Discovery of riboflavin

By 1927 a series of experiments, performed in part by Elmer McCollum and others, had shown that water-soluble vitamin B was primarily made of two parts: the anti-neuritic factor B₁ (now known as thiamine) and the more heat-stable factor B₂.^[5] By 1932 Gyorgy had found that the heat-stable B₂ was not in fact a single substance, but actually a complex made up of two factors: the growth-promoting factor (later found to be riboflavin) and the anti-pellagra factor (later found to be niacin (vitamin B₃)).^[6] Gyorgy, in collaboration with chemist Richard Kuhn and physician Th. Wagner-Jauregg at the University of Heidelberg, had noticed that rats kept on a B₂-free diet were unable to gain weight. Isolation of concentrated B₂ from yeast revealed the presence of a bright yellow-green fluorescent product that when fed to the rat, restored normal growth. The amount of growth restored was directly proportional to the intensity of the fluorescent product. The bright yellow substance had been previously found in milk by scientists Warburg and Christian, who had described the it as 'yellow oxidation ferment' but were unable to discover its function. Gyorgy, Kuhn, and Warner-Jauregg suggested the name 'flavin' for their yellow pigments and proposed that they were likely the same as the yellow pigments seen by Warberg and Christian.^[7]

By 1933, the Heidelberg team were the first to isolate crystalline flavin from milk and accordingly, termed the substance lactoflavin. They, along with other teams, went on to isolate similar flavins from many other sources such as egg white (ovoflavin) and liver (heptoflavin). All these compounds were found to be chemically identical and in 1937, the name riboflavin was formally adopted by the Council of Pharmacy and Chemistry of the American Medical Association.^[5]

Discovery of B₆

During his experiments with riboflavin, Gyorgy noticed that rats already on a thiamine-only diet developed pellagra-like symptoms, even when given pure riboflavin. The symptoms were only relieved when rats were given supplements derived from a flavin-free extract of bakers' yeast. In contrast, rats given this extract but no riboflavin failed to exhibit pellagra-like symptoms but were unable to gain weight until riboflavin was added back into the diet. These results confirmed the presence of an 'anti-pellagra' factor that was biologically distinct from the newly discovered riboflavin.^[8]

In 1934, Gyorgy named this new anti-pellagra factor B₆ in order to distinguish it from other B vitamins and set about isolating and characterizing it during his time at the University of Cambridge. In 1936, Gyorgy and his colleague, Thomas William Birch, were successful in isolating crystalline B₆ from fish and wheat germ.^[9][10]

Discovery of biotin

By 1927, scientists such as Margarete Boas and Helen Parsons had performed experiments demonstrating the symptoms associated with egg-white injury.^[11][12] They had found that rats fed large amounts of egg-white as their only protein source exhibited neurological dysfunction, dermatitis, and eventually, death. Gyorgy began investigating the factor responsible for egg-white injury in 1933 and in 1939, was successful identifying what he called vitamin H.^[13][14] Further chemical characterization of vitamin H revealed that it was water-soluble and present in high amounts in the liver.^[15][16] By this time, multiple groups had independently isolated the same compound under different names. In 1936, Kögl and Tönnis had isolated what they called biotin from egg yolk and in 1939, West had isolated what he called co-enzyme R.^[17] By 1940, it was recognized that all three compounds were identical and were collectively given the name biotin.^[18] Gyorgy continued his work on biotin and in 1941 published a paper demonstrating that egg-white injury was caused by the binding of biotin by avidin.^[19][20]

Protective factors in breast milk

In 1950, Gyorgy began investigating the microbial properties in human breast milk. He began by comparing the intestinal flora of normal breast-fed infants to those who were fed cow's milk formulas.^[21] He found that the breast-fed infants had a prevalence of a certain variant of Lactobacillus bifidus, a bacterium considered to be an essential part of normal human gut flora. Further testing revealed the presence of factors in human breast milk that acted as essential growth promoting factors to the L. bifidus variant.^[22][23]

In 1962, Gyorgy also discovered anti-staphylococcus properties of human breast milk. He injected mice with different doses of virulent Staphylococcus aureus and found that those given human breast milk obtained protection from infection, resulting in a higher survival rate than those that were given only cow's milk.^[24]