Oleuropein is a glycosylated seco-iridoid, a type of phenolic bitter compound found in green olive skin, flesh, seeds, and leaves.[1] The term oleuropein is derived from the botanical name of the olive tree, Olea europaea.
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| Names | |
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| IUPAC name
Methyl (2S,3E,4S)-4-{2-[2-(3,4-Dihydroxyphenyl)ethoxy]-2-oxoethyl}-3-ethylidene-2-(β-D-glucopyranosyloxy)-2H-pyran-5-carboxylate
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| Systematic IUPAC name
Methyl (2S,3E,4S)-4-{2-[2-(3,4-Dihydroxyphenyl)ethoxy]-2-oxoethyl}-3-ethylidene-2-{[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy}-2H-pyran-5-carboxylate | |
| Other names
2-(3,4-Dihydroxyphenyl)ethyl [(2S,3E,4S)-3-ethylidene-2-(β-D-glucopyranosyloxy)-5-(methoxycarbonyl)-3,4-dihydro-2H-pyran-4-yl]acetate
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| Identifiers | |
3D model (JSmol)
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| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.046.466 |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C25H32O13 | |
| Molar mass | 540.518 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Because of its bitter taste, oleuropein must be completely removed or decomposed to make olives edible. During processing of bitter and inedible green olives for consumption as table olives, oleuropein is removed from olives via a number of methods, including by immersion in lye.[2][3]
Chemical treatment
editOleuropein is a derivative of elenolic acid linked to the orthodiphenol hydroxytyrosol by an ester bond and to a molecule of glucose by a glycosidic bond.[4] When olives are immersed in a lye solution, the alkaline conditions lead to hydrolysis of the ester bond. The basic conditions also significantly increases the solubility of these derivatives, facilitating their release into the lye solution.[5][6]
The high pH accelerates the oxidation of the phenolics, leading to blackness, as during their normal ripening, if the solution is oxygenated by air injection (alkaline oxidation of olives is also called the California process).[7][8]
The lye solution is replaced several times until the bitter taste has dissipated. An alternative process uses amberlite macroporous resins to trap the oleuropein directly from the solution, reducing waste water while capturing the extracted molecules.[9][10]
Enzymatic hydrolysis during the maturation of olives is also an important process for the decomposition of oleuropein and elimination of its bitter taste.[6][11]
Green olive blackening
editGreen olives may be treated industrially with ferrous gluconate (0.4 wt. %)[7] to change their color to black.[12] Gluconate, an edible oxidation product of glucose, is used as non-toxic reactant to maintain Fe2+ in solution. When in contact with polyphenols, the ferrous ions form a black complex, giving the final color of the treated olives.[9][10][7] Black olives treated with iron(II) gluconate are also depleted in hydroxytyrosol, as iron salts are catalysts for its oxidation.[13]
Research
editOleuropein has been proposed as a proteasome activator.[14][15]
See also
edit- Elenolic acid (a marker for maturation of olives)
- Hydroxytyrosol
- Ligstroside, a closely related compound also found in olives
- Oleocanthal
- Olive leaf
- Olive: Traditional fermentation and curing
References
edit- ^ Rupp R. (1 July 2016). "The bitter truth about olives". National Geographic. Archived from the original on 10 July 2019. Retrieved 24 June 2019.
- ^ "How olives are made". California Olive Committee. 2017. Archived from the original on 5 August 2017. Retrieved 5 August 2017.
- ^ Colmagro S.; Collins G.; Sedgley M. "Processing technology of the table olive" (PDF). Archived (PDF) from the original on 9 August 2017. Retrieved 25 June 2019.
- ^ Panizzi, L.; Scarpati, M.L.; Oriente, E.G. (1960). "Structure of the bitter glucoside oleuropein. Note II". Gazzetta Chimica Italiana. 90: 1449–1485.
- ^ Yuan, Jiao-Jiao; Wang, Cheng-Zhang; Ye, Jian-Zhong; Tao, Ran; Zhang, Yu-Si (2015). "Enzymatic hydrolysis of oleuropein from Olea Europea (olive) leaf extract and antioxidant activities". Molecules. 20 (2): 2903–2921. doi:10.3390/molecules20022903. ISSN 1420-3049. PMC 6272143. PMID 25679050.
- ^ a b Ramírez, Eva; Brenes, Manuel; García, Pedro; Medina, Eduardo; Romero, Concepción (2016). "Oleuropein hydrolysis in natural green olives: Importance of the endogenous enzymes" (PDF). Food Chemistry. 206: 204–209. doi:10.1016/j.foodchem.2016.03.061. hdl:10261/151764. ISSN 0308-8146. PMID 27041317. Archived (PDF) from the original on 2018-07-23. Retrieved 2019-09-27.
- ^ a b c El-Makhzangy, Attya; Ramadan-Hassanien, Mohamed Fawzy; Sulieman, Abdel-Rahman Mohamed (2008). "Darkening of brined olives by rapid alkaline oxidation". Journal of Food Processing and Preservation. 32 (4): 586–599. doi:10.1111/j.1745-4549.2008.00198.x. ISSN 0145-8892.
- ^ Ziena, H.M.S.; Youssef, M.M.; Aman, M.E. (1997). "Quality attributes of black olives as affected by different darkening methods". Food Chemistry. 60 (4): 501–508. doi:10.1016/S0308-8146(96)00354-8. ISSN 0308-8146.
- ^ a b "A 'greener' way to take the bitterness out of olives". phys.org. Archived from the original on 23 June 2019. Retrieved 23 June 2019.
- ^ a b Johnson, Rebecca; Mitchell, Alyson E. (2019). "Use of Amberlite macroporous resins to reduce bitterness in whole olives for improved processing sustainability". Journal of Agricultural and Food Chemistry. 67 (5): 1546–1553. doi:10.1021/acs.jafc.8b06014. ISSN 0021-8561. PMID 30636418. S2CID 58570570. Archived from the original on 2020-06-26. Retrieved 2021-05-18.
- ^ Restuccia, Cristina; Muccilli, Serena; Palmeri, Rosa; Randazzo, Cinzia L.; Caggia, Cinzia; Spagna, Giovanni (2011). "An alkaline β-glucosidase isolated from an olive brine strain of Wickerhamomyces anomalus". FEMS Yeast Research. 11 (6): 487–493. doi:10.1111/j.1567-1364.2011.00738.x. ISSN 1567-1356. PMID 21575132.
- ^ Kumral, A.; Basoglu, F. (2008). "Darkening methods used in olive processing". Acta Horticulturae (791): 665–668. doi:10.17660/ActaHortic.2008.791.101. ISSN 0567-7572.
- ^ Vincenzo Marsilio; Cristina Campestre; Barbara Lanza (July 2001). "Phenolic compounds change during California-style ripe olive processing". Food Chemistry. 74 (1): 55–60. doi:10.1016/S0308-8146(00)00338-1.
- ^ Katsiki, Magda; Chondrogianni, Niki; Chinou, Ioanna; Rivett, A. Jennifer; Gonos, Efstathios S. (June 2007). "The olive constituent oleuropein exhibits proteasome stimulatory properties in vitro and confers life span extension of human embryonic fibroblasts". Rejuvenation Research. 10 (2): 157–172. doi:10.1089/rej.2006.0513. ISSN 1549-1684. PMID 17518699. Archived from the original on 2020-11-15. Retrieved 2020-10-15.
- ^ Zou, Ke; Rouskin, Silvia; Dervishi, Kevin; McCormick, Mark A.; Sasikumar, Arjun; Deng, Changhui; Chen, Zhibing; Kaeberlein, Matt; Brem, Rachel B.; Polymenis, Michael; Kennedy, Brian K. (2020-08-01). "Life span extension by glucose restriction is abrogated by methionine supplementation: Cross-talk between glucose and methionine and implication of methionine as a key regulator of life span". Science Advances. 6 (32): eaba1306. Bibcode:2020SciA....6.1306Z. doi:10.1126/sciadv.aba1306. ISSN 2375-2548. PMC 7406366. PMID 32821821.