Related Experiment Video
Updated: Jul 27, 2026

A Protocol for Detecting and Scavenging Gas-phase Free Radicals in Mainstream Cigarette Smoke
Published on: January 2, 2012
NMR Analytical Approach To Clarify the Antioxidative Molecular Mechanism of Catechins Using
1National Research Institute of Vegetables, Ornamental Plants and Tea, Kanaya, Shizuoka 428, Japan, and Research Laboratory of Marine Biological Science, Faculty of Agriculture, Shizuoka University, Mochimune, Shizuoka 421-01, Japan.
Abstract:
Each tea catechin was reacted with 1,1-diphenyl-2-picrylhydrazyl (DPPH), and the reaction mixture was subjected to NMR analysis. The antioxidation mechanism of (+)-catechin [(+)-C] is considered to be due to the change of the B-ring to an o-quinone structure at first because of the appearance of two carbonyl signals. This is substantiated by trapping the compound as an adduct of a 1,2-phenylenediamine to an o-quinone. (-)-Epicatechin [(-)-EC] was also confirmed to give a similar result, but in the case of (-)-epigallocatechin [(-)-EGC] and ethyl gallate (EG) no carbonyl signals were observed. The antioxidation mechanisms of (-)-EGC and EG are different from those of (+)-C and (-)-EC. This may be one of the reasons for the differences of the antioxidative activities between the two types of catechins.
More Related Videos
Related Concept Videos
Oxidation of Phenols to Quinones
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Radical Autoxidation

