826 IX. THE VITAMIN E GROUP 



C C CHj CH, CH, CH, 



I II I III 



HjCC. C ,C(CH,)-CH(CHJ,CH(CHJ,CHCH. 



vv\h; 



Red o-quiiioiie from a-tocopherol 



The only p-quinone which has been reported to be efficacious is a- 

 tocopherylquinone (also called a-tocoquinone) in which, according to 

 Emerson, Emerson, and Evans, ^^^ the activity is substantially identical 

 with that of a-tocopherol. The formula for a-tocoquinone was worked out 

 by John, Dietzel, and Emte,^^^ who reported it to be inactive, as have 

 several other groups of workers. ^^""^^^ 



V 



CHj 



C CHj CH, CH, CH, 



III I 11 



HjCC- C C— (CHj)3CH{CH2)jCH(CHj)jCHCH, 



\ % CH- 

 CH, 



a-Tocoquinone 



All the other quinones tested have given negative results. These in- 

 clude the following: durohydroquinone,"^-^**-^^^ tetraethylquinone (also 

 toxic), ^^' thymoquinone (also toxic), ^^^ trimethylquinone,'^^ 1,4-naphtho- 

 quinone,"^ 1,2-naphthoquinone (also toxic), ^^^ 2,3-dimethyl-l,4-naphtho- 

 quinone,^^" 2-methyl-l,4-naphthoquinone,^^^ 2-hydroxy-l,4-naphthoquin- 

 one,^^* 2-methoxy-l,4-naphthoquinone,^^^ anthraquinone,^^* and /3-methyl- 

 anthraquinone. ' ^^ 



(7) Hydroquinones 



Although hydroquinone lacks vitamin E activity,^** as is also the case 

 with m-xylohydroquinone,^^^'^'" both o-xylohydroquinone and p-xylohydro- 

 quinone^^* are active (in 100-mg. doses but not in 50-mg. amounts). 

 Trimethylhydroquinone has been reported both as possessing vitamin E 

 activity^^ and as devoid of such potency,"^ when given in 100-mg. quanti- 

 ties. Durohydroquinone (tetramethyl),^*^ 2,3-dimethyl-5,6,7,8-tetrahy- 

 dro-l,4-dioxynaphthalene,^''^ as well as its mono-n-decyP^'^^ ether, have 

 been cited as active. On the other hand, trimethylethyl-, and trimethyl-5- 

 acetohydroquinone gave negative results.^'" A list of the biological activity 



"3 O. H. Emerson, G. A. Emerson, and H. M. Evans, /. Biol. Chem., ISl, 409-412 

 (1939). 



1" H. M. Evans, G. A. Emerson, and O. H. Emerson, Science, 88, 38-39 (1938). 

 i« W. John and P. Gunther, Z. physiol. Chem., 254, 51-56 (1938). 

 >« F. V. Werder and T. Moll, Z. physiol Chem., S54, 39-50 (1938). 



