THK I'JlOai'llATIDIC ACIOS 407 



the leaves of plants oilier than cabbuj^e and s[)inach have not been investi- 

 gated. 



(i) Structure of the PhoKphatidic Acids 



On tiic basis of analyses and molecular weight determinations, it has 

 been proved that phosphatidic acid is a diglyceride phosphoric acid. It is 

 probable that it may exist in either the a- or the j8-form, depending upon 

 the position at which the phosphoric acid is attached. Chibnall and 

 Channon,'" suggested that it is probably an a-compound, since it was 

 shown that the barium salt of the glycerophosphate isolated was optically 

 acti\'e; however, Karrer and Salomon'* suggest that this may not be the 

 case. 



HgCOCR HjCGCR 



10, , 'l /OH 



HCOCR -„ HCO-P=0 



H rn /n I ^OH 



H,CO-P=0 h,C0\r' 



a-Pliosphatidic /3-Phosphatidic 



acid acid 



Apparently a large number of phosphatidic acids may exist, since at 

 least four component fatty acids have been reported. These include pal- 

 mitic, stearic, linoleic, and linclenic acids; no arachidonic acid has as yet 

 been found. The unsaturated greatly exceed the saturated acids. It is 

 therefore believed that there must be phosphatidic acids containing only 

 unsaturated acids in the animal body. Synthetic Q;,/3-distearoglycerophos- 

 phoric acid was first prepared by Hundeshagen in 1883,^* while Wadsworth 

 et aU^'' were able to synthesize the calcium salts of phosphatidic acid 

 through repeated treatment of the phosphatides from blood plasma with 

 0.5 A^ hydrochloric acid to remove the organic base, after which the calcium 

 was introduced into the molecule by treatment with calcium chloride and 

 ammonia. 



(2) Preparation of the Phosphatidic Acids 



The cytoplasm is first prepared from cabbage leaves by macerating them. 

 They are then washed with water, are allowed to drain through a fine sieve, 

 and the residue is warmed to 70°C The coagulum which forms is pressed 

 dry in the Buchner press. The cytoplasm so obtained is a green hard 

 mass which can be pulverized and extracted in a Soxhlet extractor, in spite 

 of the fact that it contains 40% of water. After extraction with ether for 

 40 hours, it is further treated with warm alcohol, which dissolves only a 

 small amount of material and no phosphatides. The ether residue is a 



"5^ .v. \V;uls\vurtli, Iv Mallaiier, and E. Maltancr, Am. J. Ph!/fiiol.,SO, 502-521 (1927). 



