Identification of 7-dehydrocholesterol, vitamin D3, 25(OH)-vitamin D3 and 1,25(OH)2-vitamin D3 in Solanum glaucophyllum cultures grown in absence of light.
Solanum glaucophyllum contains the calciotropic hormone 1, 25-dihydroxy-vitamin D3 (1,25(OH)2D3). The metabolic pathway leading to the formation of 1,25(OH)2D3 in the plant is largely unknown. Specifically, there is controversy about the participation of a photolytic reaction in the generation of vitamin D3 and its metabolites. To investigate the requirement for light, S. glaucophyllum tissue (callus) and cell suspension cultures grown under strict conditions of darkness were extracted with chloroform/methanol (1:2, v/v) followed by purification of the lipidic fraction by Sephadex LH-20 and high-performance liquid chromatography. HPLC peaks with elution times similar to those of authentic samples of 7-dehydrocholesterol, vitamin D3, 25(OH)D3 and 1,25(OH)2D3 were detected. The presence of 1,25(OH)2D3 was also evidenced by [3H]1,25(OH)2D3 competitive binding analysis using the chick hormone intestinal receptor. Furthermore, 7-dehydrocholesterol, vitamin D3, 25(OH)D3 and 1,25(OH)2D3 were unequivocally identified by mass spectrometry. Incubation of control samples of 7-dehydrocholesterol under the same conditions as S. glaucophyllum cultures did not result in vitamin D3 formation, excluding the influence of light in these experiments. The results suggest that a synthetic route of vitamin D3 compounds independent of light operates in Solanum glaucophyllum cultured in vitro.
Curino
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Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000 Bahía Blanca, Argentina.
Skliar
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Boland
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D001118:Argentina; D002112:Calcifediol / Q000032:analysis*; D002117:Calcitriol / Q000032:analysis*; D002478:Cells, Cultured; D002762:Cholecalciferol / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003624:Darkness; D003684:Dehydrocholesterols / Q000032:analysis*; D013058:Mass Spectrometry; D063245:Plant Development; D010944:Plants / Q000737:chemistry*
D003684:Dehydrocholesterols; D002762:Cholecalciferol; C016705:7-dehydrocholesterol; D002117:Calcitriol; D002112:Calcifediol