Experimental toxicity of verbesina encelioides in sheep and isolation of galegine.
Verbesina encelioides is a widely distributed weed in Argentina. Although it has been suspected as poisonous, there seem to be no previous reports of its toxicity in this country. Its biological activity was evaluated through an experiment in sheep. Four 5-y-old sheep, averaging 33 kg in body weight, were given a single dose of 1.0, 3.2, 5.0 or 6.3 g of dried plant material (17.9% dry matter)/kg body weight orally in a water suspension. Forty-eight hours later, the animals given 5.0 g or 6.3 g showed dullness and lack of appetite. The higher dosed sheep became recumbent a few hours later and died 60 h after dosing without showing further signs. The other animals showed no signs. Necropsy of the dead sheep showed severe lesions in different organs: liver, kidneys, lungs, lymph nodes and digestive tract. Hydrothorax was also observed. The animal receiving 5.0 g/kg was sacrificed after 72 h to determine the degree of recovery or lesions. Microscopically, severe glomerulonephrosis and congestion in the liver, with cellular degeneration and fatty changes were observed. Additionally, hemorrhagic lymph nodes, and hemorrhagic and edematous lungs were noted. No gross nor microscopic lesions were found in the sheep receiving 5.0 g/kg. Mice injected ip with the chromatographic extract died in less than 15 min. Galegine was identified in the plant material. The minimum toxic dose of 5-6 g/kg indicates a high toxicity when compared to other poisonous plants of the southeastern area of Buenos Aires province, Argentina.