Effects of the Interaction of Tannins with Co-existing Substances. I. Inhibitory Effects of Tannins on Cupric Ion-catalyzed Autoxidation of Ascorbic Acid

Abstract
Inhibitory effects of tannins on Cu2+-catalyzed autoxidation of ascorbic acid were examined. Tannic acid JP and geraniin were much more effective than the related polyphenols of smaller molecules, e.g. gallic acid and pyrogallol. Geraniin had a stronger antioxidative effect than tannic acid JP. This result is attributable to the possible chelation between the potential triketone moiety in geraniin, and the metal ion. The quantitative analysis of ascorbic acid in the reaction mixture was carried out by dual wavelength TLC-densitometry which gave reproducible results in the presence of polyphenols. Tannins are common in many chinese folk medicines and may have physiological effects.

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