Submitted to: Journal of Rapid Communications in Mass Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2011
Publication Date: 8/22/2011
Citation: Sun, J., Chen, P. 2011. Profiling the indole alkaloids in yohimbe bark with ultra-performance liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry. Journal of Rapid Communications in Mass Spectroscopy. 25:2591-2602. Interpretive Summary: An ultra-high performance liquid chromatography-ion mobility-quadrupole time-of-flight mass spectrometry (UHPLC-IM-QTOF-MS) method was developed for profiling the indole alkaloids in yohimbe bark. The indole alkaloids in yohimbe bark all share the core structure of yohimbine. This makes the separation and identification of them very difficult. With the help of advanced analytical technologies (i.e., high resolution accurate mass measurement, mass fragmentation patterns, ion mobility studies, and UHPLC chromatography), a total of 56 indole alkaloids were characterized and a few new yohimbine-like alkaloids that have not been reported previously were detected using the new approach. This represents the most complete study on naturally-occurring yohimbine-like indole alkaloids to date.
Technical Abstract: An ultra-high performance liquid chromatography-ion mobility- quadrupole time-of-flight mass spectrometry (UHPLC-IM-QTOF-MS) method was developed for profiling the indole alkaloids in yohimbe bark. Many indole alkaloids with the yohimbine core structure, plus methylated, oxidized, and reduced species, were characterized. Common fragments and mass differences are described. It was shown that the use of IM could provide another molecular descriptor; i.e., molecular shape by rotationally averaged collision cross-section was of great value for identification of constituents where reference materials are usually not available. Using the combination of high resolution (~40000) accurate mass measurement with time aligned parallel (TAP) fragmentation, MSE (where E represents collision energy), ion mobility mass spectrometry (IMS), and UPLC chromatography, a total of 56 indole alkaloids were characterized and a few new yohimbine-like alkaloids are reported for the first time.