Effect of calcium and cell immobilization on the production of choleocalciferol and its derivatives by Solanum malacoxylon cell cultures

Cell suspension cultures of Solanum malacoxylon cultivated in standard B5 medium containing 1 mM CaCl2 accumulated larger amounts of both vitamin Dg (cholecalciferol) and 25-OH D-3 (25-hydroxycholecalciferol) than cells in medium containing 10 mM CaCl2. The amount of vitamin D-3 in calcium-free medium was similar to that in standard medium, while the 25-OH D, level was 50 time greater; 1 alpha,25(OH)(2) D-3 (calcitriol) was detected only in chloroform extracts of cells cultivated in standard medium. It was found that immobilized cells accumulated vitamin D, and 25-OH D, for prolonged culture periods (up to 30 days) and were able to biotransform vitamin D, when it was supplemented as an exogenous precursor. S. malacoxylon suspension cell cultures were able to synthesize vitamin D-3, 25-OH D-3 and 1 alpha,25(OH)(2)D-3 under different; experimental conditions, therefore suggesting the presence of enzyme systems able to hydroxylate vitamin D, at positions C-25 and C-1. In Solanum malacoxylon, as in animals, the concentration of calcium may have an effect on the regulation of vitamin D-3 synthesis and the production of its hydroxylated metabolites. (C) 1997 Elsevier Science Ltd.