Determination of evodiamine and rutecarpine in human serum by liquid chromatography–tandem mass spectrometry

Evodiamine and rutecarpine are two kinds of indole alkaloids contained in the fruit of Evodiae fructus, which have been shown to exhibit various bioactivities in humans. A liquid chromatography–tandem mass spectrometric method (LC–MS/MS) was developed for the determination of evodiamine and rutecarpine in human serum. The serum was extracted by solid-phase extraction (SPE) and analyzed using a C18 column and a mobile phase consisting of methanol–water (85:15) solution containing 5 mmol/L ammonium formate at a flow rate of 0.5 mL/min. The mass spectrometer was operated in positive mode, employing the extracted ion chromatogram (EIC) for detection and quantitation of evodiamine (m/z 288) and rutecarpine (m/z 304). Good linear relationships between the peak area and the concentration were obtained in the ranges of 5.2–1040 ng/mL and 10.2–1020 ng/mL, with correlation coefficients (r) of 0.999 and 0.998, for evodiamine and rutecarpine, respectively. The repeatabilities (RSD, n=6) of quantitation for evodiamine and rutecarpine were 2.18–4.00% and 2.99–5.67%, respectively, and the recovery ranged from 90.5% to 98.1%. A comparative study of the different ionization and quantitation modes, including ESI–MS, ESI–MS/MS, APCI–MS and APCI–MS/MS, was also accomplished. The MS/MS fragmentation mechanism of the base peak ([M+H]+, m/z 304) of evodiamine was investigated in order to identify the analytes in more complicated body fluid samples.