Oleic Acid Ethyl Ester

Description

Ethyl oleate is a fatty acid ester formed by the condensation of oleic acid and ethanol. It is a colorless to light yellow liquid. Ethyl oleate is produced by the body during ethanol intoxication.
Ethyl oleate is used as a solvent for pharmaceutical drug preparations involving lipophilic substances such as steroids. It also finds use as a lubricant and a plasticizer. The Food and Drug Administration regulates its use as a food additive under "Food Additives Permitted for Direct Addition to Food for Human Consumption", 21CFR172.515.

Chemical Properties

Ethyl oleate is a pale yellow to almost colorless, mobile, oily liquid with a taste similar to olive oil and a slight odor that is not rancid. In the USP32-NF27, Ethyl oleate is described as consisting of esters of ethyl alcohol and high molecular weight fatty acids, principally oleic acid. It may contain a suitable antioxidant.

Occurrence

Reported found in cocoa, buckwheat, elderberry and babaco fruit (Carica pentagona Heilborn).

Uses

Ethyl oleate is a flavoring and fragrance agent. Usually used to prepare the oily phase of self-microemulsifying drug delivery system (SMEDDS) for tacrolimus (Tac). It was obtained by the hydrolysis of various animal and vegetable fats and oils.

Preparation

Ethyl oleate is prepared by the reaction of ethanol with oleoyl chloride in the presence of a suitable hydrogen chloride acceptor. Or by direct esterification of oleic acid with ethyl alcohol in the presence of HCl at the boil; in the presence of Twitchell’s reagent or chlorosulfonic acid.

Definition

ChEBI: Ethyl oleate is a long-chain fatty acid ethyl ester resulting from the formal condensation of the carboxy group of oleic acid with the hydroxy group of ethanol. It has a role as a plant metabolite and an acaricide. It is functionally related to an oleic acid.

Aroma threshold values

Detection: 130 to 610 ppm

General Description

Ethyl oleate is a colourless to pale yellow oily liquid that has a faint, floral note. It is neutral and is a more lipid-soluble form of oleic acid. The compound contributed to approximately 17% of the total fatty acids esterified to phosphatidylcholine in porcine platelets. The compound is one of the fatty acid ethyl esters that is generated after the breakdown of ethanol in the body. Moreover, ethyl oleate usually acts as a toxic mediator of ethanol in the heart, liver, pancreas, and brain.

Health effects

Ethyl oleate is one of the fatty acid ethyl esters (FAEE) that is formed in the body after ingestion of ethanol. There is a growing body of research literature that implicates FAEEs such as ethyl oleate as the toxic mediators of ethanol in the body (pancreas, liver, heart, and brain). Among the speculations is that ethyl oleate may be the toxic mediator of alcohol in fetal alcohol syndrome. The oral ingestion of ethyl oleate has been carefully studied and due to rapid degradation in the digestive tract it appears safe for oral ingestion. Ethyl oleate is not currently approved by the U.S. Food and Drug Administration for any injectable use. However, it is used by compounding pharmacies as a vehicle for intramuscular drug delivery, in some cases to prepare the daily doses of progesterone in support of pregnancy. Studies which document the safe use of ethyl oleate in pregnancy for both the mother and the fetus have never been performed.

Pharmaceutical Applications

Ethyl oleate is primarily used as a vehicle in certain parenteral preparations intended for intramuscular administration. It has also been used as a solvent for drugs formulated as biodegradable capsules for subdermal implantation) and in the preparation of microemulsions containing cyclosporinand norcantharidin.
Microemulsion formulations containing ethyl oleate have also been proposed for topical and ocular delivery, and for liver targeting following parenteral administration. Ethyl oleate has been used in topical gel formulations, and in self-microemulsifying drug delivery systems for oral administration.
Ethyl oleate is a suitable solvent for steroids and other lipophilic drugs. Its properties are similar to those of almond oil and peanut oil. However, it has the advantage that it is less viscous than fixed oils and is more rapidly absorbed by body tissues.
Ethyl oleate has also been evaluated as a vehicle for subcutaneous injection.

Clinical Use

Ethyl oleate is used by compounding pharmacies as a vehicle for intramuscular administration and in some cases to formulate daily doses of progesterone to support pregnancy. There are no studies to prove that the use of ethyl oleate during pregnancy is safe for both mother and foetus.

Safety

Ethyl oleate is generally considered to be of low toxicity but ingestion should be avoided. Ethyl oleate has been found to cause minimal tissue irritation. No reports of intramuscular irritation during use have been recorded.

Carcinogenicity

Not listed by ACGIH, California Proposition 65, IARC, NTP, or OSHA.

storage

Ethyl oleate should be stored in a cool, dry place in a small, wellfilled, well-closed container, protected from light. When a partially filled container is used, the air should be replaced by nitrogen or another inert gas. Ethyl oleate oxidizes on exposure to air, resulting in an increase in the peroxide value. It remains clear at 5°C, but darkens in color on standing. Antioxidants are frequently used to extend the shelf life of ethyl oleate. Protection from oxidation for over 2 years has been achieved by storage in amber glass bottles with the addition of combinations of propyl gallate, butylated hydroxyanisole, butylated hydroxytoluene, and citric or ascorbic acid. A concentration of 0.03% w/v of a mixture of propyl gallate (37.5%), butylated hydroxytoluene (37.5%), and butylated hydroxyanisole (25%) was found to be the best antioxidant for ethyl oleate.
Ethyl oleate may be sterilized by heating at 150°C for 1 hour.

Incompatibilities

Ethyl oleate dissolves certain types of rubber and causes others to swell. It may also react with oxidizing agents.

Regulatory Status

Included in the FDA Inactive Ingredients Database (transdermal preparation). Included in parenteral (intramuscular injection) and nonparenteral (transdermal patches) medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.