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

Abstract

S. malacoxylon cell cultures synthesize vitamin D 3, 25-OH D 3 and 1α,25(OH) 2 D 3 under different experimental conditions. Reduction of the Ca ++ concentration in culture medium stimulates the accumulation of D 3 and hydroxylated metabolites. Cell suspension cultures of Solanum malacoxylon cultivated in standard B5 medium containing 1 mM CaCl 2 accumulated larger amounts of both vitamin D 3 (cholecalciferol) and 25-OH D 3 (25-hydroxycholecalciferol) than cells in medium containing 10 mM CaCl 2. The amount of vitamin D 3 in calcium-free medium was similar to that in standard medium, while the 25-OH D 3 level was 50 time greater; 1α,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 3 and 25-OH D 3 for prolonged culture periods (up to 30 days) and were able to biotransform vitamin D 3 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 1α,25(OH) 2D 3 under different experimental conditions, therefore suggesting the presence of enzyme systems able to hydroxylate vitamin D 3 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.