Salicylic acid has long been a key starting material for making acetylsalicylic acid (ASA or aspirin).[8] ASA is prepared by the acetylation of salicylic acid with the acetyl group from acetic anhydride or acetyl chloride.[17] ASA is the standard to which all the other non-steroidal anti-inflammatory drugs (NSAIDs) are compared. In veterinary medicine, this group of drugs is mainly used for treatment of inflammatory musculoskeletal disorders.[18]
Bismuth subsalicylate, a salt of bismuth and salicylic acid, "displays anti-inflammatory action (due to salicylic acid) and also acts as an antacid and mild antibiotic".[3] It is an active ingredient in stomach-relief aids such as Pepto-Bismol and some formulations of Kaopectate.
Sodium salicylate is a useful phosphor in the vacuum ultraviolet spectral range, with nearly flat quantum efficiency for wavelengths between 10 and 100 nm.[22] 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.[citation needed]
Mechanism of action
Salicylic acid modulates COX-1 enzymatic activity to decrease the formation of pro-inflammatory prostaglandins. Salicylate may competitively inhibit prostaglandin formation.
Salicylic acid, when applied to the skin surface, works by causing the cells of the epidermis to slough off more readily, preventing pores from clogging up, and allowing room for new cell growth. Salicylic acid inhibits the oxidation of uridine-5-diphosphoglucose (UDPG) competitively with NADH and noncompetitively with UDPG. It also competitively inhibits the transferring of glucuronyl group of uridine-5-phosphoglucuronic acid to the phenolic acceptor.[23]
The wound-healing retardation action of salicylates is probably due mainly to its inhibitory action on mucopolysaccharide synthesis.[5]
If high concentrations of salicylic ointment are used topically, high levels of salicylic acid can enter the blood, requiring hemodialysis to avoid further complications.[24]
Cosmetic applications of the drug pose no significant risk.[25] Even in a worst-case use scenario in which one was using multiple salicylic acid-containing topical products, the aggregate plasma concentration of salicylic acid was well below what was permissible for acetylsalicylic acid (aspirin).[25] Since oral aspirin (which produces much higher salicylic acid plasma concentrations than dermal salicylic acid applications) poses no significant adverse pregnancy outcomes in terms of frequency of stillbirth, birth defects or developmental delay, use of salicylic acid containing cosmetics is safe for pregnant women.[25] Salicylic acid is present in most fruits and vegetables as for example in greatest quantities in berries and in beverages like tea.
At the laboratory scale, it can also be prepared by the hydrolysis of aspirin (acetylsalicylic acid)[26] or methyl salicylate (oil of wintergreen) with a strong acid or base; these reactions reverse those chemicals' commercial syntheses.
Willow has long been used for medicinal purposes. Dioscorides, whose writings were highly influential for more than 1,500 years,[30] used 'Itea' (which was possibly a species of willow) as a treatment for 'painful intestinal obstructions,' birth control, for 'those who spit blood,' to remove calluses and corns and, externally, as a 'warm pack for gout.' William Turner, in 1597, repeated this, saying that willow bark, 'being burnt to ashes, and steeped in vinegar, takes away corns and other like risings in the feet and toes.'[31] Some of these cures may describe the action of salicylic acid, which can be derived from the salicin present in willow. It is, however, a modern myth that Hippocrates used willow as a painkiller.[32]
It was used in Europe and China to treat these conditions.[35] This remedy is mentioned in texts from Ancient Egypt, Sumer, and Assyria.[36]
The Cherokee and other Native Americans use an infusion of the bark for fever and other medicinal purposes.[37] In 2014, archaeologists identified traces of salicylic acid on seventh-century pottery fragments found in east-central Colorado.[38]
An extract of willow bark, called salicin, after the Latin name for the white willow (Salix alba), was isolated and named by German chemist Johann Andreas Buchner in 1828.[41] A larger amount of the substance was isolated in 1829 by Henri Leroux, a French pharmacist.[42]Raffaele Piria, an Italian chemist, was able to convert the substance into a sugar and a second component, which on oxidation becomes salicylic acid.[43][44]
Salicylic acid was also isolated from the herb meadowsweet (Filipendula ulmaria, formerly classified as Spiraea ulmaria) by German researchers in 1839.[45] Their extract caused digestive problems such as gastric irritation, bleeding, diarrhea, and even death when consumed in high doses.
In 1874 the Scottish physician Thomas MacLagan experimented with salicin as a treatment for acute rheumatism, with considerable success, as he reported in The Lancet in 1876.[46] Meanwhile, German scientists tried sodium salicylate with less success and more severe side effects.[47][48]
Salicylic acid occurs in plants as free salicylic acid and its carboxylated esters and phenolic glycosides. Several studies suggest that humans metabolize salicylic acid in measurable quantities from these plants.[51] High-salicylate beverages and foods include beer, coffee, tea, numerous fruits and vegetables, sweet potato, nuts, and olive oil.[19] Meat, poultry, fish, eggs, dairy products, sugar, breads and cereals have low salicylate content.[19][52]
Salicylic acid is a phenolicphytohormone, and is found in plants with roles in plant growth and development, photosynthesis, transpiration, and ion uptake and transport.[53] Salicylic acid is involved in endogenous signaling, mediating plant defense against pathogens.[54] It plays a role in the resistance to pathogens (i.e. systemic acquired resistance) by inducing the production of pathogenesis-related proteins and other defensive metabolites.[55] SA's defense signaling role is most clearly demonstrated by experiments which do away with it: Delaney et al. 1994, Gaffney et al. 1993, Lawton et al. 1995, and Vernooij et al. 1994 each use Nicotiana tabacum or Arabidopsis expressing nahG, for salicylate hydroxylase. Pathogen inoculation did not produce the customarily high SA levels, SAR was not produced, and no pathogenesis-related (PR) genes were expressed in systemic leaves. Indeed, the subjects were more susceptible to virulent – and even normally avirulent – pathogens.[53]
Exogenously, salicylic acid can aid plant development via enhanced seed germination, bud flowering, and fruit ripening, though too high of a concentration of salicylic acid can negatively regulate these developmental processes.[56]
The volatile methyl ester of salicylic acid, methyl salicylate, can also diffuse through the air, facilitating plant-plant communication.[57] Methyl salicylate is taken up by the stomata of the nearby plant, where it can induce an immune response after being converted back to salicylic acid.[58]
Signal transduction
A number of proteins have been identified that interact with SA in plants, especially salicylic acid binding proteins (SABPs) and the NPR genes (nonexpressor of pathogenesis-related genes), which are putative receptors.[59]
^ abWishart DS, Djombou Feunang Y, Guo AC, Lo EJ, Marcu A, Grant JR, Sajed T, Johnson D, Li C, Sayeeda Z, Assempour N, Iynkkaran I, Liu Y, Maciejewski A, Gale N, Wilson A, Chin L, Cummings R, Le D, Pon A, Knox C, Wilson M. "Salycylic acid | DrugBank Online". DrugBank. 5.0.
^Madan RK, Levitt J (April 2014). "A review of toxicity from topical salicylic acid preparations". Journal of the American Academy of Dermatology. 70 (4): 788–792. doi:10.1016/j.jaad.2013.12.005. PMID24472429.
^Péc J, Strmenová M, Palencárová E, Pullmann R, Funiaková S, Visnovský P, Buchanec J, Lazarová Z (October 1992). "Salicylate intoxication after use of topical salicylic acid ointment by a patient with psoriasis". Cutis. 50 (4): 307–309. PMID1424799.
^Kuriakose G, Nagaraju N (2004). "Selective Synthesis of Phenyl Salicylate (Salol) by Esterification Reaction over Solid Acid Catalysts". Journal of Molecular Catalysis A: Chemical. 223 (1–2): 155–159. doi:10.1016/j.molcata.2004.03.057.
^Jordan RB (1983). "Metal(III)-Salicylate Complexes: Protonated Species and Rate-Controlling Formation Steps". Inorganic Chemistry. 22 (26): 4160–4161. doi:10.1021/ic00168a070.
^Kaeding WW (1 September 1964). "Oxidation of Aromatic Acids. IV. Decarboxylation of Salicylic Acids". The Journal of Organic Chemistry. 29 (9): 2556–2559. doi:10.1021/jo01032a016.
^Norn S, Permin H, Kruse PR, Kruse E (2009). "From willow bark to acetylsalicylic acid". Dansk Medicinhistorisk Årbog (in Danish). 37: 79–98. PMID20509453. S2CID10053542.
^Buchner A (1828). "Ueber das Rigatellische Fiebermittel und über eine in der Weidenrinde entdeckte alcaloidische Substanz" [On Rigatelli's antipyretic [i.e., anti-fever drug] and on an alkaloid substance discovered in willow bark]. Repertorium für die Pharmacie. Bei J. L. Schrag. pp. 405–. Noch ist es mir aber nicht geglückt, den bittern Bestandtheil der Weide, den ich Salicin nennen will, ganz frei von allem Färbestoff darzustellen. [I have still not succeeded in preparing the bitter component of willow, which I will name salicin, completely free from colored matter]
^Löwig C, Weidmann S (1839). "III. Untersuchungen mit dem destillierten Wasser der Blüthen von Spiraea Ulmaria" [III. Investigations of the water distilled from the blossoms of Spiraea ulmaria]. Annalen der Physik und Chemie; Beiträge zur Organischen Chemie (Contributions to Organic Chemistry) (46): 57–83. Löwig and Weidman called salicylic acid Spiräasaure (spiraea acid)
^Buchanan WW, Kean WF (June 2002). "The Treatment of Acute Rheumatism by Salicin, by T.J. Maclagan — The Lancet, 1876". The Journal of Rheumatology. 29 (6): 1321–1323. PMID12064852.
^Malakar S, Gibson PR, Barrett JS, Muir JG (1 April 2017). "Naturally occurring dietary salicylates: A closer look at common Australian foods". Journal of Food Composition and Analysis. 57: 31–39. doi:10.1016/j.jfca.2016.12.008.
^Chamovitz D (2012). What A Plant Knows - A Field Guide to the Senses of your Garden - and Beyond. Oxford, England: Oneworld. ISBN978-1-85168-910-1. OCLC775030365.
^Kumar, D. 2014. Salicylic acid signaling in disease resistance. Plant Science 228:127–134.