MICROWAVE-ASSISTED EXTRACTION OF THE FUNGAL METABOLITE ERGOSTEROL AND TOTAL FATTY-ACIDS

A novel microwave-assisted extraction (MAE) technique for isolating the fungal metabolite ergosterol was developed and applied to fungal hyphae and spores, mushrooms, filtered air, artificially contaminated corn, naturally contaminated grain dust, and soil. The procedure involves irradiation of milligram-sized samples in a conventional microwave oven for 35 s in the presence of methanol and aqueous sodium hydroxide and results in simultaneous extraction and saponification. Total ergosterol was determined by reversed phase high-performance liquid chromatography with ultraviolet detection at 282 nm and confirmed by gas chromatography-mass spectrometry (GC-MS). Results from a variety of fungal samples showed MAE-derived ergosterol values to be comparable with those obtained by classical solvent extraction and to significantly exceed those obtained by supercritical fluid extraction (SFE). Total fatty acid profiles of spores were determined (by GC-MS) on the same extracts as used for ergosterol analyses. The MAE: procedure is simple, rapid, reliable, and economical with respect to amounts of reagents required, especially when compared with classical solvent and SFE.