An improved method of simultaneous determination of four bioactive compounds in Evodiae Fructus using ionic liquids as mobile phase additives in high performance liquid chromatography

There are many compounds with different structures and chemical properties in Evodiae Fructus. It is hard to simultaneously determine the bioactive compounds by high performance liquid chromatography(HPLC). A new method was proposed for four bioactive compounds(synephrine, limonoids, evodiamine and rutecarpine) to be separated completely and determined accurately using ionic liquids(ILs) as mobile phase additives. The mechanism and the effect of the ILs for changing the chromatographic behaviors of the four compounds were studied by systematically changing the pH value of mobile phase, the types and concentrations of ILs as well as the concentrations of phosphate buffer. The chromatographic behaviors of the analytes with a mobile phase containing ILs complied with the stoichiometric displacement model for retention(SDM-R). All results demonstrate the dual nature of ionic liquids, which are competitive adsorption and ion-pair agent. Meanwhile, excellent linearity was observed for all the compounds with correlation coefficients between 0.9992 and 0.9998. The limit of detection and the limit of quantification of the four compounds varied from 0.47 μg/mL to 0.87 μg/mL and from 1.79 μg/mL to 2.44 μg/mL, respectively. Three kinds of Evodiae Fructus processed through different methods were analyzed via the method. The result shows that the contents of evodiamine and rutecarpine as the two main active compounds by processing with vinegar and salt are obviously higher than those of the raw products.