cholecalciferol and isotachysterol

In any food fortification program, the stability of added micronutrients is an important factor. Cholecalciferol or vitamin D3 is known to isomerise under various conditions, thereby making its analysis challenging. In the current study, the effects of different parameters, such as temperature, iodine, acidic conditions, and oxidation, on the isomerisation of vitamin D3 were studied using HPLC-DAD and UHPLC-MS/MS. Vitamin D3 thermally and reversibly transforms to pre-vitamin D3 type isomers. In the presence of iodine, cis/trans isomerisation of both cholecalciferol and pre-vitamin D3 takes place to form trans-vitamin D3 and tachysterol, respectively. Another isomer, isotachysterol, was formed under acidic conditions. The different rates of reaction of these products with a dienophile through the Diels-Alder reaction confirmed the formation of vitamin D3 isomerisation products. The derivatization enhanced the ionisation efficiency of vitamin D3 and its isomers in UHPLC-MS/MS and improved the separation and fragmentation enabling sensitive detection.

Topics: Cholecalciferol; Chromatography, High Pressure Liquid; Ergosterol; Food, Fortified; Isomerism; Tandem Mass Spectrometry

A new procedure for the isomerization of vitamin D and its metabolites is described. Vitamin D or its metabolites are dissolved in 100 microliters methanol and 10 M HC1 in 2-butanol is used as the reagent for isomerization. The isomerization reaction is carried out at 5 degrees C for 2-3 min which gives quantitative yields of isotachysterols down to 10 ng level without use of any carrier.

Topics: Calcifediol; Cholecalciferol; Chromatography, High Pressure Liquid; Ergocalciferols; Ergosterol; Isomerism; Methanol; Solvents; Temperature; Time Factors; Vitamin D

Topics: Cholecalciferol; Chromatography, Gas; Ergocalciferols; Ergosterol; Methods; Secosteroids