224 



VITAMINS 



Chemical nature 



Vitamin C isolated in crystalline form from natural sources has been 

 named L-asc6rbic acid. Its chemical constitution is shown by the struc- 

 tural formula in the following equation, which also indicates how it is 

 converted into an oxidized form: 







II 



C 



I 

 COH 



COH 



I 

 HC 



O 



-2(H) 



L-ascorbic 



acid 

 ^ oxidase 

 * +2(H) 







II 



c 



I 



c=o 



I 



c=o 



I 



HC 







HOCH 



I 

 H2COH 



L-Ascorbic acid 

 (reduced form) 



HOCH 



H,COH 



L-Dehydroascorbic acid 

 (oxidized form) 



A close resemblance to the formulas of hexose sugars is evident. 



Vitamin C is readily oxidized by mild oxidizing agents, and, in fact, 

 its tendency to lose hydrogen atoms is so great that it is actually a strong 

 reducing agent. The vitamin may function in living tissues by virtue of 



Courtesy ol' Merck &. Co., Inc. 



Fig. 9-4. L-Ascorbic acid. 



