Chemistry:Oleuropein

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Oleuropein
Oleuropein structure.svg
Names
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
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
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
UNII
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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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.

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

Oleuropein 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

Green 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

Oleuropein has been proposed as a proteasome activator.[14][15]

See also

References

  1. ↑ Rupp R. (1 July 2016). "The bitter truth about olives". National Geographic. https://www.nationalgeographic.com/people-and-culture/food/the-plate/2016/07/olives--the-bitter-truth/. 
  2. ↑ "How olives are made". California Olive Committee. 2017. http://calolive.org/our-story/how-olives-are-made/. 
  3. ↑ "Processing technology of the table olive". https://ucanr.edu/datastoreFiles/608-760.pdf. 
  4. ↑ Panizzi, L.; Scarpati, M.L.; Oriente, E.G. (1960). "Structure of the bitter glucoside oleuropein. Note II". Gazzetta Chimica Italiana 90: 1449–1485. 
  5. ↑ 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. PMID 25679050. 
  6. ↑ 6.0 6.1 Ramírez, Eva; Brenes, Manuel; García, Pedro; Medina, Eduardo; Romero, Concepción (2016). "Oleuropein hydrolysis in natural green olives: Importance of the endogenous enzymes". Food Chemistry 206: 204–209. doi:10.1016/j.foodchem.2016.03.061. ISSN 0308-8146. PMID 27041317. https://digital.csic.es/bitstream/10261/151764/1/Postprint_2016_FoodChem_V206_P204.pdf. Retrieved 2019-09-27. 
  7. ↑ 7.0 7.1 7.2 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. 
  8. ↑ 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. 
  9. ↑ 9.0 9.1 "A 'greener' way to take the bitterness out of olives". phys.org. https://phys.org/news/2019-01-greener-bitterness-olives.html. 
  10. ↑ 10.0 10.1 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. http://www.escholarship.org/uc/item/2sg8n70x. Retrieved 2021-05-18. 
  11. ↑ 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. 
  12. ↑ 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. 
  13. ↑ 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. 
  14. ↑ 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. https://pubmed.ncbi.nlm.nih.gov/17518699/. Retrieved 2020-10-15. 
  15. ↑ Zou, Ke; Rouskin, Silvia; Dervishi, Kevin; McCormick, Mark A.; Sasikumar, Arjun; Deng, Changhui; Chen, Zhibing; Kaeberlein, Matt et al. (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" (in en). Science Advances 6 (32): eaba1306. doi:10.1126/sciadv.aba1306. ISSN 2375-2548. PMID 32821821. Bibcode: 2020SciA....6.1306Z. 



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