Palmitic acid

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Palmitic acid[1]
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Template:Longitem Template:Chembox Elements/molecular formula
Molar mass Template:Chem molar mass
Appearance White crystals
Density 0.852 g/cm3 (25 °C)[2]
0.8527 g/cm3 (62 °C)[3]
Melting point Template:Chembox CalcTemperatures
Boiling point Template:Chembox CalcTemperatures
Solubility Soluble in amyl acetate, alcohol, CCl4,[4] C6H6
Very soluble in CHCl3[3]
Solubility in ethanol 2 g/100 mL (0 °C)
2.8 g/100 mL (10 °C)
9.2 g/100 mL (20 °C)
31.9 g/100 mL (40 °C)[5]
Solubility in methyl acetate 7.81 g/100 g[4]
Solubility in ethyl acetate 10.7 g/100 g[4]
Vapor pressure 0.051 mPa (25 °C)[3]
1.08 kPa (200 °C)
28.06 kPa (300 °C)[6]
Acidity (pKa) 4.75 [3]
Template:Longitem −198.6·10−6 cm3/mol
Template:Longitem 1.43 (70 °C)[3]
Viscosity 7.8 cP (70 °C)[3]
Template:Longitem 463.36 J/(mol·K)[6]
Template:Longitem 452.37 J/(mol·K)[6]
Template:Longitem −892 kJ/mol[6]
Template:Longitem 10030.6 kJ/mol[3]
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Palmitic acid (hexadecanoic acid in IUPAC nomenclature) is a fatty acid with a 16-carbon chain. It is the most common saturated fatty acid found in animals, plants and microorganisms.[7][8] Its chemical formula is Template:Chem2, and its C:D ratio (the total number of carbon atoms to the number of carbon-carbon double bonds) is 16:0. It is a major component of palm oil from the fruit of Elaeis guineensis (oil palms), making up to 44% of total fats. Meats, cheeses, butter, and other dairy products also contain palmitic acid, amounting to 50–60% of total fats.[9]

Palmitates are the salts and esters of palmitic acid. The palmitate anion is the observed form of palmitic acid at physiologic pH (7.4). Major sources of C16:0 are palm oil, palm kernel oil, coconut oil, and milk fat.[10]

Dietary palmitic acid intake is associated with an increased cardiovascular disease risk through raising low-density lipoprotein.[11]

Occurrence and production

Palmitic acid was discovered by saponification of palm oil, which process remains today the primary industrial route for producing the acid.[12] Triglycerides (fats) in palm oil are hydrolysed by high-temperature water and the resulting mixture is fractionally distilled.[13]

Dietary sources

Palmitic acid is produced by a wide range of plants and organisms, typically at low levels. Among common foods it is present in milk, butter, cheese, and some meats, as well as cocoa butter, olive oil, soybean oil, and sunflower oil, (see table).[14] Karukas contain 44.90% palmitic acid.[15] The cetyl ester of palmitic acid, cetyl palmitate, occurs in spermaceti.

Palmitic acid content of common foods
Food % of total calories
Palm oil 45.1%
Beef tallow 26.5%
Butter fat 26.2%
Cocoa butter 25.8%
Lard 24.8%
Cottonseed oil 24.7%
Chicken 23.2%
Corn oil 12.2%
Peanut oil 11.6%
Soybean oil 11%
Coconut oil 8.4%
Palm kernel oil 8%
Rapeseed oil 3.6%
Source:[16]

Biochemistry

Palmitic acid is the first fatty acid produced during fatty acid synthesis and is the precursor to longer fatty acids. As a consequence, palmitic acid is a major body component of animals. In humans, one analysis found it to make up 21–30% (molar) of human depot fat,[17] and it is a major, but highly variable, lipid component of human breast milk.[18] Palmitic acid comprises nearly half of total human brain saturated fatty acids.[19]

Palmitate negatively feeds back on acetyl-CoA carboxylase (ACC), which is responsible for converting acetyl-CoA to malonyl-CoA, which in turn is used to add to the growing acyl chain, thus preventing further palmitate generation.[20] Some proteins are modified by the addition of a palmitoyl group in a process known as palmitoylation. Palmitoylation is important for localisation of many membrane proteins.

Applications

Surfactant

Palmitic acid is used to produce soaps, cosmetics, and industrial mold release agents. These applications use sodium palmitate, which is commonly obtained by saponification of palm oil. To this end, palm oil, rendered from palm trees (species Elaeis guineensis), is treated with sodium hydroxide (in the form of caustic soda or lye), which causes hydrolysis of the ester groups, yielding glycerol and sodium palmitate.

Foods

Because it is inexpensive and adds texture and "mouthfeel" to processed foods (convenience food), palmitic acid and its sodium salt find wide use in foodstuffs. Sodium palmitate is permitted as a natural additive in organic products.[21]

Military

Aluminium salts of palmitic acid and naphthenic acid were the gelling agents used with volatile petrochemicals during World War II to produce napalm. The word "napalm" is derived from the words naphthenic acid and palmitic acid.[22]

Research

It is well accepted in the medical community that palmitic acid from dietary sources raises low-density lipoprotein (LDL) and total cholesterol.[16][23][24][25] The World Health Organization have stated there is convincing evidence that palmitic acid increases cardiovascular disease risk.[26] Palmitic acid intake is associated with an increased cancer risk, including prostate cancer.[27][28]

A 2021 review indicated that replacing dietary palmitic acid and other saturated fatty acids with unsaturated fatty acids, such as oleic acid, could reduce several biomarkers of cardiovascular and metabolic diseases.[29]

See also

References

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  1. ↑ Merck Index, 12th Edition, 7128.
  2. ↑ a b c d Sigma-Aldrich Co., Palmitic acid. Retrieved on 2014-06-02.
  3. ↑ a b c d e f g CID 985 from PubChemTemplate:EditAtWikidataTemplate:WikidataCheck
  4. ↑ a b c d Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ a b c d n-Hexadecanoic 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 2014-05-11)
  7. ↑ Gunstone, F. D., John L. Harwood, and Albert J. Dijkstra. The Lipid Handbook, 3rd ed. Boca Raton: CRC Press, 2007. Template:ISBN | Template:ISBN
  8. ↑ The most common fatty acid is the monounsaturated oleic acid. See: https://pubchem.ncbi.nlm.nih.gov/compound/965#section=Top
  9. ↑ Template:Cite Q
  10. ↑ Script error: No such module "Citation/CS1".
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  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ a b Nelson, Gary J. (1991). Health Effects of Dietary Fatty Acids. American Oil Chemists' Society. pp. 84-86. Template:ISBN
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Script error: No such module "citation/CS1". Pathway Map 00061
  21. ↑ US Soil Association standard 50.5.3
  22. ↑ Script error: No such module "Citation/CS1".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ Mensink, Ronald P. (2016). "Effects of saturated fatty acids on serum lipids and lipoproteins: a systematic review and regression analysis". World Health Organization. Retrieved 14 March 2023.
  25. ↑ Rao, Gundu HR. (2020). Clinical Handbook of Coronary Artery Disease. Jaypee Brothers Medical Publishers. pp. 186-187. Template:ISBN
  26. ↑ "Diet, Nutrition and the Prevention of Chronic Diseases". World Health Organization. p. 82. Retrieved 16 March 2023.
  27. ↑ Script error: No such module "Citation/CS1".
  28. ↑ Script error: No such module "Citation/CS1".
  29. ↑ Script error: No such module "Citation/CS1".

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External links

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