Analysis of swainsonine: Extraction methods, detection, and measurement inpopulations of locoweeds (Oxytropis spp.)

An analytical method has been developed to measure the locoweed toxin, swai nsonine, in locoweed plant material. Dry ground plant samples were extracte d using a small-scale liquid/liquid extraction procedure followed by isolat ion of the swainsonine by solid phase extraction with a cation-exchange res in. Detection and quantitation of the swainsonine were accomplished using r eversed phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry (LC-MS2), The limit of quantitation was estimated to be 0.001% swainsonine by weight in dry pla nt material, which corresponds to the lower threshold for toxicity of locow eeds. The method of analysis was applied to the analysis of Oxytropis seric ea (white locoweed) and Oxytropis lambertii (Lambert locoweed) plant sample s to measure the variability of individual plant swainsonine levels within populations and within species. Individual plant variability was found to b e highly significant for both O. sericea and O. lambertii populations. The. ,combined three-year mean swainsonine values taken, from three populations of O. sericea ranged from 0.046% in Utah to 0.097% in a New Mexico populati on. Sixteen individual populations of O. lambertii were sampled from eight different U.S. states. Swainsonine was detected at levels > 0.001% in only 5 of the 16 collection sites. Those populations of O. lambertii found to co ntain higher swainsonine levels were restricted to the most southern and we stern portion of its distribution, and all were identified as belonging to var. bigelovii, whereas var. articulata and var. lambertii samples containe d swainsonine,at levels < 0.001%.