The biological activity and tissue distribution of 2',3'-dihydrophylloquinone in rats.

Abstract 2′,3′-Dihydrophylloquinone (dihydro-K 1 ) is a hydrogenated form of vitamin K 1 (K 1 ), which is produced during the hydrogenation of K 1 -rich plant oils. In this study, we found that dihydro-K 1 counteracts the sodium warfarin-induced prolonged blood coagulation in rats. This indicates that dihydro-K 1 functions as a cofactor in the posttranslational γ-carboxylation of the vitamin K-dependent coagulation factors. It was also found that dihydro-K 1 as well as K 1 inhibits the decreasing effects of warfarin on the serum total osteocalcin level. In rats, dihydro-K 1 is well absorbed and detected in the tissues of the brain, pancreas, kidney, testis, abdominal aorta, liver and femur. K 1 is converted to menaquinone-4 (MK-4) in all the above-mentioned tissues, but dihydro-K 1 is not. The unique characteristic of dihydro-K 1 possessing vitamin K activity and not being converted to MK-4 would be useful in revealing the as yet undetermined physiological function of the conversion of K 1 to MK-4.