Structural Analysis and Identity Confirmation of Anthocyanins in Brassica oleracea Extracts by Direct Injection Ion Mobility-Mass Spectrometry

Abstract

Anthocyanins are a subclass of plant-derived flavonoids that demonstrate immense structural heterogeneity which is challenging to capture in complex extracts by traditional liquid chromatography–mass spectrometry (MS)-based approaches. Here, we investigate direct injection ion mobility-MS as a rapid analytical tool to characterize anthocyanin structural features in red cabbage (Brassica oleracea) extracts. Within a 1.5 min sample run time, we observe localization of structurally similar anthocyanins and their isobars into discrete drift time regions based upon their degree of chemical modifications. Furthermore, drift time-aligned fragmentation enables simultaneous collection of MS, MS/MS, and collisional cross-section data for individual anthocyanin species down to a low picomole scale to generate structural identifiers for rapid identity confirmation. We finally identify anthocyanins in three other Brassica oleracea extracts based on red cabbage anthocyanin identifiers to demonstrate our high-throughput approach. Direct injection ion mobility-MS therefore provides wholistic structural information on structurally similar, and even isobaric, anthocyanins in complex plant extracts, which can inform the nutritional value of a plant and bolster drug discovery pipelines.