Document: The medicinal properties of plants are due to its chemicals. Plants synthesize many compounds called primary metabolites that are essential to their existence. These include proteins, lipids and carbohydrates that are used for subsistence and reproduction; in not only the plant itself but also the animals that feed on them. In addition, plants synthesize an extraordinary range of other compounds, called secondary metabolites, whose functions are far from being unanimously accepted. Many secondary metabolites can be broadly considered to be "antibiotics" as they protect plants against fungi, bacteria, animals and even other plants. Secondary metabolites include two types of compounds: phenol and flavonoids compounds. Phenol compound are involved in plant-plant interactions (allelopathy, and inhibitions of both germination and growth). These compounds include lignin, flavonoids, phenylpropanoids, anthocyanins and "nitrogen compounds including alkaloids and glycosides. Recently, Phenol compounds have drawn much attention due to their antioxidants properties and their potential beneficial implications for human health, such as the treatment and the prevention of cancer, cardiovascular disease and other inflammatory diseases. Polyphenol are composed of various phenol compounds such as phenolic acid, catechins, flavonoids, and tannins. Phenols, which are aromatic organic compounds, are present in many plants. They usually have antiseptic, antibacterial actions. The simplest is phenol (an antimicrobial) present in thyme oil. The phenolic acids have antioxidant and protective effects against cardiovascular disease and cancer. Other phenols have analgesics, anti-inflammatory, cholesterol-lowering, hypotensive, anticoagulant, anti-allergenic, hypotensive, and hepato-protective effects [10] . Flavonoids are pigments giving color to flowers and are present in some leaves. These substances can be yellow (origin of the word Flav), red, blue or purple. The main properties of flavonoids are their veinotonic, protective (vessels), anti-cholesterol or antioxidants effects [11, 12] . Tannins are phenol compounds that precipitate proteins. These complex compounds may be soluble in water or alcohol, are the flavonoid family. Tannins are widely distributed in the plant kingdom. They are common both in gymnosperms and angiosperms. Within angiosperms, tannins are more common in dicotyledons than they are in monocotyledons. Tannins can be found mainly in the cortex, roots, fruits and leaves. They have especially astringent properties. Tannins are mainly used externally, particularly to treat patients with injuries, wounds or hemorrhoids. Internally they are also used to treat patients with diarrhea and gastroenteritis. Tannins also exhibit antioxidant and antibacterial properties [13] . Catechin is a molecule of the flavonoid family; the name comes from the fact that this molecular compounds found in the fruits of Acacia catechu. Catechins are astringent juices from various sources and involve decoction of the fruit of Areca catechu L. (Palms), and the wood of the Acacia catechu. Catechins are present in significant quantities in green tea. The fermentation of the leaves being stopped soon after harvest, they are barely oxidized, which is the reason that green tea retains most of its original catechins , which gives them their slightly bitter and astringent taste. Green tea con-tains flavonoids 70% of which are catechins. Interesting amounts of catechins also e
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