Paul Karrer Nobel laureate discoverer of Vitamins A, B2, E, K

Paul Karrer – discoverer of Vitamins A, B2, E, K

Article on Paul Karrer

Biography & Contributions

Paul Karrer was a Swiss organic chemist and Nobel laureate born on April 21, 1889 – died on June 18, 1971. Karrer investigated the constitution of carotenoids, flavins, and vitamins A and B2.

Karrer's early research involved the study of complex metal compounds and moved gradually into investigation of the molecules of proteins, peptides, and amino acids.

His early research concerned on plant pigments and yellow carotenoids and also showed that some of these substances are transformed into vitamin A in the animal body. Vitamin A, also called retinal, is present in the retina of the eye and is important for vision. Lack of vitamin A causes night blindness. Karrer's demonstration that vitamin A was nearly identical to half of a carotene molecule, containing a regular, and ring like formation of hydrogen, oxygen, and carbon atoms.

His work led to the establishment of the correct constitutional formula for beta-carotene. Later, Karrer confirmed the structure of ascorbic acid (vitamin C) and extended his researches into the vitamin B2 and E. 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.


Carotenoids are organic pigments that are found in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms, including some bacteria and some fungi. Carotenoids are usually lipophilic due to the presence of long unsaturated aliphatic chains as in some fatty acids.


Beta-Carotene is a strongly colored red-orange pigment abundant in plants and fruits. It is an organic compound and chemically is classified as a hydrocarbon and specifically as a terpenoid (isoprenoid), reflecting its derivation from isoprene units. Beta-Carotene is biosynthesized from geranylgeranyl pyrophosphate. It is a member of the carotenes, which are tetraterpenes, synthesized biochemically from eight isoprene units and thus having 40 carbons.


Riboflavin is a yellow-orange solid substance and part of the vitamin B group. It is the central component of the cofactors FAD and FMN and as such required for a variety of flavor protein enzyme reactions including activation of other vitamins. It is used in baby foods, breakfast cereals, pastas, sauces, processed cheese, fruit drinks, vitamin-enriched milk products, and some energy drinks.

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