Flavonoids

Flavonoid - From Wikipedia, the free encyclopedia

The term flavonoid refers to a class of plant secondary metabolites based around a phenylbenzopyrone structure. Flavonoids are most commonly known for their antioxidant activity. Flavonoids are also commonly referred to as bioflavonoids in the media – these terms are equivalent and interchangeable, since all flavonoids are biological in origin.

The flavonoid synthetic pathway begins with a product of glycolysis, phosphoenolpyruvate, entering into the Shikimate pathway to yield phenylalanine. Phenylalanine is the starting material of the phenylpropanoid metabolic pathway, from which 4-Coumaryl-CoA is produced. This can be combined with Malonyl-CoA to yield the true backbone of flavonoids, a group of compounds called chalcones. Ring-closure of these compounds results in the familiar form of flavonoids, a three-ringed phenolic structure (polyphenols). The metabolic pathway continues through a series of enzymatic modifications to yield flavanones → dihydroflavonols → anthocyanins. Along this pathway many products can be formed, including the flavonols, flavan-3-ols, proanthocyanidins (tannins) and a host of other polyphenolics.

Flavonoids are widely distributed in plants fulfilling many functions including producing yellow or red/blue pigmentation in flowers and protection from attack by microbes and insects. The widespread distribution of flavonoids, their variety and their relatively low toxicity compared to other active plant compounds (for instance alkaloids) mean that many animals, including humans, ingest significant quantities in their diet. Flavonoids have been found in high concentrations in butterflies and moths sequestered from dietary intake at the larval stage and then stored in adult tissues.

Flavonoids have been referred to as "nature's biological response modifiers" because of strong experimental evidence of their inherent ability to modify the body's reaction to allergens, viruses, and carcinogens. They show anti-allergic, anti-inflammatory^[1] , anti-microbial and anti-cancer activity. In addition, flavonoids act as powerful antioxidants, protecting against oxidative and free radical damage.

Consumers and food manufacturers have become interested in flavonoids for their medicinal properties, especially their potential role in the prevention of cancers and cardiovascular disease. The beneficial effects of fruit, vegetables, and tea or even red wine have been attributed to flavonoid compounds rather than to known nutrients and vitamins.

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