450 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



acid is combined. The structures of the a- and /3-phosphatidylserine are 

 represented in the accompanying formulas. 



HjCO-CR H,CO-CR 



HCO-CR' HCO-P-OCH,CHCOOH 



H3CO-P-OCH3CHCOOH H.COCR' NHj 



a-Phosphatidyl- /3-Pliosphatidyl- 



serine serine 



(4) Inositol Phosphatides 



The occurrence of inositol as a component of soybean phosphatides was 

 discovered by Klenk and Sakai,^"^ although Anderson ^^^ had previously 

 proved that this lipid was present in tubercle bacilli. Folch and Woolley^^ 

 were the first to demonstrate inositol as a constituent of an animal phospha- 

 tide which was isolated both from the brain and from the spinal cord. It 

 was noted that the so-called brain cephalin was especially rich in this sub- 

 stance. The inositol-containing phosphatide was prepared as a friable 

 white powder which contained 4.5% of phosphorus and about 1% of nitro- 

 gen, all of which was in the form of amino nitrogen. The inositol content 

 varied between 6.8 and 8.6%, although one preparation contained as much 

 as 10%. About one-fourth of the brain cephalin, or 0.4% of the net weight 

 of the brain, was found to be made up of the inositol-containing phospho- 

 hpid. 



By the use of fractional precipitation of a chloroform solution of brain 

 cephalin with increasing proportions of alcohol, Folch^^ was able to separate 

 practically pure inositol phosphatide in the portion which was least soluble 

 in alcohol. Glycerophosphoric acid and serine were prepared from this 

 fraction. It was believed that the presence of serine indicated that the 

 product was contaminated with phosphatidylserine. 



Woolley,^"* using the Folch method^^ for the fractionation of the phospha- 

 tides, prepared an inositol-containing lipid from soybean oil which contained 

 as much as 16% of inositol. It was found to contain carbohydrate, oleic 

 acid, phosphorus, and inositol in approximately molecular ratios; therefore, 

 this author believed the preparation to be essentially pure. Because this 

 substance is a lipid which contains inositol, Woolley proposed calling the 

 product soybean lipositol. 



Although Woolley has not suggested a structural formula for lipositol, the 

 products of complete acid hydrolysis have been identified as inositol, phos- 

 phoric acid, oleic acid, saturated fatty acids, a black, humin-like material, 



302 E. Klenk and R. Sakai, Z. physiol. Chem., 258, 33-38 (1939). 



303 R. J, Anderson, J. Am. Chem. Soc, 52, 1607-1608 (1930). 

 «>* D. W. Woolley, J. Biol. Chem., I47, 581-591 (1943). 



