Isoalloxazine

Isoalloxazine is the structural foundation of flavins such as riboflavin (vitamin B2) and is a heterocyclic compound.

[2] It has a tricyclic structure which means it has three interconnected rings of atoms and is a tautomer of alloxazine.

[1] The structure is formed by primary-secondary aromatic o-diamines and they are a high-melting crystalline substance.

[1] The R-group is used to attach various flavin groups It has a similar structure to pteridines which has two interconnected rings.

Isoalloxazine rings can exist in different redox and ionization states depending on the chemistry of FMN and FAD associated with it.

Isoalloxazine Structure
Ionization and redox states of the isoalloxazine ring