Potencies of Vitamin Ki and of 2-Methyl-1,4-Naphthoquinone

Abstract

In a previous investigation 1 we have confirmed the report of the marked antihemorrhagic activity of 2-methyl-1,4-naphthoquinone. 2 A careful comparison of the potencies of this compound and of pure vitamin K₁ by our 18-hour procedure 3 showed that the latter is approximately one-half as active as the former. In view of this observation and the report that by the 6-hour procedure vitamin Ki is only 1/30 as potent as 2-methyl-1,4-naphthoquinone, 4 it seems desirable to publish the results that we have obtained in a comparison of the potencies of the two compounds by the 6-hour observation period.

Experimental. In our experiments, we have used for the evaluation of the response of the chicks: (1) the percentage of chicks showing a clotting time of less than 10 minutes; 3 (2) the mean clotting time; (3) the mean prothrombin time. 5 Following Ansbacher's suggestion, a solution of the compound in cod liver oil was administered and the blood drawn 6 hours later for the evaluation of the reaction. Each assay included the response of the same lot of deficient chicks to the administration of one or 2 dosages of each compound and the mean clotting time of a control group. The data are summarized in the table.

In Experiments 1, 2, 3 and 4 the volume of cod liver oil used for administration of the compounds was 0.10 cc; in Experiments 5 and 6 only 0.05 cc was used. From other reports and the data of this paper it appears likely that in experiments in which the response is restricted to a period of 6 hours or less the volume of oil used may play a role in the absorption of vitamin Ki and therefore in