Flavonoid

Flavonoids (or bioflavonoids; from the Latin word flavus, meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants. Blackberry, black currant, chokeberry, and red cabbage are examples of plants with rich contents of flavonoids. In plant biology, flavonoids fulfill diverse functions, including attraction of pollinating insects, antioxidant protection against ultraviolet light, deterrence of environmental stresses and pathogens, and regulation of cell growth. Although commonly consumed in human and animal plant foods and in dietary supplements, flavonoids are not considered to be nutrients or biological antioxidants essential to body functions, and have no established effects on human health or prevention of diseases. Chemically, flavonoids have the general structure of a 15-carbon skeleton consisting of two phenyl rings (A and B) and a heterocyclic ring (C, the ring containing the embedded oxygen). This carbon structure can be abbreviated C6-C3-C6. According to the IUPAC nomenclature, they can be classified into flavonoids or bioflavonoids, isoflavonoids, derived from 3-phenylchromen-4-one (3-phenyl-1,4-benzopyrone) structure, and neoflavonoids, derived from 4-phenylcoumarin (4-phenyl-1,2-benzopyrone) structure. As ketone-containing compounds, the three flavonoid classes are grouped as anthoxanthins (flavones and flavonols). This class was the first to be termed bioflavonoids. The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds, which are more specifically termed flavanoids.