in the biosynthetic pathway between lanosterol and ergosterol. Target for antiprotozoal drugs Some protozoa, including Trichomonas and Leishmania are inhibited by drugs that target ergosterol synthesis and function As a vitamin D2 precursor Ergosterol is a biological precursor of vitamin D2, the chemical name of which is ergocalciferol. Exposure of white button mushrooms to UV-C irradiation at 0.403 mW per cm2 intensity from 30 cm distance produced time-dependent increases in vitamin D2 concentrations. This happens naturally to a certain extent, and many mushrooms are irradiated after harvest to increase their vitamin D content. Fungi are also grown industrially so that ergosterol can be extracted and converted to Vitamin D for sale as a dietary supplement and food additive. Preparations of irradiated ergosterol containing a mixture of previtamin and vitamin D2 were called viosterol in the 1930s. Toxicity Ergosterol powder is an irritant to skin, eyes, and the respiratory tract. Ingestion of large amounts can cause hypercalcemia, which (if prolonged) can lead to calcium salt deposits in the soft tissues and kidneys. See also Mushrooms and vitamin D References Sterols Nutrition Cell biology Vitamin D