II. CHEMISTRY 181 



centrated samples of \itamiii C were found to vary in their activity, an ob- 

 servation which we can well understand, bearing in mind the labile nature 

 of \'itamin C, some of them were so active that it seems surprising that 

 they ditl not crystallize. At that time such samples could not be used by 

 the organic chemist for precise chemical investigations, but examination 

 of them enabled Zilva to establish the general properties of the vitamin. 

 It was clear from his investigations that the active principle was water- 

 soluble and that it was an organic substance with extremely strong re- 

 ducing properties which did not contain nitrogen. It was also recognized 

 that the acti\'e principle was probably related to the sugars and that solu- 

 tions of it readily decomposed when exposed to air and especially in the 

 presence of alkali.'' In making use of phenolindophenol to determine the 

 reducing power of \'itamin C concentrates, Zilva also made the signifi- 

 cant observation that the physiological activity was proportional to the re- 

 ducing power. He made the further discovery that freshly oxidized solutions 

 (which are now known to contain dehydroascorbic acid) still retained their 

 activity. It was this fact which led Zilva to point out that the reducing and 

 antiscorbutic properties might not arise from one and the same sub- 

 stance.^ This apparent anomaly was resolved by Tillmans, who was also 

 interested in the relationship between the antiscorbutic principle and the 

 reducing factor. He correctly concluded that the vitamin could be revers- 

 il)ly oxidized and that both the oxidized and the reduced forms were physio- 

 logically active.^"" 



WTiile the later stages of this work had been going on, Szent-Gyorgyi, 

 in investigating oxidation-reduction systems in plants and animals, suc- 

 ceeded in isolating from orange juice, from cabbage juice, from the adrenal 

 glands of oxen, and later from paparika a crystalline optically active sub- 

 stance with the formula CeHgOe . The substance was acidic in nature, it 

 exhibited very strong reducing properties, and it gave color tests charac- 

 teristic of the sugars. For these reasons he named it "hexuronic acid."'-' '' 

 The isolation by King shortly thereafter of an antiscorbutically active 

 crystalline substance from lemon juice, ^^ coupled with the demonstration by 



^ S. J. B. Connell and S. S. Zilva, Biochem. J. 18, 641 (1924). 

 » S. S. Zilva, Biochem. J. 21, 689 (1927). 

 » J. Tillmans, Z. Untersuch. Lebensm. 60, 34 (1930). 



1" J. Tillmans, P. Ilirsch, and W. Hirsch, Z. Untersuch. Lebensm.. 63, 1 (1932); J. 

 Tillmans, P. Ilirsch, and F. Siebert, ibid. 63, 21 (1932); J. Tillmans, P. Hirsch, and 

 J. Jackisch, ibid. 63, 241, 276 (1932); J. Tillmans, P. Hirsch, and H. Dick, ibid. 63, 

 267 (1932). 

 " J. Tillmans, P. Hinsch, and R. Vaubel, Z. Untersuch. Lebensm. 65, 145 (1933). 

 12 A. Szent-Gyorgyi, Biochem. J. 22, 1387 (1928). 

 '3 J. L. Svirbely and A. Szent-Gyorgyi, Biochem. J. 27, 279 (1933). 

 '^ W. A. Waugh and C. G. King, J. Biol. Chem. 97, 325 (1932). 



