212 ASCORBIC ACID 



due to a more rapid inactivation of oxidase enzymes by heat than by the 

 faulty techniques employed for extraction in the cold.^'^ When proper pre- 

 cautions are observed to prevent oxidation of ascorbic acid, there is little 

 evidence of any increase of ascorl)ic acid on heating; in fact the reverse is 

 true. A bound form of ascorbic acid was alleged to have been isolated from 

 cabbage and cauliflower/ but later workers have not confirmed this J 



1. Site of Formation 



It is not known whether ascorbic acid is synthesized in any one tissue or 

 is capable of being synthesized by all tissues in either the plant or animal. 

 In animal tissues it has been suggested that ascorbic acid is synthesized 

 in both intestinaP and liver tissue,^ although the evidence so far available 

 favors the liver as the site of formation. The recent alternative suggestion 

 that the suprarenal gland may be the chief organ in the animal synthesizing 

 ascorbic acid is based on the experimental observation that the ascorbic 

 acid excreted by rats after adrenalectomy falls to very low values.^ In 

 intact animals the greatest excretion of the vitamin occurred just prior to 

 sexual maturity, suggesting that the activity of endocrine glands other 

 than the adrenal may also influence the synthesis. Histochemical studies of 

 the animal cell have shown that ascorbic acid appears in highest concen- 

 tration in the Golgi apparatus and mitochondria, i" and in scorbutic animals 

 these constituents of the cell show changes which are rectified on the addi- 

 tion of ascorbic acid." There is no evidence to suggest, however, that ascor- 

 bic acid is synthesized in these structures. 



All plant tissues contain ascorbic acid except woody tissues; seeds are 

 also devoid of it, but the vitamin is formed in the early stages of germina- 

 tion.^2 In the later development of the plant, ascorbic acid is formed continu- 

 ally in the green organs,^^- ^"^ and rmmerous attempts have been made to 

 identify the chloroplasts as the sites of ascorbic acid synthesis. The reduc- 

 tion of AgNOs is said to occur only in the chloroplasts,^* and this action 



3 K. Wacholder and A. O. Kreut, Hoppe-Seyler's Z. physiol. Cheni. 264, 254 (1940). 



" A. Fujita and T. Ebihara, Biochem. J., 301, 229 (1939). 



6 L. J. Harris and M. Olliver, Biochem. J. 36, 155 (1942). 



6 B. Ghosh and B. C. Guha, J. Indian Chem. Soc. 16, 505 (1939). 



' F. Widenbauer and K. Koschorrech, Biochem. Z. 291, 209 (1937). 



«M. N. Rudra, Nature 144, 868 (1939). 



9M. E. Dumm and E. P. Ralli, Endocrinology 45, 188 (1949). 

 10 G. Bourne, Australian J. Exptl. Biol. Med. Sci. 13, 239 (1935). 

 " A. Miwa, Oriental J. Diseases Infants 26, 3 (1939). 

 12 L. J. Harris and S. N. Ray, Biochem. J. 27, 580 (1933). 

 " A. Giroud, R. Ratsimamanga, andC. P. Leblond, Compt. rend. soc. biol. 117, 612 



(1934). 

 »* L. Randoin, A. Giroud, and C. P. Leblond, Bull. soc. chim. biol. 17, 1649 (1935). 

 '^ A. Giroud, C. P. Leblond, and R. Ratsimamanga, Compt. rend. soc. biol. 117, 614 

 (1934). 



