Threonine (α-amino-3-hydroxybutanoic acid) is the α-((R)-1-hydroxy-1-ethyl)-substituted amino acid of proteins. Amino acids play a key metabolic function in the human body and are constituents of proteins. It is a proteinogenic essential amino acid that belongs to the aspartate family, is not synthesised in humans, animals and therefore must be ingested with food. It is also a residual part of proteins such as elastin, collagen, tooth enamel. It prevents the accumulation of fat in the liver by metabolising porphyrin. 

α-amino acids that have similar physical structures undergo similar changes with regard to solubility in water/ethanol mixtures, and technologies to separate α-amino acids from industrial residues, which may not even be innocuous, are constantly being improved. However, many data on the solubility in water-ethanol and ethanol of some α-amino acids are contradictory or even lacking, and the effects of ethanol on the solubility of amino acids may be different. Overall, the scientific literature considers that α-amino acids do not pose significant problems for human health when taken orally, except in people with certain genetic diseases.

Food safety: amino acid α generally considered safe.

Cosmetic safety: amino acid α generally considered safe when formulated to be non-irritant.

It appears as a white crystalline powder or as beige crystals. Slightly sweet taste. Soluble in formic acid, in water, practically insoluble in ethanol and ether.

What it is used for and where

Agrochemical intermediate, for food, flavours and fragrances.

Medical

Threonine performs the function of incorporating intestinal mucosa into proteins and synthesises secretory glycoproteins, protecting the intestinal barrier.

Food

Used in food supplements or added to food to improve the nutritional value of proteins. As food additives they perform different functions: preservatives, flavour enhancers, food supplements and more.

Cosmetics

Incorporated into skin care products for a nourishing effect on proteins, collagen. Amino acids together with their salts are used in cosmetics as conditioning agents for both hair and skin (e.g. as moisturisers and other similar functions). Moisturisers are different in nature: the best are the natural ones that exploit the mechanism of integration between the ingredient and the skin by moisturising the horny hydrolipid film, i.e. the thin protective layer that covers the epidermis protecting it from harmful external microbes, keeping the skin moisturised and supple and its pH or acidity value between 4 and 6.  Then there are the occlusive moisturisers, usually derived from petroleum (Paraffinum, Paraffinum liquidum and others), but also triglycerides, lanolin oil, natural or synthetic waxes, fatty acid esters and others that create an artificial occlusive layer on the stratum corneum of the skin with the advantage of accelerating the protective process but with the disadvantage of preventing the skin's natural transpiration.

Animal feeding

Threonine has important physiological roles in the animal body: it promotes growth, improves immune function and, in animal feed, reduces the protein requirements of livestock and poultry. In practice, its function is to balance dietary amino acids by bringing the ratio of amino acids closer to the ideal protein. It facilitates fattening, egg production and lactation.

Treonina studies

Typical commercial product characteristics L-Threonine

Appearance	White powder
Boiling Point	345.8±32.0°C at 760 mmHg
Melting Point	255°C
Flash Point	162.9±25.1°C
Density	1.3±0.1 g/cm3
Loss on drying	≤1.0%
Water	≤0.5%
Sulphated ash	≤0.5%/g
Residue on ignition	≤0.03%
Total Impurity	≤0.2%
Refraction Index	1.507
PSA	83.55000
LogP	-1.23
Vapor Pressure	0.0±1.7 mmHg at 25°C
Safety

• Molecular Formula   C₄H₉NO₃
• Linear Formula   CH₃CH(OH)CH(NH₂)CO₂H
• Molecular Weight    119.12
• Exact Mass   119.058243
• CAS  72-19-5
• UNII    2ZD004190S
• EC Number   200-774-1
• DSSTox Substance ID  DTXSID2046412
• IUPAC  (2S,3R)-2-amino-3-hydroxybutanoic acid
• InChI=1S/C4H9NO3/c1-2(6)3(5)4(7)8/h2-3,6H,5H2,1H3,(H,7,8)/t2-,3+/m1/s1 
• InChl Key      AYFVYJQAPQTCCC-GBXIJSLDSA-N
• SMILES   CC(C(C(=O)O)N)O
• MDL number  MFCD00064270
• PubChem Substance ID    24900544
• ChEBI    16857
• JECFA    2119
• Beilstein    1721646
• RXCUI   10524   
• NSC   760118
• RTECS   XO8590000
• FEMA    4710   
• NCI   C29602
• eCl@ss    32160406
• NACRES  NA.26

Synonyms

• L-Threonine
• (2S,3R)-2-Amino-3-hydroxybutyric acid
• L-alpha-Amino-beta-hydroxybutyric acid
• L-thr
• L-2-Amino-3-hydroxybutyric acid
• Threoninum