Biopotency of vitamin K. I. Antihemorrhagic properties of structural analogs of phylloquinone as determined by curative prothrombin time tests.

Relative antihemorrhagic properties of structural analogs of transphylloquinone (vitamin K1) have been determined by curative prothrombin time tests with vitamin K-deficient chicks. Analogs (where applicable) and the phylloquinone standard had (all-) rac-trans configuration, and all compounds were well characterized (structure, purity, trans: cis). Compounds were administered as single oral doses according to the up-and-down procedure. Estimation of mean effective doses allowed a reliable calculation of relative activities for analogs in comparison with vitamin K1 standard. 2', 3'-Dihydro-phylloquinone had a relative activity of only 6.7%, i.e. it was about 15 times less active than phylloquinone. Further reduction of this analog led to 2',3',5,6,7,8-hexahydro-phylloquinone which was completely inactive. Analogs with oxygen functions in the side chain, 6'-hydroxy-K1, 6'-oxo-K1, and 7'-hydroxy-6'-oxo-K1, displayed relative activities of 20.5%, 31.9%, and 30.5%, respectively. Phylloquinone-2,3-epoxide was 1.7 times more active than the phylloquinone standard. An analog with a 7-carbon side chain ending with a carboxy group (in mammals a urinary metabolite of vitamin K1) and its corresponding ethyl ester derivative were practically inactive.