Malic acid


Malic acid
Malic acid
Identifiers
CAS number 6915-15-7 YesY
PubChem 525
ChemSpider 510 YesY, 83793 D-(+)-malic acid YesY, 193317 L-(-)-malic acid YesY
UNII 817L1N4CKP YesY
EC number 230-022-8
KEGG D04843 YesY
ChEBI CHEBI:6650 YesY
Jmol-3D images Image 1
Properties
Molecular formula C4H6O5
Molar mass 134.09 g mol−1
Density 1.609 g cm−3
Melting point

130 °C, 403 K, 266 °F

Solubility in water 558 g/L (at 20 °C)[1]
Acidity (pKa) pKa1 = 3.40, pKa2 = 5.20 [2]
Related compounds
Other anions malate
Related carboxylic acids succinic acid
tartaric acid
fumaric acid
Related compounds butanol
butyraldehyde
crotonaldehyde
sodium malate
 YesY acid (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L- and D-enantiomers), though only the L-isomer exists naturally. The salts and esters of malic acid are known as malates. The malate anion is an intermediate in the citric acid cycle.

Contents

Biochemistry

L-Malic acid is the naturally occurring form, whereas a mixture of L- and D-malic acid is produced synthetically.

Malate plays an important role in biochemistry. In the C4 carbon fixation process, malate is a source of CO2 in the Calvin cycle. In the citric acid cycle, (S)-malate is an intermediate, formed by the addition of an -OH group on the si face of fumarate. It can also be formed from pyruvate via anaplerotic reactions.

Malate is also synthesized by the carboxylation of phosphoenolpyruvate in the guard cells of plant leaves. Malate, as a double anion, often accompanies potassium cations during the uptake of solutes into the guard cells in order to maintain electrical balance in the cell. The accumulation of these solutes within the guard cell decreases the solute potential, allowing water to enter the cell and promote aperture of the stomata.

Malic acid in food

Malic acid was first isolated from apple juice by Carl Wilhelm Scheele in 1785. Antoine Lavoisier in 1787 proposed the name acide malique which is derived from the Latin word for apple, mālum.[3] Malic acid contributes to the sourness of green apples. It is present in grapes and in most wines with concentrations sometimes as high as 5 g/l.[4] It confers a tart taste to wine, although the amount decreases with increasing fruit ripeness. The process of malolactic fermentation converts malic acid to much milder lactic acid.

Malic acid, when added to food products, is denoted by E number E296. Malic acid is the source of extreme tartness in USA-produced confectionery, the so-called extreme candy. It is also used with or in place of the less sour citric acid in sour sweets. These sweets are sometimes labeled with a warning stating that excessive consumption can cause irritation of the mouth. It is approved for use as a food additive in the EU,[5] USA[6] and Australia and New Zealand[7] (where it is listed by its INS number 296).

Production and main reactions

Malic acid is produced industrially by the double hydration of maleic anhydride.[8]

Self-condensation of malic acid with fuming sulfuric acid gives the pyrone coumalic acid:[9]

Coumalic Acid Synthesis

Malic acid was important in the discovery of the Walden inversion and the Walden cycle, in which (-)-malic acid first is converted into (+)-chlorosuccinic acid by action of phosphorus pentachloride. Wet silver oxide then converts the chlorine compound to (+)-malic acid, which then reacts with PCl5 to the (-)-chlorosuccinic acid. The cycle is completed when silver oxide takes this compound back to (-)-malic acid.

Interactive pathway map

Click on genes, proteins and metabolites below to link to respective articles.[10]

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Citric_acid_cycle edit

See also

References

  1. ^ chemBlink Online Database of Chemicals from Around the World
  2. ^ Dawson, R. M. C. et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  3. ^ The Origin of the Names Malic, Maleic, and Malonic Acid Jensen, William B. J. Chem. Educ. 2007, 84, 924. Abstract
  4. ^ "Methods For Analysis of Musts and Wines", Ough and Amerine, John Wiley and Sons, 2nd Edition, 1988, page 67
  5. ^ UK Food Standards Agency: "Current EU approved additives and their E Numbers". http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist. Retrieved 2011-10-27. 
  6. ^ US Food and Drug Administration: "Listing of Food Additives Status Part II". http://www.fda.gov/Food/FoodIngredientsPackaging/FoodAdditives/ucm191033.htm#ftnT. Retrieved 2011-10-27. 
  7. ^ Australia New Zealand Food Standards Code"Standard 1.2.4 - Labelling of ingredients". http://www.comlaw.gov.au/Details/F2011C00827. Retrieved 2011-10-27. 
  8. ^ Karlheinz Miltenberger "Hydroxycarboxylic Acids, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry,2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13 507
  9. ^ Richard H. Wiley and Newton R. Smith (1963), "Coumalic acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0201 ; Coll. Vol. 4: 201 
  10. ^ The interactive pathway map can be edited at WikiPathways: "TCACycle_WP78". http://www.wikipathways.org/index.php/Pathway:WP78. 

External links



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Look at other dictionaries:

  • Malic acid — Malic Ma lic, a. [L. malum an apple: cf. F. malique.] (Chem.) Pertaining to, or obtained from, apples; as, malic acid. [1913 Webster] {Malic acid}, (Chem.) a hydroxy acid ({HO.CO.CH2.CH(OH).CO.OH}) obtained from unripe fruit (such as green apples …   The Collaborative International Dictionary of English

  • malic acid — [mal′ik, mā′lik] n. [Fr acide malique < L malum < Gr mēlon, apple] a crystalline acid, COOHCH2CH(OH)COOH, occurring in apples and other fruits …   English World dictionary

  • malic acid — Hydroxysuccinic acid; an acid found in apples and various other tart fruits; an intermediate in the tricarboxylic acid cycle, the glyoxylate cycle, and in a shuttle system. SYN: monohydroxysuccinic acid. * * * malic acid n any of three optical… …   Medical dictionary

  • malic acid — noun Etymology: French acide malique, ultimately from Latin malum apple, from Greek mēlon, malon Date: 1790 a crystalline dicarboxylic acid C4H6O5; especially the levorotatory isomer of malic acid that is found in various fruits (as apples) and… …   New Collegiate Dictionary

  • malic acid — obuolių rūgštis statusas T sritis chemija formulė HOOCCH(OH)CH₂COOH atitikmenys: angl. malic acid rus. яблочная кислота ryšiai: sinonimas – hidroksibutano dirūgštis …   Chemijos terminų aiškinamasis žodynas

  • malic acid — [ malɪk] noun Chemistry a crystalline acid present in unripe apples and other fruits. Origin C18: malic from Fr. malique, from L. malum apple …   English new terms dictionary

  • malic acid — noun A colourless crystalline dicarboxylic acid, hydroxy malonic acid, found in wine, apples and other fruit; it is converted to lactic acid by malo lactic fermentation. Syn: E296, acidity regulator …   Wiktionary

  • malic acid — /mælɪk ˈæsəd/ (say malik asuhd) noun a crystalline, dibasic hydroxy acid, C2H3OH(COOH)2, occurring in small amounts in almost all living cells as a component of the citric acid cycle, and in greater amounts in apples, grapes, and other fruits …   Australian English dictionary

  • malic acid — англ. яблочная кислота (едкая органическая кислота, изначально присутствующая в виноградных ягодах и, соответственно, в сусле; может придать вкусу вина излишнюю едкость и терпкость, поэтому в производстве большинства красных и некоторых белых вин …   Англо-русский толковый словарь "Вино"

  • malic acid — n. acid in fruits (such as in apples and tomatoes) …   English contemporary dictionary


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