Mechanism of Biological Action of Vitamin K and its Synthetic Analogues

THE correlation between structure and biological action of the vitamin K group is an object of many investigations. However, in spite of much experimental material we still lack a satisfactory explanation of both the established correlations and of the mechanism of biological action of the natural vitamins K 1 and K 2 and of their synthetic analogues. It was, already in 1939 that L. F. Fieser first suggested tlie hypothesis 1 further developed in 1941 2 that the biological activity of most analogues of vitamin K is due not to these substances as such, but to the quinones of the type of the natural vitamin into which they are transformed within the organism as a result of biological synthesis. As to the mechanism of biological action of the vitamin itself, this question remains open. L. F. Fieser's hypothesis is far from being in accord with much experimental evidence, nor does it offer a satisfactory explanation of much of it. At the same time it strikingly contradicts the notion that a perceptible, although slight, antihæmorrhagic activity is shown by phthalic acid 3 . This discrepancy is particularly noteworthy in view of the fact established in this laboratory that a high antihæmorrhagic activity is characteristic of the diethyl ether of phthalic acid (the biological assay was carried out by B. A. Kudriashev). The possibility of transformation, within the organism, of phthalic acid into compounds of the 1,4-naphthoquinone series is indeed extremely doubtful.