Analysis of endophyte toxins: fescue and other grasses toxic to livestock.

Abstract

Research on livestock toxicoses caused by Acremonium (endophyte)-infected grasses strongly implicate the ergopeptine alkaloids with A. coenophialum-infected fescue and paxilline and the lolitrem alkaloids with A. lolii-infected perennial ryegrass as the causative agents. Isolation, identification, and detection of these toxins involves extraction with appropriate solvents, clean-up procedures, and chromatographic methods with known standards. Thin-layer, high-performance liquid and gas chromatography along with ultraviolet and mass spectrometric (i.e., electron impact, chemical ionization, tandem mass) characterizations have been reported. These methods have varying degrees of success depending on the matrix from which the alkaloids have been extracted. Ergovaline is the primary ergopeptine alkaloid isolated from cultures of A. coenophialum and also from infected fescue grass and seeds toxic to livestock. Other compounds isolated from the endophyte-infected fescue include: lysergic acid amide (ergine), the clavine class of ergot alkaloids (chanoclavine I, agroclavine, elymoclavine, penniclavine), the pyrrolizidine alkaloids (N-formylloline, N-acetylloline, N-methyloline, N-acetylnorloline), and the unique pyrrolopyrazine alkaloid peramine. The loline alkaloids and peramine have been more associated with the insect-deterrent properties of the endophyte-infected fescue than with livestock toxicoses. Also, both peramine and the ergopeptine alkaloids (ergovaline, ergotamine) have been isolated from A. lolii-infected perennial ryegrass. More recently, paxilline and lolitrem B have been detected in laboratory cultures of A. coenophialum isolated from tall fescue. The ergot alkaloids in endophyte-infected perennial ryegrass may be more related to decreased animal productivity (weight gains, reproduction problems), whereas the lolitrems cause the staggers syndrome. The detection, isolation, identification, and analyses of these compounds from Acremonium-infected grasses is presented.