Tannins as hydrogen carriers in biological oxidation.

EVIDENCE has been piresented [Roberts, 1939; 1940] which indicates that the effect of extensive bruising on tea leaf is to decrease the activity of the H-carrying coenzymes (cozymase). In the so-called tea fermentation which follows this bruising, it was established that carbohydrate oxidation, as measured by the rate of CO2 production, parallels tannin oxidation. Further, if excess ascorbic acid be added to the system the primary oxidation product of tea tanpin is reduced again immediately on its formation, and until the whole of the ascorbic acid has been oxidized no carbohydrate oxidation is apparent. These observations led to the conclusion that in tea fermentation, the tannin acted as one of the H-carriers in the oxidative stages of carbohydrate breakdown. The possibility that cozymase was completely or almost completely inactivated by mechanical damage to the leafwas not considered, as it was believed that an o-quinone could not function as a H-acceptor in the absence of cozymase (Co). The later stages in the reactions in dilute suspensions of minced tea leaf were therefore considered to be