GC‐MS of some Amaryllidaceae alkaloids of homolycorine type

Rationale

Gas chromatography-mass spectrometry (GC-MS) is the most frequently applied technique for analysis of Amaryllidaceae alkaloids in plant extracts. These compounds, known for their potent bioactivities, are 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 EIMS mode leading to problematic identification in complex plant extracts.

Methods

Eleven standard homolycorine-type alkaloids (isolated and identified by 1D and 2D nuclear magnetic resonance) were subjected to separation with gas chromatography and studied with electron impact mass spectrometry including single quadropole (GC-EIMS), tandem (GC-EIMS/MS), and high resolution (GC-HR-EIMS) detectors, as well as with chemical ionisation mass spectrometry (GC-CIMS). Alkaloid fractions from two Hippeastrum species and Clivia miniata were subjected to GC-EIMS and GC-CIMS for alkaloid identification.

Results

GC-EIMS in combination with GC-CIMS provided significant structural information for homolycorine-type alkaloids with C3-C4 double bond facilitating their unambiguous identification. Based on the obtained typical fragmentation, other eleven homolycorine-type compounds were identified in extracts from two Hippeastrum species by parallel GC-EIMS, GC-CIMS and LC-ESI/ToF/MS and in extracts from Clivia miniata by GC-EIMS.

Conclusion

GC-MS can be successfully applied for identification of new and known homolycorine-type alkaloids, as well as for chemotaxonomical and chemoecological studies, among others within the Amaryllidoideae subfamily.