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Flavonoids of Cocoa Inhibit Recombinant Human 5-Lipoxygenase

Recently flavonoids, such as epicatechin, have been reported to improve health. Flavonoids protect the cardiovascular system by endothelium-dependent relaxation, increase of prostacyclin release, inhibition of oxidation of low density lipoproteins and inhibition of platelet aggregation. Flavonoids also act as anti-inflammatory agents by scavenging peroxynitrite and modulation of expression and secretion of interleukins. The phytochemical epicatechin and its oligomer procyanidin are present in relative high quantities in cacao and cacao products such as chocolate. The intake of cacao results in an increased plasma level of epicatechin, and a reduced plasma level of proinflammatory cysteinyl leukotrienes. These leukotrienes are formed via the 5-lipoxygenase pathway of arachidonic acid metabolism. The biological activity of procyanidins is still unclear. Previous in vivo studies have showed only limited breakdown of procyanidins into epicatechin. The purpose of this study was to investigate if flavonoids (epicatechin and its polymers) in cacao regulated 5-lipoxygenase.

The enzyme 5-lipoxygenase was allowed to react with arachidonic acid while using different dosages of epicatechin. The researchers found that epicatechin reduced hydrolysis and production of byproducts in a dose-dependent manner. The enzyme 5-lipoxygenases catalyze the dioxygenation of arachidonic acid to 5-HpETE and the conversion of 5-HpETE to 5,6-LTA4. Epicatechin and small procyanidins inhibited both processes. Dimers of epicatechin showed also inhibitory effects whereas larger polymers showed little to no activity. Other studies have shown that the intake of cacao decreased the plasma levels of cysteinyl leukotrienes by 30 percent.

The study concluded that epicatechin and its low-molecular procyanidins inhibit 5-lipoxygenase, which might explain the anti-inflammatory action of cacao.

Source: T Schewe, H K?hn and H Sies. Flavonoids of Cocoa Inhibit Recombinant Human 5-Lipoxygenase. Journal of Nutrition. 132:1825-1829, 2002

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