Isolation, identification, and chemical synthesis of 8 alpha,25-dihydroxy-9,10-seco-4,6,10(19)-cholestatrien-3-one. A new metabolite of 25-hydroxyvitamin D3 produced by mouse myeloid leukemia cells (M1).

It is known that phagocytic cells such as monocyte-macrophages and myeloid leukemia cells metabolize 25-hydroxyvitamin D3 to 10-oxo-19-nor-25-hydroxyvitamin D3. Now we have found that phagocytic cells metabolize 25-hydroxyvitamin D3 not only to 10-oxo-19-nor-25-hydroxyvitamin D3 but also to a new metabolite eluted just after 24R,25-dihydroxyvitamin D3 on straight phase high pressure liquid chromatography with a 2-propanol-hexane solvent system. The new metabolite, produced by murine myeloid leukemia cells (M1), was isolated in pure form and identified as 8,25-dihydroxy-9,10-seco-4,6,10(19)-cholestatrien-3-one on the basis of mass, ultraviolet, infrared, and proton magnetic resonance spectra. The 8 alpha-hydroxy epimer of the putative metabolite was chemically synthesized in two steps starting from 25-hydroxyvitamin D3. The spectral data and chromatographic behavior of chemically synthesized 8 alpha,25-dihydroxy-9,10-seco-4,6,10(19)-cholestatrien-3-one coincided exactly with those of the isolated metabolite, indicating that the stereochemistry of the hydroxyl group at the 8-position is alpha. On the basis of the structural characteristics of the two metabolites produced from 25-hydroxyvitamin D3 (the present metabolite and 10-oxo-19-nor-25-hydroxyvitamin D3), it is suggested that dioxygenases are involved in the production of these metabolites from 25-hydroxyvitamin D3 in phagocytic cells.