Spectroscopic Studies on the Oxidation of Catechin in Aqueous Solution

Abstract

The spectroscopic behavior of catechin (5,7,3',4'-tetrahydroxyflavan-3-ol), has been studied in the presence and the absence of air using UV-vis absorption spectrophotometry and fluorescence spectroscopy. The UV-vis absorption spectrum of catechin shows a very sharp and strong absorption maximum peak at 275 nm in deaerated water. New absorption maximum peaks appeared in aerated water, as well as in basic aqueous solution, caused by the oxidation of catechin. The absorbances in the UV-vis absorption spectrum of catechin decreased when the solution was left in the dark for a long time. The fluorescence emission spectrum of catechin after a long time period differs markedly from that in freshly prepared solution; the fluorescence maxia shifted as time passes after adding catechin to the solutions. When the deaerated basic catechin solutions were left in the dark for a long time, their fluorescence quantum yields were found to be nearly zero. This suggests that the oxidized catechin molecules were seen to have slowly undergone successive chemical reactions in basic buffer solution.

Determination of Total Phenolic Compounds in Common Beverages Using CdTe Quantum Dots

“…During the oxidation of catechin at high pH, the catechol moiety dissociates first yielding the ionic form, which subsequently undergoes oxidation leading to the formation of the quinoid form (Bark et al . ). The formed quinones are electron acceptors (Suchetti et al .…”

Studies on the Interaction between Catechin and Metal Ions

“…19 The solution did not display a yellowish color, even though it was left in the dark at room temperature…”

“…Some papers reported that oxidation of catechin is mainly carried out in the dissociation of catechol moiety in the initial state. 7,19 It might be therefore concluded that the -OH part of the catechol moiety bound to catechin molecule is first dissociated its anion form and then the ionized chemical species are converted into the oxidized form called quinones receiving help from metal ions.…”

Electrochemical Study of Trametes Versicolor Laccase Compatibility to Different Polyphenolic Substrates

“…The assumption that (+)-catechin (analogue of catechol) is a substrate for laccase Trametes versicolor was confirmed by the change of colour of the supporting electrolyte to yellow during cyclic voltammetry at the CPE/Laccase biosensor (not shown), which was caused by formation of (+)-catechin quinone [22,23]. This phenomenon was not observed at the bare CPE with the same working conditions.…”