Simultaneous analysis of the lipophilic and hydrophilic markers ofEchinacea plant extracts by capillary electrophoresis

The phytochemical profile of Echinacea plant extracts has been obtained by a CD-MEKC method using sodium dodecyl sulfate (SDS) as surfactant and hydroxypropyl-β-cyclodextrin (HP-β-CD). The separation of the major lipophilic markers of E. purpurea (alkyl isobutylamides and alkyl methylbutylamides; designated as alkamides) was affected by the nature and concentration of both SDS and CD, while the nature, concentration, and pH of running buffer exerted little influence on the migration of alkamides. On the other hand, the separation of hydrophilic compounds of the different Echinacea species (caffeoyl conjugates, namely: echinacoside, cynarin, chlorogenic acid, caffeic acid, caftaric acid, and cichoric acid) were strongly influenced by the nature, concentration, and pH of running buffer. Thus a step-by-step optimization procedure was carried out in order to choose the best BGE able to provide simultaneous separation of both alkamides and phenolic compounds. By using a SDS/HP-β-CD mixture of concentration 110 mM/100 mM in a BGE consisting of Britton-Robinson buffer (10 mM, pH 8.0), complete separation of all the principal phytochemical markers of Echinacea species was achieved in less than 10 min. The proposed conditions were applied to the evaluation of the phytochemical profile of Echinacea purpurea plant extract; quantitative determination was performed on the hydrophilic caffeoyl conjugates in commercially available phytopharmaceutical products.