242 ASCORBIC ACID 



the biological action of folic acid, it provides a possible explanation of the 

 previously reported relationships between folic acid and ascorbic acid.^"'^^* 



8. Ascorbic Acid and Formation of Intercellular Substances 



AND Collagen 



Another well-founded function of ascorbic acid is its participation in the 

 formation of intercellular substances of cartilage, dentine, and bone, and 

 the collagen of fibrous tissues. The pathological symptoms of the scorbutic 

 state in which there is a disturbance of the metabolism which affects the 

 bones and teeth, and hemorrhagic lesions in other tissues, appear to be 

 associated with the basic fvmction of ascorbic acid. The biochemical ex- 

 planation of these pathological changes is still unknown and is therefore 

 outside the scope of this review. The marked decrease in the phosphatase 

 activity of scorbutic tissue may, however, be a contributory factor. 



V. Estimation 



MAMIE OLLIVER 



A. BIOLOGICAL METHODS 



The biological method for the estimation of vitamin C is specific for 

 antiscorbutic activity and, as such, can be accepted as the final standard of 

 reference in cases where it is suspected that the accuracy of the chemical 

 or physical procedures might be affected by the presence of interfering 

 substances. The biological test will measure the total amount of vitamin C 

 present, i.e., both in the reduced form of ascorbic acid itself and also in 

 the reversibly oxidized form of dehydroascorbic acid (the latter, however, 

 generally occurring in natural products in no more than relatively small 

 traces). The applicability of the biological method may be limited only if 

 the potency of the test material is too low for it to be measured accurately 

 or if the sample is poorly absorbed. 



Rats cannot be used as test animals for ascorbic acid assay oAving to their 

 ability to synthesize the vitamin, but guinea pigs have proved satisfactory. 

 A method based upon the determination of the minimum amount of sample 

 needed to prevent signs of scurvy in the guinea pig was originally devised 

 by Sherman and his coworkers.^- ^ The animals were fed on a basal diet 



1" C. A. Nichol and A. D. Welch, Proc. Soc. Exptl. Biol. Med. 74, 52 (1950). 

 i'8 Nutrition Rev. 7, 49 (1949). 



1 H. C. Sherman, V. K. LaMer, and H. L. Campholl, ./. Am. Chem.Soc. 44, 165 (1922). 



* H. C. Sherman and S. L. Smith, The Vitamins, 2nd ed. American Chemical 

 Society, Monograph Series, Chemical Catalog Co., New York, 1931. 



