The discovery and characterization of riboflavin.

The first observation of a pigment in milk with yellow-green fluorescence can be traced to the English chemist Alexander Wynter Blyth in 1872, but it was not until the early 1930s that the substance was characterized as riboflavin. Interest in accessory food factors began in the latter half of the 19th century with the discovery of the first vitamin, thiamin. Thiamin was water soluble and given the name vitamin B(1). However, researchers realized that there were one or more additional water-soluble factors and these were called the vitamin B-2 complex. The search to identify these accessory food factors in milk, whole wheat, yeast, and liver began in the early 1900s. As there is no classical nutritional disease attributable to riboflavin deficiency, it was the growth-stimulating properties of the food extracts given to young rats that provided the tool with which to investigate and eventually extract riboflavin. Riboflavin was the second vitamin to be isolated and the first from the vitamin B-2 complex; the essential nature of the vitamin as a food constituent for man was shown in 1939.