Hydroxytyrosol is an organic compound with the formula (HO)2C6H3CH2CH2OH. It is a phenylethanoid, i.e. a relative of phenethyl alcohol. Its derivatives are found in a variety of natural sources, notably olive oils and wines. Hydroxytyrosol is a colorless solid,[3][4] although samples often turn beige during storage. It is a derivative, formally speaking, of catechol.
It or its derivatives occurs in olives and in wines[5][6]
Occurrence
Olives
Oleuropein, bitter compound, an ester of hydroxytyrosol found in green olive skin
The olives, leaves, and olive pulp contain large amounts of hydroxytyrosol derivative Oleuropein, more so than olive oil.[1] 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.[7] The ripening of an olive substantially increases the amount of hydroxytyrosol.[8] Processed olives, such as the common canned variety containing iron(II) gluconate, contained little hydroxytyrosol, as iron salts are catalysts for its oxidation.[9]
In the United States, hydroxytyrosol is considered to be a safe ingredient (GRAS) in processed foods at levels of 5 mg per serving.[11]
Function and production
In nature, hydroxytyrosol is generated by the hydrolysis of oleuropein that occurs during olive ripening. Oleuropein accumulates in olive leaves and fruit as a defense mechanism against pathogens and herbivores. During olive ripening or when the olive tissue is damaged by pathogens, herbivores, or mechanical damage, the enzyme β-glucosidase catalyzes hydroxytyrosol synthesis via hydrolysis from oleuropein.[12]
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 of 2.43 hours.[13]
Mediterranean diet
Mediterranean diets, characterized by regular intake of olive oil, have been shown to positively affect human health, including reduced rates of cardiovascular diseases.[5][14][15] Research on consumption of olive oil and its components includes hydroxytyrosol and oleuropein, which may inhibit oxidation of LDL cholesterol – a risk factor for atherosclerosis, heart attack or stroke.[16] The daily intake of hydroxytyrosol within the Mediterranean diet is estimated to be between 0.15 and 30 mg.[17]
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.[18]
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,[18] providing a health claim 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.[19]
See also
Echinacoside, a hydroxytyrosol-containing glycoside
^ abBaldioli M, Servili M, Perretti G, Montedoro GF (1996). "Antioxidant activity of tocopherols and phenolic compounds of virgin olive oil". Journal of the American Oil Chemists' Society. 73 (11): 1589–1593. doi:10.1007/BF02523530. S2CID84749200.
^de Pablos RM, Espinosa-Oliva AM, Hornedo-Ortega R, Cano M, Arguelles S (May 2019). "Hydroxytyrosol protects from aging process via AMPK and autophagy; a review of its effects on cancer, metabolic syndrome, osteoporosis, immune-mediated and neurodegenerative diseases". Pharmacological Research. 143: 58–72. doi:10.1016/j.phrs.2019.03.005. PMID30853597. S2CID73726654.
^ ab"Scientific Opinion on the substantiation of health claims related to polyphenols in olive and protection of LDL particles". European Food Safety Authority. 8 April 2011. Retrieved 2021-04-13. From oxidative damage (ID 1333, 1638, 1639, 1696, 2865), maintenance of normal blood HDL cholesterol concentrations (ID 1639), maintenance of normal blood pressure (ID 3781), "anti-inflammatory properties" (ID 1882), "contributes to the upper respiratory tract health" (ID 3468), "can help to maintain a normal function of gastrointestinal tract" (3779), and "contributes to body defences against external agents" (ID 3467) pursuant to Article 13(1) of Regulation (EC) No 1924/2006
