Ergosterol was discovered over 100 years ago in the plant pathogenic ergot fungus Claviceps purpurea. Ergosterol is the major fungal membrane sterol that regulates membrane fluidity, plasma membrane biogenesis and function. Antifungal drugs such as Amphotericin B exerts its action by simply binding ergosterol. Vitamin D2 (ergocalciferol) is derived from ergosterol by UVB irradiation. Ergocalciferol is used for treating low parathyroid hormone levels, rickets (a vitamin D deficiency condition), and low phosphate levels in the body.