title: Synthesis and composition of vitamin D-3 metabolites in Solanum malacoxylon.
abstract: The synthesis of vitamin D-3 hydroxylated metabolites in Solanum malacoxylon was investigated. When crude leaf homogenates and subcellular fractions were incubated with [3H]vitamin D-3 and [3H]25-hydroxy-vitamin D-3 under conditions described for animal vitamin D-3-25-hydroxylase and 25-hydroxy-vitamin D-3-1 alpha-hydroxylase, respectively, labelled metabolites identified on the basis of their chromatographic properties as 25-hydroxy-vitamin D-3 and 1,25-dihydroxy-vitamin D-3 were formed. Other unidentified product metabolites were also detected. Vitamin D-3-25-hydroxylase activity was localized in microsomes and 25-hydroxy-vitamin D-3-1 alpha-hydroxylase in mitochondria and microsomes. Chromatography of sterols isolated from leaf extracts preincubated with beta-glucosidase on Sephadex LH-20 columns permitted the isolation of three biologically active fractions with elution properties similar to vitamin D-3, 25-hydroxy-vitamin D-3 and 1,25-dihydroxy-vitamin D-3, respectively. Ultraviolet spectra characteristic of vitamin D-3 and its metabolites were obtained after purification of the fractions by TLC. Co-chromatography of individual fractions with authentic metabolites on TLC provided further evidence that the plant contains vitamin D-3, 25-hydroxy-vitamin D-3 and 1,25-dihydroxy-vitamin D-3 as glucoside derivatives. These results suggest that a similar pathway of vitamin D-3 hydroxylation as in animals may be operative in S. malacoxylon.
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D000818:Animals; D002645:Chickens; D002762:Cholecalciferol / Q000378:metabolism* / Q000494:pharmacology; D053493:Cholestanetriol 26-Monooxygenase; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D010944:Plants / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D002762:Cholecalciferol; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase