The Extraction and Analysis of Sterols from Yeast

The study of sterols is of both practical and theoretical interest, being important in the analysis of the action of antifungal compounds, in vitamin D production and investigating the role of sterols in cell division, mating ( 1 ), and ethanol tolerance. The extraction of sterols from yeast is both rapid and simple, the effectiveness of the basic method being reflected by the fact that it has not been significantly altered since being performed by Woods ( 2 ) in 1971. The method involves saponification of harvested cell material followed by solvent extraction to recover the nonsaponifiable fraction, which contains the cellular sterols. The principal sterol, in yeast, is ergosterol (Fig. 1 ). Other sterols identified include intermediates in the pathway of ergosterol biosynthesis or those appearing upon inhibition of biosynthesis. These may differ from each other only in the stereochemical orientation of one of their methyl substituents or in the position of unsaturation. For instance, episterol and fecosterol, which both lie on the ergosterol biosynthesis pathway, differ only in that episterol has a Δ ⁷ double bond, whereas fecosterol is Δ ⁸ sterol.

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