Alkaloid levels of a tall larkspur species in southwestern Alberta

Abstract

Tall larkspurs (Delphinium spp.) are widely distributed in western North America and they kill more cattle on rangelands than any other poisonous plant. In Alberta, Canada, D. brownii Rydb. has a long history of causing cattle poisoning. The neurotoxic norditerpenoid alkaloid methyllycaconitine (MLA) was first detected in D. brownii over 50 years ago. A 2-year (1996 to 1997) survey was conducted on the levels of MLA in D. brownii collected at 5 sites in the foothills of southwestern Alberta. The vegetative stage of growth yielded the highest levels of MLA and the decline and change in concentration during that interval could be predicted on the basis of Julian day alone. The MLA levels during bud to pod development were not significantly different but they exceeded the reported levels for MLA in low larkspur by 5-to 10-fold. A new method is described for the determination of MLA by HPLC.