Catechins antioxidative effects

TANG s z, KERRY J p, SHEEHAN D, BUCKLY D J and MORRISSEY p A (2001) Antioxidative effect of dietary tea catechins on lipid oxidation of long-term frozen stored chicken meat , Meat Sci, 56, 285-90. 

Flavonoids are chain-breaking antioxidants in lipid-like solvents like chlorobenzene, although the k(inh) is smaller than for a-tocopherol and the lag-phase accordingly less evident. For peroxidating lipids in chlorobenzene the clear lag-phase for a-tocopherol became longer when quercetin or catechin were present. The effect appears to be additive and a regeneration of a-tocopherol by quercetin or catechin in this lipid-like solvent should rather be termed a co-antioxidative effect (Pedrielli and Skibsted, 2002). 

Yoneda T, Hiramatsu M, Sakamoto M, Togasaki K, Komatsu M, Yamaguchi K. 1995. Antioxidant effects of beta catechin. Biochem Mol Biol Int 35 995-1008. 

Miyazawa T. Absorption, metabolism and antioxidative effects of tea catechins in humans. Biofactors 2000 13 55-59. 

Antioxidants such as a-tocopherol, ascorbic acid and tea catechin can effectively inhibit the oxidation of vegetable oils and development of rancidity in food lipids. However, it has been difficult to protect fish oils containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) against oxidative deterioration and an effective antioxidant method for fish oils is required. As shown in Figure 5, oxidation of ethyl DHA was completely inhibited in the cathodic solution, although it was more easily oxidized in distilled water or in the NaCl solution, therefore, the cathodic solution may be useful as an effective antioxidant for fish oils. 

Biological Antioxidant Models. Tea extracts, tea polyphenol fractions, and purified catechins have all been shown to be effective antioxidants in biologically-based model systems. A balance between oxidants and antioxidants is critical for maintenance of homeostasis. Imbalances between free radicals and antioxidants may be caused by an increased production of free radicals or decreased effectiveness of the antioxidants within the reaction system. These imbalances can be caused by the radicals overwhelming the antioxidants within the system, or by an excess of antioxidants leading to a prooxidant functionaHty (105—118). When antioxidant defense systems are consistently overwhelmed by oxidative reactions, significant damage can... 

Nowadays, consumers would like those antioxidants present in food products not only to stabilise food lipids, but also to be absorbed through the intestinal wall and protect the lipids of blood plasma against oxidation. This effect is relatively evident in the case of tocopherols (which are liposoluble) or ascorbic acid (which is hydrophilic), but much less evidence is available on antioxidants of medium polarity, such as flavonoids, rosemary oleoresins or green or black tea catechins. 

NICOLI M c, CALLIGARIS s and MANZOCCO L (2000) Effect of enzymatic and chemical oxidation on the antioxidant capacity of catechin model systems and apple derivatives , JAgric Food Chem, 48 (10) 4576-80. 

Anthocyanins and anthocyanidins, compounds present with high structural diversity in fruits and wines, showed a pattern as antioxidants different from that of the tea catechins with respect to the effect of substituents. In a liposomal model system induced peroxidation was inhibited increasingly by anthocyanins/ anthocyanidins with an increasing number of hydroxyl groups in the B-ring (Fig. 16.6), while the opposite was seen for the catechins (Seeram and Nair, 2002). For anthocyanidins, the presence of a 3-hydroxy group is important... 

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