360 INOSITOLS 



In order to differentiate between inositol and glycerol which might be 

 present in the solution, a titration is carried out 90 minutes after the start 

 of the periodate oxidation. At that time 100% of the glycerol but only 

 2 % of the inositol has been oxidized by the periodate. 



In an earlier application^- of the periodate oxidation method, the in- 

 ositol-periodate mixture was treated after 24 hours with 0.1 A'^ AS2O3 and 

 20 % KI, and 10 minutes later the excess AS2O3 was titrated with standard 

 iodine solution. 



More recently ^^ the CO 2 which was produced during the periodate oxi- 

 dation was determined in a Warburg apparatus. At 30°, between 1.1 and 1.3 

 moles of CO 2 were produced in 4 hours from 1 mole of inositol. Interfering 

 sugars were destroyed by heating the mixture with MgO at 100°. Lactic 

 acid was removed by alcohol and ether extractions. 



It would appear that at the low temperatures used by Piatt and Glock^" 

 there is little formation of CO2 (in 48 hours), whereas at the higher tem- 

 perature used by Fleury and Recoules^^ some CO2 is produced. The source 

 of the CO2 has been determined by Fleury, who has shown^ that oxidation 

 of inositol by periodate at 30° takes place in two steps. The first is a rapid 

 one in which 2 moles of formic acid and 2 moles of glycolic acid are formed, 

 within a few minutes, from each mole of inositol. This is followed by a 

 slow phase in which the glycolic acid is oxidized by the periodate according 

 to equation 2. This reaction is still incomplete after several days. 



2CH2OHCOOH + 40 -^ 2HC00H + 2CO2 + 2H2O (2) 



The possibility of estimating inositol by determining the amount of 

 glycolic acid formed during periodate oxidation led Fleury and his co- 

 workers to develop a semimicro method for determining this compound.®- ^* 

 In this method the violet color obtained by heating glycolic acid with 

 chromotropic acid and H2SO4 is measured. 



3. Other Chemical Methods 



The Hagedorn-Jensen method for determining sugars has been used for 

 inositol estimation. ^^ Also, inositol in the form of its hexaphosphate ester 

 (phytin) has been estimated'® by determining the amount of organic phos- 

 phate in a partially purified tissue extract. 



" P. Fleury and A. Recoules, Compl. rend. 227, 691 (1948). 



1* P. Fleury, J. E. Courtois, and R. Perles, Mikrochemie ver. Mikrochim. Acta 36/37, 

 863 (1951) [C. A. 45, 5073 (1951)]. 



15 W. R. Todd, J. Vreeland, J. Myers, and E. S. West, J. Biol. Chem. 127, 269 (1939). 



16 J. E. Courtois and C. Perez, Bull. soc. chim. biol. 30, 195 (1948). 



