Ascorbic acid inferences

For convenience we have divided the studies into those that evaluate quantitative effects, that is, in vitro (Table III), and those in which inhibition of nitrosation is inferred from the absence of an expected toxic effect in intact animals (Table IV). It is remarkable that ascorbic acid is effective in systems as different as bacon fat and gastric juice. 

It is of interest to note that when solutions of ascorbic acid and the polymer which have been treated with a sequestering resin are allowed to react, the rate is much lower, indicating the importance of the role of the metal ions. A probable inference from this is that most if not all studies of oxidation effects of L-ascorbic acid have involved metal-ion catalysis (presumably by iron or copper ions). The function of the ascorbic acid in such systems would then be to regenerate the Fe or Cu ions which are the actual catalysts. In the reaction of iron(iii) with penicillamine, redox reactions involving molecular oxygen are observed in basic media with the formation of red complexes. In acid conditions, however, a less stable blue species is observed. 

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