358 INOSITOLS 



It is tempting to assume that inositol is synthesized from glucose in 

 plant tissues and that the reverse reaction can take place in the animal. 

 The fact remains, however, that up to the present no unequivocal experi- 

 ments to demonstrate either conversion have been reported. 



VII. Estimation of Inositol 



Although qualitative color tests for inositol (e.g., the Scherer test) have 

 been developed, none of them can be used for a quantitative determina- 

 tion of the vitamin. Neither is there a specific chemical reaction of any 

 sort by which inositol can be determined unequivocally in biological ma- 

 terial. This lack of specificity is due in part to the fact that there are a 

 number of biologically inactive isomers of inositol and in part to the simi- 

 larity of inositol to the sugars in structure and chemical reactivity. Any 

 chemical determination of inositol requires, therefore, a preliminary separa- 

 tion and purification of the vitamin to remove sugars. Such procedures 

 inevitably result in losses of material and are less desirable for a quantita- 

 tive determination of the vitamin than are the microbiological procedures 

 which require no separation of the vitamin from the tissues. The recently 

 developed paper chromatographic method, however, is a promising im- 

 provement in the chemical determination of inositol. 



A. BY ISOLATION 

 ARTHUR H. LIVERMORE 



The earliest methods for determination of inositol were developed before 

 it was recognized to be a vitamin. Scherer^ in 1850 discovered inositol in 

 animal tissues and determined its presence after precipitating it with basic 

 lead acetate, a reagent used also by many subsequent investigators. Scherer 

 found^ that, by treating the inositol first with nitric acid and then with 

 ammonia and calcium chloride and finally evaporating the solution, he 

 obtained a red-colored product. It has been shown that this colored com- 

 pound is a salt either of rhodizonic acid or of tetrahydroxyquinone.^' ^ 

 This test is quite specific for the inositol structure and has been used as a 

 qualitative test for inositol by many investigators (see, for example, Hutt 



'J. Scherer, Ann. Chem. Justus Liebigs 73, 322 (1850). 



2 J. Scherer, Ann. Chem. Justus Liebigs 81, 375 (1852); Beilsteins Handbuch der 

 Organischen Chemie VI, 1196 (1923). 



3 F. A. Hoglan and E. Bartow, /. Am. Chem. Soc. 62, 2397 (1940). 

 * P. W. Preisler and L. Berger, /. Am. Chem. Soc. 64, 67 (1942). 



