III. INDUSTRIAL PREPARATION 499 



C. PROPERTIES AND POTENCY OF AVAILABLE PREPARATIONS 



1. Natural Tocophkrols 



Wheat germ oil concentrates and unsaponifiable fractions are primarily 

 of historical interest, since, in the early days of tocopherol use, these prep- 

 arations alone were available. However, there is even yet some manufac- 

 ture of wheat germ oil concentrates, and, as shown in Table I, they are 

 brown oil preparations relatively susceptil)le to oxidative destruction and 

 possessing only about 10 I.U. of vitamin E activity per gram. 



The second listed tocopherol preparation in Table I is typical of a type 

 of mixed tocopherol concentrate prepared from vegetable oils in which 

 the total tocopherol content may be 300 mg. per gram to GOO mg. per gram 

 and the a form of tocopherol constitutes at least 50 % of the total. Conse- 

 ciuently, in the example listed. Type 4-50 concentrate contains 250 mg. 

 of a-tocopherol per gram. Since this is (i-a-tocopherol in the free alcohol 

 form, 250 mg. furnishes a biopotency of (250 X 0.92) 230 I.U. per gram.^^ 

 Furthermore, the antioxidant potency of these concentrates is very high 

 l)ecause of the free tocopherol content. 



(/-a-Tocopheryl acetate concentrate, Type 6-35, is representative of a 

 series of preparations in which the tocopherol is present in the acetic acid 

 ester form, has practically no antioxidant acti\dty, but does have excep- 

 tional stability and high biopotency. The example in Table I supplies 475 

 I.U. of vitamin E per gram concentrate as the result of its content of 350 

 mg. of c?-a-tocopheryl acetate per gram (350 X 1.36).'''' ^' 



The last natural-type product in Table I is pure rf-a-tocopheryl ace- 

 tate, a light-yellow viscous oil with the highest biopotency of any vitamin 

 E product, 1360 I.U. per gram.^' 



2. Synthetic Tocopherols 



The two synthetic preparations available are clear viscous oils with a 

 biological potency of 680 I.U. per gram for the a-tocopheroP^ and 1000 

 I.U. per gram (by definition) for the a-tocopheryl acetate. Synthetic a- 

 tocopherol and a-tocopheryl acetate are racemic mixtures of from two to 

 eight isomers, depending upon whether natural or synthetic phytol was 

 used in the synthesis (Fig. 1). The separation and isolation of the natural 

 d isomer of a-tocopherol can be effected by resolution of the bromocamphor- 

 sulfonates.^- 



Esters of natural or synthetic a-tocopherol, other than the acetates, and 

 tocopheramine"*'^ are occasionally prepared. For example, succinates, acid 



" P. L. Harris and M. I. Ludwig, /. Biol. Chein. 180, 611 (1949). 



3" P. L. Harris and M. I. Ludwig, /. Biol. Chem. 179, 1111 (1949). 



31 P. L. Harris, Ann. X. Y. Acad. Set. 52, 342 (1949). 



'2 P. Karrer, U.S. Pat. 2,215,398 (Sept. 17, 1940). 



" L. I. Smith, W. B. Renfrew, Jr., and J. W. Opie, J. Am. Chem. Sac. 64, 1082 (1942). 



