a colorless, crystalline, water-insoluble sterol, C28H43OH, that occurs in ergot and yeast and that, when irradiated with ultraviolet light, is converted to vitamin D.
Main Entry: er·gos·ter·ol Pronunciation: (")&r-'gäs-t&-"rol, -"rOl Function: noun : a crystalline steroid alcoholC28H44O that occurs especially in yeast, molds, and ergot and is converted by ultraviolet irradiation ultimately into vitamin D2
ergosterol er·gos·ter·ol (ûr-gŏs'tə-rôl', -rōl') n. A crystalline sterol synthesized by yeast from sugars or derived from ergot and converted to vitamin D2 when exposed to ultraviolet radiation.