![Bilobol (5-[(Z)-pentadec-8-enylo]resorcinol) Bilobol.svg](http://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Bilobol.svg/350px-Bilobol.svg.png)
Alkylresorcinols (ARs), also known as resorcinolic lipids, are amphiphilic phenolic lipids characterised by a non-polar odd-numbered alkyl side chain with up to 27 carbon atoms attached to a polar resorcinol (1,3-dihydroxybenzene) ring. [1] [2] [3]
Alkylresorcinols (ARs), also known as resorcinolic lipids, are amphiphilic phenolic lipids characterised by a non-polar odd-numbered alkyl side chain with up to 27 carbon atoms attached to a polar resorcinol (1,3-dihydroxybenzene) ring. [1] [2] [3]
Alkylresorcinols are relatively rare in nature and are reported to be found in fungi, bacteria, and some lower and higher plants. DB-2073 is an antibiotic isolated from the broth culture of Pseudomonas sp. [4] They are also the main constituents of the outer shell of the cyst of Azotobacter . [5]
Among the plant sources, the shell oil of cashew nut (Anacardium occidentale L.) has the highest amount of ARs, which consists of 20% phenolic lipids. [2] Moreover, ARs were found in the peels and pulp of peas (Pisum sativum L.), [6] pulp and leaves of ginkgo (Ginkgo biloba L.), [7] pulp and peels of mango (Mangifera indica L.), [8] and in some cereals. In the case of cereals, the hyaline layer, inner pericarp, and testa showed the highest amounts of AR. [3] [9]
The alkylresorcinols alkyl chain, present in cereals, ranges from 15 to 25 carbon atoms. [3] [10] ARs have been reported to be present in high amounts in rye, wheat, and triticale, and in low concentrations in barley, maize, oat, and millet, [11] [12] while no information is at present available for Khorasan wheat. They are most abundant in the bran fractions (2600-4100 μg/g; 0.1-0.3% of dry weight), [13] whereas they are in trace amounts in strachy endosperm and germ. [9] They can also be found in rice, though not in the edible parts of the rice plant. [14]
Their presence in the endosperm (the part of cereal grain that is used to make white flour), means that alkylresorcinols can be used as 'biomarkers' for people who eat foods containing wholegrain wheat and rye, rather than cereal products based on white flour. [15] Moreover, they were thought to have anti-nutritive properties (e.g. decreasing growth of pigs and chickens fed rye), but this theory has been discredited, and a number of animal studies have demonstrated that they have no obvious negative effect on animals or humans. [15]
Increasing evidence from human intervention trials suggests that they are the most promising biomarker of whole grain wheat and rye intake. [16] [17] Alkylresorcinol metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3,5-dihydroxyphenylpropionoic acid (DHPPA) were first identified in urine [18] and can be quantified in urine [19] and plasma, [20] and may be an alternative, equivalent biomarker of whole grain wheat intake. [21]
The average intake of alkylresorcinols in the UK is around 11 mg/person/day, and in Sweden is around 20 mg/person/day. [22] This varies widely depending on whether people normally consume wholegrain/wholemeal/brown bread, which is high in alkylresorcinols (300-1000 μg/g), or white wheat bread, which has very low concentrations of alkylresorcinols (<50 μg/g).
Recently, alkylresorcinols have been widely recognised as a biomarker for the presence of cereals in archaeological pottery. They were previously found in a well-preserved Bronze Age wooden container from Switzerland, [23] and coarse ware vessels from a Roman cavalry barrack at Vindolanda. [24] A study [24] demonstrated that the survival of ARs is highly dependent on the cooking procedures and burial conditions. However, if recoverable, analysis of these phenolic lipids in archaeological contexts is valuable as it can help explain the uptake and spread of cereal processing of past communities in particular regions. [23] [25]
In vitro studies have shown that alkylresorcinols may prevent cells turning cancerous, but that they do not have any effect on cells that are already cancerous. [15] Alkylresorcinols also increase gamma-tocopherol levels in rats when fed in high amounts (0.2% of total diet and above). [18]
The alkylresorcinols in Grevillea banksii and Grevillea 'Robyn Gordon' are responsible for contact dermatitis. [26]
Sorgoleone is a hydrophobic root exudate of Sorghum bicolor . [27]
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants are frequently added to industrial products, such as polymers, fuels, and lubricants, to extend their usable lifetimes. Foods are also treated with antioxidants to forestall spoilage, in particular the rancidification of oils and fats. In cells, antioxidants such as glutathione, mycothiol or bacillithiol, and enzyme systems like superoxide dismutase, can prevent damage from oxidative stress.
Rye is a grass grown extensively as a grain, a cover crop and a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to both wheat and barley. Rye grain is used for flour, bread, beer, crispbread, some whiskeys, some vodkas, and animal fodder. It can also be eaten whole, either as boiled rye berries or by being rolled, similar to rolled oats.
Flavan-3-ols are a subgroup of flavonoids. They are derivatives of flavans that possess a 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. Flavan-3-ols are structurally diverse and include a range of compounds, such as catechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, proanthocyanidins, theaflavins, thearubigins. They play a part in plant defense and are present in the majority of plants.
Polyphenols are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments.
Bran, also known as miller's bran, is the hard layers of cereal grain surrounding the endosperm. It consists of the combined aleurone and pericarp. Corn (maize) bran also includes the pedicel. Along with the germ, it is an integral part of whole grains, and is often produced as a byproduct of milling in the production of refined grains.
Secoisolariciresinol diglucoside (SDG) is an antioxidant phytoestrogen present in flax, sunflower, sesame, and pumpkin seeds. In food, it can be found in commercial breads containing flaxseed. It is a precursor of mammal lignans which are produced in the colon from chemicals in foods.
The lignans are a large group of low molecular weight polyphenols found in plants, particularly seeds, whole grains, and vegetables. The name derives from the Latin word for "wood". Lignans are precursors to phytoestrogens. They may play a role as antifeedants in the defense of seeds and plants against herbivores.
A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm.
Ferulic acid is a hydroxycinnamic acid; it is an organic compound with the formula (CH3O)HOC6H3CH=CHCO2H. The name is derived from the genus Ferula, referring to the giant fennel (Ferula communis). Classified as a phenolic phytochemical or polyphenol, ferulic acid is an amber colored solid. Esters of ferulic acid are found in plant cell walls, covalently bonded to hemicellulose such as arabinoxylans. Salts and esters derived from ferulic acid are called ferulates.
The vitamin E family comprises four tocotrienols and four tocopherols. The critical chemical structural difference between tocotrienols and tocopherols is that tocotrienols have unsaturated isoprenoid side chains with three carbon-carbon double bonds versus saturated side chains for tocopherols.
p-Coumaric acid is an organic compound with the formula HOC6H4CH=CHCO2H. It is one of the three isomers of hydroxycinnamic acid. It is a white solid that is only slightly soluble in water but very soluble in ethanol and diethyl ether.
Diferulic acids (also known as dehydrodiferulic acids) are organic compounds that have the general chemical formula C20H18O8, they are formed by dimerisation of ferulic acid. Curcumin and curcuminoids, though having a structure resembling diferulic acids', are not formed that way but through a condensation process. Just as ferulic acid is not the proper IUPAC name, the diferulic acids also tend to have trivial names that are more commonly used than the correct IUPAC name. Diferulic acids are found in plant cell walls, particularly those of grasses.
Arabinoxylan is a form of the hemicellulose xylan found in both the primary and secondary cell walls of plants which in addition to xylose contains substantial amounts of another pentose sugar, arabinose. The term arabinoxylan usually refers to feruloyl-arabinoxylan from grasses and other commelinids containing moieties of the phenolic ferulic acid that can undergo oxidative coupling forming crosslinks between arabinoxylan chains and with lignin. Whilst arabinose has been found linked to xylan in non-commelinid plants, ferulic acid has not been reported on these and unlike feruloyl-arabinoxylan these arabinoxylans are not monophyletic. The remainder of this article refers to feruloyl-arabinoxylan from cell walls of grasses and other commelinid species.
Syringic acid is a naturally occurring phenolic compound and dimethoxybenzene that is commonly found as a plant metabolite.
In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants.
3,5-Dihydroxybenzoic acid is a dihydroxybenzoic acid. It is a colorless solid.
3,5-Dihydroxyphenylpropionoic acid is a metabolite of alkylresorcinols, first identified in human urine and can be quantified in urine and plasma, and may be an alternative, equivalent biomarker of whole grain wheat intake.
Phenolic lipids are a class of natural products composed of long aliphatic chains and phenolic rings. Phenolic lipids occur in plants, fungi and bacteria.
Urolithin A is a metabolite compound resulting from the transformation of ellagitannins by the gut bacteria. It belongs to the class of organic compounds known as benzo-coumarins or dibenzo-α-pyrones. Its precursors – ellagic acids and ellagitannins – are ubiquitous in nature, including edible plants, such as pomegranates, strawberries, raspberries, walnuts, and others.
In archaeology, organic residue analysis (ORA) is the investigation of micro-remains either trapped in or adhered to artefacts from the past. These organic residues can be composed of lipids, proteins, starches and sugars.
