Valine: History and Discovery

In 1901, the German chemist Hermann Emil Fischer broke down the milk protein casein, separated out its building blocks, and reported a small new amino acid he called — in the end — valine, a name borrowed by way of valeric acid from the garden herb valerian. That moment is the one most chemistry textbooks record as valine's discovery, and it sits inside one of the great stories of early biochemistry: Fischer's decade-long campaign to take proteins apart amino acid by amino acid and put them back together, work that helped win him a Nobel Prize. But the record holds an honest complication: a careful nineteenth-century historian credited an earlier chemist, Eugen von Gorup-Besanez, with finding valine back in 1856. This article tells what the historical record actually supports — the naming, the disputed priority, the way valine took its place among the "essential" amino acids through the patient rat-and-human experiments of William Cumming Rose in the 1930s, and the broader nineteenth- and twentieth-century arc that turned proteins from a mystery into a chemistry. Where the facts are firm we say so; where a claim is contested or uncertain, we name it as such.

Table of Contents

  1. What Valine Is, in Plain Terms
  2. Emil Fischer and the 1901 Isolation from Casein
  3. Where the Name Comes From: Valerian to Valine
  4. A Disputed Priority: Gorup-Besanez and 1856
  5. The Bigger Picture: Naming "Protein" and Taking It Apart
  6. Becoming "Essential": William Cumming Rose in the 1930s
  7. A Hard Lesson: Maple Syrup Urine Disease
  8. From Bench to Everyday Life
  9. Research Papers and References
  10. Connections
  11. Featured Videos

What Valine Is, in Plain Terms

Before the history, a one-paragraph reminder of what we are talking about. Valine is one of the twenty amino acids that proteins are built from — the small molecules that link together, like beads on a string, to make every protein in your body and your food. Valine is one of the three branched-chain amino acids (the other two are leucine and isoleucine), so called because their chemical "side chain" forks like a twig instead of running straight. It is also one of the nine essential amino acids: your body cannot manufacture it, so every bit of valine you contain came originally from something you ate.

Those two facts — that valine is a real, definite chemical compound, and that it is essential to human life — are the spine of its history. The first had to be established by chemists who could isolate and name it; the second had to be proven by nutrition scientists who could show, with careful experiments, that a person deprived of valine cannot stay healthy. The story below is really the story of those two discoveries, made decades apart by very different kinds of researchers.

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Emil Fischer and the 1901 Isolation from Casein

The discovery most reference works attach to valine is well documented and easy to state: in 1901, the German chemist Hermann Emil Fischer (1852–1919) isolated valine from casein, the principal protein of milk. The Encyclopaedia Britannica records it plainly, describing valine as "an amino acid obtained by hydrolysis of proteins and first isolated by the German chemist Emil Fischer (1901) from casein." This is the date and the discoverer that standard sources credit.

To understand what Fischer actually did, it helps to picture the method. A protein is a long chain of amino acids; to find out what a protein is made of, a chemist boils it in acid — a process called hydrolysis — which snips the chain back into its individual amino-acid beads. The hard part is then separating that mixture and identifying each component, because many amino acids are chemically similar and stubborn to crystallise apart. Fischer was a master of exactly this kind of painstaking separation. Working through the proteins of milk, blood, and other tissues around the turn of the twentieth century, he and his group pulled out and characterised amino acid after amino acid, valine among them.

An important detail of the chemistry came a few years later. Amino acids can exist as two mirror-image forms, like a left and a right hand; in 1906 Fischer settled which mirror-image form of this molecule occurs in natural proteins, and it was in that context that the short name was fixed. So a fair way to put it is this: 1901 is the year of the isolation that is usually cited as the discovery, and 1906 is when Fischer pinned down the precise three-dimensional form and the name as we now use it.

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Where the Name Comes From: Valerian to Valine

The name "valine" has a small, pleasant history of its own that runs back, surprisingly, to a flowering herb. Chemically, valine is closely related to a fatty acid called valeric acid (also written valerianic acid). Valeric acid, in turn, takes its name from the plant valerian (Valeriana officinalis), the same valerian long used as a sleep and calming herb, because the acid was first obtained from valerian root. So the chain of naming runs: valerian (the plant) → valeric acid (the fatty acid found in it) → valine (the amino acid built on the same carbon skeleton).

The formal chemical name Fischer worked with was the mouthful α-aminoisovaleric acid — literally, valeric acid with an amino group added. "Valine" is essentially a tidy short form carved out of that longer name. It is a nice reminder that chemical names are not random labels: read carefully, they often carry a fossil of where a compound came from or what it resembles. In valine's case, the fossil points all the way back to a fragrant garden plant.

This origin is purely linguistic, and it is worth being clear about that. The amino acid valine and the herb valerian are connected only through the name of a shared chemical relative — valine is not derived from valerian, does not come from it in the body or the diet, and shares none of valerian's sedative reputation. The link is a chapter in the history of chemical naming, not a biological relationship.

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A Disputed Priority: Gorup-Besanez and 1856

Histories of science are full of quiet priority disputes, and valine has one worth telling honestly. While Fischer's 1901 isolation is the date most textbooks give, there is a documented claim that valine was actually found decades earlier. A 1981 historical study of nineteenth-century chemistry and medicine in Erlangen, Germany, examined the career of the chemist Eugen Franz Freiherr von Gorup-Besanez (1817–1878) and concluded that "his greatest contribution was the discovery of the amino acid valine." By the dates of Gorup-Besanez's work, that discovery is placed around 1856, when he is reported to have obtained the substance from a pancreatic extract, established that it was a new compound, and worked out its chemical formula — without going on to settle its three-dimensional structure or fix the name.

How can a compound have two discovery dates? This is more common in early chemistry than it sounds. A nineteenth-century chemist might isolate a substance, describe some of its properties, and move on — without fully establishing its structure, its purity, or even being certain it was a single distinct compound rather than a mixture. Decades later, with better methods, another chemist could isolate the same substance cleanly, prove its structure, and give it the name that stuck. Both did real work; which one "discovered" it then becomes partly a matter of where you set the bar. Some sources accordingly describe valine as first obtained by Gorup-Besanez in the 1850s, with Fischer later establishing the modern, structurally defined compound and the name.

The careful conclusion is this: the most commonly cited discovery is Fischer's 1901 isolation from casein, and that is the attribution you will meet in most reference works; but there is a genuine, documented earlier claim crediting Gorup-Besanez with finding valine around 1856. This page reports both and treats the priority as a real historical question rather than pretending it is settled. What is not in dispute is that valine's identity as a definite amino acid was firmly nailed down by Fischer's era. One often-noted consequence of this long, two-stage history is that valine is sometimes cited as the amino acid with the longest gap between its first isolation and the coining of its modern name — roughly half a century separating Gorup-Besanez's 1856 work from Fischer's naming of "valin" in 1906.

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The Bigger Picture: Naming "Protein" and Taking It Apart

Valine's isolation only makes sense against the backdrop of how the whole idea of proteins and amino acids came together in the nineteenth and early twentieth centuries. The word protein itself was introduced in 1838: the Dutch chemist Gerardus Johannes Mulder used it for the nitrogen-rich substances that seemed fundamental to living tissue, on a suggestion from the influential Swedish chemist Jöns Jacob Berzelius. The name was chosen from the Greek prôteios, meaning "primary" or "holding first place" — a deliberate statement that these were the foremost substances of life. (Berzelius and Mulder are both named in the historical record; the exact share of credit for coining the term is itself mildly debated, which is fitting for a field this old.)

Once proteins had a name, the obvious question was what they were made of — and answering it took the better part of a century of isolating amino acids one at a time. The very first to be obtained was asparagine in 1806, pulled from asparagus juice by the French chemists Louis-Nicolas Vauquelin and Pierre-Jean Robiquet. Glycine followed from gelatin in 1820 (Henri Braconnot called it "sugar of gelatin" for its sweet taste); tyrosine was isolated from cheese in 1846 and named from the Greek tyros, "cheese." Valine, found in this same long campaign, was a relatively late and inconspicuous arrival — a small, plain molecule with none of the dramatic backstory of an asparagus extract or a cheese-derived name, but a genuine piece of the protein puzzle all the same.

The chemist who did most to turn this collection of isolated amino acids into a coherent picture of how proteins are built was, once again, Emil Fischer. He was awarded the 1902 Nobel Prize in Chemistry — in the committee's words, "in recognition of the extraordinary services he has rendered by his work on sugar and purine syntheses" — but it was in the years right around that prize that he tackled proteins. Fischer broke proteins down into their amino acids and then, crucially, learned to link amino acids back together in the laboratory: his group made the first simple synthetic peptide (a glycine–glycine pair) in 1901 and went on to build chains of many linked amino acids. This work established that proteins are, in essence, long chains of amino acids joined end to end — the framework into which every individual amino acid, valine included, finally fit.

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Becoming "Essential": William Cumming Rose in the 1930s

Isolating valine answered the question "what is it?" A second, equally important discovery answered a different question: "do we actually need it in our food?" That answer came from the American biochemist William Cumming Rose (1887–1985) and his co-workers at the University of Illinois, in a remarkable series of feeding experiments running through the 1930s.

Rose's tool was the concept of nitrogen balance. Protein is rich in nitrogen, so by carefully measuring the nitrogen a subject takes in (as food) against the nitrogen they lose (in urine and waste), a researcher can tell whether the body is building tissue or breaking it down. If you put an animal — or a person — on a diet of purified amino acids and then leave one amino acid out, and they slide into negative nitrogen balance and stop thriving, you have shown that the missing amino acid is one the body cannot make for itself. It is essential, in the precise nutritional sense: required from the diet.

Working first with rats on diets of purified amino acids, Rose's group sorted the amino acids into those the animal could synthesise and those it could not. Famously, in this work Rose also discovered the last of the twenty common amino acids to be identified — threonine, in 1935 — when he traced the failure of his amino-acid mixtures to a missing growth factor and isolated the new compound responsible. Once the full set was in hand, he and his collaborators carried the method into human studies in the 1940s and 1950s, feeding adult volunteers diets in which single purified amino acids could be removed one at a time. From this human work Rose established that eight amino acids are dietary essentials for adults — and valine was on that list, alongside isoleucine, leucine, lysine, methionine, phenylalanine, threonine, and tryptophan. (Modern nutrition usually counts nine essential amino acids by adding histidine, which later work showed to be required as well.)

This is the discovery that gives valine its everyday significance. Fischer's chemistry told us valine exists; Rose's nutrition told us valine matters — that it belongs to the short list of amino acids a human diet must supply, day in and day out, for a body to maintain and rebuild itself. Rose also went on to estimate how much of each essential amino acid people need, laying the groundwork for the dietary requirements still referenced today.

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A Hard Lesson: Maple Syrup Urine Disease

Part of valine's twentieth-century history is medical rather than chemical, and it came from studying what happens when the body cannot handle the branched-chain amino acids properly. In maple syrup urine disease (MSUD), a rare inherited disorder first described in the 1950s, a faulty enzyme leaves the body unable to break down valine, leucine, and isoleucine. These amino acids and their by-products build up to toxic levels, and one striking sign — the one that named the condition — is that affected infants' urine and earwax carry a sweet, maple-syrup-like smell.

MSUD is included here not to alarm but because it sharpened scientific understanding of valine itself. It demonstrated, in the starkest possible way, that valine is not simply a passive building block: the body actively metabolises it through a specific enzyme pathway, and that pathway has to work. The discovery and study of MSUD helped map exactly how branched-chain amino acids are processed, and it is also the reason that valine, normally a wholesome dietary nutrient, must be carefully restricted in people with this particular genetic condition. It is a vivid illustration of a recurring theme in nutrition: the same molecule the body cannot live without can, in the wrong metabolic circumstances, cause harm — and that the dose, the context, and the individual all matter.

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From Bench to Everyday Life

From the 1960s onward, valine's history becomes the quieter, cumulative story of a nutrient settling into science and daily life. With its essentiality established and its metabolism understood, valine took its place in the dietary guidelines and food-composition tables that nutritionists and food scientists use, and the World Health Organization and national bodies set reference intakes for it and the other essential amino acids. As industrial fermentation matured, valine and its branched-chain partners began to be produced on a large scale — for animal feed, clinical nutrition, and the supplement industry — rather than only being extracted from proteins one batch at a time.

Two strands of modern interest grew directly out of the early discoveries. From the nutritional side came the long study of the branched-chain amino acids in exercise, muscle maintenance, and the medical nutrition of liver disease — the practical questions of who benefits from extra valine and how much. From the clinical side, the lessons of MSUD fed into newborn screening and the broader understanding of how the body routes these amino acids. The detailed modern evidence — what valine does in muscle, metabolism, and the brain, and how to get enough of it — is covered in the companion Valine Benefits articles and on the main Valine page. This history is concerned with how we came to know valine at all.

Seen whole, valine's story is a small but clear example of how science learns. A nineteenth-century chemist may have glimpsed it; Fischer isolated and named it cleanly at the turn of the twentieth century and placed it within the new chemistry of proteins; Rose proved a generation later that we cannot do without it; and the study of a rare disease showed precisely how the body handles it. Each step was made by a different kind of researcher asking a different kind of question — and the unglamorous little molecule named, of all things, after a garden herb turned out to be one of the indispensable threads of human life.

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Research Papers and References

The list below pairs key historical and peer-reviewed sources with curated PubMed topic-search links into the literature on valine, the branched-chain amino acids, and the history of amino-acid and protein chemistry. Author names, titles, and journals are given as plain text; only the stable DOI, PMID, or archive link is hyperlinked, and each opens in a new tab. Encyclopaedia and museum reference entries (Britannica, NobelPrize.org) are named in the article as background sources.

  1. Simmer HH. Medicine and chemistry around the middle of the 19th century in Erlangen. Eugen Franz Freiherr von Gorup-Besanez (1817–1878). Journal of Clinical Chemistry and Clinical Biochemistry. 1981;19(7):497–509. — PMID: 7035607
  2. Simoni RD, Hill RL, Vaughan M. The discovery of the amino acid threonine: the work of William C. Rose. Journal of Biological Chemistry. 2002;277(37):E25. — PMID: 12218068
  3. The Nobel Prize in Chemistry 1902 — Hermann Emil Fischer, "in recognition of the extraordinary services he has rendered by his work on sugar and purine syntheses." The Nobel Foundation. — NobelPrize.org — Chemistry 1902
  4. Strauss BS. A physician's biochemistry: the history of the discovery of the amino acids and the elucidation of the genetic code (context for nineteenth- and twentieth-century amino-acid isolation). — PubMed: history of amino-acid isolation
  5. Valine — metabolism and the branched-chain amino acids (review literature) — PubMed: valine and branched-chain amino-acid metabolism
  6. Maple syrup urine disease — branched-chain amino-acid disorder — PubMed: maple syrup urine disease

External Authoritative Resources

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Connections

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