Eugenol

Eugenol is a Colorless or very pale straw-colored oily liquid. 

Very slightly soluble in water, miscible with alcohol and oils, soluble in Propylene glycol, and in dilute aqueous alkali. Viscosity and color increase with age and exposure to air and daylight

FEMA GRAS No.2467. 

Profile:

• 📂 CAS N° 97-53-0

• ⚖️ MW — 164.2 g/mol

• 📝 Odor Type — Spicy

• 📈 Odor Strength — Medium, 52 hours tenacity on paper.

• 👃🏼 Odor Profile — Powerful, warm-spicy, rather dry and almost sharp odor, drier and harder than that of Clove bud oil, less peppery-woody than that of Clove leaf oil. 

• 👅 Flavor Profile — Warm-spicy taste, somewhat burning unless highly diluted. The taste is usually followed by a warm mouthfeel, then a burning sensation, delay, and sequence depending upon the acidity or alkalinity of the saliva. Pungency depends upon the concentration of Eugenol. 

• ⚗️ Uses — Extensively used in perfume compositions, conventionally in Carnation, for which purpose the author would recommend iso-Eugenol in spite of the almost unanimous use of Eugenol in published formulations. For incense, Oriental fragrances, Rose bases, certain types of Fougere, “Blue-Grass” type fragrances, etc. and in all variations of modern Spice types, Eugenol is commonly used in large amounts. 

  For flavors, this phenol is used not only in spice complexes, but also as a modifier in Mint flavors, Nut flavors, various fruit complexes, and rare flavors such as date.Eugenol is in no way a substitute for Clove bud oil in flavors, but it may add to the strength and give a clove-like note to combination-spice flavors. Concentrations in finished consumer products range from 10 to 100 ppm in candies and baked goods, up to 200 ppm in meat products and up to 500 ppm in chewing gum. It may reach the same level in toothpaste but is normally lower than 300 ppm in oral products. 

  This compound is listed on the EFFA list of European flavor ingredients and is FEMA 2467. Widely used either in clove oil, in which it occurs or as a pure material, p-eugenol has a desirable odor in addition to the mild warming properties it displays. Eugenol has been used in the treatment of dental pain for hundreds of years and is still used to the present day. Eugenol is also a key component of vanilla flavors. 

Other Uses:

Eugenol is used in perfumes, flavorings, and essential oils. It is also used as a local antiseptic and anesthetic. Eugenol can be combined with zinc oxide to form zinc oxide eugenol which has restorative and prosthodontic applications in dentistry. For example, zinc oxide eugenol is used for root canal sealing.

Attempts have been made to develop eugenol derivatives as intravenous anesthetics, as an alternative to propanidid which produces unacceptable side effects around the site of injection in many patients.

It can be used to reduce the presence of Listeria monocytogenes and Lactobacillus sakei in food.

It is also used in manufacturing stabilizers and antioxidants for plastics and rubbers.

It is one of many compounds that 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. It also attracts female cucumber beetle. It was recently discovered that eugenol and isoeugenol, 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 so far.

Clove oil is growing in popularity as an an-aesthetic for use on aquarium fish as well as on wild fish when sampled for research and management purposes. 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.

Production:

Produced by isolation from Clove leaf oil, or Clove stem oil, or Cinnamon leaf oil, occasionally from Bay leaf oil or from Clove bud oil. 

With a Clove leaf oil price of U.S. S 2.20 to 3.30 per kilo (1967-1968), there was no interest in promoting synthetic methods of making Eugenol.

This phenol remains one of the most important perfumes and flavor chemicals exclusively made from natural sources by simple isolation (alkali wash). Clove leaf oil has been extremely stable in price until late 1967 when it increased significantly over a period of 1968. Even the subsequently higher prices for all Eugenol products have not encouraged the research on an economical method of making Eugenol from a non-natural source. 

Synthesis: One method uses Guaiacol as a starting material. Although Guaiacol is present in wood tar, it is most conveniently prepared from Catechol (Pyrocatechol) by Monomethylation. Catechol is obtained from Phenol which is a coal tar derivative. When Guaiacol is reacted with Allyl chloride the Guaiacol allyl ether can be rearranged to Eugenol

The production of Eugenol from Coniferyl alcohol - widely distributed in the plant Kingdom - is of no immediate importance. 

Natural Occurrence:

Eugenol naturally occurs in several plants, including the following:

• Cloves (Syzygium aromaticum)

• Cinnamon

• Cinnamomum tamala

• Nutmeg (Myristica fragrans)

• Ocimum basilicum (sweet basil)

• Ocimum gratissimum (African basil)

• Ocimum tenuiflorum (syn. Ocimum sanctum, tulsi or holy basil)

• Japanese star anise

• Lemon balm

• Dill

• Pimenta racemosa

• Vanilla

• Bay laurel

• Celery

• Ginger

• Wormwood

Toxicity:

Eugenol is hepatotoxic, meaning it may cause damage to the liver. Overdose is possible, causing a wide range of symptoms from blood in the patient's urine, to convulsions, diarrhea, nausea, unconsciousness, dizziness, or rapid heartbeat. According to a published 1993 report, a 2-year-old boy nearly died after taking between 5 and 10 ml.

Allergies:

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

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

Sources:

• Fulvio Ciccolo

• Perfume and Flavor Chemicals Steffen Arctander

• Chemistry and Technology of Flavors and Fragrances David Rowe

• National Center for Biotechnology Information (2020). PubChem Compound Summary for CID 3314, Eugenol. Retrieved November 25, 2020 from https://pubchem.ncbi.nlm.nih.gov/compound/Eugenol.