362 INOSITOLS 



free vitamin, meso-inositol, has growth-promoting activity for yeast.^^-^^ 

 Bound forms, such as phytic acid and those occurring in Upids, are in- 

 active. For estimation of total inositol, therefore, hydrolysis of the sample 

 is essential. Treatment of the finely divided sample with 18% HCl under 

 reflux for 6 hours, followed by evaporation of excess HCl and neutralization 

 of the dissolved residue, is the method of choice.^^ 



Of the several suggested yeast growth procedures, an unpublished modi- 

 fication of the procedure of Atkin et al}^^ for determination of vitamin Be 

 is simple and highly satisfactory. Inositol is omitted from the basal medium, 

 and an excess of pyridoxine is added. Increased growth of the test organ- 

 ism, Saccharomyces carlshergensis 4228, in response to increased amounts 

 of inositol is obtained in the concentration range of to 1 7 of inositol per 

 milliliter. Incubation is for 18 to 24 hours, with shaking, at 30°. Other 

 details of the assay resemble those for vitamin Be assay with the same 

 organism,^^'' and have also been given in detail elsewhere.^^'' Good results are 

 also obtainable by the method of Woolley,^^ which employs a strain of 

 Saccharomyces cerevisae as the test organism; the basal medium, however, 

 is much more troublesome to prepare, and the method does not appear to 

 possess compensating advantages. 



A fundamentally different assay procedure for inositol is possible by use 

 of an inositol-less mutant of Neurospora crassa}^^' "" ' ^^ The amount of my- 

 celium formed in response to added inositol is determined by direct weigh- 

 ing after 3 days of incubation. Although the procedure appears accurate, 

 it is more tedious than yeast assay and requires considerably longer time. 



None of the lactic acid bacteria or artificially induced mutants of bac- 

 teria require inositol; indeed, it is not certain whether or not bacterial 

 cells contain any of this substance. Assay procedures that utilize such 

 organisms consequently are not available. 



28 D. W. Woolley, in Biological Symposia, XII. Estimation of the Vitamins, p. 279, 



Jaques Cattell Press, Lancaster, Pa., 1947. 

 2to L. Atkin, A. S. Schultz, W. L. Williams, and C. N. Frey, Ind. Eng. Chem. Anal. Ed. 



15, 141 (1943). 

 "b E. E. Snell, in Vitamin Methods, Vol. I, p. 327, Academic Press, New York, 1950. 

 " G. W. Beadle, /. Biol. Chem. 146, 109 (1942). 

 28 E. L. Tatum, M. G. Ritchie, E. V. Cowdry, and L. F. Wicks J. Biol. Chem. 163, 



675 (1946). 



