VITAMIN B2

also called Riboflavin, a yellow, water-soluble organic compound that occurs abundantly in whey (the watery part of milk) and in egg white. An essential nutrient for animals, it can be synthesized by green plants and by most bacteria and fungi. The greenish yellow fluorescence of whey and egg white is caused by the presence of vitamin B2. Riboflavin was isolated in pure form in 1933 and was first synthesized in 1935. Vitamin B2 functions as part of metabolic systems concerned with the oxidation of carbohydrates and amino acids, the constituents of proteins. Like vitamin B1 (thiamine), it is active not in the free form but in more complex compounds known as coenzymes, such as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), or flavoprotein. Vitamin B2 is widely distributed in both plants and animals, but its abundance varies considerably. Milk, eggs, leafy vegetables, kidney, and liver are good dietary sources. An adult human needs 1.2 to 1.7 mg of the vitamin per day.