Inactivation of Vitamin K by Light. ∗

Abstract

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.