Antioxidants catechins

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... 

Therefore depending upon the conditions used to simulate either in vitro or in vivo oxidation, catechins or other phenolic compounds display differences in their antioxidant properties. Catechins also limited the consumption of a-tocopherol, allowing it to act as a scavenger within cell membranes whilst the catechins scavenged aqueous peroxyl radicals near the membrane surface (Pietta and Simonetti, 1998). 

CHEN z Y and chan p t (1996) Antioxidative activity of green tea catechins in canola oil , Chem and Phsics of Lipids, 82, 163-72. 

KAJiMOTO G (1963) On the antioxidative components and antiseptic components in tea. Part 111. The synergistic action of caffeine to catechin components , Nihon Shokuhin... 

MATSuzAKi T and KARA Y (1985) Antioxidative activity of tea leaf catechins , JAgric Chem Soc Jpn, 59, 129-34. 

SCOTT B c, BUTLER J, HALLIWELL B and ARUOMA o I (1993) Evaluation of the antioxidant actions of ferulic acid and catechins , Free Radical Res Commun, 19, 241-53. 

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. 

TANG s z, KERRY J P, SHEEHAN D and BUCKLY D J (2002) Antioxidative mechanisms of tea catechins in chicken meat systems , Food Chem, 76, 45-51. 

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. 

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). 

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... 

CHEN z-Y, WANG L Y, CHAN p T, ZHANG z, CHUNG H Y and LIANG c (1998) Antioxidative activity of green tea catechin extract compared with that of rosemary extract, JAOCS, 75 (9), 1141-5. 

GUO Q, ZHAO B, SHEW s, Hou J, HU J and xiN w (1999) ESR study of the structure -antioxidant activity relationship of tea catechins and their epimers, Biochem Biophys Acta, 1427, 13-23. 

HUANG s w and frankel e n (1997) Antioxidant activity of tea catechins in different lipid systems, J Agric Food Chem, 45, 3033-8. 

PEDRiELLi p and SKIBSTED L H (2002) Antioxidant syneigy and regeneration effect of quercetin, (-)epicatechin, and (+)-catechin on a-tocopherol in homogeneous solutions of peroxidating methyl linoleate, JAgric Food Chem, 50, 7138-44. 

PEDRIELLI p, HOLKERi L M and SKIBSTED L H (2001b) Antioxidant activity of (+)-catechin. Rate constant for hydrogen atom transfer to peroxyl radicals, Eur Food Res Technol, 213, 405-8. 

Superoxide anion scavenging activity of the enzymatically synthesized poly(catechin) was evaluated. Poly(catechin), synthesized by HRP catalyst, greatly scavenged superoxide anion in a concentration-dependent manner, and almost completely scavenged at 200 p.M of a catechin unit concentration. The laccase-catalyzed synthesized poly(catechin) also showed excellent antioxidant property. Catechin showed pro-oxidant property in concentrations lower than 300 jlM. These results demonstrated that the enzymatically synthesized poly(catechin) possessed much higher potential for superoxide anion scavenging, compared with intact catechin. 

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