Cocoa is rich in antioxidant polyphenols. Recently polyphenols, mainly flavonoids, received a lot of interest of scientists. Flavonoids have many health benefits. They are antioxidants and scavenge free radicals. Flavonoids have also non-antioxidant functions and can directly influence some enzymatic systems. This study is about the influence of cacao polyphenols on leukotriene and nitric oxide metabolism and on myeloperoxidase-induced modification of low density lipoproteins. Leukotrienes are important agents in the inflammatory response. Leukotrienes are derived from arachidonic acid by the enzyme 5-lipoxygenase. Some leuktronies have a chemotactic effect and help to attract neutrophils to tissue. Leukotrienes can also cause vasoconstriction and increase vascular permeability. Nitric oxide is an important signalling molecule. The endothelium of blood vessels releases nitric oxide to signal the surrounding smooth muscle to relax, resulting dilated blood vessels and increased blood flow. Previous studies have indicated that cacao decreased plasma levels of proinflammatory cysteinyl leukotrienes.
The aim of this study was to investigate if cocoa polyphenols interact with arachidonic acid metabolism and inhibit human 5-lipoxygenase. In vitro tests showed that epicatechin and other flavan-3-ols inhibited 5-lipoxygenase, which implies that these phytochemicals may have anti-leukotriene action. Not only epicatechin but also the oligomeric procyanidins inhibited the lipoxygenases.
Myeloperoxidase is another oxidant enzyme in the process of inflammation and atherogenesis. When phagocytes, such as macrophages, are activated by inflammatory stimuli, they release myeloperoxidase into the extracellular space. This release of myeloperoxidase also occurs in atherosclerotic lesions. Myeloperoxidase interacts with low density lipoproteins and catalysis oxidation. Studies have shown that epicatechin, procyanidins and other flavonoids inhibit this oxidation process.
A test was carried out on 20 persons with risk for cardiovascular diseases. They received either a placebo drink, a cacao drink low in flavan-3-ols or a cacao drink high in flavan-3-ols. The researchers found that only the cocoa drink with high levels of flavan3-ol caused a significant increase of nitroso compounds in the serum and flow-mediated dilation of the brachial artery.
Oxidation of low density lipoproteins is the first step of atherogenesis. Myeloperoxidase is a mediator in this oxidation process. Epicatechin or other cacao flavonoids surpressed myeloperoxidase, resulting in reduced oxidation of low density lipoproteins.