Erucic acid

Erucic acid
IUPAC name (Z)-Docos-13-enoic acid
Identifiers
CAS number	112-86-7 Y
PubChem	5281116
ChemSpider	4444561 Y
UNII	075441GMF2 Y
KEGG	C08316 Y
ChEBI	CHEBI:28792 Y
ChEMBL	CHEMBL1173380 Y
Jmol-3D images	Image 1
SMILES O=C(O)CCCCCCCCCCC\C=C/CCCCCCCC
InChI InChI=1S/C22H42O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(23)24/h9-10H,2-8,11-21H2,1H3,(H,23,24)/b10-9- Y Key: DPUOLQHDNGRHBS-KTKRTIGZSA-N Y InChI=1/C22H42O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22(23)24/h9-10H,2-8,11-21H2,1H3,(H,23,24)/b10-9- Key: DPUOLQHDNGRHBS-KTKRTIGZBD
Properties
Molecular formula	C22H42O2
Molar mass	338.57 g mol−1
Appearance	White waxy solid
Density	0.860 g/cm3
Melting point	33.8 °C; 92.8 °F; 306.9 K
Boiling point	381.5 °C (decomposes)
Solubility in water	Insoluble
Solubility in methanol and ethanol	Soluble
Hazards
Flash point	349.9 °C; 661.8 °F; 623.0 K
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Erucic acid is a monounsaturated omega-9 fatty acid, denoted 22:1ω9. It has the formula CH₃(CH₂)₇CH=CH(CH₂)₁₁COOH. It is prevalent in wallflower seed with a reported content of 20 to 54% in high erucic acid rapeseed oil,^[1] and 42% in mustard oil. Erucic acid is also known as cis-13-docosenoic acid and the trans isomer is known as brassidic acid.

Uses

Erucic acid has many of the same uses as mineral oils, but it is more readily biodegradable than some. It has limited ability to polymerize and dry for use in oil paints. Like other fatty acids, it can be converted into surfactants or lubricants, and can be used as a precursor to bio-diesel fuel.

Derivatives of erucic acid have many further uses, such as behenyl alcohol (CH₃(CH₂)₂₁OH), a pour point depressant (enabling liquids to flow at a lower temperature), and silver behenate, for use in photography.^[2] It is also used as an ingredient in appetite suppressants.

Sources of erucic acid

The seed oil of the rape plant is rich in erucic acid.

The name erucic means: of or pertaining to eruca; which is a genus of flowering plants in the family Brassicaceae. It is also the Latin for colewort, which today is better known as kale.

Erucic acid is produced naturally (together with other fatty acids) across a great range of green plants, but especially so in members of the brassica family. For industrial purposes, a Low-Erucic Acid Rapeseed (LEAR) has been developed, which contains fats derived from oleic acid instead of erucic acid.^[3]

Biochemistry

Erucic acid is produced by elongation of oleic acid via oleoyl-coenzyme A and malonyl-CoA.^[4] Erucic acid is broken down into shorter-chain fatty acids in the human liver by the long-chain Acyl CoA dehydrogenase enzyme.

Health effects

The effects of erucic acid from edible oils on human health are controversial. However no negative health effects have ever been documented in humans.^[5]

Mustard oil was once considered unsuitable for human consumption in the United States, Canada, and the European Union due to the high content of erucic acid. This is because of early studies in rats. Subsequent studies on rats have shown that they are less able to digest vegetable fats (whether they contain erucic acid or not) than humans and pigs.^[6][7][8] Chariton et al. suggests that in rats: “Inefficient activation of erucic acid to erucyl-CoA and a low level of activity of triglyceride lipase and enzymes of betaoxidation for erucic acid probably contribute to the accumulation and retention of cardiac lipid.”^[9] Before this process was fully understood it led to the belief that erucic acid and mustard oil were both highly toxic to humans. The high percentage of erucic acid in mustard oil has led to the latter being banned for food use in the European Union and other countries.

Epidemiological studies suggest that, in regions where mustard oil is still used in a traditional manner, mustard oil may afford some protection against cardiovascular diseases. In this sense “traditional” means that (a) the oil is used fresh; and (b) vegetable fats count only as a small percentage of the total caloric intake. Whether this effect is due to the nature of erucic acid per se to make the blood platelets less sticky, or to the presence of a reasonably high percentage of α-linolenic acid, or to a combination of properties of fresh unrefined oil, is as yet uncertain. Care needs to be taken with such epidemiological studies to exclude the possibility of early deaths from other causes skewing the results. The fact that early asymptomatic coronary disease is readily detectable post mortem and is absent in the mustard oil cohorts tends to add weight to the hypothesis that mustard oil is protective.^[10]

A four-to-one mixture of erucic acid and oleic acid constitutes Lorenzo's oil; an experimental treatment for the rare neurobiology disorder adrenoleukodystrophy. Thrombocytopenia has been seen in patients treated with Lorenzo’s oil, probably related to its erucic acid content.^[11]

However, for the reasons given above, it is not advisable for nursing mothers or babies to eat food containing erucic acid.^[5][12]

Health concerns

Before genetic engineering, plant breeders were aiming to produce a less-bitter-tasting multi-purpose oil from rapeseed that would appeal to a larger market by making it more palatable for cattle and other livestock. While it was possible to breed out much of the pungent-tasting glucosinolates, one of the dominant erucic acid genes would get stripped out of the genome as well, greatly reducing its valuable erucic acid content.^{[citation needed]} Studies on rats show lipidosis problems when fed high quantities of erucic acid, however, so this did not hinder saleability.^[9] Later trials showed that rats had the same problems with other vegetable fatty acids,^[13] because rats are poor at metabolising some fats.^[14] The plant breeding industry later changed "low erucic acid" to be its unique selling proposition over that of its competitors.^{[citation needed]}

There are not many studies done on humans with erucic acid; the majority are carried out by the food science industry on animals. Animal studies failed to show negative events occurring from feeding of erucic acid, and the studies were repeated under increasingly unnatural scenarios. In one case, neonate piglets that have a limited ability to absorb these fats had their normal sow's milk replaced solely with rapeseed oil for one hundred percent of their calorific needs.^[14] The studies showed that lipidoses suffered by the piglets proved to be only a transient effect; the liver automatically responded by increasing enzyme levels to cope with the unusual diet, and the lipidoses subsided.

A 2006 study reported higher rates of lung cancer in countries with populations that cook over solid fuel wood and biomass fires and stoves. The possibility of production of smoke from heated oil was also considered, and it was established that rapeseed oil, which contains erucic acid, can cause increased lung carcinomas through emissions under high heat. However, the report also showed a variety of other cooking oils also did this at similar heats.^[15]

Cardiac concerns

The levels of erucic acid in human foods are restricted, in part, over concerns that it may adversely affect heart tissue.^[5] Erucic acid is preferentially absorbed in myocardium tissue^[16] but is not metabolized there.^[14]

In 2003 Food Standards Australia set a Provisional Tolerable Daily Intake (PTDI) of about 500 mg/day of erucic acid, based on "the level that is associated with increased myocardial lipidosis in nursling pigs."^[5] "There is a 120-fold safety margin between this level and the level that is associated with increased myocardial lipidosis in nursling pigs. The dietary exposure assessment has concluded that the majority of exposure to erucic acid by the general population would come from the consumption of canola oil. The dietary intake of erucic acid by an individual consuming at the average level is well below the PTDI, therefore, there is no cause for concern in terms of public health and safety. However, the individual consuming at a high level has the potential to approach the PTDI. This would be particularly so if the level of erucic acid in canola oil was to exceed 2% of the total fatty acids."^[5]

Low erucic acid rapeseed

Food grade rapeseed oil (also known as canola oil, rapeseed 00 oil, low erucic acid rapeseed oil, LEAR oil, and rapeseed canola-equivalent oil) is regulated to a maximum of 2% erucic acid by weight in the USA.^[17] and 5% in the EU,^[18] with special regulations for infant food.

References