CHAPTER IX 



Citric Acid and Inositol 



Citric acid. Occurrence and distribution. Influence of male sex hormone. 

 Citric acid in the female prostate. Metabolism and role of seminal citric 

 acid. 



Inositol. Occurrence and distribution. mesolnosiioX as a major con- 

 stituent of the seminal vesicle secretion in the boar. Physiological function. 

 Relation to other seminal constituents. 



Citric acid and inositol which will be considered jointly in this 

 chapter, are both macro-constituents of the seminal plasma. In the 

 past these two chemical substances, much like fructose, have re- 

 ceived attention chiefly from plant biochemists, not unnaturally, 

 since they occur in plants in much larger quantities and more 

 commonly than in the animal kingdom. Similarly, ergothioneine was 

 at first associated only with the fungi, until at a much later date 

 small amounts of it have been detected in red blood cells and more 

 recently, it was found to be a normal constituent of boar semen. 



CITRIC ACID 



Occurrence and distribution 



More than a century passed after Scheele's (1784) isolation of 

 crystalline citric acid from lemon juice before this tricarboxylic acid 

 was discovered in the animal body and identified as a major chemical 

 constituent of milk, urine, bone and semen. The discovery in semen 

 was made in Thunberg's laboratory at Lund, by Schersten (1929, 

 1936), who noted that semen rapidly decolorizes methylene blue on 

 addition of 'citrico-dehydrogenase', an enzyme prepared by Thun- 

 berg from cucumber seeds. This observation was strengthened by 

 chemical identification based on isolation of crystalline citric acid 

 and the preparation of pentabromoacetone, a derivative formed 

 from citric acid on oxidation with permanganate and bromine, in 



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