Lactic acid

Names Preferred IUPAC nameOther names Identifiers 1720251 ChEBIChEMBLChemSpiderECHA InfoCard100.000.017EC NumberE numberE270 (preservatives)362717 KEGGRTECS numberUNIIUN number3265 Properties C₃H₆O₃Molar mass90.078 g·mol Melting point18 °C (64 °F; 291 K) Boiling point122 °C (252 °F; 395 K) at 15mmHg 86.1% w/w at 20°C
88.6% w/w at 25°C Acidity (pK_a) 3.86, 15.1 Thermochemistry 1361.9kJ/mol, 325.5kcal/mol, 15.1kJ/g, 3.61kcal/g Related compounds lactate Pharmacology G01AD01 (WHO) QP53AG02 (WHO) Hazards GHS labelling: H315, H318P280, P305+P351+P338

Lactic acid is an organic acid with the molecular formula C₃H₆O₃. In its solid state, it is white and in its liquid state is miscible with water. When dissolved, it forms a colorless solution. Production includes both artificial synthesis and natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate (or the lactate anion). The name of the derived acyl group is lactoyl.

Lactic acid is chiral, consisting of two enantiomers. One is known as L-lactic acid, (S)-lactic acid, or (+)-lactic acid, and the other, its mirror image, is D-lactic acid, (R)-lactic acid, or (−)-lactic acid. A mixture of the two in equal amounts is called DL-lactic acid, or racemic lactic acid.

In animals, L-lactate is constantly produced from pyruvate via the enzymelactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. This reaction is reversible and redox-linked: LDH reduces pyruvate to lactate using NADH as an electron donor. Lactic acid is produced in human tissues when the demand for oxygen is limited by the supply. The process of lactic acidosis produces lactic acid, which results in an , which can be resolved or repaid when tissue oxygenation improves.

The concentration of blood lactate is usually 1–2mMTooltip millimolar at rest, but can rise to over 20mM during intense exertion and as high as 25mM afterward.

In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as cavities. In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassiumcations along with lactate and chlorideanions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid after blood loss due to trauma, surgery, or burns.