Extraction-Spectrophotometric Determination of Berberine in Crude Drugs by the Formation of a New Ion Associate

Abstract

A sensitive and selective method based on the formation of ternary complexes of berberine, quinidine and a divalent anion of dibasic acid dyes (A^2-) such as Bromophenol Blue, Bromochlorophenol Blue and Bromocresol Green is described. Berberine was extracted in large amounts into 1, 2-dichloroethane with A^2-; only in the presence of quinidine in a neutral aqueous media. Berberine could react in 1, 2-dichloroethane with A^2- to give a blue product. In addition, the extractability of Berberine in a neutral aqueous media could be enhanced by the formation of bulky ternary complexes (berberine⁺-A^2--quinidine⁺); the selectivity was improved because most of the amines and alkaloids did not react with A^2- in the above-mentioned media. The blue complexes can be used for a sensitive and selective spectrophotometric determination of berberine in crude drugs.