Anhydrovitamin A, and Rehydrovitamin A,. II

In a previous publication (l), we reported that when 1 mg of a pure concentrate of anhydrovitamin A2 (4’-ethoxy anhydrovitamin Ai, E:%m at 370 rnp = 2248 in light petroleum ether), and 0.5 mg of a-tocopherol are fed daily to vitamin A-deficient rats, growth is resumed, xerophthalmic lesions are cured, and a new compound named rehydrovitamin A* showing absorption maxima at 330,348, and 365 rnp can be obtained from the livers. In analogy to rehydrovitamin Ai (2), a tentative structure (4’-ethoxy rehydrovitamin Al) was assigned to rehydrovitamin AZ (1). Since anhydrovitamin AZ has an ethoxy group in the p-ionone ring (3), the growth-promoting activity of this compound was surprising. In this paper, the biological activity of crystalline anhydrovitamin AZ, assayed by the rat growth method of U.S.P. XIII (4), is reported. Further, the site of conversion of anhydrovitamin Az to rehydrovitamin AZ in the rat is discussed.