Technical note: an improved method for extraction and quantification of toxic phenethylamines from Acacia berlandieri

N-methyl-beta-phenethylamine (NMPEA) has been previously identified as the toxin causing locomotor ataxia in sheep and goats grazing the browse plant, Acacia berlandieri. We describe a simplified procedure for extraction and quantification of naturally occurring beta-phenethylamines from this Acacia species. Dried, ground plant tissue was extracted (1:20 wt/vol) with 1% glacial acetic acid and filtered. The filtrate was passed through a high-sulfonated polymeric solid-phase extraction (SPE) tube, which retained the compounds of interest (tyramine, hordenine, NMPEA) but allowed many impurities co-extracted from the plant tissue to be washed through. Amines were eluted from the tube, then separated and detected by reversed-phase HPLC. Extracted amines were resolved by HPLC in < 15 min, and UV-absorbance spectra matched those of authentic standards. Recovery efficiency of amine standards (125 micrograms/mL) from SPE tubes averaged 97, 101, and 98% for tyramine, hordenine, and NMPEA, respectively. Excess sample loss was prevented and the large volumes of solvents required for liquid-liquid extraction eliminated by use of solid-phase extraction techniques.