The 1938 Nobel Prize in Chemistry rewarded a prime example of how the bonds between different scientific disciplines can form in the most unexpected places. In this instance, a chemist’s curiosity for unusual interactions between molecules provided a crucial biological connection to understanding essential food nutrients important for health and disease.
Richard Kuhn was fascinated by a class of organic compounds called polyenes, on account of their distinctive long chains of carbon atoms linked by alternating double and single bonds. Kuhn was interested in investigating how these unique chemical chains affected the basic characteristics of polyene molecules, like their ability to interact with light. As polyenes form the basis of many natural pigments in plants and animals called carotenoids, Kuhn shifted his research focus towards investigating the chemical characteristics of these compounds. During this time, Kuhn resurrected chromatography, a method used for separating all the components present in complex mixtures, which for years had drifted into obscurity because researchers had difficulties reproducing the technique. Adapting and refining these chromatography methods allowed Kuhn to isolate and prepare a host of known and previously unknown carotenoids in their pure form; and he meticulously documented how tiny variations in their chemical structures affect their biological functions.
The fact that several vitamins are also members of the carotenoid family led Kuhn to shift his focus once again. His first major breakthrough in this field came in clarifying Paul Karrer‘s early results concerning the structural formula of beta-carotene, the precursor of vitamin A. Kuhn showed that beta-carotene naturally exists in more than one form that can be converted into the active vitamin. In collaboration with Paul György, Kuhn isolated and purified the essential component of vitamin B2 from milk and eggs, called riboflavin, and he subsequently provided definitive proof that riboflavin simulates growth in animals. Kuhn’s Prize in Chemistry was the third Nobel Prize awarded in two years for breakthroughs in vitamins, a testimony to how the science of vitamins dominated this period of the research scene.