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Salicilna kiselina (od latinske riječi Salix - vrba) je beta hidroksilna kiselina formule C6H4(OH)COOH. Javlja se u formi bezbojnih kristala i slabo je rastvorna u vodi. Hemijski je slična aktivnoj komponenti aspirina (acetilsalicilnoj kiselini) i glavna je sirovina za njegovu proizvodnju.
Biljni hormon
Salicilna kiselina je fenolni fitohormon, a ima ulogu u rastu i razvoju biljaka, fotosintezi, transpiraciji, apsorpciji i transportu iona. Također, inducira specifične promjene u anatomiji lista i strukturi hloroplasta. Učestvuje i u endogenoj signalizaciji, kao posrednik u odbrani biljke od patogena.[1] Signal za odbranu od patogena se može prenijeti sa jedne biljke na drugu pomoću isparljivog estera salicilne kiseline, metil salicilata. [2]
Proizvodnja
Salicilna kiselina je organska kiselina koja nastaje biosintezom iz aminokiseline fenilalanina.
Natrijum salicilat se dobiva reakcijom natrijum fenolata (natrijumove soli fenola) sa ugljik dioksidom na visokom pritisku (100 atm) i temperaturi (390K) (tzv. Kolbe-Schmittova reakcija). Zakiseljavanjem produkta sulfatnom kiselinom dobiva se salicilna kiselina:
Može se dobiti hidrolizom Aspirina (acetilsalicilne kiseline)[3] ili metil salicilata sa jakom kiselinom ili bazom.
Historija
Grčki ljekar Hipokrat je u 5. stoljeću p.n.e. zabilježio da gorki prah, ekstrhovan iz kore vrbe, olakšava bolove i umanjuje groznicu. Ovaj lijek se također spominje u tekstovima antičkog Sumera, Libanona i Asirije. a koristili su je i Cherokee indijanci i drugi američki starosjedioci.[4] Unutrašnja kora vrbe se koristila za smanjivanje bola kod različitih bolesti. Edward Stone je 1763. godine primjetio da kora vrbe uspješno smanjuje groznicu.[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.
Medicinska i kozmetička upotreba
It is known for its ability to ease aches and pains and reduce fevers. The medicinal properties of salicylate, mainly for fever relief, have been known since ancient times, and it was used as an anti-inflammatory drug.[6]
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.[7] It works as a keratolytic 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. 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.[8][9]
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.
Druge upotrebe
- 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.[10] 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.
Sigurnost
Salicylic acid has an ototoxic effect by inhibiting prestin.[11] 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.[12]
Salicylic acid overdose can lead to salicylate intoxication, which often presents clinically in a state of metabolic acidosis with compensatory respiratory alkalosis. In patients presenting with an acute overdose, a 16% morbidity rate and a 1% mortality rate are observed. [13]
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.[14]
Although there is not data to support the association of salicylic acid to Reye's Syndrome, the National Reye's Syndrome Foundation cautions against the usage of these substances, and other substances similar to aspirin on children and adolescents. [15]
Također pogledajte
Vanjski linkovi
Reference
- ^ S. Hayat, A. Ahmad (2007). Salicylic acid - A Plant Hormone. Springer. ISBN 1402051832.
- ^ p.306 Plant Physiology Third Edition Taiz and Zeiger 2002
- ^ "Hydrolysis of ASA to SA". Pristupljeno July 31 2007. Nepoznati parametar
|dateformat=zanemaren (pomoć); Provjerite vrijednost datuma u parametru:|accessdate=(pomoć)CS1 održavanje: nepreporučeni parametar (link) - ^ 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:10.1098/rstl.1763.0033.
- ^ Philip A. Mackowiak (2000). "Brief History of Antipyretic Therapy". Clinical Infectious Diseases,. 31: 154–156. doi:10.1086/317510.CS1 održavanje: dodatna interpunkcija (link)
- ^ http://www3.interscience.wiley.com/journal/119449119/abstract?CRETRY=1&SRETRY=0
- ^ Grimes P.E. (1999). "The Safety and Efficacy of Salicylic Acid Chemical Peels in Darker Racial-ethnic Groups". Dermatologic Surgery. 25: 18–22. doi:10.1046/j.1524-4725.1999.08145.x.
- ^ Roberts W. E. (2004). "Chemical peeling in ethnic/dark skin". Dermatologic Therapy. 17 (2): 196. doi:10.1111/j.1396-0296.2004.04020.x.
- ^ JAR Samson Techniques of Vacuum Ultraviolet Spectroscopy
- ^ Wecker, H.; Laubert, A. (2004). "Reversible hearing loss in acute salicylate intoxication". HNO (jezik: German). 52 (4): 347–51. doi:10.1007/s00106-004-1065-5. PMID 15143764.CS1 održavanje: više imena: authors list (link) CS1 održavanje: nepoznati jezik (link)
- ^ Acne and Pregnancy
- ^ http://emedicine.medscape.com/article/818242-overview
- ^ "Beta Hydroxy Acids in Cosmetics". Pristupljeno 2007-11-23. CS1 održavanje: nepreporučeni parametar (link)
- ^ "Asprin / Salicylates and Reye's Syndrome". Pristupljeno 2009-05-22. CS1 održavanje: nepreporučeni parametar (link)