stylistic:style_transfer, linguistic:voice_change, structural:expansion
Flavonoids are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids have the general structure of a 15-carbon skeleton, which consists of two phenyl rings and a heterocyclic ring. 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
  - neoflavonoids, derived from 4-phenylcoumarin (4-phenyl-1,2-benzopyrone) structure The three flavonoid classes above are all ketone-containing compounds and as such, anthoxanthins. 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 cycles or heterocycles in the flavonoid backbone are generally called ring A, B, and C. Ring A usually shows a phloroglucinol substitution pattern.