The most important of the provitamins D2; ultraviolet irradiation converts e. to lumisterol, tachysterol, and ergocalciferol; main sterol in yeast, ergot, and molds. SYN: ergosterin.
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er·gos·ter·ol (.)ər-'gäs-tə-.rȯl, -.rōl n a crystalline steroid alcohol C28H44O that occurs esp. in yeast, molds, and ergot and is converted by ultraviolet irradiation ultimately into vitamin D2
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n.
a plant sterol that, when irradiated with ultraviolet light, is converted to ergocalciferol (vitamin D2). See vitamin D.
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er·gos·te·rol (ər-gosґtə-rol″) a sterol occurring mainly in yeast and forming ergocalciferol (vitamin D2) upon irradiation by ultraviolet rays or electronic bombardment. Called also provitamin D2>.Medical dictionary. 2011.