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Journal of Nutrition Vol. 30 No. 3 September 1945, pp. 193-199
Copyright © 1945 by American Society for Nutrition
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Physiological Availability of the Vitamins

III. The Effect of Dietary Ascorbic Acid Oxidase1

Melvin Hochberg, Daniel Melnick and Bernard L. Oser

Food Research Laboratories, Inc., Long Island City, New York

In vitro tests have emphasized the rapidity with which the ascorbic acid oxidase in vegetables can oxidize ascorbic acid to and beyond the dehydroascorbic stage. Simple incubation of the dietary mixture at body temperature for a period of 6 hours resulted in a loss of approximately 60% of the biologically active vitamin. The amount of enzyme present in the homogenized diet was sufficient to catalyze oxidation of added ascorbic acid to and beyond the dehydroascorbic acid stage.

The results of the human availability study indicate that no greater destruction of either the naturally occurring ascorbic acid or of the extra ascorbic acid ingested takes place in vivo prior to absorption. Apparently ascorbic acid oxidase is destroyed or its activity is inhibited in the gastrointestinal tract. Oxidation of the vitamin to dehydroascorbic acid may have occurred but in view of the biological activity of this partially oxidized form of the vitamin, this is of no importance nutritionally.

1 Some of the results in this paper were presented in summary before the Division of Biological Chemistry at the 108th meeting of the American Chemical Society, New York, N. Y. The expenses of these studies were defrayed by a grant from Lever Brothers Company, Cambridge, Mass.

Manuscript received 11 April 1945.




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