Vitamin C in Vegetables

The oxidation of ascorbic acid to dehydroascorbic acid may be cat,alyzed by copper (1, 8)) by ot,her metals (11) and metallic compounds, by norit charcoal (5)) and by an enzyme or enzyme complex (12, 13). The dehydroascorbic acid has an antiscorbutic activity similar to that of ascorbic acid (6) and may be reduced to the latter by the use of H,S and other reductants (14) The existence of ascorbic acid oxidase in cabbage leaves was shown by Szent-GyGrgyi (12) in 1931. Tauber, Kleiner? and Mishkind (13) prepared from Hubbard squash a highly actrive enzyme which is claimed to be specific for ascorbic acid inasmuch as it does not catalyze the oxidation of cysteine, tyrosine, glutathione, and phenols. The ascorbic acid may further change into a compound which cannot be reduced to ascorbic acid and which is inactive as an antiscorbutic agent,. According to Borsook and Jeffreys (3), this compound, yet unidentified, is not an oxidation product. The present paper deals with the enzyme complex participating in the oxidation of ascorbic acid in spinach, beans, peas, pumpkin, turnips, and cabbage. Results of experiments dealing with the thermal inactivation of the enzyme are presented and the practical importance of the enzyme from the standpoint of nutrition and food preservation is discussed.