lactoflavin

The chemical composition of both ovoflavin and lactoflavin proved to be virtually identical.

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

"The beautiful yellow pigments" turned out to be riboflavin, although Kuhn called it both lactoflavin and ovoflavin because they had first abstracted it from milk and egg whites.

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

Fortunately, they soon discovered a breakdown product of lactoflavin, called lumiflavin, which they were able to crystallize.

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

Determining if the flavins were precursors or the vitamin itself was initially elusive due to difficulties crystallizing the lactoflavin, which hindered the structural analysis.

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

Finally they had proof that lactoflavin was vitamin

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

And after determining the structure of lumiflavin, they were able to extrapolate enough information to synthesize lactoflavin and thereby determine its composition.

Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms 2010

His important contributions to the chemistry of the flavins led to identification of lactoflavin as part of the complex originally thought to be vitamin B2.

Paul Karrer - Biography 1966

The lactoflavin, for instance, combines, with the aid of phosphoric acid, with an albuminous substance, and only in this way the yellow respiratory ferment is formed.

Nobel Prize in Chemistry 1937 - Presentation Speech 1966