Levels of a neurotoxic alkaloid in a species of low larkspur

Abstract

A survey of the levels of the neurotoxic diterpenoid alkaloid methyllycaconitine (MLA) in low larkspur (Delphinium nuttallianum Pritz.) was conducted at 4 diverse rangeland sites in southern British Columbia. Freeze-dried plant samples representing 3 stages of growth over 2 growing seasons were analyzed for MLA by high pressure liquid chromatography. Significant differences were found among experimental sites (P<0.001) with higher levels of MLA (>0.2% on a dry weight basis) being associated with sites at higher elevations (900-975 m). At one site, an exceptional level of MLA (>0.3%) was observed during the flower bud stage of growth but in general the alkaloid levels remained fairly constant with advancing stages of growth. Measurement of the MLA concentrations in different plant parts revealed that reproductive parts contained higher levels of MLA than vegetative parts and this may well explain the increased toxicity of the upper portions of the plant.