This MedLibrary.org supplementary page on Salicylate is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Salicylic acid | |
|---|---|
 |
 |
| IUPAC name | 2-Hydroxybenzoic acid |
| Identifiers | |
| CAS number | [69-72-7] |
| EINECS number | |
| SMILES |
|
| ChemSpider ID | |
| Properties | |
| Molecular formula | C7H6O3 |
| Molar mass | 138.123 g/mol |
| Density | 1.44 g/cm³ (at 20 °C) |
| Melting point |
159 °C |
| Boiling point |
211 °C (2666 Pa) |
| Related compounds | |
| Related compounds | Methyl salicylate, Benzoic acid, Phenol, Aspirin, 4-Hydroxybenzoic acid, Magnesium salicylate, Bismuth subsalicylate (Pepto Bismol), Sulfosalicylic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
|
Salicylic acid (from the Latin word for the willow tree, Salix, from whose bark it can be obtained) is a beta hydroxy acid (BHA) with the formula C6H4(OH)CO2H, where the OH group is adjacent to the carboxyl group. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin. It is probably best known as a compound that is chemically similar to but not identical to the active component of aspirin (acetylsalicylic acid). In fact, salicylic acid is a metabolite of aspirin, the product of esterase hydrolysis in the liver. It is poorly soluble in water (0.2 g/100 ml H2O at 20°C).[1]
Contents |
Plant hormone
Salicylic acid (SA) is a phytohormone; and a phenol, ubiquitous in plants generating a significant impact on plant growth and development, photosynthesis, transpiration, ion uptake and transport and also induces specific changes in leaf anatomy and chloroplast structure. SA is recognized as an endogenous signal, mediating in plant defense, against pathogens[2] It plays a role in the resistance of pathogens by inducing the production of 'pathogenesis-related proteins'. It is involved in the systemic acquired resistance [SAR] in which a pathogenic attack on older leaves causes the development of resistance in younger leaves, though whether SA is the transmitted signal is debatable.
Production
Salicylic acid is an organic acid biosynthesized from the amino acid phenylalanine.
Sodium salicylate is commercially prepared by treating sodium phenoxide with a high pressure of carbon dioxide at high temperature via the Kolbe-Schmitt reaction. Acidification of the product solution gives salicylic acid:
It can be prepared by the hydrolysis of Aspirin (acetylsalicylic acid)[3] or methyl salicylate (Oil of Wintergreen) with a strong acid or base.
History
The Greek physician Hippocrates wrote in the 5th century BC about a bitter powder extracted from willow bark that could ease aches and pains and reduce fevers. This remedy was also mentioned in texts from ancient Sumer, Lebanon, and Assyria. The Cherokee and other Native Americans used an infusion of the bark for fever and other medicinal purposes for centuries.[4] The medicinal part of the plant is the inner bark and was used as a pain reliever for a variety of ailments. The Reverend Edward (Edmund) Stone, a vicar from Chipping Norton, Oxfordshire, England, noted in 1763 that the bark of the willow was effective in reducing a fever.[5]
The active extract of the bark, called salicin, after the Latin name for the white willow (Salix alba), was isolated in crystalline form in 1828 by Henri Leroux, a French pharmacist, and Raffaele Piria, an Italian chemist. Piria was able to convert the substance into a sugar and a second component, which on oxidation becomes salicylic acid.
Salicylic acid was also isolated from the herb meadowsweet (Filipendula ulmaria, formerly classified as Spiraea ulmaria) by German researchers in 1839. While their extract was somewhat effective, it also caused digestive problems such as gastric irritation, bleeding, diarrhea, and even death when consumed in high doses.
Medicinal and cosmetic uses
Also known as 2-hydroxybenzoic acid, one of several beta hydroxy acids (compare to AHA), salicylic acid is a key ingredient in many skin-care products for the treatment of acne, psoriasis, calluses, corns, keratosis pilaris, and warts. It works by causing the cells of the epidermis to shed more readily, preventing pores from clogging up, and allowing room for new cell growth. Because of its effect on skin cells, salicylic acid is used in several shampoos used to treat dandruff. Salicylic acid is also used as an active ingredient in gels which remove warts. Use of concentrated solutions of salicylic acid may cause hyperpigmentation on unpretreated skin for those with darker skin types (Fitzpatrick phototypes IV, V, VI), as well as with the lack of use of a broad spectrum sunblock.[6][7]
The medicinal properties of salicylate, mainly for fever relief, have been known since ancient times, and it was used as an anti-inflammatory drug.[8]
Aspirin (acetylsalicylic acid or ASA) can be prepared by the esterification of the phenolic hydroxyl group of salicylic acid.
Subsalicylate in combination with bismuth form the popular stomach relief aid known commonly as Pepto-Bismol. When combined, the two key ingredients help control diarrhea, nausea, heartburn, and gas. It is also a very mild antibiotic.
Choline salicylate is used topically to relieve the pain of aphthous ulcers.
Other uses
- Although toxic in large quantities, salicylic acid is used as a food preservative and antiseptic in toothpaste. For some people with salicylate sensitivity even these small doses can be harmful.
- Sodium salicylate is a useful phosphor in the vacuum ultraviolet with nearly flat quantum efficiency for wavelengths between 10 to 100 nm.[9] It fluoresces in the blue at 420 nm. It is easily prepared on a clean surface by spraying a saturated solution of the salt in methanol followed by evaporation.
- Methyl salicylate is used as a liniment, to soothe joint and muscle pain.
Safety
Salicylic acid has an ototoxic effect by inhibiting prestin.[10] It can induce transient hearing loss in zinc-deficient individuals.
This finding is based on clinical studies with rats. An injection of salicylic acid induced hearing loss in zinc-deficient rats, while a simultaneous injection of zinc reversed the hearing loss. An injection of magnesium in the zinc-deficient rats did not reverse the salicylic acid-induced hearing loss.
Salicylic acid is used to treat acne, warts and other dermatological problems. There are no studies specifically looking at topical salicylic acid in pregnancy. Oral salicylic acid (aspirin) has not been associated with an increase in malformations if used during the first trimester, but use in late pregnancy has been associated with bleeding, especially intracranial bleeding (Rumack et al., 1981). The risks of aspirin late in pregnancy are probably not relevant for a topical exposure to salicylic acid, even late in the pregnancy, because of its low systemic levels. Topical salicylic acid is common in many over-the-counter dermatological agents, and the lack of adverse reports suggests a low teratogenic potential.[11]
Some people are hypersensitive to salicylic acid and related compounds.
The United States Food and Drug Administration recommends the use of sun protection when using skincare products containing salicylic acid (or any other BHA) on sun-exposed skin areas.[12]
Footnotes
- ^ "Salicilyc acid". Retrieved on 2008-10-13.
- ^ S. Hayat, A. Ahmad (2007). Salicylic acid - A Plant Hormone. Springer. ISBN 1402051832.
- ^ "Hydrolysis of ASA to SA". Retrieved on July 31, 2007.
- ^ Paul B. Hemel and Mary U. Chiltoskey, Cherokee Plants and Their Uses -- A 400 Year History, Sylva, NC: Herald Publishing Co. (1975); cited in Dan Moerman, A Database of Foods, Drugs, Dyes and Fibers of Native American Peoples, Derived from Plants.[1] A search of this database for "salix AND medicine" finds 63 entries.
- ^ Stone, E (1763). "An Account of the Success of the Bark of the Willow in the Cure of Agues". Philosophical Transactions 53: 195–200. doi:.
- ^ Grimes P.E. (1999). "The Safety and Efficacy of Salicylic Acid Chemical Peels in Darker Racial-ethnic Groups". Dermatologic Surgery 25: 18–22. doi:.
- ^ Roberts W. E. (2004). "Chemical peeling in ethnic/dark skin". Dermatologic Therapy 17 (2): 196. doi:.
- ^ Philip A. Mackowiak (2000). "Brief History of Antipyretic Therapy". Clinical Infectious Diseases, 31: 154–156. doi:.
- ^ JAR Samson Techniques of Vacuum Ultraviolet Spectroscopy
- ^ Wecker, H.; Laubert, A. (2004). "Reversible hearing loss in acute salicylate intoxication" (in German). HNO 52 (4): 347–51. doi:. PMID 15143764.
- ^ Acne and Pregnancy
- ^ "Beta Hydroxy Acids in Cosmetics". Retrieved on 2007-11-23.
|
||||||||||||||||||||
|
|||||||||||
|
|||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||||||
|
||||||||
Wikipedia content modification information:
- This page was last modified on 13 October 2008, at 15:50.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Salicylate".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.