Hydroxytyrosol is an organic compound with the formula . Classified as a

phenylethanoid Phenylethanoids are a type of phenolic compounds characterized by a phenethyl alcohol structure. Tyrosol and hydroxytyrosol are examples of such compounds. Glycosides The red deadnettle (''Lamium purpureum'') contains phenylethanoid glycosides ...

, i.e. a relative of

phenethyl alcohol Phenethyl alcohol, or 2-phenylethanol, is the organic compound that consists of a phenethyl group (C6H5CH2CH2) attached to OH. It is a colourless liquid that is slightly soluble in water (2 ml/100 ml H2O), but miscible with most organic solvents. ...

, Its derivatives are found in a variety of natural sources, notably olive oils and wines. The compound is colorless solid. although commercial samples are often beige. It is a derivative, formally speaking, of

catechol Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ...

. It or its derivatives occurs in olives and in wines

Occurrence

Olives

left, Oleuropein,_a_bitter_component_found_in_green_olive_skin,_is_an_ester_of_hydroxytyrosol..html" ;"title="olive.html" ;"title="Oleuropein, a bitter component found in green olive">Oleuropein, a bitter component found in green olive skin, is an ester of hydroxytyrosol.">olive.html" ;"title="Oleuropein, a bitter component found in green olive">Oleuropein, a bitter component found in green olive skin, is an ester of hydroxytyrosol. The olives, leaves, and olive pulp contain large amounts of hydroxytyrosol derivative Oleuropein, more so than olive oil). Unprocessed, green (unripe) olives, contain between 4.3 and 116 mg of hydroxytyrosol per 100g of olives, while unprocessed, black (ripe) olives contain up to 413.3 mg per 100g. The ripening of an olive substantially increases the amount of hydroxytyrosol. Processed olives, such as the common canned variety containing iron(II) gluconate, contained little hydroxytyrosol, as iron salts are catalysts for its oxidation.

Food safety

Hydroxytyrosol is considered safe as a

novel food A novel food is a type of food that does not have a significant history of consumption or is produced by a method that has not previously been used for food. Designer food Designer food is a type of novel food that has not existed on any regional ...

for human consumption, with a

no-observed-adverse-effect level The no-observed-adverse-effect level (NOAEL) denotes the level of exposure of an organism, found by experiment or observation, at which there is no biologically or statistically significant increase in the frequency or severity of any adverse effe ...

of 50 mg/kg body weight per day, as evaluated by the

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002, ...

(EFSA). In the United States, hydroxytyrosol is considered to be a safe ingredient ( GRAS) in processed foods at levels of 5 mg per serving.

Function and production

In nature, hydroxytyrosol is generated by the

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

oleuropein Oleuropein is a glycosylated seco-iridoid, a type of phenolic bitter compound found in green olive skin, flesh, seeds, and leaves. The term oleuropein is derived from the botanical name of the olive tree, ''Olea europaea''. Because of its bitter ...

that occurs during olive ripening. Oleuropein accumulates in olive leaves and fruit as a defense mechanism against

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

s and

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

s. During olive ripening or when the olive tissue is damaged by pathogens, herbivores, or mechanical damage, the enzyme

β-glucosidase β-Glucosidase (EC 3.2.1.21; systematic name β-D-glucoside glucohydrolase) is an enzyme that catalyses the following reaction: : Hydrolysis of terminal, non-reducing β-D-glucosyl residues with release of β-D-glucose Structure β-Glucosidase ...

catalyzes hydroxytyrosol synthesis via hydrolysis from oleuropein.

Metabolism

Shortly after olive oil consumption, 98% of hydroxytyrosol in plasma and urine appears in conjugated forms (65% glucuronoconjugates), suggesting extensive first-past metabolism and a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 2.43 hours.

Mediterranean diet

Mediterranean diet The Mediterranean diet is a diet inspired by the eating habits of people who live near the Mediterranean Sea. When initially formulated in the 1960s, it drew on the cuisines of Greece, Italy, France and Spain. In decades since, it has also incor ...

s, characterized by regular intake of olive oil, have been shown to positively affect human health, including reduced rates of

cardiovascular diseases Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, ...

. Research on consumption of olive oil and its components includes hydroxytyrosol and oleuropein, which may inhibit oxidation of LDL cholesterol a

risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...

for atherosclerosis, heart attack or stroke. The daily intake of hydroxytyrosol within the Mediterranean diet is estimated to be between 0.15 and 30 mg/day.

Regulation

Europe

The EFSA has issued a scientific opinion on health claims in relation to dietary consumption of hydroxytyrosol and related polyphenol compounds from olive fruit and oil, and protection of blood lipids from potential oxidative damage. EFSA concluded that a cause-and-effect relationship existed between the consumption of hydroxytyrosol and related compounds from olives and olive oil and protection of blood lipids from oxidative damage, providing a

health claim A health claim on a food label and in food marketing is a claim by a manufacturer of food products that their food will reduce the risk of developing a disease or condition. For example, it is claimed by the manufacturers of oat cereals that oat ...

for consumption of olive oil polyphenols containing at least 5 mg of hydroxytyrosol and its derivatives (oleuropein complex and tyrosol) per 20 g of olive oil.

References

{{Estrogen receptor modulators GPER agonists Phenylethanoids Phenol antioxidants Monoamine oxidase inhibitors Phytoestrogens