BETEROXANTHIN. 397 



On treatment with methyl iodid it can be readily converted into 

 theobromin and into caffein. Like heteroxanthin it can be subjected 

 to electrolytic reduction. 



According to Albanesi it is more diuretic than 7-methyl xanthin 

 (heteroxanthin). When fed to rabbits it is in part excreted as such 

 and is unaccompanied by xanthin (Kriiger and Schmidt). The 

 greater portion is probably broken up into products simpler than 

 the purins. (See also p. 407.) 



Heteroxanthin or 7-methyl xanthin, CjH^NPj, was isolated 

 from urine in 1884 by Salomon, and again in 1893 by Balke. The 

 amount present constitutes about two-thirds of that of 1 -methyl 

 xanthin (p. 389). It is a remarkable fact that this base occurs in 

 dog's urine unaccompanied by paraxanthin, and the same seems to 

 hold true for the urine of leucocythaemic persons. Salomon examined 

 the liver, muscles, and kidneys of a dog, but was unable to obtain any 

 heteroxanthin or paraxanthin, and the total amount of xanthin bodies 

 present was about normal. For that reason he inclined to the belief 

 that these two bases may possibly have their origin in the kidney. 

 A certain amount of heteroxanthin may unquestionably be derived 

 from the corresponding guanin derivative — epiguanin (p. 386) ; and its 

 presence in normal dog's urine would indicate that it is in part a 

 product of the metabolism of nuclein. The greater part of the 

 heteroxanthin is known, however, to result from the cleavage of 

 higher homologues present in the food such as caffein and theo- 

 bromin (p. 406). 



Paraxanthin and heteroxanthin are not present in the urine or 

 kidneys of the cow. Salomon found this base in the urine of one out 

 of two leuksemic patients; in one with splenic tumor, and three 

 times out of ten normal urines. The amount of xanthin bodies 

 present in the urine is unaffected by phosphorus poisoning. Unlike 

 the other xanthin bodies, heteroxanthin has not as yet been isolated 

 from plants, meat extract, or guano. Neither it or paraxanthin 

 have been found in bull's testicles (Inoko). 



Heteroxanthin has been prepared synthetically by Fischer* out of 

 theobromin. "With phosphorus oxychlorid this yields a 7-methyl 

 2-6-dichlorpurin which on heating with concentrated hydrochloric 

 acid gives heteroxanthin. With slight modification the same method 

 yields paraxanthin, 7-methyl hypoxanthin, 7-methyl guanin, and 

 1-7-dimethyl guanin. A similar transformation of theobromin into 

 heteroxanthin occurs in the animal body, the methyl group in posi- 

 tion three being usually least firmly held in place. Heteroxanthin 

 can be readily methylated to theobromin and to caffein. 



Heteroxanthin forms a white amorphous powder, which some- 

 times on prolonged contact with water forms microscopic crystalline 



^Berichte, 30, 2400. 



