Anthocyanidin

Flavylium cation (Formula: C₁₅H₁₁O⁺, molar mass: 207.24 g/mol, exact mass : 207.08098995 u) with a benzopyrylium(chromenylium) component

Molecule in 3D of the anthocyanidin cyanidin

Not to be confused with anthocyanins, their sugar-containing counterparts.

Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion (chromenylium is referred also to as benzopyrylium). They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the 2-phenylchromenylium cation, also known as flavylium cation. As shown in the figure below, the phenyl group at the 2-position can carry different substituents. The counterion of the flavylium cation is mostly chloride. With this positive charge, the anthocyanidins differ from other flavonoids.

pH

The stability of anthocyanidins is dependant on pH. At a low pH (acidic conditions), colored anthocyanidins are present, whereas at a higher pH (basic conditions) the colorless chalcones forms are present.

Classification

3-Deoxyanthocyanidins are a class of anthocyanidins lacking an hydroxyl group on carbon 3.

Selected anthocyanidins and their substitutions

Anthocyanidin	Basic structure	R3'	R4'	R5'	R3	R5	R6	R7
Aurantinidin		−H	−OH	−H	−OH	−OH	−OH	−OH
Cyanidin		−OH	−OH	−H	−OH	−OH	−H	−OH
Delphinidin		−OH	−OH	−OH	−OH	−OH	−H	−OH
Europinidin		−OCH3	−OH	−OH	−OH	−OCH3	−H	−OH
Luteolinidin		−OH	−OH	−H	−H	−OH	−H	−OH
Pelargonidin		−H	−OH	−H	−OH	−OH	−H	−OH
Malvidin		−OCH3	−OH	−OCH3	−OH	−OH	−H	−OH
Peonidin		−OCH3	−OH	−H	−OH	−OH	−H	−OH
Petunidin		−OH	−OH	−OCH3	−OH	−OH	−H	−OH
Rosinidin		−OCH3	−OH	−H	−OH	−OH	−H	−OCH3