You are using an unsupported browser. Please upgrade your browser to a newer version to get the best experience on Human Metabolome Database.
Record Information
StatusExpected but not Quantified
Creation Date2012-09-06 15:16:49 UTC
Update Date2020-07-08 18:02:29 UTC
Secondary Accession Numbers
  • HMDB14312
Metabolite Identification
Common Name(S)-Lipoic acid
DescriptionLipoic acid (LA), also known as alpha-lipoic acid (ALA) is an organosulfur compound derived from octanoic acid. The carbon atom at C6 is chiral and the molecule exists as two enantiomers (R)-(+)-lipoic acid (RLA) and (S)-(-)-lipoic acid (SLA) and as a racemic mixture (R/S)-lipoic acid (R/S-LA). Only the (R)-(+)-enantiomer exists in nature and is an essential cofactor of four mitochondrial enzyme complexes. Endogenously synthesized RLA is essential for life and aerobic metabolism. The precursor to lipoic acid, octanoic acid, is made via fatty acid biosynthesis in the form of octanoyl-acyl carrier protein. In eukaryotes, a second fatty acid biosynthetic pathway in mitochondria is used for this purpose. The octanoate is transferred from a thioester of acyl carrier protein to an amide of the lipoyl domain by an octanoyltransferase. The sulfur centers are inserted into the 6th and 8th carbons of octanoate via a radical SAM mechanism, by lipoyl synthase. Lipoic acid can be removed whenever proteins are degraded and by the action of the enzyme lipoamidase. Free lipoate can be attached to the lipoyl domain by the enzyme lipoate protein ligase. The ligase activity of this enzyme requires ATP. Lipoate protein ligases proceed via an enzyme-bound lipoyl adenylate intermediate. Both RLA and R/S-LA are available as over-the-counter nutritional supplements and have been used nutritionally and clinically since the 1950s for various diseases and conditions. It is often regarded as a vitamin-like antioxidant. Lipoic acid is generally involved in oxidative decarboxylations of keto acids and is presented as a growth factor for some organisms. Some studies have suggested that the S-enantiomer has an inhibiting effect on the R-enantiomer, reducing its biological activity substantially and adding to oxidative stress rather than reducing it (PMID: 8573188 , 7669066 ). Furthermore, the S-enantiomer has been found to reduce the expression of GLUT-4s in cells, responsible for glucose uptake, and hence reduce insulin sensitivity (PMID: 9252495 ).
(S)-(-)-Lipoic acidChEBI
(S)-1,2-Dithiolane-3-pentanoic acidChEBI
(S)-alpha-Lipoic acidChEBI
L-1,2-Dithiolane 3-valeric acidChEBI
L-6,8-Thioctic acidChEBI
L-6-Thioctic acidChEBI
Lipoic acidChEBI
Thioctic acid L-formChEBI
(S)-a-Lipoic acidGenerator
(S)-α-lipoic acidGenerator
L-1,2-Dithiolane 3-valerateGenerator
Thioctate L-formGenerator
Acid, alpha-lipoicMeSH, HMDB
Thioctic acidMeSH, HMDB
alpha Lipoic acidMeSH, HMDB
(-)-Thioctic acidHMDB
(3S)-1,2-Dithiolane-3-pentanoic acidHMDB
(S)-Lipoic acidHMDB
(S)-Thioctic acidHMDB
S-(-)-alpha-Lipoic acidHMDB
S-(-)-α-Lipoic acidHMDB
1,2-Dithiolane-3-valeric acidHMDB
1,2-Dithiolane-3-pentanoic acidHMDB
5-(1,2-Dithiolan-3-yl)pentanoic acidHMDB
5-(1,2-Dithiolan-3-yl)valeric acidHMDB
6,8-Thioctic acidHMDB
6-Thioctic acidHMDB
Chemical FormulaC8H14O2S2
Average Molecular Weight206.326
Monoisotopic Molecular Weight206.043521072
IUPAC Name5-[(3S)-1,2-dithiolan-3-yl]pentanoic acid
Traditional NameS-LA
CAS Registry Number1077-27-6
InChI Identifier
Chemical Taxonomy
Description belongs to the class of organic compounds known as lipoic acids and derivatives. Lipoic acids and derivatives are compounds containing a lipoic acid moiety (or a derivative thereof), which consists of a pentanoic acid (or derivative) attached to the C3 carbon atom of a 1,2-dithiolane ring.
KingdomOrganic compounds
Super ClassOrganoheterocyclic compounds
Sub ClassLipoic acids and derivatives
Direct ParentLipoic acids and derivatives
Alternative Parents
  • Lipoic_acid_derivative
  • Medium-chain fatty acid
  • Heterocyclic fatty acid
  • Thia fatty acid
  • Fatty acyl
  • Fatty acid
  • 1,2-dithiolane
  • Organic disulfide
  • Monocarboxylic acid or derivatives
  • Carboxylic acid
  • Carboxylic acid derivative
  • Hydrocarbon derivative
  • Organooxygen compound
  • Organic oxide
  • Organic oxygen compound
  • Carbonyl group
  • Aliphatic heteromonocyclic compound
Molecular FrameworkAliphatic heteromonocyclic compounds
External Descriptors

Biological location:


Naturally occurring process:


Biological role:

Industrial application:

Physical Properties
Experimental Properties
Melting PointNot AvailableNot Available
Boiling PointNot AvailableNot Available
Water Solubility0.22 g/LNot Available
LogP2.1Not Available
Predicted Properties
Water Solubility0.22 g/LALOGPS
pKa (Strongest Acidic)4.52ChemAxon
Physiological Charge-1ChemAxon
Hydrogen Acceptor Count2ChemAxon
Hydrogen Donor Count1ChemAxon
Polar Surface Area37.3 ŲChemAxon
Rotatable Bond Count5ChemAxon
Refractivity54.37 m³·mol⁻¹ChemAxon
Polarizability21.91 ųChemAxon
Number of Rings1ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleNoChemAxon
Spectrum TypeDescriptionSplash KeyView
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Positivesplash10-052r-0920000000-cf913d1d1afc04e5450cSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Positivesplash10-0bti-5910000000-294c510229247ef63f20Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Positivesplash10-0bvi-9600000000-f8f54eb79c5d4d5bef48Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 10V, Negativesplash10-0a4i-0920000000-5a823a30dd1fb434e5b1Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 20V, Negativesplash10-0kmu-1910000000-6f491a68afd82922e71bSpectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - 40V, Negativesplash10-0a4i-9200000000-330e4766f82ed571497bSpectrum
Biological Properties
Cellular Locations
  • Cytoplasm
  • Membrane
Biospecimen Locations
  • Blood
  • Urine
Tissue LocationsNot Available
Normal Concentrations
BloodExpected but not QuantifiedNot QuantifiedNot AvailableNot AvailableTaking drug identified by DrugBank entry DB00166 details
UrineExpected but not QuantifiedNot QuantifiedNot AvailableNot AvailableTaking drug identified by DrugBank entry DB00166 details
Abnormal Concentrations
Not Available
Associated Disorders and Diseases
Disease ReferencesNone
Associated OMIM IDsNone
DrugBank IDNot Available
Phenol Explorer Compound IDNot Available
FooDB IDNot Available
KNApSAcK IDNot Available
Chemspider ID392857
KEGG Compound IDNot Available
BioCyc IDNot Available
BiGG IDNot Available
Wikipedia LinkLipoic_acid
METLIN IDNot Available
PubChem Compound445125
PDB IDNot Available
ChEBI ID43796
Food Biomarker OntologyNot Available
VMH IDNot Available
MarkerDB ID
Synthesis ReferenceNot Available
Material Safety Data Sheet (MSDS)Not Available
General References
  1. Perham RN: Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu Rev Biochem. 2000;69:961-1004. [PubMed:10966480 ]
  2. REED LJ, DeBUSK BG, GUNSALUS IC, HORNBERGER CS Jr: Crystalline alpha-lipoic acid; a catalytic agent associated with pyruvate dehydrogenase. Science. 1951 Jul 27;114(2952):93-4. [PubMed:14854913 ]
  3. Biewenga GP, Dorstijn MA, Verhagen JV, Haenen GR, Bast A: Reduction of lipoic acid by lipoamide dehydrogenase. Biochem Pharmacol. 1996 Feb 9;51(3):233-8. doi: 10.1016/0006-2952(95)02124-8. [PubMed:8573188 ]
  4. Loffelhardt S, Bonaventura C, Locher M, Borbe HO, Bisswanger H: Interaction of alpha-lipoic acid enantiomers and homologues with the enzyme components of the mammalian pyruvate dehydrogenase complex. Biochem Pharmacol. 1995 Aug 25;50(5):637-46. doi: 10.1016/0006-2952(95)00175-y. [PubMed:7669066 ]
  5. Streeper RS, Henriksen EJ, Jacob S, Hokama JY, Fogt DL, Tritschler HJ: Differential effects of lipoic acid stereoisomers on glucose metabolism in insulin-resistant skeletal muscle. Am J Physiol. 1997 Jul;273(1 Pt 1):E185-91. doi: 10.1152/ajpendo.1997.273.1.E185. [PubMed:9252495 ]


General function:
Involved in oxidoreductase activity
Specific function:
This enzyme is required for electron transfer from NADP to cytochrome P450 in microsomes. It can also provide electron transfer to heme oxygenase and cytochrome B5.
Gene Name:
Uniprot ID:
Molecular weight:
  1. Dudka J: Decrease in NADPH-cytochrome P450 reductase activity of the human heart, Liver and lungs in the presence of alpha-lipoic acid. Ann Nutr Metab. 2006;50(2):121-5. Epub 2006 Jan 2. [PubMed:16391466 ]
  2. Wen B, Coe KJ, Rademacher P, Fitch WL, Monshouwer M, Nelson SD: Comparison of in vitro bioactivation of flutamide and its cyano analogue: evidence for reductive activation by human NADPH:cytochrome P450 reductase. Chem Res Toxicol. 2008 Dec;21(12):2393-406. doi: 10.1021/tx800281h. [PubMed:19548358 ]
  3. Gan L, von Moltke LL, Trepanier LA, Harmatz JS, Greenblatt DJ, Court MH: Role of NADPH-cytochrome P450 reductase and cytochrome-b5/NADH-b5 reductase in variability of CYP3A activity in human liver microsomes. Drug Metab Dispos. 2009 Jan;37(1):90-6. doi: 10.1124/dmd.108.023424. Epub 2008 Oct 6. [PubMed:18838505 ]
General function:
Involved in catalytic activity
Specific function:
Catalyzes the radical-mediated insertion of two sulfur atoms into the C-6 and C-8 positions of the octanoyl moiety bound to the lipoyl domains of lipoate-dependent enzymes, thereby converting the octanoylated domains into lipoylated derivatives (By similarity).
Gene Name:
Uniprot ID:
Molecular weight:
  1. Morikawa T, Yasuno R, Wada H: Do mammalian cells synthesize lipoic acid? Identification of a mouse cDNA encoding a lipoic acid synthase located in mitochondria. FEBS Lett. 2001 Jun 1;498(1):16-21. [PubMed:11389890 ]
  2. Yasuno R, Wada H: Biosynthesis of lipoic acid in Arabidopsis: cloning and characterization of the cDNA for lipoic acid synthase. Plant Physiol. 1998 Nov;118(3):935-43. [PubMed:9808738 ]
  3. Ollagnier-de Choudens S, Fontecave M: The lipoate synthase from Escherichia coli is an iron-sulfur protein. FEBS Lett. 1999 Jun 18;453(1-2):25-8. [PubMed:10403368 ]
  4. Wrenger C, Muller S: The human malaria parasite Plasmodium falciparum has distinct organelle-specific lipoylation pathways. Mol Microbiol. 2004 Jul;53(1):103-13. [PubMed:15225307 ]
  5. Gunther S, McMillan PJ, Wallace LJ, Muller S: Plasmodium falciparum possesses organelle-specific alpha-keto acid dehydrogenase complexes and lipoylation pathways. Biochem Soc Trans. 2005 Nov;33(Pt 5):977-80. [PubMed:16246025 ]
General function:
Involved in transporter activity
Specific function:
Transports pantothenate, biotin and lipoate in the presence of sodium.
Gene Name:
Uniprot ID:
Molecular weight:
  1. Prasad PD, Wang H, Huang W, Fei YJ, Leibach FH, Devoe LD, Ganapathy V: Molecular and functional characterization of the intestinal Na+-dependent multivitamin transporter. Arch Biochem Biophys. 1999 Jun 1;366(1):95-106. [PubMed:10334869 ]
  2. Dey S, Subramanian VS, Chatterjee NS, Rubin SA, Said HM: Characterization of the 5' regulatory region of the human sodium-dependent multivitamin transporter, hSMVT. Biochim Biophys Acta. 2002 Mar 19;1574(2):187-92. [PubMed:11955628 ]
  3. Griffin JB, Stanley JS, Zempleni J: Synthesis of a rabbit polyclonal antibody to the human sodium-dependent multivitamin transporter. Int J Vitam Nutr Res. 2002 Jul;72(4):195-8. [PubMed:12214555 ]
General function:
Involved in catalytic activity
Specific function:
Has medium-chain fatty acid:CoA ligase activity with broad substrate specificity (in vitro). Acts on acids from C(4) to C(11) and on the corresponding 3-hydroxy- and 2,3- or 3,4-unsaturated acids (in vitro). Functions as GTP-dependent lipoate-activating enzyme that generates the substrate for lipoyltransferase (By similarity).
Gene Name:
Uniprot ID:
Molecular weight:
Guanosine triphosphate + (S)-Lipoic acid → Pyrophosphate + lipoyl-GMPdetails
General function:
Involved in catalytic activity
Specific function:
Catalyzes the transfer of the lipoyl group from lipoyl-AMP to the specific lysine residue of lipoyl domains of lipoate-dependent enzymes (By similarity).
Gene Name:
Uniprot ID:
Molecular weight:
  1. Gunther S, McMillan PJ, Wallace LJ, Muller S: Plasmodium falciparum possesses organelle-specific alpha-keto acid dehydrogenase complexes and lipoylation pathways. Biochem Soc Trans. 2005 Nov;33(Pt 5):977-80. [PubMed:16246025 ]
  2. Fujiwara K, Toma S, Okamura-Ikeda K, Motokawa Y, Nakagawa A, Taniguchi H: Crystal structure of lipoate-protein ligase A from Escherichia coli. Determination of the lipoic acid-binding site. J Biol Chem. 2005 Sep 30;280(39):33645-51. Epub 2005 Jul 25. [PubMed:16043486 ]
  3. Gueguen V, Macherel D, Neuburger M, Pierre CS, Jaquinod M, Gans P, Douce R, Bourguignon J: Structural and functional characterization of H protein mutants of the glycine decarboxylase complex. J Biol Chem. 1999 Sep 10;274(37):26344-52. [PubMed:10473591 ]
  4. Macherel D, Bourguignon J, Forest E, Faure M, Cohen-Addad C, Douce R: Expression, lipoylation and structure determination of recombinant pea H-protein in Escherichia coli. Eur J Biochem. 1996 Feb 15;236(1):27-33. [PubMed:8617275 ]
  5. Fujiwara K, Hosaka H, Matsuda M, Okamura-Ikeda K, Motokawa Y, Suzuki M, Nakagawa A, Taniguchi H: Crystal structure of bovine lipoyltransferase in complex with lipoyl-AMP. J Mol Biol. 2007 Aug 3;371(1):222-34. Epub 2007 May 26. [PubMed:17570395 ]