Cyanidin
Cyanidin is a natural organic compound. It is a particular type of anthocyanidin. It is a pigment found in many red berries including grapes, bilberry, blackberry, blueberry, cherry, cranberry, elderberry, hawthorn, loganberry, açai berry and raspberry. It can also be found in other fruits such as apples and plums, and in red cabbage and red onion. It has a characteristic reddish-purple color, though this can change with pH; solutions of the compound are red at pH < 3, violet at pH 7-8, and blue at pH > 11. In certain fruits, the highest concentrations of cyanidin are found in the seeds and skin. In a recent study, cyanidin was found to be a potent sirtuin 6 activator.List of cyanidin derivatives
Cyanidin can be synthesized in berry plants through the shikimate pathway and polyketide synthase III. The shikimate pathway is a biosynthetic pathways that uses the starting materials Phosphoenolpyruvic acid and Erythrose 4-phosphate to form shikimic acid, which then further reacts to form specific aromatic amino acids. L-phenylalanine, which is necessary in the production of cyanidin, is synthesized through the shikimate pathway.
In the synthesis of L-phenylalanine, chorismate undergoes a Claisen rearrangement by a Chorismate mutase enzyme to form prephenate. Prephenate undergoes dehydration, decarboxylation, and transamination with Pyridoxal phosphate and alpha-Ketoglutaric acid to form L-phenylalanine.
L-phenylalanine then undergoes an elimination of the primary amine with Phenylalanine ammonia-lyase to form cinnamate. Through an oxidation with oxygen gas and NADPH, a hydroxyl group is added to the para position of the aromatic ring. The compound then reacts with Coenzyme A, CoA ligase, and ATP to attach CoA to the carboxylic acid group. The compound reacts with naringenin-chalcone synthase and malonyl CoA to add three more keto groups to the benzene ring through PKS III. Aureusidin synthase catalyses the aromatization and cyclization of the newly added carbonyl groups and facilitates the release of CoA to reform the carboxylic acid. The compound then spontaneously cyclizes to form naringenin.
Naringenin is then converted to cyanidin through several oxidizing and reducing steps. First naringenin is reacted with two equivalents of oxygen gas, alpha-Ketogluteratic acid, and flavanone 3-hydroxylase to form dihydrokaempferol. The compound is then treated with NADPH and dihydroflavinol 4-reductase to form leucopelargonidin, which is further oxidized with oxygen gas, alpha-Ketogluteratic acid, and anthocyanidin synthase. This compound is spontaneously dehydrated to form cyanidin.
