Examination of alkaloidal constituents of zanthoxylum usambarense by a combination of ion-pair extraction and ion-pair chromatography using sodium perchlorate

Abstract

Quaternary alkaloids of the stem of Zanthoxylum usambarense, an important medicinal plant in Kenya utilized for the treatment of pneumonia and rheumatism, were examined by a combination of ion-pair extraction and preparative ion-pair high performance liquid chromatography (HPLC), in which sodium perchlorate was used as an ion-pair reagent. Quaternary bases were extractable from aqueous solution into I ,2-dichloroethane in the presence of perchlorate in acidic conditions. The phenomenon is explained in terms of ion-pair extraction between alkaloidal cation and perchlorate anion. The quaternary alkaloidal fraction thus obtained was well separated by means of ion-pair HPLC in which sodium perchlorate was also utilized. Furthermore, the solvent system was easily applied to preparative HPL " yielding the pure perchlorate of each alkaloid. Eight quaternary bases in Z. usambarense were thus obtained and their structures were elucidated. One of them wa a new quaternary base of the tetrahydroproloberberine type, which was named (-)-usambarine.