and a heat-stable substance called B2. Vitamin B2 was tentatively identified to be the factor necessary for preventing pellagra, but that was later confirmed to be due to niacin (vitamin B3) deficiency. The confusion was due to the fact that riboflavin (B2) deficiency causes stomatitis symptoms similar to those seen in pellagra, but without the widespread peripheral skin lesions. For this reason, early in the history of identifying riboflavin deficiency in humans the condition was sometimes called "pellagra sine pellagra" (pellagra without pellagra). In 1935, Paul Gyorgy, in collaboration with chemist Richard Kuhn and physician T. Wagner-Jauregg, reported that rats kept on a B2-free diet were unable to gain weight. Isolation of B2 from yeast revealed the presence of a bright yellow-green fluorescent product that restored normal growth when fed to rats. The growth restored was directly proportional to the intensity of the fluorescence. This observation enabled the researchers to develop a rapid chemical bioassay in 1933, and then isolate the factor from egg white, calling it ovoflavin. The same group then isolated the a similar preparation from whey and called it lactoflavin. In 1934, Kuhn's group identified the chemical structure of these flavins as identical, settled on "riboflavin" as a name, and were also able to synthesize the vitamin. Circa 1937, riboflavin was also referred to as "Vitamin G". In 1938, Richard Kuhn was awarded the Nobel Prize in Chemistry for his work on vitamins, which had included B2 and B6. In 1939, it was confirmed that riboflavin is essential for human health through a clinical trial conducted by William H. Sebrell and Roy E. Butler. Women fed a diet low in riboflavin developed stomatitis and other signs of deficiency, which were reversed when treated with synthetic riboflavin. The symptoms returned when the supplements were stopped. References B vitamins Coenzymes E-number additives Flavins Food colorings Primary alcohols Secondary alcohols Wikipedia medicine articles ready to translate World Health Organization essential medicines Ophthalmology drugs