The influence of animal tissues on the oxidation of ascorbic acid

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Abstract
The reducing substances similar to ascorbic acid in normal and tumor tissue are unaltered in amt. by incubation of whole or minced tissue with or without phosphate or glucose for periods up to 4 hrs. at 37[degree]C. Small amts. of animal tissues or tissue extracts prevent the aerobic oxidation of ascorbic acid solns. Glutathione, cysteine, cystine and H2S prevent the aerobic oxidation of ascorbic acid, but protection by tissue extracts cannot be wholly explained by these facts. The protective activity of tissues is unaffected by iodoacetic acid, and dialyzed extracts retain their protective power in full. Protective properties are present, in reduced amt., in extracts which have been boiled, or precipitated with mercuric acetate or trichloracetic acid. Ascorbic acid is relatively stable in glass-distilled water. Cu, and to a less extent Fe, and especially mixtures of the 2, act as positive catalysts in the aerobic oxidation of ascorbic acid. Lemon juice contains no protective mechanism other than the low pH.