with natural lactone. It appears that 23(S),25-dihydroxyvitamin D3, but not 25,26-dihydroxyvitamin D3, is a natural precursor in the synthesis of 25-hydroxyvitamin D3-26,23-lactone; this result also implies that the configuration of the lactone at C-23 is S.
mesh_terms: D015650:24,25-Dihydroxyvitamin D 3; D000818:Animals; D002112:Calcifediol / Q000031:analogs & derivatives*; D002645:Chickens; D004100:Dihydroxycholecalciferols / Q000378:metabolism*; D006887:Hydroxycholecalciferols / Q000096:biosynthesis* / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D007783:Lactones / Q000096:biosynthesis
chemical_list: D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D007783:Lactones; D015650:24,25-Dihydroxyvitamin D 3; C026396:calcifediol lactone; D002112:Calcifediol