S. B. Binkley

Inactivation of vitamin K by light.

In an earlier note, 1 we reported the isolation of crystalline material from alfalfa which after 4 recrystallizations still had the activity ascribed to Vitamin K. Since our observations were still incomplete it was impossible to state with certainty that we had isolated Vitamin K. Some time after this work, it was found that although we could obtain crystals with approximately the same melting point, solutions of these crystals did not restore the coagulation time to nomal values. Frankly, we admit that we have been unable to duplicate the work reported last summer and, moreover, thus far do not have any explanation which appears to be satisfactory. In seeking an explanation of our unexpected results, we recalled that Almquist 2 , 3 had reported briefly on the loss of activity of preparations exposed to sunlight and on the stability of the vitamin exposed to artificial illumination. The effect of sunlight has been confirmed but in addition we have found that highly purified preparations dissolved in various solvents rapidly lose activity on exposure to the illumination from ordinary daylight bulbs. On the other hand, our crude extracts of alfalfa have been found to be quite stable, no special precautions regarding light being necessary. However, as the potency is increased to 500 or 1000 units (Thayer, et al. 4 ) per milligram, the lability is such that decomposition has frequently occurred in spite of our precautions. Experimental. Two preparations were used in our experiments on the effect of light: (a) a non-crystalline product obtained from alfalfa having a potency of approximately 1000 units per milligram and (b) a crystalline product (MP. 50.5–52.0°) obtained from putrefied fish meal. The latter had been recrystallized 10 times from various solvents without detectable alteration of its potency, which was approximately 600 units per milligram.

Assay of vitamin K concentrates.

Summary A curative method of assay of Vitamin K based on Trevans principles of bioassay has been found to give satisfactory results.

The Assay of Vitamins K1 and K2

Summary 1. The potency of Vitamin K1 is approximately 1000 of our units per milligram; K2 approximately 660. 2. The 18-hour assay procedure gives satisfactory results. 3. In a slightly modified Almquist 7-day curative method, 80 micrograms per kilo of diet of K1 and 160 micrograms per kilo of diet of K2 are adequate.

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

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 Ansbachers 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

Bioassay of Water-Soluble Antihemorrhagic Compounds by Intravenous Administration.

Summary Using intravenous administration it has been found that on a molecular basis the potencies of all the compounds with the exception of the disulfate are approximately equal to that of the standard, Z-methyl-l,4-naphthoquinone. The disul fate is about onethird as potent on a niolecular basis, but owing to the much larger molecular weight its activity per milligram is somewhat less than one-sixth that of 2-methyl-1, 4-naphthoquinone.