Flavonoid
Flavonoids are a class of plant secondary metabolites. Flavonoids were referred to as Vitamin P from the mid-1930s to early 50s, but the term has since fallen out of use. According to the IUPAC nomenclature, they can be classified into: ▪
flavonoids or
bioflavonoids ▪
isoflavonoids, derived from 3-phenylchromen-4-one structure ▪
neoflavonoids, derived from 4-phenylcoumarine structure The three flavonoid classes above are all ketone-containing compounds, and as such, are 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 cycle or heterocycles in the flavonoid backbone are generally called ring A, B and C. Ring A usually shows a phloroglucinol substitution pattern.