A simple thin-layer chromatographic method for the detection of ergovaline in leaf sheaths of tall fescue (Festuca arundinacea) infected with Neotyphodium coenophialum

Toxicology Laboratory, Instituto de Patobiologia, CICVyA, Instituto Nacional de Tecnologia Agropecuaria, Castelar, Argentina.

A relatively simple and inexpensive thin-layer chromatographic (TLC) method is described for the detection and semiquantitative measurement of ergovaline in leaf sheaths of tall fescue (Festuca arundinacea). Samples were finely ground and extracted with methanol. The extracts were filtered and the methanol was evaporated. The aqueous residue was extracted with hexane, followed by chloroform at pH 9. The chloroform extract was concentrated and further purified on a preparative silica gel TLC plate, developed with toluene/ethyl acetate/acetonitrile (50:10:40). The ergovaline band was scraped and eluted with methanol. The eluant was concentrated and an aliquot was applied to a silica gel TLC plate. The plate was developed successively with chloroform/acetone/acetic acid (90:10:5) and chloroform/ethanol (9:1). Ergovaline was visualized with p-dimethylaminobenzaldehyde and sulfuric acid. Semiquantitation of ergovaline was achieved by comparison with a known standard of ergotamine, which was shown to have the same Rf as ergovaline in this system. Spike recovery of ergotamine averaged 60%, with a limit of detection of 200 microg/kg of dry tall fescue leaf sheaths. The method was applied to 15 tall fescue samples with varying degrees of fungal infection, and ergovaline was identified in all contaminated samples with endophyte infection above 15%. Thin-layer chromatography may be also applicable for tall fescue seed, where the ergovaline content is usually higher and the amount of interfering pigments is much lower.