Alkylresorcinol

Bilobol (5-[(Z)-pentadec-8-enylo]resorcinol)

Alkylresorcinols, also known as resorcinolic lipids, are phenolic lipids composed of long aliphatic chains and resorcinol-type phenolic rings.

Natural sources of alkylresorcinols

Alkylresorcinols are relatively rare in nature, with the main known sources being wheat, rye, barley, triticale (cereal grasses), the fruit of Gingko biloba Bilobol, a mollusc and some species of bacteria.

DB-2073 (2-n-hexyl-5-n-propylresorcinol)

DB-2073 is an antibiotic isolated from the broth culture of Pseudomonas sp. They are also the main constituents of the outer shell of the cyst of Azotobacter.

Occurrence in cereals

Alkylresorcinols are present in high amounts in the bran layer (e.g. pericarp, testa and aleurone layers) of wheat and rye (0.1-0.3 % of dry weight). 5-Alkylresorcinols can also be found in rice, though not in the edible parts of the rice plant.

They are only present in very low amounts in the endosperm (the part of cereal grain that is used to make white flour), which 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.

Alkylresorcinols 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.

Biomarkers of a whole grain diet

Increasing evidence from human intervention trials suggests that they are the most promising biomarker of whole grain wheat and rye intake. Alkylresorcinol metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3,5-dihydroxyphenylpropionoic acid (DHPPA) were first identified in urine and can be quantified in urine and plasma, and may be an alternative, equivalent biomarker of whole grain wheat intake.

The average intake of alkylresorcinols in the UK is around 11 mg/person/day, and in Sweden is around 20 mg/person/day. 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).

Possible biological activities

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. Alkylresorcinols also increase gamma-tocopherol levels in rats when fed in high amounts (0.2% of total diet and above.

The alkylresorcinols in Grevillea banksii and Grevillea 'Robyn Gordon' are responsible for contact dermatitis.

Trivial names of some resorcinolic lipids

• olivetol
• persoonol
• grevillol
• ardisinol I
• ardisinol II
• adipostatin A
• adipostatin B
• bilobol
• hexylresorcinol
• hydrobilobol
• cardol
• rucinol
• irisresorcinol
• panosialin
• stemphol
• R-leprosol
• α-leprosol
• merulinic acid
• xenognosin

Derivatives

Sorgoleone is a hydrophobic root exudate of Sorghum bicolor.