Gas chromatography–mass spectrometry of some homolycorine‐type Amaryllidaceae alkaloids

Abstract

RationaleGas chromatography–mass spectrometry (GC–MS) is the most frequently applied technique for analyzing Amaryllidaceae alkaloids in plant extracts. Having these compounds, known for their potent bioactivities, is a distinctive chemotaxonomic feature of the Amaryllidoideae subfamily (Amaryllidaceae). The Amaryllidaceae alkaloids of homolycorine type with a C3–C4 double bond generally show molecular and diagnostic ions at the high‐mass region with low intensity in the EIMS mode, leading to problematic identification in complex plant extracts.MethodsEleven standard homolycorine‐type alkaloids (isolated and identified by 1D and 2D nuclear magnetic resonance) were subjected to separation with GC and studied with electron impact mass spectrometry (EIMS) including single quadrupole (GC–EIMS), tandem (GC–EIMS/MS), and high‐resolution (GC–HR‐EIMS) detectors, as well as with chemical ionization mass spectrometry (GC–CIMS). Alkaloid fractions from two Hippeastrum species and Clivia miniata were subjected to GC–EIMS and GC–CIMS for alkaloid identification.ResultsGC–EIMS in combination with GC–CIMS provided significant structural information of homolycorine‐type alkaloids with C3–C4 double bond, facilitating their unambiguous identification. Based on the obtained typical fragmentation, other 11 homolycorine‐type compounds were identified in extracts from two Hippeastrum species by parallel GC–EIMS, GC–CIMS, and liquid chromatography–electrospray ionization time‐of‐flight mass spectrometry and in extracts from C. miniata by GC–EIMS.ConclusionsGC–MS can be successfully applied for the identification of new and known homolycorine‐type alkaloids, among others within the Amaryllidoideae subfamily, as well as for chemotaxonomical and chemoecological studies.