High Resolution Ion Mobility-ESI-MS for efficient profiling of natural products

Abstract

The efficient analytical profiling of molecules in plant or fungal extracts represents a key element in natural product research. These complex extracts are typically characterized by highly chemodiverse secondary metabolites and by the presence of many multiple isomers. HPLC and UHPLC coupled with mass spectrometry are the most frequently used methods to analyze these types of samples but these techniques sometimes fail to resolve multiple isomers especially when used in a high throughput mode. In such cases, Ion Mobility Spectrometry (IMS) is an attractive alternative for the efficient separation of mixtures containing isomers, without increasing cycle time and with minimal additional experimental complexity [1,2]. In this study, the potential of High Resolution IMS-MS has been evaluated and compared to UHPLC-MS, for the analysis of closely related isomeric flavonoids and their glycosides. On a time scale of a few minutes, the flavonoid aglycones were all separated by ion mobility, but not by UHPLC. The glycosides were better resolved by IMS-MS, but not completely separated by both methods. The ion mobility resolving power was routinely > 150, indicating that the system provided sufficient resolution for a separation of isomeric natural products even in complex samples. Furthermore, HPLC-IMS-MS and UHPLC-MS were evaluated for the analysis of extracts from complex fungal co-cultures and mono-cultures. This study demonstrates that isomeric natural products can be better resolved by IMS-MS compared to UPLC-MS. Moreover, a significant number of compounds were detected by direct analysis of the fungal extracts using IMS-MS and were not detected by UHPLC-MS or MS only. These results suggest that high resolution IMS is well suited for the separation of isomeric compounds (even in high-throughput metabolomics studies) and appears as an attractive alternative to established UHPLC-MS methods.