Page 12 - CS06_Hudz

 Various subgroups of flavonoids are classified according to the
substitution patterns of ring C. Both the oxidation state of
the heterocyclic ring and the position of ring B are important
in the classification.

 The chemical structure of flavonoids is based on a C 15 skeleton
with a pyrane ring bearing a second aromatic ring B in

position 2, 3 or 4. Pyrane, condensed with ring A, forms flavan
(phenylbenzopyrane). Oxidized flavan has in its structure g-
pyrone.

 All flavonoids – approximately 4000 – have a common
biosynthetic origin, and therefore possess the same basic
structural element, namely the 2-phenylchromane skeleton.

flavan (2-phenylchromane, 2-
phenylbenzopyrane)

Principles of classification