Profiling of Dehydropyrrolizidine Alkaloids and their N-Oxides in Herbarium-Preserved Specimens of Amsinckia Species Using HPLC-esi(+)MS

摘要

Species of the Amsinckia genus (Boraginaceae) are known to produce potentially hepato-, pneumo-, and/or genotqxic dehydropyrrolizidine alkaloids. However, the taxonomic differentiation of Amsinckia species can be very subtle and there seems to be marked differences in toxicity toward grazing livestock. Methanol extracts of mass-limited leaf samples from herbarium specimens (collected from 1899 to 2013) of 10 Amsinckia species and one variety were analyzed using HPLC- esi(+)MS and MS/MS for the presence of potentially toxic dehydropyrrolizidine alkaloids and/or their N-oxides. Dehydropyrrolizidifie alkaloids were detected in all specimens examined ranging from about 1 to 4000 μg/g of plant. Usually occurring mairily as their N-oxides, the predominant alkaloids were the epimeric lycopsamine and intermedine. Also sometimes observed inhighef concentrations were the 3'- and 7-acetyl derivatives of lycopsamine/intermedine and their N-oxides. Within a designated species, an inconsistent profile was often observed that may be due to natural variation, taxonomic misassignment, or nonuffiform degradation due to plant collection and storage differences.