Spectroscopic and pulse radiolysis studies of the antioxidant properties of (+)catechin: metal chelation and oxidizing radical scavenging

Abstract

Catechin (5,7,3 ,4 -tetrahydroxyflavan-3-ol, Cat), a compound suggested to give protection to living organisms both by direct scavenging of free radicals and metal chelation, was investigated in the presence of Zn(II) and Cu(II) ions by different techniques.The UV/vis, Raman and IR studies were useful to assess the chelation sites, the relevant interaction of Cat with Cu(II) ions, as well as the weak affinity with Zn(II). Cat acts as a bidentate ligand through the catechol moiety on B-ring, but the metal complex structure depends on the metal. In particular, some autoxidation processes may be involved in the formation of the Cu-Cat complexes. The protonation state of the B-ring plays an important role both in metal chelation and scavenging activity of Cat.Information on the reactivity of the free Cat towards oxidizing radicals with different redox properties were obtained by pulse radiolysis. In all cases the relatively stable phenoxyl radicals resulted to be formed.

Studies on the Interaction between Catechin and Metal Ions

“…7 Various metal ions such as Cu , and Ca 2+ exist in the human body. These divalent metal ions are vital for all type of biological functions such as gene expression, apoptosis, enzyme regulation and neurotransmission.…”

“…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.…”

Spectroscopic Study on the Anti-oxidant Properties of Flavonoid Galangin

“…They are contained in green tea, red wine and numerous fruits and vegetables. [9][10][11] Catechin (5,7,3',4'-tetrahydroxyflavan-3-ol), the major constituent of green tea, is one of the flavanol compounds. This substance is a polyphenolic compound in which there are 5 hydroxyl groups.…”

The Relationships between Dyeing Methods and Dyeability in Hair Colouring by Utilising Enzymatic Oxidation of (+)-Catechin

“…The (+)-catechin ((+)-(2R,3S)-5,7,3',4'-tetrahydroxyflavan-3-ol; Cat Figure 1(a)) is one of the flavonoids extracted from tea plants, gambir (Uncaria gambir), areca (Areca catechu) and so on. The Cat shows reductive action and its catechol group forms complexes with metal ions [5] [6].…”