Conversion of vitamin K-1 to 2',3'-dihydrovitamin K-1 during the hydrogenation of vegetable oils

When vitamin K-1 (phylloquinone) was measured by HPLC in foods containing partially hydrogenated vegetable oils, a peak corresponding to the retention time of 2',3'-dihydrovitamin K-1 was observed. Dihydrovitamin K-1 has a molecular mass 2 Da greater than that of vitamin K-1 due to saturation of the 2',3' double bond of the side chain. For confirmation of this putative compound, samples of a commercial shortening, soybean oil, and soybean oil subjected to light and heavy hydrogenation were purified by preparative HPLC and analyzed by GC/MS. Authentic dihydrovitamin K-1 and the oil samples produced molecular ions at m/z 452 and fragment ions at m/z 186. Although absolute levels of both vitamin K-1 and dihydrovitamin K-1 decreased with an increase in hydrogenation, there was an overall increase in the ratio of dihydrovitamin K-1 to vitamin K-1. The biological activity of dihydrovitamin K-1 remains to be determined; however, if biologically active, it could have a significant role in vitamin K nutriture.