# Wax ester

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A wax ester (WE) is an ester of a fatty acid and a fatty alcohol. Wax esters comprise the main components of three commercially important waxes: carnauba wax, candelilla wax, and beeswax. [1]

In chemistry, an ester is a chemical compound derived from an acid in which at least one –OH (hydroxyl) group is replaced by an –O–alkyl (alkoxy) group. Usually, esters are derived from a carboxylic acid and an alcohol. Glycerides, which are fatty acid esters of glycerol, are important esters in biology, being one of the main classes of lipids, and making up the bulk of animal fats and vegetable oils. Esters with low molecular weight are commonly used as fragrances and found in essential oils and pheromones. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties. Esters usually have a sweet smell and are considered high-quality solvents for a broad array of plastics, plasticizers, resins, and lacquers. They are also one of the largest classes of synthetic lubricants on the commercial market.

In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with a long aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually not found in organisms, but instead as three main classes of esters: triglycerides, phospholipids, and cholesterol esters. In any of these forms, fatty acids are both important dietary sources of fuel for animals and they are important structural components for cells.

Fatty alcohols (or long-chain alcohols) are usually high-molecular-weight, straight-chain primary alcohols, but can also range from as few as 4–6 carbons to as many as 22–26, derived from natural fats and oils. The precise chain length varies with the source. Some commercially important fatty alcohols are lauryl, stearyl, and oleyl alcohols. They are colourless oily liquids (for smaller carbon numbers) or waxy solids, although impure samples may appear yellow. Fatty alcohols usually have an even number of carbon atoms and a single alcohol group (–OH) attached to the terminal carbon. Some are unsaturated and some are branched. They are widely used in industry. As with fatty acids, they are often referred to generically by the number of carbon atoms in the molecule, such as "a C12 alcohol", that is an alcohol having 12 carbons, for example dodecanol.

## Contents

Wax esters are formed by combining one fatty acid with one fatty alcohol:

${\displaystyle {\ce {RCOOH + R'OH <=> RCOOR' + H2O}}}$

Various types of wax esters exist. Some are saturated, and others contain unsaturated centers. Saturated wax esters have higher melting points and are more likely to be solid at room temperature. Unsaturated wax esters have a lower melting point and are more likely to be liquid at room temperature. Both fatty acids and fatty alcohols may have of different carbon chain length. In the end, there are many different possible combinations of fatty acids and fatty alcohols and each combination will have a unique set of properties in terms of steric orientation and phase transition.

The chain lengths of fatty acids and fatty alcohols in naturally occurring wax esters vary. The fatty acids in wax esters derived from plants typically range from C12-C24, and the alcohols in plant waxes tend to be very long, typically C24-C34. [2] The fatty acids and fatty alcohols of wax esters from different marine animals show major differences. Wax esters of sperm whales contain C12 fatty acids and C14 fatty acid and alcohols. Monounsaturated C18 is the dominant fatty acid of most fish wax esters, with the exception of roe wax esters, which have sizeable amounts of polyunsaturated fatty acids such as 20:5n-3, 22:5n-3 and 22:6n-3. The fatty acids of wax esters of certain zooplankton largely reflects the fatty acids of phytoplankton, and contain high amounts of C14 and C16, as well as 20:5n-3, 22:5n-3 and 22:6n-3 and monounsaturated C20 and C22 are the principal fatty alcohols. [3]

Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5(n-3). It also has the trivial name timnodonic acid. In chemical structure, EPA is a carboxylic acid with a 20-carbon chain and five cis double bonds; the first double bond is located at the third carbon from the omega end.

Docosapentaenoic acid (DPA) designates any straight chain 22:5 fatty acid, that is a straight chain open chain type of polyunsaturated fatty acid (PUFA) which contains 22 carbons and 5 double bonds. DPA is primarily used to designate two isomers, all-cis-4,7,10,13,16-docosapentaenoic acid and all-cis-7,10,13,16,19-docosapentaenoic acid. They are also commonly termed n-6 DPA and n-3 DPA, respectively; these designations describes the position of the double bond being 6 or 3 carbons closest to the (omega) carbon at the methyl end of the molecule and is based on the biologically important difference that n-6 and n-3 PUFA are separate PUFA classes, i.e. the omega-6 fatty acids and omega-3 fatty acids, respectively. Mammals, including humans, can not interconvert these two classes and therefore must obtain dietary essential PUFA fatty acids from both classes in order to maintain normal health.

Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. In physiological literature, it is given the name 22:6(n-3). It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk, fish oil, or algae oil.

## Natural sources of wax esters

Beeswax is 70-80% wax esters. These esters are derived from C12-C20 fatty acids. The remaining content of beeswax are wax acids (>C20) and paraffins. In 1976, an estimated 10,000-17,000 tons were harvested. The primary use was in candles. The esters in carnauba wax consist of ca 20% cinnamic acid derivatives, which may be related to the hardness of this wax. [1]

### Other, minor wax esters

Wax esters are commonly found in shellfish and as a part of the cuticle of arthropods. In leaves, they prevent loss of water. [4]

Shellfish is a food source and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found in freshwater. In addition, a few species of land crabs are eaten, for example Cardisoma guanhumi in the Caribbean.

A cuticle, or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non-homologous, differing in their origin, structure, function, and chemical composition.

An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans. The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora. Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthopods are bilaterally symmetrical and their body possesses an external skeleton. Some species have wings.

Nuts from jojoba store as much as 50% of wax esters. These wax esters, which are monounsaturated, are very similar to sperm oil. [1]

Jojoba, with the botanical name Simmondsia chinensis, and also known as goat nut,deer nut,pignut,wild hazel,quinine nut,coffeeberry, and gray box bush, is native to Southwestern North America. Simmondsia chinensis is the sole species of the family Simmondsiaceae, placed in the order Caryophyllales.

Sperm oil is a waxy liquid obtained from sperm whales. It is a clear, yellowish liquid with a very faint odor. Sperm oil has a different composition from common whale oil, obtained from rendered blubber. Although it is traditionally called an "oil", it is technically a liquid wax. It is composed of wax esters with a small proportion of triglycerides, an ester of an unsaturated fatty acid and a branched-chain fatty alcohol. It is a natural antioxidant and heat-transfer agent. Through catalytic reaction, it carries phosphorus and sulfur derivatives providing anti-wear and friction modification. In the late 18th and early 19th centuries, sperm oil was prized as an illuminant for its bright, odorless flame and as a lubricant for its low viscosity and stability. It was supplanted in the late 19th century by less expensive alternatives such as kerosene and petroleum-based lubricants. With the 1987 international ban on whaling, sperm oil is no longer legally sold.

Marine organisms like dinoflagellates, pelagic invertebrates, and fishes store low-density wax esters in their swim bladders or other tissues to provide buoyancy. [5]

Wax esters per se are a normal part of the diet of humans as a lipid component of certain foods, including unrefined whole grain cereals, seeds, and nuts. [2] Wax esters are also consumed in considerable amounts by certain populations that regularly eat fish roe [6] or certain fish species. That said, wax esters are not typically consumed in appreciable quantities in diets containing many processed foods. [2]

## Metabolism

Lipases and carboxyl esterases that hydrolyze triglycerides have demonstrated enzymatic activity towards wax esters. Kinetic data show that EPA and DHA provided as wax esters reaches a maximal concentration at approximately 20 h post-consumption, and may indicate delayed absorption of the fatty acids. [7]

## Bioavailability

There has been a common understanding that wax esters are poorly absorbed by humans, partly due to outbreaks of the purgative effect named keriorrhea, associated with consumption of oilfish (Ruvettus pretiosus) and escolar (Lepdocybium flavobrunneum). Fillets from these fish species contain up to 20% fat, where 90% of the fat comes as wax esters, resulting in a typical intake of more than 30 000 mg wax esters from one single meal. Orange roughy (Hoplostethus atlanticus) is an attractive food fish with 5,5% fat, where 90% of the fat comes as wax esters. Consumption of this fish gives no unpleasant adverse effects, most likely due to the relatively low fat content that provides approximately 10 000 mg wax ester per 200 grams serving of fish.

In 2015 a randomized, two-period crossover human study, showed that EPA and DHA from oil extracted from the small crustacean Calanus finmarchicus was highly bioavailable and the study concluded that oil from C. finmarchicus could serve as a relevant source of the healthy omega-3 fatty acids EPA, DHA and SDA. 86% of the oil from C. finmarchicus comes as wax esters. [7]

Studies on mice have shown that, despite consuming diets containing similar amounts of EPA and DHA, blood levels of both EPA and DHA were significantly higher in mice fed a diet supplemented with oil from C. finmarchicus compared to those fed an EPA+DHA ethyl ester enriched diet. [8] Furthermore, oil from C. finmarchicus has been observed to have beneficial effects on obesity-related abnormalities in rodent models of diet-induced obesity at EPA and DHA fatty acid concentrations considerably lower than the concentrations used in similar earlier studies using other sources of EPA and DHA. [9] [10] Taken together, based on the available in vitro data, animal data, and the findings of the Cook et al. study [7] demonstrating that circulating concentrations of EPA and DHA remained elevated up to 72 h after a single serving of 4 g oil from C. finmarchicus the hydrolyzed products of wax ester digestion are most likely slowly absorbed in vivo.

## Role as a nutrient

Marine wax esters have become a focus of attention due to documented positive effects on widespread medical conditions related to the unhealthy western lifestyle. [9] [10]  Harvesting on a lower trophic level on short-lived organisms would be more sustainable and the products would be less prone to environmental toxins and pollutants. Norwegian company Wax ester-based products from the small crustacean Calanus finmarchicus have been commercialized. [11]

## Related Research Articles

Omega−3 fatty acids, also called ω−3 fatty acids or n−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond three atoms away from the terminal methyl group in their chemical structure. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), found in plant oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both commonly found in marine oils. Marine algae and phytoplankton are primary sources of omega−3 fatty acids. Common sources of plant oils containing ALA include walnut, edible seeds, clary sage seed oil, algal oil, flaxseed oil, Sacha Inchi oil, Echium oil, and hemp oil, while sources of animal omega−3 fatty acids EPA and DHA include fish, fish oils, eggs from chickens fed EPA and DHA, squid oils, and krill oil.

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them.

Cod liver oil is a dietary supplement derived from liver of cod fish (Gadidae). As with most fish oils, it contains the omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Cod liver oil also contains vitamin A and vitamin D. Historically, it was given to children because vitamin D had been shown to prevent rickets, a consequence of vitamin D deficiency.

An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond.

Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is the most common saturated fatty acid found in animals, plants and microorganisms. Its chemical formula is CH3(CH2)14COOH, and its C:D is 16:0. As its name indicates, it is a major component of the oil from the fruit of oil palms (palm oil). Palmitic acid can also be found in meats, cheeses, butter, and other dairy products. Palmitates are the salts and esters of palmitic acid. The palmitate anion is the observed form of palmitic acid at physiologic pH (7.4).

Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 cis-9. It has the formula CH3(CH2)7CH=CH(CH2)7COOH. The name derives from the Latin word oleum, which means oil. It is the most common fatty acid in nature. Salts of oleic acid are called oleates.

Fish oil is oil derived from the tissues of oily fish. Fish oils contain the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), precursors of certain eicosanoids that are known to reduce inflammation in the body and improve hypertriglyceridemia. There has been a great deal of controversy in recent years about the role of fish oil in cardiovascular disease, with recent meta-analyses reaching different conclusions about its potential impact. The most promising evidence supports supplementation for prevention of cardiac death.

In biochemistry and nutrition, monounsaturated fatty acids (abbreviated MUFAs, or more plainly monounsaturated fats) are fatty acids that have one double bond in the fatty acid chain with all of the remainder carbon atoms being single-bonded. By contrast, polyunsaturated fatty acids (PUFAs) have more than one double bond.

Vegetarian nutrition is the set of health-related challenges and advantages of vegetarian diets.

Polyunsaturated fats are fats in which the constituent hydrocarbon chain possesses two or more carbon–carbon double bonds. Polyunsaturated fat can be found mostly in nuts, seeds, fish, seed oils, and oysters. "Unsaturated" refers to the fact that the molecules contain less than the maximum amount of hydrogen. These materials exist as cis or trans isomers depending on the geometry of the double bond.

Omega-9 fatty acids are a family of unsaturated fatty acids which have in common a final carbon–carbon double bond in the omega−9 position; that is, the ninth bond from the methyl end of the fatty acid.

The effects on humans of the ω-3 (omega-3) and ω-6 (omega-6) essential fatty acids (EFAs) are best characterized by their interactions; they cannot be understood separately.

Interesterified fat is a type of oil where the fatty acids have been moved from one triglyceride molecule to another. This is generally done to modify the melting point, slow rancidification and create an oil more suitable for deep frying or making margarine with good taste and low saturated fat content. It is not the same as partial hydrogenation which produces trans fatty acids, but interesterified fats used in the food industry can come from hydrogenated fat, for simplicity and frugality.

Calanus finmarchicus is a species of copepods and a part of zooplankton, which is found in enormous amounts in the northern Atlantic Ocean.

Ethyl eicosapentaenoic acid is a derivative of the omega-3 fatty acid eicosapentaenoic acid (EPA) that is used in combination with changes in diet to lower triglyceride levels in adults with severe hypertriglyceridemia. This was the second class of fish oil-based drug to be approved for use as a drug and was approved by the FDA in 2012. These fish oil drugs are similar to fish oil dietary supplements but the ingredients are better controlled and have been tested in clinical trials.

Omega-3 carboxylic acids (Epanova) is an FDA approved prescription medication used alongside a low fat and low cholesterol diet that lowers high triglyceride (fat) levels in adults with very high levels. This was the third class of fish oil-based drug to be approved for use as a drug. The first approval was granted in the US came in 2014. These fish oil drugs are similar to fish oil dietary supplements but the ingredients are better controlled and have been tested in clinical trials.

Calanus hyperboreus is a copepod found in the Arctic and northern Atlantic. It occurs from the surface to depths of 5,000 metres (16,000 ft).

## References

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