On the chemical oxidation of berberine

Berberine is an antiseptic isolated from several plants. Klunge proposed a test for identification of this four ring isoquinoline alkaloid. He used a solution of berberine, chlorine water and hydrochloric acid or sulphuric acid, obtaining a red colour. In this communication the reaction route to the oxidation product is described. There is a ionic mechanism that ends in a red ortho-benzoquinone. The key intermediate displays an organic hypochlorite and a hemiacetal with a hydroxymethyl group. The reactive species in this oxidation process is hypochlorous acidium ion. Finally, interaction with a hydrion degrades the molecule, giving a red o-benzoquinone, the colour observed in the test, plus formaldehyde. The quinone has been obtained by electrochemical oxidation of berberine, a much more complicated method than a simple and rapid chemical test. A second oxidation product was obtained electrochemically, involving oxidation of the methylene in the five member ring to carbonyl. We provide a synthesis of this compound.