Finally they had proof that lactoflavin was vitamin.    From Wordnik.com.  [Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms] Reference

The chemical composition of both ovoflavin and lactoflavin proved to be virtually identical.    From Wordnik.com.  [Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms] Reference

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.    From Wordnik.com.  [Paul Karrer - Biography] Reference

And after determining the structure of lumiflavin, they were able to extrapolate enough information to synthesize lactoflavin and thereby determine its composition.    From Wordnik.com.  [Richard Kuhn and the Chemical Institute: Double Bonds and Biological Mechanisms] Reference