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L-Threonine(CAS No. 72-19-5)

L-Threonine C4H9NO3 (cas 72-19-5) Molecular Structure

72-19-5 Structure

Identification and Related Records

【CAS Registry number】
Butanoic acid, 2-amino-3-hydroxy-, (R-(R*,S*))-
Threonine [USAN:INN]
Treonina [Spanish]
(2R,3R)-2-amino-3-hydroxy-butanoic acid
Threonine, L-
(2S,3R)-2-Amino-3-hydroxybutyric acid
L-alpha-Amino-beta-hydroxybutyric acid
Threoninum [Latin]
Threonine (VAN)
L-2-Amino-3-hydroxybutyric acid
L-Threonine(Feed Grade)
L-Threonine Aji97
Threonine, L- (8CI)
(2S,3R)-2-amino-3-hydroxy-butanoic acid
[R-(R*,S*)]-2-Amino-3-hydroxybutanoic acid
L-Threonine (9CI)
Threonine (USP)
【Molecular Formula】
C4H9NO3 (Products with the same molecular formula)
【Molecular Weight】
【Canonical SMILES】
【MOL File】

Chemical and Physical Properties

White crystalline powder
1.307 g/cm3
【Melting Point】
256 °C (dec.)(lit.)
【Boiling Point】
345.8 °C at 760 mmHg
【Flash Point】
162.9 °C
-28.4 o (C=6, H2O)
90 G/L (20 oC)
90 g/L (20 oC)
Colorless crystals
Stable. Incompatible with strong oxidizing agents.
【HS Code】
【Storage temp】
Store at RT.
【Spectral properties】
Optically active
MASS: 26149 (NIST/EPA/MSDC Mass Spectral Database, 1990 version)
1H NMR: 11978 (Sadtler Research Laboratories spectral collection)
Raman: 423 (Sadtler Research Laboratories spectral collection)
IR: 21317 (Sadtler Research Laboratories IR grating collection)
【Computed Properties】
Molecular Weight:119.11916 [g/mol]
Molecular Formula:C4H9NO3
H-Bond Donor:3
H-Bond Acceptor:4
Rotatable Bond Count:2
Exact Mass:119.058243
MonoIsotopic Mass:119.058243
Topological Polar Surface Area:83.6
Heavy Atom Count:8
Formal Charge:0
Isotope Atom Count:0
Defined Atom Stereocenter Count:0
Undefined Atom Stereocenter Count:2
Defined Bond Stereocenter Count:0
Undefined Bond Stereocenter Count:0
Covalently-Bonded Unit Count:1
Feature 3D Acceptor Count:3
Feature 3D Donor Count:2
Feature 3D Anion Count:1
Feature 3D Cation Count:1
Effective Rotor Count:2
Conformer Sampling RMSD:0.4
CID Conformer Count:23

Safety and Handling

【Hazard Codes】
Xi: Irritant;
【Risk Statements】
【Safety Statements 】
【Hazard Note】

Hazard Codes: Xi
Risk Statements: 36/37/38: Irritating to eyes, respiratory system and skin?
Safety Statements: 24/25-37/39-26
24/25:? Avoid contact with skin and eyes?
37/39:? Wear suitable gloves and eye/face protection?
26:? In case of contact with eyes, rinse immediately with plenty of water and seek medical advice?
WGK Germany: 3
Hazard Note: Irritant
HS Code: 29225000

【Exposure Standards and Regulations】
L-Threonine is a food additive permitted for direct addition to food for human consumption, as long as 1) the quantity of the substance added to food does not exceed the amount reasonably required to accomplish its intended physical, nutritive, or other technical effect in food, and 2) any substance intended for use in or on food is of appropriate food grade and is prepared and handled as a food ingredient.
Drug products containing certain active ingredients offered over-the-counter (OTC) for certain uses. A number of active ingredients have been present in OTC drug products for various uses, as described below. However, based on evidence currently available, there are inadequate data to establish general recognition of the safety and effectiveness of these ingredients for the specified uses: threonine is included in weight control drug products.
Threonine used as a nutrient and/or dietary supplement in animal drugs, feeds, and related products is generally recognized as safe when used in accordance with good manufacturing or feeding practice.

1. First Aid Measures?of L-Threonine (CAS NO.72-19-5):
Ingestion: If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid.
Inhalation: Remove from exposure to fresh air immediately. Get medical aid if cough or other symptoms appear.
Skin: Get medical aid if irritation develops or persists. Flush skin with plenty of soap and water.
Eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid.
2. Handling and Storage:
Storage: Store in a tightly closed container. Store in a cool, dry, well-ventilated area away from incompatible substances.
Handling: Wash thoroughly after handling. Use with adequate ventilation. Minimize dust generation and accumulation. Avoid breathing dust, vapor, mist, or gas. Avoid contact with eyes, skin, and clothing. Keep container tightly closed. Avoid ingestion and inhalation.

【Octanol/Water Partition Coefficient】
log Kow = -2.94
【Disposal Methods】
SRP: Expired or waste pharmaceuticals shall carefully take into consideration applicable DEA, EPA, and FDA regulations. It is not appropriate to dispose by flushing the pharmaceutical down the toilet or discarding to trash. If possible return the pharmaceutical to the manufacturer for proper disposal being careful to properly label and securely package the material. Alternatively, the waste pharmaceutical shall be labeled, securely packaged and transported by a state licensed medical waste contractor to dispose by burial in a licensed hazardous or toxic waste landfill or incinerator.
SRP: At the time of review, regulatory criteria for small quantity disposal are subject to significant revision, however, household quantities of waste pharmaceuticals may be managed as follows: Mix with wet cat litter or coffee grounds, double bag in plastic, discard in trash.
SRP: Criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Use and Manufacturing

【Use and Manufacturing】
Methods of Manufacturing

Hydrolysis of protein (casein), organic synthesis.
U.S. Production

Production volumes for non-confidential chemicals reported under the Inventory Update Rule. Year Production Range (pounds) 1986 No Reports 1990 No Reports 1994 10 thousand - 500 thousand 1998 No Reports 2002 No Reports

Biomedical Effects and Toxicity

【Therapeutic Uses】
L-threonine has been used clinically with the aim of increasing glycine concentrations in the cerebral spinal fluid of patients with spasticity. When given in amounts of 4.5 to 6.0 g/day for 14 days, no adverse clinical effects were noted in such patients.
/Experimental Therapy/ To determine whether the naturally occurring amino acid threonine, a potential precursor for glycine biosynthesis in the spinal cord, has an effect on spasticity in multiple sclerosis, 26 ambulatory patients were entered into a randomized crossover trial. Threonine administered at a total daily dose of 7.5 g reduced signs of spasticity on clinical examination, although no symptomatic improvement could be detected by the examining physician or the patient. In contrast to the side effects of sedation and increased motor weakness associated with antispasticity drugs commonly used for the treatment of multiple sclerosis, no side effects or toxic effects of threonine were identified... [Hauser SL et al; Arch Neurol 49 (9): 923-6 (1992). Available from, as of March 17, 2010:]
【Biomedical Effects and Toxicity】
Although the free amino acids dissolved in the body fluids are only a very small proportion of the body's total mass of amino acids, they are very important for the nutritional and metabolic control of the body's proteins. ... Although the plasma compartment is most easily sampled, the concentration of most amino acids is higher in tissue intracellular pools. Typically, large neutral amino acids, such as leucine and phenylalanine, are essentially in equilibrium with the plasma. Others, notably glutamine, glutamic acid, and glycine, are 10- to 50-fold more concentrated in the intracellular pool. Dietary variations or pathological conditions can result in substantial changes in the concentrations of the individual free amino acids in both the plasma and tissue pools. /Amino acids/
After ingestion, proteins are denatured by the acid in the stomach, where they are also cleaved into smaller peptides by the enzyme pepsin, which is activated by the increase in stomach acidity that occurs on feeding. The proteins and peptides then pass into the small intestine, where the peptide bonds are hydrolyzed by a variety of enzymes. These bond-specific enzymes originate in the pancreas and include trypsin, chymotrypsins, elastase, and carboxypeptidases. The resultant mixture of free amino acids and small peptides is then transported into the mucosal cells by a number of carrier systems for specific amino acids and for di- and tri-peptides, each specific for a limited range of peptide substrates. After intracellular hydrolysis of the absorbed peptides, the free amino acids are then secreted into the portal blood by other specific carrier systems in the mucosal cell or are further metabolized within the cell itself. Absorbed amino acids pass into the liver, where a portion of the amino acids are taken up and used; the remainder pass through into the systemic circulation and are utilized by the peripheral tissues. /Amino acids/
About 11 to 15 g of nitrogen are excreted each day in the urine of a healthy adult consuming 70 to 100 g of protein, mostly in the form of urea, with smaller contributions from ammonia, uric acid, creatinine, and some free amino acids. These are the end products of protein metabolism, with urea and ammonia arising from the partial oxidation of amino acids. Uric acid and creatinine are indirectly derived from amino acids as well. The removal of nitrogen from the individual amino acids and its conversion to a form that can be excreted by the kidney can be considered as a two-part process. The first step usually takes place by one of two types of enzymatic reactions: transamination or deamination. Transamination is a reversible reaction that uses ketoacid intermediates of glucose metabolism (e.g., pyruvate, oxaloacetate, and alpha-ketoglutarate) as recipients of the amino nitrogen. Most amino acids can take part in these reactions, with the result that their amino nitrogen is transferred to just three amino acids: alanine from pyruvate, aspartate from oxaloacetate, and glutamate from alpha-ketoglutarate. Unlike many amino acids, branched-chain amino acid transamination occurs throughout the body, particularly in skeletal muscle. Here the main recipients of amino nitrogen are alanine and glutamine (from pyruvate and glutamate, respectively), which then pass into the circulation. These serve as important carriers of nitrogen from the periphery (skeletal muscle) to the intestine and liver. In the small intestine, glutamine is extracted and metabolized to ammonia, alanine, and citrulline, which are then conveyed to the liver via the portal circulation. Nitrogen is also removed from amino acids by deamination reactions, which result in the formation of ammonia. A number of amino acids can be deaminated, either directly (histidine), by dehydration (serine, threonine), by way of the purine nucleotide cycle (aspartate), or by oxidative deamination (glutamate). ... Glutamate is also formed in the specific degradation pathways of arginine and lysine. Thus, nitrogen from any amino acid can be funneled into the two precursors of urea synthesis, ammonia and aspartate.
Although it seems clear that the efficiency of dietary protein digestion (in the sense of removal of amino acids from the small intestinal lumen) is high, there is now good evidence to show that nutritionally significant quantities of indispensable amino acids are metabolized by the tissues of the splanchnic bed, including the mucosal cells of the intestine. Thus, less than 100% of the amino acids removed from the intestinal lumen appear in the peripheral circulation, and the quantities that are metabolized by the splanchnic bed vary among the amino acids, with intestinal threonine metabolism being particularly high.
Eight preterm infants (x +/- SD birth weight: 1.1 +/- 0.1 kg; gestational age: 29 +/- 2 wk) were studied during 2 periods. During period A, 40% of total intake was administered enterally and 60% was administered parenterally. Total threonine intake was 58 +/- 6 umol/kg/ hr. During period B, the infants received full enteral feeding, and the total threonine intake was 63 +/- 6 umol/kg/hr. Dual stable-isotope tracer techniques were used to assess splanchnic and whole-body threonine kinetics. RESULTS: The fractional first-pass threonine uptake by the intestine was remarkably high in both periods: 82 +/- 6% during partial enteral feeding and 70 +/- 6% during full enteral feeding. Net threonine retention was not affected by the route of feeding. CONCLUSION: In preterm infants, the splanchnic tissues extract a very large amount of the dietary threonine intake, which indicates a high obligatory visceral need for threonine, presumably for the purposes of synthesis. [Van der Schoor SR et al; Am J Clin Nutr 86 (4): 1132-8 (2007). Available from, as of March 17, 2010:] PubMed Abstract
Plasma threonine concentrations are elevated in infants fed formula containing a whey-to-casein protein ratio of 60:40 compared with concentrations in infants fed formula containing a ratio of 20:80 or human milk (60:40). ... Threonine kinetics were examined in 17 preterm infants (gestational age: 31+/-2 wk: birth weight: 1720+/-330 g) by using an 18-hr oral infusion of [1-13C]threonine at a postnatal age of 21+/-11 d and weight of 1971+/-270 g. Five infants received breast milk. Formula-fed infants (n = 12) were randomly assigned to receive 1 of 3 formulas (5.3 g protein/MJ) that differed only in the whey-to-casein ratio (20:80, 40:60, and 60:40). RESULTS: Threonine intake increased significantly in formula-fed infants with increasing whey content of the formula (48.5, 56.4, and 63.2 umol/kg/hr, respectively; pooled SD: 2.2; P = 0.0001), as did plasma threonine concentrations (228, 344, and 419 umol/L, respectively; pooled SD: 75; P = 0.03). Despite a generous threonine intake by infants fed breast milk (58.0+/-16.0 umol/kg/hr, plasma threonine concentrations remained low (208+/-41 umol/L). Fecal threonine excretion and net threonine tissue gain, estimated by nitrogen balance, did not differ significantly among groups. Threonine oxidation did not differ significantly among formula-fed infants but was significantly lower in formula-fed infants fed than in infants fed breast milk (17.1% compared with 24.3% of threonine intake, respectively). CONCLUSION: Formula-fed infants have a lower capacity to oxidize threonine than do infants fed breast milk. [Darling PB et al; Am J Clin Nutr 69 (1): 105-14 (1999). Available from, as of March 17, 2010:] PubMed Abstract
To study the effect of different threonine intakes on plasma and tissue amino acid concentrations, 24 young male Wistar rats were fed three experimental diets based on a mixture of bovine proteins with a whey protein/casein ratio of 60/40 with different threonine contents [group A, 0.86 g of threonine/100 g (n = 8); group B, 1.03 g of threonine/100 g (n = 8); group C, 2.21 g of threonine/100 g (n = 8)]. Eight animals were fed a typical rat diet based on bovine casein as controls. After a feeding period of 15 d, amino acids were measured in plasma and in homogenates of the cerebral cortex, brain stem, liver, and muscle. There was a significant correlation between threonine intake and plasma threonine levels (r = 0.687, p PubMed Abstract
A study was undertaken in eight healthy young men to examine the effects of varying intakes of threonine on plasma free threonine concentrations and threonine kinetics, using a 3 hr constant intravenous infusion of L-[1-13C]threonine. Subjects consumed diets based on an L-amino acid mixture, in which the quality of threonine was reduced every 7 days. On the last day of each diet period, determinations of plasma threonine flux and threonine oxidation were carried out while subjects consumed small meals, each supplying 1/12 daily intake, at hourly intervals. Threonine oxidation rates fell with reduced threonine intake, reaching a relatively constant level at intakes of 20 mg/kg/day and below. These metabolic data are discussed in relation to the currently established value of 7 mg/kg/day as the upper range of the threonine requirement for healthy young adults. It is concluded that actual threonine requirements may be considerably higher for this age group. [Zhao XH et al; Am J Clin Nutr 43 (5): 795-802 (1986). Available from, as of March 17, 2010:] PubMed Abstract
The high requirement of the gut for threonine has often been ascribed to the synthesis of mucins, secreted threonine-rich glycoproteins protecting the intestinal epithelium from injury. This requirement could be even greater during intestinal inflammation, when mucin synthesis is enhanced. ...This study ... used an animal model to investigate the effects of an acute ileitis on threonine splanchnic fluxes. Eight adult multi-catheterized were fed with an enteral solution. Four of them were subjected to experimental ileitis involving direct administration of trinitrobenzene sulfonic acid (TNBS) into the ileum (TNBS-treated group) and the other 4 were not treated (control group). Threonine fluxes across the portal-drained viscera (PDV) were quantified with the use of simultaneous i.g. L-[(15)N]threonine and i.v. L-[U-(13)C]threonine infusions. Ileal mucosa was sampled for mucin fractional synthesis rate measurement, which was greater in the TNBS-treated group (114 +/- 15%/d) than in the control group (61 +/- 8%/d) (P = 0.021). The first-pass extraction of dietary threonine by the PDV and liver did not differ between groups and accounted for approximately 27 and 10% of the intragastric delivery, respectively. PDV uptake of arterial threonine increased from 25 +/- 14 umol/kg/hr in the control group to 171 +/- 35 umol/kg/hr in the TNBS-treated group (P
The whole-body threonine requirement in parenterally fed piglets is substantially lower than that in enterally fed piglets, indicating that enteral nutrition induces intestinal processes in demand of threonine. /It was/ hypothesized that the percentage of threonine utilization for oxidation and intestinal protein synthesis by the portal-drained viscera (PDV) increases when dietary protein intake is reduced. Piglets (n = 18) received isocaloric normal or protein-restricted diets. After 7 h of enteral feeding, total threonine utilization, incorporation into intestinal tissue, and oxidation by the PDV, were determined with stable isotope methodology [U-(13)C threonine infusion]. Although the absolute amount of systemic and dietary threonine utilized by the PDV was reduced in protein-restricted piglets, the percentage of dietary threonine intake utilized by the PDV did not differ between groups (normal protein 91% vs. low protein 85%). The incorporation of dietary threonine into the proximal jejunum was significantly different compared with the other intestinal segments. Dietary, rather than systemic threonine was preferentially utilized for protein synthesis in the small intestinal mucosa in piglets that consumed the normal protein diet (P
Five pregnant sheep (130+/-1.0 days after conception) were infused for 2 hr with a threonine (THR) solution (4.4+/-0.2 umol/kg/min). Plasma amino acids, glucose and lactate, hematocrit, blood O(2) content in maternal arterial, uterine venous, umbilical arterial and venous blood were measured. Uterine and umbilical blood flows were measured before and during the infusion and were used to calculate uterine and umbilical uptakes. Maternal and fetal plasma insulin and glucagon concentrations were also measured. The THR infusion increased maternal plasma THR (904 vs 236 uM, P
In most animals, ingestion of a diet lacking an essential amino acid (EAA) gives rise to anorexia within a few hours. The first signal in this feeding response may be the fall in plasma levels of the limiting EAA. In the present study, we measured plasma amino acid levels and food intake after the first exposure to either a threonine-devoid (THR-DEV) or corrected (COR) diet in 16 rats bearing a chronic jugular catheter for blood sampling. Food intake was reduced 165 min (p

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