Butyric acid

Source: Wikipedia, the free encyclopedia.

Butyric acid
Skeletal structure of butyric acid
Skeletal structure of butyric acid
Flat structure of butyric acid
Flat structure of butyric acid
Space filling model of butyric acid
Names
Preferred IUPAC name
Butanoic acid[1]
Other names
Ethylacetic acid
1-Propanecarboxylic acid
Propylformic acid
C4:0 (
Lipid numbers
)
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.003.212 Edit this at Wikidata
EC Number
  • Butyric acid: 203-532-3
IUPHAR/BPS
KEGG
MeSH Butyric+acid
RTECS number
  • Butyric acid: ES5425000
UNII
UN number 2820
  • InChI=1S/C4H8O2/c1-2-3-4(5)6/h2-3H2,1H3,(H,5,6) checkY
    Key: FERIUCNNQQJTOY-UHFFFAOYSA-N checkY
  • Butyric acid: InChI=1/C4H8O2/c1-2-3-4(5)6/h2-3H2,1H3,(H,5,6)
    Key: FERIUCNNQQJTOY-UHFFFAOYAP
  • Butyric acid: O=C(O)CCC
Properties
C
3H
7COOH
Molar mass 88.106 g·mol−1
Appearance Colorless liquid
Odor Unpleasant, similar to vomit or body odor
Density 1.135 g/cm3 (−43 °C)[2]
0.9528 g/cm3 (25 °C)[3]
Melting point −5.1 °C (22.8 °F; 268.0 K)[3]
Boiling point 163.75 °C (326.75 °F; 436.90 K)[3]
Sublimes at −35 °C
ΔsublHo = 76 kJ/mol[4]
Miscible
Solubility Miscible with ethanol, ether. Slightly soluble in CCl4
log P 0.79
Vapor pressure 0.112 kPa (20 °C)
0.74 kPa (50 °C)
9.62 kPa (100 °C)[4]
5.35·10−4 L·atm/mol
Acidity (pKa) 4.82
−55.10·10−6 cm3/mol
Thermal conductivity
 1.46·105 W/m·K
1.398 (20 °C)[3]
Viscosity 1.814 cP (15 °C)[5]
1.426 cP (25 °C)
Structure
Monoclinic (−43 °C)[2]
C2/m[2]
a = 8.01 Å, b = 6.82 Å, c = 10.14 Å[2]
α = 90°, β = 111.45°, γ = 90°
0.93 D (20 °C)[5]
Thermochemistry
178.6 J/mol·K[4]
222.2 J/mol·K[5]
Std enthalpy of
formation
(ΔfH⦵298)
 −533.9 kJ/mol[4]
Std enthalpy of
combustion
(ΔcH⦵298)
 2183.5 kJ/mol[4]
Hazards
GHS labelling:
GHS05: Corrosive[6]
Danger
H314[6]
P280, P305+P351+P338, P310[6]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 71 to 72 °C (160 to 162 °F; 344 to 345 K)[6]
440 °C (824 °F; 713 K)[6]
Explosive limits
 2.2–13.4%
Lethal dose or concentration (LD, LC):
2000 mg/kg (oral, rat)
Safety data sheet (SDS) External MSDS
Related compounds
Pentanoic acid
Related compounds
 1-Butanol
Butyraldehyde
Methyl butyrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Butyric acid (

Salts and esters of butyric acid are known as butyrates or butanoates. The acid does not occur widely in nature, but its esters are widespread. It is a common industrial chemical[7]
and an important component in the mammalian gut.

History

Butyric acid was first observed in an impure form in 1814 by the French chemist

Academy of Sciences in Paris, France. Henri Braconnot, a French chemist, was also researching the composition of butter and was publishing his findings and this led to disputes about priority. As early as 1815, Chevreul claimed that he had found the substance responsible for the smell of butter.[8] By 1817, he published some of his findings regarding the properties of butyric acid and named it.[9] However, it was not until 1823 that he presented the properties of butyric acid in detail.[10] The name butyric acid comes from βούτῡρον
, meaning "butter", the substance in which it was first found. The Latin name butyrum (or buturum) is similar.

Occurrence

Triglycerides of butyric acid compose 3–4% of butter. When butter goes rancid, butyric acid is liberated from the glyceride by hydrolysis.[11] It is one of the fatty acid subgroup called short-chain fatty acids. Butyric acid is a typical carboxylic acid that reacts with bases and affects many metals.[12] It is found in

parts per million. In food manufacturing, it is used as a flavoring agent.[15]

In humans, butyric acid is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (HCA2), a Gi/o-coupled G protein-coupled receptor.[16][17]

Butyric acid is present as its octyl ester in parsnip (Pastinaca sativa)[18] and in the seed of the ginkgo tree.[19]

Production

Industrial

In industry, butyric acid is produced by

oxidised to the final product.[7]

H2 + CO + CH3CH=CH2 → CH3CH2CH2CHOoxidation→butyric acid

It can be separated from aqueous solutions by saturation with salts such as calcium chloride. The calcium salt, Ca(C4H7O2)2 · H2O, is less soluble in hot water than in cold.

Microbial biosynthesis

One pathway for butyrate biosynthesis. Relevant enzymes: acetoacetyl-CoA thiolase, NAD- and NADP-dependent 3-hydroxybutyryl-CoA dehydrogenase, 3-hydroxybutyryl-CoA dehydratase, and NAD-dependent butyryl-CoA dehydrogenase.

Butyrate is produced by several fermentation processes performed by obligate anaerobic bacteria.[20] This fermentation pathway was discovered by Louis Pasteur in 1861. Examples of butyrate-producing species of bacteria:

The pathway starts with the

pyruvate:ferredoxin oxidoreductase. Two molecules of carbon dioxide (CO2) and two molecules of hydrogen
(H2) are formed as waste products. Subsequently, ATP is produced in the last step of the fermentation. Three molecules of ATP are produced for each glucose molecule, a relatively high yield. The balanced equation for this fermentation is

C6H12O6 → C4H8O2 + 2CO2 + 2H2

Other pathways to butyrate include succinate reduction and crotonate disproportionation.

Action Responsible enzyme
Acetyl coenzyme A converts into
acetoacetyl coenzyme A
acetyl-CoA-acetyl transferase
Acetoacetyl coenzyme A converts into
β-hydroxybutyryl CoA
β-hydroxybutyryl-CoA dehydrogenase
β-hydroxybutyryl CoA converts into
crotonyl CoA
crotonase
Crotonyl CoA converts into
butyryl CoA
(CH3CH2CH2C=O−CoA)
butyryl CoA dehydrogenase
A phosphate group replaces CoA to form butyryl phosphate
phosphobutyrylase
The phosphate group joins
butyrate
 butyrate kinase

Several species form

n-butanol
in an alternative pathway, which starts as butyrate fermentation. Some of these species are:

These bacteria begin with butyrate fermentation, as described above, but, when the pH drops below 5, they switch into butanol and acetone production to prevent further lowering of the pH. Two molecules of butanol are formed for each molecule of acetone.

The change in the pathway occurs after acetoacetyl CoA formation. This intermediate then takes two possible pathways:

  • acetoacetyl CoA → acetoacetate → acetone
  • acetoacetyl CoA → butyryl CoA → butyraldehyde → butanol

For commercial purposes Clostridium species are used preferably for butyric acid or butanol production. The most common species used for probiotics is the Clostridium butyricum.[21]

Fermentable fiber sources

Highly-fermentable fiber residues, such as those from

colonic bacteria into short-chain fatty acids (SCFA) including butyrate, producing more SCFA than less fermentable fibers such as celluloses.[14][22] One study found that resistant starch consistently produces more butyrate than other types of dietary fiber.[23] The production of SCFA from fibers in ruminant animals such as cattle is responsible for the butyrate content of milk and butter.[13][24]

Fructans are another source of prebiotic soluble dietary fibers which can be digested to produce butyrate.

oligofructose, and inulin.[27][28]

Reactions

Butyric acid reacts as a typical carboxylic acid: it can form amide, ester, anhydride, and chloride derivatives.[29] The latter, butyryl chloride, is commonly used as the intermediate to obtain the others.

Uses

Butyric acid is used in the preparation of various butyrate esters. It is used to produce cellulose acetate butyrate (CAB), which is used in a wide variety of tools, paints, and coatings, and is more resistant to degradation than cellulose acetate.[30] CAB can degrade with exposure to heat and moisture, releasing butyric acid.[31]

Low-molecular-weight esters of butyric acid, such as methyl butyrate, have mostly pleasant aromas or tastes.[7] As a consequence, they are used as food and perfume additives. It is an approved food flavoring in the EU FLAVIS database (number 08.005).

Due to its powerful odor, it has also been used as a fishing bait additive.

bitterling.[33] The substance has been used as a stink bomb by the Sea Shepherd Conservation Society to disrupt Japanese whaling crews.[34]

Pharmacology

Human enzyme and GPCR binding[35][36]
Inhibited enzyme IC50 (nM) Entry note
HDAC1 16,000
HDAC2
 12,000
HDAC3 9,000
HDAC4 2,000,000 Lower bound
HDAC5
 2,000,000 Lower bound
HDAC6 2,000,000 Lower bound
HDAC7 2,000,000 Lower bound
HDAC8 15,000
HDAC9 2,000,000 Lower bound
CA1
 511,000
CA2
 1,032,000
GPCR
target
pEC50
 Entry note
FFAR2
 2.9–4.6 Full agonist
FFAR3
 3.8–4.9 Full agonist
HCA2 2.8 Agonist

Pharmacodynamics

Butyric acid (pKa 4.82) is fully

anion
is the material that is mainly relevant in biological systems. It is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (HCA2, also known as GPR109A), a Gi/o-coupled G protein-coupled receptor (GPCR),[16][17]

Like other

transcription factors will be unable to access regions where histones are tightly associated with DNA (i.e., non-acetylated, e.g., heterochromatin).[medical citation needed] Therefore, butyric acid is thought to enhance the transcriptional activity at promoters,[39]
which are typically silenced or downregulated due to histone deacetylase activity.

Pharmacokinetics

Butyrate that is produced in the colon through microbial fermentation of dietary fiber is primarily absorbed and metabolized by

SLC27A4 (FATP4).[35][42]

Metabolism

Butyric acid is metabolized by various human

butyryl–CoA, and is produced as follows:[43]

Adenosine triphosphate + butyric acid + coenzyme A → adenosine monophosphate + pyrophosphate + butyryl-CoA

As a

colon (colonocytes).[25] Without butyrates, colon cells undergo autophagy (i.e., self-digestion) and die.[45]

In humans, the butyrate precursor tributyrin, which is naturally present in butter, is metabolized by triacylglycerol lipase into dibutyrin and butyrate through the reaction:[46]

Tributyrin + H2O → dibutyrin + butyric acid

Biochemistry

Butyrate has numerous effects on

FFAR3, and HCA2).[37][47]

In the mammalian gut

Butyrate is essential to host immune homeostasis.[37] Although the role and importance of butyrate in the gut is not fully understood, many researchers argue that a depletion of butyrate-producing bacteria in patients with several vasculitic conditions is essential to the pathogenesis of these disorders. A depletion of butyrate in the gut is typically caused by an absence or depletion of butyrate-producing-bacteria (BPB). This depletion in BPB leads to microbial dysbiosis. This is characterized by an overall low biodiversity and a depletion of key butyrate-producing members. Butyrate is an essential microbial metabolite with a vital role as a modulator of proper immune function in the host. It has been shown that children lacking in BPB are more susceptible to allergic disease[48] and Type 1 Diabetes.[49] Butyrate is also reduced in a diet low in dietary fiber, which can induce inflammation and have other adverse affects insofar as these short-chain fatty acids activate PPAR-γ.[50]

Butyrate exerts a key role for the maintenance of immune homeostasis both locally (in the gut) and systemically (via circulating butyrate). It has been shown to promote the differentiation of regulatory T cells. In particular, circulating butyrate prompts the generation of extrathymic regulatory T cells. The low-levels of butyrate in human subjects could favor reduced regulatory T cell-mediated control, thus promoting a powerful immuno-pathological T-cell response.[51] On the other hand, gut butyrate has been reported to inhibit local pro-inflammatory cytokines. The absence or depletion of these BPB in the gut could therefore be a possible aide in the overly-active inflammatory response. Butyrate in the gut also protects the integrity of the intestinal epithelial barrier. Decreased butyrate levels therefore lead to a damaged or dysfunctional intestinal epithelial barrier.[52]

In a 2013 research study conducted by Furusawa et al., microbe-derived butyrate was found to be essential in inducing the differentiation of colonic regulatory T cells in mice. This is of great importance and possibly relevant to the pathogenesis and vasculitis associated with many inflammatory diseases because regulatory T cells have a central role in the suppression of inflammatory and allergic responses.[53] In several research studies, it has been demonstrated that butyrate induced the differentiation of regulatory T cells in vitro and in vivo.[54] The anti-inflammatory capacity of butyrate has been extensively analyzed and supported by many studies. It has been found that microorganism-produced butyrate expedites the production of regulatory T cells, although the specific mechanism by which it does so unclear.[55] More recently, it has been shown that butyrate plays an essential and direct role in modulating gene expression of cytotoxic T-cells.[56] Butyrate also has an anti-inflammatory effect on neutrophils, reducing their migration to wounds. This effect is mediated via the receptor HCA1[57]

In the gut microbiomes found in the class Mammalia, omnivores and herbivores have butyrate-producing bacterial communities dominated by the butyryl-CoA:acetate CoA-transferase pathway, whereas carnivores have butyrate-producing bacterial communities dominated by the butyrate kinase pathway.[58]

The odor of butyric acid, which emanates from the sebaceous follicles of all mammals, works on the tick as a signal.

Immunomodulation and inflammation

Butyrate's effects on the immune system are mediated through the inhibition of class I

FFAR3 (GPR41).[38][59] Among the short-chain fatty acids, butyrate is the most potent promoter of intestinal regulatory T cells in vitro and the only one among the group that is an HCA2 ligand.[38] It has been shown to be a critical mediator of the colonic inflammatory response. It possesses both preventive and therapeutic potential to counteract inflammation-mediated ulcerative colitis and colorectal cancer
.

Butyrate has established antimicrobial properties in humans that are mediated through the

histone deacetylase inhibition. While transient IFN-γ signaling is generally associated with normal host immune response, chronic IFN-γ signaling is often associated with chronic inflammation. It has been shown that butyrate inhibits activity of HDAC1 that is bound to the Fas gene promoter in T cells, resulting in hyperacetylation of the Fas promoter and up-regulation of Fas receptor on the T-cell surface.[62]

Similar to other HCA2 agonists studied, butyrate also produces marked anti-inflammatory effects in a variety of tissues, including the brain, gastrointestinal tract, skin, and vascular tissue.[63][64][65] Butyrate binding at FFAR3 induces neuropeptide Y release and promotes the functional homeostasis of colonic mucosa and the enteric immune system.[66]

Cancer

Butyrate has been shown to be a critical mediator of the colonic inflammatory response. It is responsible for about 70% of energy from the colonocytes, being a critical SCFA in colon

Sp1 transcription factor activity and downregulating vascular endothelial growth factor gene expression.[73]

In summary, the production of

probiotics) that feed on, or ferment prebiotics, which are plant products that contain dietary fiber. These short-chain fatty acids benefit the colonocytes by increasing energy production, and may protect against colon cancer by inhibiting cell proliferation.[22]

Conversely, some researchers have sought to eliminate butyrate and consider it a potential cancer driver.[74] Studies in mice indicate it drives transformation of MSH2-deficient colon epithelial cells.[75]

Potential treatments from butyrate restoration

Owing to the importance of butyrate as an inflammatory regulator and immune system contributor, butyrate depletions could be a key factor influencing the pathogenesis of many

Fecal microbiota transplants (to restore BPB and symbiosis in the gut) could be effective by replenishing butyrate levels. In this treatment, a healthy individual donates their stool to be transplanted into an individual with dysbiosis. A less-invasive treatment option is the administration of butyrate—as oral supplements or enemas—which has been shown to be very effective in terminating symptoms of inflammation with minimal-to-no side-effects. In a study where patients with ulcerative colitis were treated with butyrate enemas, inflammation decreased significantly, and bleeding ceased completely after butyrate provision.[76]

Addiction

Butyric acid is an

histone-modifying enzymes that can cause histone deacetylation and repression of gene expression. HDACs are important regulators of synaptic formation, synaptic plasticity, and long-term memory formation. Class I HDACs are known to be involved in mediating the development of an addiction.[77][78][79] Butyric acid and other HDAC inhibitors have been used in preclinical research to assess the transcriptional, neural, and behavioral effects of HDAC inhibition in animals addicted to drugs.[79][80][81]

Butyrate salts and esters

The butyrate or butanoate

carboxylate salt or ester
of butyric acid.

Examples

Salts

Esters

See also

Notes

  1. ^ Most of the butyrate that is absorbed into blood plasma from the colon enters the circulatory system via the portal vein; most of the butyrate that enters the circulatory system by this route is taken up by the liver.[39]

References

 This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Butyric Acid". Encyclopædia Britannica (11th ed.). Cambridge University Press.

  1. ISBN 978-0-85404-182-4
    .
  2. ^
    doi:10.1107/S0365110X6200328X
    .
  3. ^
    ISBN 978-1-4200-9084-0
    .
  4. ^ a b c d e Butanoic acid in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 27 October 2020)
  5. ^ a b c "Butanoic acid". Chemister.ru. 19 March 2007. Retrieved 27 October 2020.
  6. ^ a b c d e Sigma-Aldrich Co., Butyric acid. Retrieved on 27 October 2020.
  7. ^
    ISBN 978-3527306732
    .
  8. ^ Chevreul (1815) "Lettre de M. Chevreul à MM. les rédacteurs des Annales de chimie" (Letter from Mr. Chevreul to the editors of the Annals of Chemistry), Annales de chimie, 94 : 73–79; in a footnote spanning pages 75–76, he mentions that he had found a substance that is responsible for the smell of butter.
  9. ^ Chevreul (1817) "Extrait d'une lettre de M. Chevreul à MM. les Rédacteurs du Journal de Pharmacie" (Extract of a letter from Mr. Chevreul to the editors of the Journal of Pharmacy), Journal de Pharmacie et des sciences accessoires, 3 : 79–81. On p. 81, he named butyric acid: "Ce principe, que j'ai appelé depuis acid butérique, … " (This principle [i.e., constituent], which I have since named "butyric acid", … )
  10. ^ E. Chevreul, Recherches chimiques sur les corps gras d'origine animale [Chemical researches on fatty substances of animal origin] (Paris, France: F.G. Levrault, 1823), pages 115–133.
  11. doi:10.3168/jds.S0022-0302(83)82052-9
    .
  12. ^ ICSC 1334 – Butyric acid. Inchem.org (23 November 1998). Retrieved on 2020-10-27.
  13. ^
    PMID 29231905
    .
  14. ^
    PMID 26963409
    .
  15. ^ "Butyric acid". The Good Scents Company. Retrieved 26 October 2020.
  16. ^
    PMID 21454438
    .
  17. ^ a b Offermanns S, Colletti SL, IJzerman AP, Lovenberg TW, Semple G, Wise A, Waters MG. "Hydroxycarboxylic acid receptors". IUPHAR/BPS Guide to Pharmacology. International Union of Basic and Clinical Pharmacology. Retrieved 13 July 2018.
  18. S2CID 23512190
    .
  19. ISBN 978-0-7167-1007-3
    . Retrieved 11 October 2018.
  20. PMID 18218779
    .
  21. doi:10.1016/S0032-9592(99)00007-2
    .
  22. ^
    PMID 14747692
    .
  23. PMID 11157351
    .
  24. PMID 1779073
    .
  25. ^
    PMID 27446020
    .
  26. ^ "Frequently asked questions in the area of diet and IBS". Department of Gastroenterology Translational Nutrition Science, Monash University, Victoria, Australia. Retrieved 24 March 2016.
  27. S2CID 20666740
    .
  28. PMID 25680668
    .
  29. ISBN 978-0-85186-884-4
    .
  30. ^ Lokensgard, Erik (2015). Industrial Plastics: Theory and Applications (6th ed.). Cengage Learning.
  31. ^ Williams, R. Scott. "Care of Plastics: Malignant plastics". WAAC Newsletter. Vol. 24, no. 1. Conservation OnLine. Retrieved 29 May 2017.
  32. ^ Freezer Baits Archived 25 January 2010 at the Wayback Machine, nutrabaits.net
  33. doi:10.1046/j.1467-2979.2003.00121.x
    .
  34. ^ Japanese Whalers Injured by Acid-Firing Activists Archived 8 June 2010 at the Wayback Machine, newser.com, 10 February 2010
  35. ^ a b c d "Butyric acid". IUPHAR/BPS Guide to Pharmacology. International Union of Basic and Clinical Pharmacology. Retrieved 13 July 2018.
  36. ^ a b "Butanoic acid and Sodium butyrate". BindingDB. The Binding Database. Retrieved 27 October 2020.
  37. ^
    PMID 25875123
    . Short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, which are produced by gut microbial fermentation of dietary fiber, are recognized as essential host energy sources and act as signal transduction molecules via G-protein coupled receptors (FFAR2, FFAR3, OLFR78, GPR109A) and as epigenetic regulators of gene expression by the inhibition of histone deacetylase (HDAC). Recent evidence suggests that dietary fiber and the gut microbial-derived SCFAs exert multiple beneficial effects on the host energy metabolism not only by improving the intestinal environment, but also by directly affecting various host peripheral tissues.
  38. ^
    PMID 25741338.
    Figure 1: Microbial-derived molecules promote colonic Treg differentiation.
  39. ^
    PMID 26868600
    .
  40. ISSN 0312-5963
    . Retrieved 18 March 2024. the middle and inferior rectal veins drain the lower part of the rectum and venous blood is returned to the inferior vena cava. Therefore, drugs absorbed in the latter system will be delivered preferentially to the systemic circulation, bypassing the liver and avoiding first-pass metabolism
  41. PMID 15717057
    . Other in vivo studies in our laboratories indicated that several compounds including acetate, propionate, butyrate, benzoic acid, salicylic acid, nicotinic acid, and some β-lactam antibiotics may be transported by the MCT at the BBB.21 ... Uptake of valproic acid was reduced in the presence of medium-chain fatty acids such as hexanoate, octanoate, and decanoate, but not propionate or butyrate, indicating that valproic acid is taken up into the brain via a transport system for medium-chain fatty acids, not short-chain fatty acids.
  42. ^
    PMID 23789956
    . Monocarboxylate transporters (MCTs) are known to mediate the transport of short chain monocarboxylates such as lactate, pyruvate and butyrate. ... MCT1 and MCT4 have also been associated with the transport of short chain fatty acids such as acetate and formate which are then metabolized in the astrocytes [78]. ... SLC5A8 is expressed in normal colon tissue, and it functions as a tumor suppressor in human colon with silencing of this gene occurring in colon carcinoma. This transporter is involved in the concentrative uptake of butyrate and pyruvate produced as a product of fermentation by colonic bacteria.
  43. ^ a b Butyric acid. University of Alberta. Retrieved 15 August 2015. {{cite encyclopedia}}: |website= ignored (help)
  44. ^ "Butanoate metabolism – Reference pathway". Kyoto Encyclopedia of Genes and Genomes. Kanehisa Laboratories. 1 November 2017. Retrieved 1 February 2018.
  45. PMID 21531334
    .
  46. ^ "triacylglycerol lipase – Homo sapiens". BRENDA. Technische Universität Braunschweig. Retrieved 25 May 2015.
  47. S2CID 22633025
    .
  48. PMID 31279007
    .
  49. PMID 30356183
    .
  50. S2CID 220337072
    .
  51. PMID 25435420
    .
  52. PMID 30077182
    .
  53. PMID 29067994
    .
  54. S2CID 4408815
    .
  55. PMID 24226773
    .
  56. PMID 30258117
    .
  57. PMID 33064972
    .
  58. PMID 25343515
    .
  59. ^
    PMID 24828484.
    Table 3: Select human antimicrobial peptides and their proposed targets
    Table 4: Some known factors that induce antimicrobial peptide expression
  60. PMID 22194341
    .
  61. PMID 21464244
    .
  62. PMID 22517765
    .
  63. PMID 25766751
    .
  64. PMID 23526298
    .
  65. PMID 26773933
    .
  66. PMID 25545642
    .
  67. PMID 24567795
    .
  68. S2CID 148568580
    .
  69. PMID 15213223
    .
  70. PMID 19707587
    .
  71. S2CID 18573671
    .
  72. PMID 22517765
    .
  73. PMID 18655767
    .
  74. ^ "Low-carb diet cuts risk of colon cancer, study finds | University of Toronto Media Room". media.utoronto.ca. Retrieved 4 May 2016.
  75. PMID 25036629
    .
  76. PMID 1612357
    .
  77. PMID 21989194
    .
  78. PMID 23643695
    .
  79. ^
    PMID 25486626
    .
  80. S2CID 40791780
    .
  81. PMID 28682229
    .

External links

Wikimedia Commons has media related to Butyric acid.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Butyric_acid&oldid=1218594083"