n. (context chemistry English) Any of many compounds that are plant metabolites, being formally derived from flavone; they have antioxidant properties.
Chemically, they have the general structure of a 15-carbon skeleton, which consists of two phenyl rings (A and B) and heterocyclic ring (C). 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-phenyl chromen-4-one (3-phenyl-1,4- benzopyrone) structure
- neoflavonoids, derived from 4-phenyl coumarine (4-phenyl-1,2- benzopyrone) structure
The three flavonoid classes above are all ketone-containing compounds, and as such, are 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. The three cycle or heterocycles in the flavonoid backbone are generally called ring A, B and C. Ring A usually shows a phloroglucinol substitution pattern.