296 THE BIOCHEMISTRY OF B VITAMINS 



of milk and liver xanthopterin oxidase and xanthine oxidase. 174d - e A later 

 report 174f indicated that the effect was due to an impurity, probably a 

 pteridyl aldehyde photofission product, which also had the ability to 

 inhibit rabbit liver quinine oxidase. It is at present uncertain whether 

 or not this impurity could account for the undesirable neurological effects 

 observed in the treatment of macrocytic anemias with synthetic folic 

 acid. (p. 416) 



It has recently been reported that the feeding of 300 to 500 mg of 

 adenine per day to dogs produces a pellagra-like condition, and it seems 

 possible that the large excess of this substance might well interfere by 

 competition with the function or synthesis of some other metabolite. 175 



Mention has previously been made (p. 260) of the toxic effect of lyco- 

 marasmine upon certain species, and the reversal of this effect by strepo- 

 genin. In species that require nutritional strepogenin, it seems apparent 

 that the ingestion of quantities of the tomato wilt might readily influence 

 nutritional requirements for strepogenin. 



It is also worthy of passing mention that such synthetic products as 

 araboflavin and dulcitoflavin inhibit riboflavin activity in rats; 176 and 

 naturally occurring analogues of a similar nature, should they exist, might 

 be expected to be similarly effective in causing increased requirements for 

 riboflavin in the diet. These and other synthetic inhibitors are considered 

 in a later section. 



Miscellaneous Antivitamin Effects. Various other instances of anti- 

 vitamin effects have been reported from time to time in the literature, 

 but have not appeared to be of sufficient importance to merit further 

 study. A review of these reports would be tedious and uninformative. 

 Mention should be made, however, of several recent reports of this general 

 nature. 



With the advent of rapid transportation and refrigeration, a variety 

 of new and strange food plants may appear in the markets of the civilized 

 world. It should be anticipated that from some of these, unique dietary 

 problems may arise. The fact that a plant has been utilized as a food 

 by some remote native population is not in itself a guarantee of the de- 

 sirability of its incorporation into a diet. Indeed, B vitamin deficiencies 

 are common among primitive tribes (contrary to the general opinion), 

 and have probably existed from prehistoric times. While this is due to 

 a wide variety of factors, antivitamin effects play at least some part. 

 An interesting example of these points is the case of manioc. 177 A prepara- 

 tion of this plant, called "gari," is one of the staple foods in Nigeria, 

 although its incorporation into the diet produces a syndrome (in native 

 school children), which is improved considerably by riboflavin (but not 

 niacin) and cured by the administration of marmite. 



