Eugenol

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Contents

Eugenol
Eugenol2DCSD.svg
Eugenol-3D-balls.png
Names
Preferred IUPAC name
2-Methoxy-4-(prop-2-en-1-yl)phenol
Other names
  • 4-Allyl-2-methoxyphenol
  • 2-Methoxy-4-(2-propenyl)phenol
  • Eugenic acid
  • Caryophyllic acid
  • 1-Allyl-3-methoxy-4-hydroxybenzene
  • Allylguaiacol
  • 2-Methoxy-4-allylphenol
  • 4-Allylcatechol-2-methyl ether
Identifiers
3D model (JSmol)
1366759
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.355 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 202-589-1
KEGG
PubChem CID
UNII
  • InChI=1S/C10H12O2/c1-3-4-8-5-6-9(11)10(7-8)12-2/h3,5-7,11H,1,4H2,2H3 Yes check.svgY
    Key: RRAFCDWBNXTKKO-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C10H12O2/c1-3-4-8-5-6-9(11)10(7-8)12-2/h3,5-7,11H,1,4H2,2H3
    Key: RRAFCDWBNXTKKO-UHFFFAOYAJ
  • Oc1ccc(cc1OC)CC=C
Properties
C10H12O2
Molar mass 164.204 g·mol−1
Density 1.06 g/cm3
Melting point −7.5 °C (18.5 °F; 265.6 K)
Boiling point 254 °C (489 °F; 527 K)
Acidity (pKa)10.19 at 25 °C
−1.021×10−4 cm3/mol
Viscosity
  • 9.12 mPa·s at 20 °C
  • 5.99 mPa·s at 30 °C [1]
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point 104 °C (219 °F; 377 K)
Related compounds
Related compounds
2-Phenethyl propionate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Eugenol /ˈjɪnɒl/ is an allyl chain-substituted guaiacol, a member of the allylbenzene class of chemical compounds. [2] It is a colorless to pale yellow, aromatic oily liquid extracted from certain essential oils especially from clove, nutmeg, cinnamon, basil and bay leaf. [3] [4] [5] [6] It is present in concentrations of 80–90% in clove bud oil and at 82–88% in clove leaf oil. [7] Eugenol has a pleasant, spicy, clove-like scent. [8] The name is derived from Eugenia caryophyllata, the former Linnean nomenclature term for cloves. The currently accepted name is Syzygium aromaticum. [9]

Biosynthesis

The biosynthesis of eugenol begins with the amino acid tyrosine. L-tyrosine is converted to p-coumaric acid by the enzyme tyrosine ammonia lyase (TAL). [10] From here, p-coumaric acid is converted to caffeic acid by p-coumarate 3-hydroxylase using oxygen and NADPH. S-Adenosyl methionine (SAM) is then used to methylate caffeic acid, forming ferulic acid, which is in turn converted to feruloyl-CoA by the enzyme 4-hydroxycinnamoyl-CoA ligase (4CL). [11] Next, feruloyl-CoA is reduced to coniferaldehyde by cinnamoyl-CoA reductase (CCR). Coniferaldeyhyde is then further reduced to coniferyl alcohol by cinnamyl-alcohol dehydrogenase (CAD) or sinapyl-alcohol dehydrogenase (SAD). Coniferyl alcohol is then converted to an ester in the presence of the substrate CH3COSCoA, forming coniferyl acetate. Finally, coniferyl acetate is converted to eugenol via the enzyme eugenol synthase 1 and the use of NADPH.[ citation needed ]

Biosynthesis of eugenol Eugenol biosynthesis .tif
Biosynthesis of eugenol

Pharmacology

Eugenol and thymol possess general anesthetic properties. Like many other anesthetic agents, these 2-alkyl(oxy)phenols act as positive allosteric modulators of the GABA A receptor. Although eugenol and thymol are too toxic and not potent enough to be used clinically, these findings led to the development of 2-substituted phenol anesthetic drugs, including propanidid (later withdrawn) and the widely used propofol. [12] Eugenol and the structurally similar myristicin, have the common property of inhibiting MAO-A and MAO-B in vitro. [13] [14]

Eugenol acts on the NDMA receptors as an antagonist, as well as the histamine receptors as an antagonist, but the exact specifics of this are unknown.

In humans, complete excretion occurs within 24 hour and metabolites are mostly conjugates of eugenol. [15]

Uses

Humans

Eugenol is used as a flavor or aroma ingredient in teas, meats, cakes, perfumes, cosmetics, flavorings, and essential oils. [2] [16] [17] It is also used as a local antiseptic and anaesthetic. [18] [19] Eugenol can be combined with zinc oxide to form zinc oxide eugenol which has restorative and prosthodontic applications in dentistry. For persons with a dry socket as a complication of tooth extraction, packing the dry socket with a eugenol-zinc oxide paste on iodoform gauze is effective for reducing acute pain. [20] Eugenol-zinc oxide paste is also used for root canal sealing. [21]

Insects and fish

It is attractive to males of various species of orchid bees, which apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. [22] It also attracts female cucumber beetles. [23]

Eugenol and isoeugenol, which both are floral volatile scent compounds, are catalyzed by a single type of enzyme in the genus Gymnadenia and the gene encoding for this enzyme is the first functionally characterized gene in these species. [24] Eugenol is an ingredient in some insecticides. [2]

Clove oil is common as an anesthetic for use on aquarium fish as well as on wild fish when sampled for research and management purposes. [25] [26] Where readily available, it presents a humane method to euthanize sick and diseased fish either by direct overdose or to induce sleep before an overdose of eugenol. [27] [28]

Other

Eugenol is an ingredient in some fungicides and weed control products used in agricultural practices in the European Union. [2] It is used in hundreds of household products, such as pesticides, pet care, laundry, cleaning, and paper or vehicle products. [2]

Toxicity

Taken orally in high doses for chronic periods, eugenol may cause liver toxicity. [16] An overdose is possible, causing a wide range of symptoms, such as hematuria (blood in urine), convulsions, diarrhea, nausea, sedation, delirium, unconsciousness, dizziness, tachycardia (rapid heart rate), or acute kidney injury. [16] [29] N-acetylcysteine may be used to treat people with eugenol or clove oil overdose. [30]

As an allergenic

Eugenol is subject to restrictions on its use in perfumery, [31] as some people may become sensitised to it, however, the degree to which eugenol can cause an allergic reaction in humans is disputed. [32]

Eugenol is a component of balsam of Peru, to which some people are allergic. [33] [34] When eugenol is used in dental preparations such as surgical pastes, dental packing, and dental cement, it may cause contact stomatitis and allergic cheilitis. [33] The allergy can be discovered via a patch test. [33]

Natural occurrence

Eugenol naturally occurs in numerous plants, including the following:

See also

Related Research Articles

<span class="mw-page-title-main">Clove</span> Spice, flower buds of Syzygium aromaticum

Cloves are the aromatic flower buds of a tree in the family Myrtaceae, Syzygium aromaticum. They are native to the Maluku Islands, or Moluccas, in Indonesia, and are commonly used as a spice, flavoring, or fragrance in consumer products, such as toothpaste, soaps, or cosmetics. Cloves are available throughout the year owing to different harvest seasons across various countries.

<span class="mw-page-title-main">Essential oil</span> Hydrophobic liquid containing volatile aroma compounds from plants

An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the oil of the plant from which they were extracted, such as oil of clove. An essential oil is essential in the sense that it contains the essence of the plant's fragrance—the characteristic fragrance of the plant from which it is derived. The term "essential" used here does not mean indispensable or usable by the human body, as with the terms essential amino acid or essential fatty acid, which are so called because they are nutritionally required by a living organism.

<span class="mw-page-title-main">Basil</span> Important culinary herb

Basil, also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" refers to the variety also known as sweet basil or Genovese basil. Basil is native to tropical regions from Central Africa to Southeast Asia. In temperate climates basil is treated as an annual plant, however, basil can be grown as a short-lived perennial or biennial in warmer horticultural zones with tropical or Mediterranean climates.

Zinc oxide eugenol (ZOE) is a material created by the combination of zinc oxide and eugenol contained in clove oil. An acid-base reaction takes place with the formation of zinc eugenolate chelate. The reaction is catalysed by water and is accelerated by the presence of metal salts. ZOE can be used as a dental filling material or dental cement in dentistry. It is often used in dentistry when the decay is very deep or very close to the nerve or pulp chamber. Because the tissue inside the tooth, i.e. the pulp, reacts badly to the drilling stimulus, it frequently becomes severely inflamed and precipitates a condition called acute or chronic pulpitis. This condition usually leads to severe chronic tooth sensitivity or actual toothache and can then only be treated with the removal of the nerve (pulp) called root canal therapy. For persons with a dry socket as a complication of tooth extraction, packing the dry socket with a eugenol-zinc oxide paste on iodoform gauze is effective for reducing acute pain. The placement of a ZOE "temporary" for a few to several days prior to the placement of the final filling can help to sedate the pulp. But, ZOE had in vitro cytotoxicity majorly due to release of Zn ions, not eugenol. In spite of severe in vitro cytotoxicity, ZOE showed relatively good biocompatibility in animal study when ZOE was applied on dentin. When ZOE was used as dentin-protective based materials, use of dental composite resin on ZOE was strongly prevented due to its inhibition of resin polymerization through radical scavenging effect. It is classified as an intermediate restorative material and has anaesthetic and antibacterial properties. The exact mechanism of anesthetic effect from ZOE was not revealed perfectly, but possibly through anti-inflammatory effect, modulating immune-cells to less inflamed status.

<span class="mw-page-title-main">Linalool</span> Chemical compound with a floral aroma

Linalool refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent. A colorless oil, linalool is classified as an acyclic monoterpenoid. In plants, it is a metabolite, a volatile oil component, an antimicrobial agent, and an aroma compound. Linalool has uses in manufacturing of soaps, fragrances, food additives as flavors, household products, and insecticides. Esters of linalool are referred to as linalyl, e.g. linalyl pyrophosphate, an isomer of geranyl pyrophosphate.

<i>Ocimum tenuiflorum</i> Species of flowering plant

Ocimum tenuiflorum, commonly known as holy basil or tulsi, is an aromatic perennial plant in the family Lamiaceae. It is native to tropical and subtropical regions of Australia, Malesia, Asia, and the western Pacific. It is widely cultivated throughout the Southeast Asian tropics. This plant has escaped from cultivation and has naturalized in many tropical regions of the Americas. It is an agricultural and environmental weed.

Guaiacol is an organic compound with the formula C6H4(OH)(OCH3). It is a phenolic compound containing a methoxy functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs widely in nature and is a common product of the pyrolysis of wood.

<span class="mw-page-title-main">Caryophyllene</span> Chemical compound

Caryophyllene, more formally (−)-β-caryophyllene (BCP), is a natural bicyclic sesquiterpene that is a constituent of many essential oils, especially clove oil, the oil from the stems and flowers of Syzygium aromaticum (cloves), the essential oil of Cannabis sativa, copaiba, rosemary, and hops. It is usually found as a mixture with isocaryophyllene and α-humulene, a ring-opened isomer. Caryophyllene is notable for having a cyclobutane ring, as well as a trans-double bond in a 9-membered ring, both rarities in nature.

<span class="mw-page-title-main">Oil of clove</span> Oil of cloves

Oil of clove, also known as clove oil or eugenol, is an essential oil extracted from the clove plant, Syzygium aromaticum. Clove oil is commonly used in aromatherapy and for flavoring food, tea, and toothpaste. In alternative medicine, it may be used as a topical medication to relieve toothache. There is insufficient medical evidence to support its use as an analgesic for treating pain.

<span class="mw-page-title-main">Fenchol</span> Chemical compound

Fenchol or 1,3,3-trimethyl-2-norbornanol is a monoterpenoid and an isomer of borneol. It is a colorless or white solid. It occurs widely in nature.

<span class="mw-page-title-main">Rosmarinic acid</span> Chemical compound found in a variety of plants

Rosmarinic acid, named after rosemary, is a polyphenol constituent of many culinary herbs, including rosemary, perilla, sage, mint, and basil.

<span class="mw-page-title-main">Luting agent</span>

A luting agent is a dental cement connecting the underlying tooth structure to a fixed prosthesis. To lute means to glue two different structures together. There are two major purposes of luting agents in dentistry – to secure a cast restoration in fixed prosthodontics, and to keep orthodontic bands and appliances in situ.

<span class="mw-page-title-main">Methyl cinnamate</span> Chemical compound

Methyl cinnamate is the methyl ester of cinnamic acid and is a white or transparent solid with a strong, aromatic odor. It is found naturally in a variety of plants, including in fruits, like strawberry, and some culinary spices, such as Sichuan pepper and some varieties of basil. Eucalyptus olida has the highest known concentrations of methyl cinnamate (98%) with a 2–6% fresh weight yield in the leaf and twigs.

<span class="mw-page-title-main">Oleanolic acid</span> Pentacyclic chemical compound in plant leaves and fruit

Oleanolic acid or oleanic acid is a naturally occurring pentacyclic triterpenoid related to betulinic acid. It is widely distributed in food and plants where it exists as a free acid or as an aglycone of triterpenoid saponins.

<i>Ocimum gratissimum</i> Basil species, strong cloves smell

Ocimum gratissimum, also known as clove basil, African basil, and in Hawaii as wild basil, is a species of basil. It is native to Africa, Madagascar, southern Asia, and the Bismarck Archipelago, and naturalized in Polynesia, Hawaii, Mexico, Panama, West Indies, Brazil, and Bolivia.

<i>Ocimum basilicum <span style="font-style:normal;">var.</span> minimum</i> Variety of basil

Greek basil is a flowering herb and cultivar of basil.

<span class="mw-page-title-main">Acetyleugenol</span> Chemical compound

Acetyleugenol is a phenylpropanoid compound found in cloves. It is the second in abundance to the related compound eugenol in certain extract preparations. Like eugenol, its found in several plants such as Acacia nilotica and Piper betle and has similar antibacterial and antifungal properties on C. albicans and S. mutans. It inhibits aggregation of platelets and has partial agonistic activity on AhR.

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