346 INOSITOLS 



phosphate has been isolated as an hydrolysis product of the phosphatides 

 from the tubercle bacillus^^ and from soybean.^* However, inositol diphos- 

 phate was obtained by Folch*^ from brain phosphatide. Periodate oxidation 

 demonstrated that the phosphate groups were in meta position to one an- 

 other. The brain phosphatide contains, in addition to inositol diphosphate, 

 an equimolar proportion of fatty acid (of rather high equivalent weight) 

 and glycerol. Soybean "lipositol"^^ was found to contain m^/o-inositol, 

 galactose, oleic acid, a mixture of three saturated fatty acids — cerebronic, 

 palmitic, and stearic — phosphoric acid, L(-f) -tartaric acid, and smaller 

 quantities of ethanolamine. Folch^^^ has obtained from a purified soybean 

 phosphatide: inositol 2 (moles), carbohydrate (as galactose) 2, phosphoric 

 acid 2, glycerol 2, fatty acids 3, and amine 1. 



Claude^* has found that inositol is present in relatively high concentra- 

 tion in the mitochondria and submicroscopic particles (microsomes) of 

 the liver cell. Approximately 40 to 45 % of the dry weight of the microsomes 

 is lipid material, and 2 % of this is inositol. Claude calculates that, if all 

 the inositol were bound as "lipositol," this component would comprise 

 more than one-fourth of the total lipid and almost one-half of the phos- 

 pholipid. 



b. Phytic Acid 



In plant materials, and especially in the seeds of the grasses, a major 

 part of the inositol is present as the hexaphosphoric ester. ^^'^^ This com- 

 pound is called phytic acid, and its mixed calcium and magnesium salt is 

 called phytin. The phytic acid of corn is the source of commercial inositol 

 (Section III). Several possible formulas have been proposed for phytin or 

 phytic acid, including those in which adjacent phosphoric groups may 

 combine to form pyrophosphate linkages or in which hydroxyphosphoric 

 acid groups may be present. 



Although a specific biological function for this compound has not been 

 established, it is known to act as a reservoir of phosphate which becomes 

 available to the young plant at germination. Complexes between phytic 

 acid and animal or plant proteins have been obtained by a number of 

 workers. However, it appears likely that these are merely non-specific 

 combinations, for the phytic acid may be separated by dialysis.^* 



" J. Folch and D. W. WooUey, /. Biol. Chem. 142, 963 (1942). 



« J. Folch, J. Biol. Chem. 177, 505 (1949). 



^' L. B. Macpherson and C. C. Lucas, Federation Proc. 6, 273 (1947). 



"a J. Folch, Federation Proc. 6, 252 (1947). 



5" A. Claude, J. Exptl. Med. 84, 61 (1946). 



66 S. Posternak, Compt. rend. 137, 202 337, 439 (1903). 



66 C. Neuberg, Biochem. Z. 9, 557 (1908). 



" R. J. Anderson, J. Biol. Chem. 44, 429 (1920). 



68 J. Bourdillon, /. Biol. Chem. 189, 65 (1951). 



