Carotene and Vitamin A

Carotene was adopted as a temporary international standard for Vitamin A potency by the Permanent Standards Commission of the Health Organization of the League of Nations. Since then much interest has been shown in an exact determination of the value of this unit in terms of the Sherman Unit. The earlier literature assigns values between 2 λ and 20 λ of carotene as meeting the requirements for one Sherman Unit, while the more recent results of Polak and Stokvis 1 give values as low as 0.5 λ of carotene to one Sherman Unit. This paper is offered as a further contribution to this subject.

In preparing carotene from carrots by a modification of the method given by Schertz, 2 part of the carotene extracted was obtained in crystalline form and part remained in the concentrated petroleum ether extract. After removal of the petroleum ether by evaporation under proper conditions, a deep red carrot oil remained. Moore 3 found carrot oil potent as a source of Vitamin A. However, his work was not quantitative on the basis of the content of pigment. Hence, the questions arose, whether or not the pigment which remained in the carrot oil was as potent a source of Vitamin A as that which crystallized, and whether there was any growth-promoting factor in carrot oil other than that due to its carotene content when all the color in the carrot oil is considered as carotene. To determine this biologically, 2 test solutions were prepared as follows:

Solution 1. Crystalline Carotene Dissolved in Wesson Oil: A sample of carotene isolated from carrots was found to have a purity of 79% when tested by a modification of the potassium dichromate comparison method of Palmer, 4 based on the earlier results of Willstatter and Stall. 5.1 mg. of this carotene were dissolved in 100 cc. of Wesson Oil, thus giving the oil an actual carotene content of 0.001 mg. (1 λ) in each drop from a pipette standardized to deliver 40 drops per cc.