Identification of a lycopsamine-N-oxide chemotype of Amsinckia intermedia

► Amsinckia intermedia was analysed for pyrrolizidine alkaloids using HPLC-esiMS. ► This chemotype produces lycopsamine/lycopsamine-N-oxide almost exclusively. ► The N-oxide concentrations exceeded the free base form until seed set. ► Total lycopsamine concentration decreased across the growing season. ► This chemotype is unlike any reported chemotype of Amsinckia spp.