Isolation, identification, and biological activity of 25-hydroxy-24-oxovitamin D3: a new metabolite of vitamin D3 generated by in vitro incubations with kidney homogenates.

A metabolite of 25-hydroxyvitamin D3 has been isolated in pure form from incubation mixtures containing kidney homogenates of chicks given large doses of vitamin D3. The isolation involved methanol--chloroform extraction and six steps of column chromatography. The metabolite was identified as 25-hydroxy-24-oxovitamin D3 by means of ultraviolet absorption spectrometry, mass spectrometry, infrared spectrometry, nuclear magnetic resonance spectrometry, and specific chemical reactions. Use of a sensitive in situ technique revealed that 25-hydroxy-24-oxovitamin D3 enhances intestinal calcium transport in rats approximately as effectively as 24,25-dihydroxyvitamin D3 does. In contrast, 25-hydroxy-24-oxovitamin D3 appeared to be less active than 24,25-dihydroxyvitamin D3 in chicks 24 h after intravenous injection.