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Salicylic acid (from the Latin word for the willow tree, Salix, from whose bark it can be obtained) is a beta hydroxy acid
Beta hydroxy acid

A beta hydroxy acid is an organic compound which contains a carboxylic acid functional group and hydroxyl functional group separated by two carbon atoms....
 (BHA) with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C6H4(OH)COOH, where the OH group is adjacent to the carboxyl group
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
. This colorless crystalline organic acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
 is widely used in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
 and functions as a plant hormone
Plant hormone

Plant hormones are chemicals that regulate plant growth. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations....
. It is derived from the metabolism of salicin. In addition to being a compound that is chemically similar to but not identical to the active component of aspirin
Aspirin

Aspirin , also known as acetylsalicylic acid , is a salicylate medication, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication....
 (acetylsalicylic acid), it is probably best known for its use in anti-acne treatments.






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Salicylic acid (from the Latin word for the willow tree, Salix, from whose bark it can be obtained) is a beta hydroxy acid
Beta hydroxy acid

A beta hydroxy acid is an organic compound which contains a carboxylic acid functional group and hydroxyl functional group separated by two carbon atoms....
 (BHA) with the formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 C6H4(OH)COOH, where the OH group is adjacent to the carboxyl group
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
. This colorless crystalline organic acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
 is widely used in organic synthesis
Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
 and functions as a plant hormone
Plant hormone

Plant hormones are chemicals that regulate plant growth. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations....
. It is derived from the metabolism of salicin. In addition to being a compound that is chemically similar to but not identical to the active component of aspirin
Aspirin

Aspirin , also known as acetylsalicylic acid , is a salicylate medication, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication....
 (acetylsalicylic acid), it is probably best known for its use in anti-acne treatments. It is poorly soluble in water (0.2 g/100 ml H2O at 20°C).

Plant hormone

Salicylic acid (SA) is a phenol
Phenol

Phenol, also known as carbolic acid, is a toxic, white crystalline solid with a sweet tarry odor, commonly referred to as a "hospital smell"....
ic phytohormone and is found in plants with roles in plant growth and development, photosynthesis
Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
, transpiration
Transpiration

Transpiration is the evaporation of water from the aerial parts of plants, especially leaf but also Plant stems, flowers and roots. Leaf surfaces are dotted with openings called stoma that are bordered by guard cells....
, ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
 uptake and transport. SA also induces specific changes in leaf anatomy and chloroplast
Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....
 structure. SA is involved in endogenous
Endogenous

The word endogenous means "arising from within", the opposite of exogenous....
 signaling, mediating in plant defense against pathogens. It plays a role in the resistance to pathogens by inducing the production of 'pathogenesis-related proteins'. It is involved in the systemic acquired resistance
Systemic acquired resistance

In plants, systemic acquired resistance is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen....
 [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 biosynthesize
Biosynthesis

Biosynthesis is a phenomenon wherein chemical compounds are produced from simpler reagents. Biosynthesis, unlike chemosynthesis, takes place within living organisms and is generally catalyst by enzymes....
d from the amino acid phenylalanine
Phenylalanine

Phenylalanine is an a-amino acid with the chemical formula HO2CCHCH2C6H5, which is found naturally in the breast milk of mammals and manufactured for food and drink products and are also sold as nutritional supplements for their reputed analgesic and antidepressant effects....
.

Sodium salicylate
Sodium salicylate

Sodium salicylate is a sodium salt of salicylic acid. It can be prepared from sodium phenolate and carbon dioxide under higher temperature and pressure....
 is commercially prepared by treating sodium phenolate (the sodium salt of phenol
Phenol

Phenol, also known as carbolic acid, is a toxic, white crystalline solid with a sweet tarry odor, commonly referred to as a "hospital smell"....
) with carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 at high pressure (100 atm) and high temperature (390K) - a method known as the Kolbe-Schmitt reaction
Kolbe-Schmitt reaction

The Kolbe-Schmitt reaction/Kolbe process is a carboxylation chemical reaction that proceeds by heating sodium phenolate with carbon dioxide under pressure , then treating the product with sulfuric acid....
. Acidification of the product with sulfuric acid
Sulfuric acid

Sulfuric acid, hydrogen2sulfuroxygen4, is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry....
 gives salicylic acid:

Kolbe Schmitt



It can be prepared by the hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 of Aspirin
Aspirin

Aspirin , also known as acetylsalicylic acid , is a salicylate medication, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication....
 (acetylsalicylic acid) or methyl salicylate
Methyl salicylate

Methyl salicylate is a natural product of many species of plants. Some of the plants producing it are called wintergreens, hence the common name....
 (Oil of Wintergreen) with a strong acid or base.

History


The Greek physician Hippocrates
Hippocrates

Hippocrates of Cos II or Hippokrates of Kos - ancient Greek: ; Hippokr?tes was an Ancient Greece physician of the Age of Pericles, and was considered one of the most outstanding figures in the history of medicine....
 wrote in the 5th century BC about a bitter powder extracted from willow
Willow

Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere....
 bark that could ease aches and pains and reduce fevers. This remedy was also mentioned in texts from ancient Sumer
Sumer

Sumer was a civilization and a historical region located in Southern Iraq , known as the Cradle of civilization. It lasted from the first settlement of Eridu in the Ubaid period through the Uruk period and the Dynastic periods until the rise of Babylon in the early 2nd millennium BC....
, Lebanon
Lebanon

Lebanon , officially the Republic of Lebanon or Lebanese Republic , is a country in Western Asia, on the eastern shore of the Mediterranean Sea....
, and Assyria
Assyria

Assyria was a political state centered on the Upper Tigris river, in Mesopotamia , that came to rule regional empires a number of times in history....
. The Cherokee
Cherokee

The Cherokee are a Native Americans in the United States people orginally from the Southeastern United States . They are linguistically connected to speakers of the Iroquoian language....
 and other Native Americans used an infusion of the bark for fever and other medicinal purposes for centuries. 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
Chipping Norton, Oxfordshire

Chipping Norton is a town in the Cotswold Hills in Oxfordshire, England, about southwest of Banbury. It is the highest town above Elevation in Oxfordshire....
, England
England

native_name =|conventional_long_name = England|common_name = England|image_flag = Flag of England.svg|image_coat = England COA.svg|symbol_type = Royal Coat of Arms...
, noted in 1763 that the bark of the willow was effective in reducing a fever.

The active extract of the bark, called salicin, after the Latin
Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
 name for the white willow (Salix alba), was isolated in crystalline form in 1828 by Henri Leroux, a French
France

France , officially the French Republic , is a country whose Metropolitan France is located in Western Europe and that also comprises various Overseas departments and territories of France....
 pharmacist, and Raffaele Piria, an Italian
Italy

Italy , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia....
 chemist. Piria was able to convert the substance into a sugar and a second component, which on oxidation becomes salicylic acid
Salicylic acid

Salicylic acid is a beta hydroxy acid with the chemical formula C6H4COOH, where the OH group is adjacent to the carboxylic acid....
.

Salicylic acid was also isolated from the herb meadowsweet
Meadowsweet

Filipendula ulmaria, commonly known as Meadowsweet, is a Perennial plant herb in the family Rosaceae, which grows in damp meadows. It is native throughout most of Europe and western Asia though it has been successfully introduced and naturalized in North America....
 (Filipendula ulmaria
Filipendula

Filipendula is a genus of 12 species of perennial plant herbaceous flowering plants in the family Rosaceae, native to the temperate regions of the Northern Hemisphere....
, formerly classified as Spiraea ulmaria
Spiraea

'Spiraea' is a genus of about 80-100 species of shrubs in the Rosaceae, subfamily Spiraeoideae. They are native to the temperate Northern Hemisphere, with the greatest diversity in eastern Asia....
) by German researchers in 1839. While their extract was somewhat effective, it also caused digestive problems such as gastric irritation, bleeding, diarrhea
Diarrhea

In medicine, diarrhea, also spelled diarrhoea , is characterized by frequent loose or liquid bowel movements. The spelling of "diarrhea" is an appropriation of the Greek "diarrhoia" meaning "a flowing through." ....
, and even death when consumed in high doses.

Medicinal and cosmetic uses

It is known for its ability to ease aches and pains and reduce fevers. The medicinal properties of salicylate, mainly for fever
Fever

Fever is a frequent medical sign that describes an increase in internal body temperature to levels above normal. Fever is most accurately characterized as a temporary elevation in the body's thermoregulatory set-point, usually by about 1?2 ?C ....
 relief, have been known since ancient times
1763

Year 1763 was a common year starting on Saturday of the Gregorian calendar ....
, and it was used as an anti-inflammatory drug.

Also known as 2-hydroxybenzoic acid, one of several beta hydroxy acids (compare to AHA
Alpha hydroxy acid

a-hydroxy acids, or alpha hydroxy acids , are a class of chemical compounds that consist of a carboxylic acid substituted with a hydroxyl on the adjacent carbon....
), salicylic acid is a key ingredient in many skin-care products for the treatment of acne
Acne vulgaris

Acne vulgaris is a skin condition caused by changes in the pilosebaceous units . Severe acne is inflammation, but acne can also manifest in noninflammatory forms....
, psoriasis
Psoriasis

Psoriasis is a chronic, non-contagious autoimmune disease which affects the skin and joints. It commonly causes red scaly patches to appear on the skin....
, callus
Callus

A callus is an especially toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure or other irritation....
es, corns
Callus

A callus is an especially toughened area of skin which has become relatively thick and hard in response to repeated friction, pressure or other irritation....
, keratosis pilaris
Keratosis pilaris

Keratosis pilaris is a very common genetics Hair follicle condition that is manifested by the appearance of rough bumps on the skin, hence referred to as chicken skin....
, and wart
Wart

A wart is generally a small, rough tumor, typically on hands and feet but often other locations, that can resemble a cauliflower or a solid blister....
s. It works by causing the cells of the epidermis
Epidermis (skin)

The epidermis is the outermost layer of the skin, composed of terminally differentiated stratified squamous epithelium, acting as the body's major barrier against an inhospitable environment....
 to shed more readily, preventing pores
Sebaceous gland

Sebaceous glands are small glands in the skin which secrete an oily matter in the hair follicles to lubricate the skin and hair of animals. In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles....
 from clogging up, and allowing room for new cell growth. Because of its effect on skin cells, salicylic acid is used in several shampoo
Shampoo

Shampoo is a hair care product used for the removal of sebum, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair....
s used to treat dandruff
Dandruff

Dandruff is due to the excessive shedding of dead skin cells from the scalp. As it is normal for skin cell s to die and flake off, a small amount of flaking is normal and in fact quite common....
. Salicylic acid is also used as an active ingredient in gels that remove wart
Wart

A wart is generally a small, rough tumor, typically on hands and feet but often other locations, that can resemble a cauliflower or a solid blister....
s. Use of concentrated solutions of salicylic acid may cause hyperpigmentation
Hyperpigmentation

In dermatology, hyperpigmentation is the darkening of an area of skin or nail caused by increased melanin....
 on unpretreated skin for those with darker skin types (Fitzpatrick
Fitzpatrick scale

The Fitzpatrick Scale is a numerical classification schema for the color of skin. It was developed in 1975 by T.B. Fitzpatrick, a Harvard dermatologist, as a way to classify the response of different types of skin to UV light....
 phototypes IV, V, VI), as well as with the lack of use of a broad spectrum sunblock.

Salicylic Acid Pads
Aspirin
Aspirin

Aspirin , also known as acetylsalicylic acid , is a salicylate medication, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication....
 (acetylsalicylic acid or ASA) can be prepared by the esterification
Esterification

Esterification is the general name for a chemical reaction in which two reactants form an ester as the product . Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odor....
 of the phenolic hydroxyl group of salicylic acid.

Subsalicylate in combination with bismuth
Bismuth

Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....
 form the popular stomach relief aid known commonly as Pepto-Bismol
Bismuth subsalicylate

Bismuth subsalicylate, with a chemical formula C7H5BiO4, is a drug used to treat nausea, heartburn, indigestion, diarrhea, and other temporary discomforts of the stomach and gastrointestinal tract....
. When combined, the two key ingredients help control diarrhoea, nausea, heartburn, and gas. It is also a very mild antibiotic
Antibiotic

In common usage, an antibiotic is a substance or compound that kills or inhibits the growth of bacteria. Antibiotics belong to the group of antimicrobial compounds used to treat infections caused by microorganisms, including fungus and protozoa....
.

Choline
Choline

Choline is an organic compound, classified as a water-soluble essential nutrient and usually grouped within the Vitamin B complex. This natural amine is found in the lipids that make up cell membranes and in the neurotransmitter acetylcholine....
 salicylate is used topically to relieve the pain of aphthous ulcer
Aphthous ulcer

An aphthous ulcer, also known as canker sore, is a type of oral ulcer, which presents as a painful open sore inside the mouth or upper throat, caused by a break in the mucous membrane....
s.

Other uses

  • Although toxic in large quantities, salicylic acid is used as a food preservative and antiseptic
    Antiseptic

    Antiseptics are antimicrobials that are applied to living biological tissue/skin to reduce the possibility of infection, sepsis, or putrefaction....
     in toothpaste
    Toothpaste

    Toothpaste is a paste or gel dentifrice used to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it can aid in the removal of dental plaque and food from the teeth, aid in the elimination and/or masking of halitosis and deliver active ingredients such as fluoride or xylitol to prevent tooth...
    . For some people with salicylate sensitivity
    Salicylate sensitivity

    Salicylate sensitivity, also known as salicylate intolerance, is any adverse effect that occurs when a normal amount of salicylate is introduced into a person's body....
     even these small doses can be harmful.
  • Sodium salicylate is a useful phosphor
    Phosphor

    A phosphor is a substance that exhibits the optical phenomenon of phosphorescence .Phosphors are transition metal compounds or rare earth element compounds of various types....
     in the vacuum ultraviolet with nearly flat quantum efficiency for wavelengths between 10 to 100 nm. 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
    Methanol

    Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula carbonhydrogen3oxygenhydrogen ....
     followed by evaporation.


  • Methyl salicylate
    Methyl salicylate

    Methyl salicylate is a natural product of many species of plants. Some of the plants producing it are called wintergreens, hence the common name....
     is used as a liniment
    Liniment

    File:Herb Knudson's Surgical 11.jpgLiniment, from the Latin linere, to anoint, is a medicated topical preparation for application to the skin....
    , to soothe joint and muscle pain.


Safety

Salicylic acid has an ototoxic effect by inhibiting prestin
Prestin

Prestin is the motor protein of the outer hair cell of the inner ear of the mammalian cochlea. It is highly expressed in the outer hair cells, and is not expressed in the nonmotile inner hair cells....
. It can induce transient hearing loss in zinc
Zinc

Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
-deficient individuals.

This finding is based on clinical studies with rat
Rat

Rats are various medium sized, long-tailed rodents of the Family Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus....
s. 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
Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
 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.

Some people are hypersensitive to salicylic acid and related compounds
Salicylate sensitivity

Salicylate sensitivity, also known as salicylate intolerance, is any adverse effect that occurs when a normal amount of salicylate is introduced into a person's body....
.

The United States Food and Drug Administration
Food and Drug Administration

The U.S. Food and Drug Administration is an Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, dietary supplements, Medications, vaccines, Biopharmaceutical, blood transfusion, medical devices, Electromagnetic radiation-emitting devices, veteri...
 recommends the use of sun protection when using skincare products containing salicylic acid (or any other BHA) on sun-exposed skin areas.

See also

Trolamine salicylate
Trolamine salicylate

Trolamine salicylate is an organic compound which is the salt formed between triethanolamine and salicylic acid.It is used as an ingredient in sunscreens, analgesic creams, and cosmetics....


External links



Footnotes