Ergocalciferol is vitamin D2. Ergocalciferol is a fat-soluble vitamin that regulates calcium and phosphorus metabolism. Vitamin D is important for the absorption of calcium from the stomach and for the functioning of calcium in the body. Ergocalciferol is 9. 10-secoergosta-5,7,10(19),22-tetraen-3- 01,(3b,5Z,7E,22E)-, (C28H44O) with a molecular weight of 39665. Ergocalciferol is a white, colorless crystal, insoluble in water, soluble in organic solvents, and slightly soluble in vegetable oils. It is affected by air and by light. Ergosterol or provitamin d2 is found in plants and yeast and has no antiarichitic activity. Vitamin D2 is derived from fungal and plant sources. Vitamin D2 is also known as ergocalciferol.