How Oleuropein Influences Extra Virgin Olive Oil Taste and Health Benefits

Oleuropein, one of the major phe­no­lic com­pounds found in extra vir­gin olive oil, is key to many olive oil health ben­e­fits and even its fla­vor. 

The olive tree pro­duces the com­pound as a defen­sive mech­a­nism, its bit­ter­ness act­ing as a nat­ural deter­rent to pests. That same bit­ter­ness trans­lates to a marker of qual­ity in oil.

Oleuropein, iden­ti­fied as the first sec­oiri­doid in olive oil by Panizzi et al. in 1958, is a sig­nif­i­cant com­po­nent of olive polyphe­nols. Its pres­ence in olives and oil varies depend­ing on the olive vari­ety, milling tech­niques and tech­nol­ogy and stor­age con­di­tions. 

Oleuropein serves as a qual­ity marker through­out pro­duc­tion. The bit­ter, pun­gent taste of extra vir­gin olive oil pri­mar­ily arises from its main phe­no­lic com­pounds, includ­ing oleo­can­thal, hydrox­y­ty­rosol and oleu­ropein. 

Extensive research has explored the ben­e­fi­cial effects of oleu­ropein on ail­ments includ­ing can­cer, hyper­ten­sion, heart issues and var­i­ous viral and bac­te­r­ial dis­eases.

How oleu­ropein impacts sen­sory attrib­utes

Research con­ducted by Andrewes and col­leagues in 2003 iso­lated and eval­u­ated indi­vid­ual phe­no­lic com­pounds present in olive oil. 

They found that the com­pound p‑HPEA-EDA, a sec­oiri­doid deriv­a­tive of oleu­ropein, elicited a strong burn­ing pun­gent sen­sa­tion at the back of the throat, con­tribut­ing sig­nif­i­cantly to the oil’s pun­gent attribute. In con­trast, another com­pound, 3,4‑DHPEA-EDA, pro­duced only a slight burn­ing or numb­ing sen­sa­tion, pre­dom­i­nantly per­ceived on the tongue.

Further analy­sis using the cal­cium mobi­liza­tion func­tional assay revealed that sev­eral phe­no­lic com­pounds acti­vate bit­ter taste recep­tors TAS2R1, TAS2R8 and TAS2R14. 

Ligstroside agly­con and oleu­ropein agly­con were iden­ti­fied as the most potent bit­ter tas­tants in olive oil. TAS2R8 and TAS2R1 were found to be the pri­mary bit­ter taste recep­tors respond­ing to phe­no­lic com­pounds, with oleu­ropein acti­vat­ing TAS2R8 exclu­sively, albeit with lower potency com­pared to the algy­cons.

While oleu­ropein has low potency towards the recep­tor TAS2R8, research sug­gests that the intensely bit­ter sen­sa­tion expe­ri­enced when chew­ing raw olives is pri­mar­ily due to the spon­ta­neous con­ver­sion of oleu­ropein into agly­con forms. 

Oleuropein and oleu­ropein glu­cosi­dase are typ­i­cally found in sep­a­rate cel­lu­lar com­part­ments and only come into con­tact when olive fruit cells are dam­aged, such as dur­ing chew­ing or crush­ing for oil pro­duc­tion.

Oleuropein’s role in olive oil health ben­e­fits

Oleuropein and its deriv­a­tive, hydrox­y­ty­rosol, pos­sess potent antiox­i­dant prop­er­ties, con­tribut­ing to olive oil’s rep­u­ta­tion for com­bat­ing inflam­ma­tion and asso­ci­ated dis­eases. 

Notably, oleu­ropein has demon­strated a capac­ity to sig­nif­i­cantly reduce blood pres­sure, both sys­tolic and dias­tolic, in ani­mal mod­els, align­ing with olive leaf’s tra­di­tional use in treat­ing hyper­ten­sion. 

Recent stud­ies reveal that oleu­ropein’s mech­a­nism in reduc­ing blood pres­sure involves pro­tect­ing the hypo­thal­a­mus from oxida­tive stress through Nrf2-medi­ated sig­nal­ing, offer­ing poten­tial as a pre­ven­tive and ther­a­peu­tic approach for hyper­ten­sion.

Beyond blood pres­sure reg­u­la­tion, oleu­ropein exhibits var­i­ous health-pro­mot­ing func­tions, includ­ing car­dio­pro­tec­tion, anti-inflam­ma­tory, antiox­i­dant, anti-can­cer, anti-angio­genic and neu­ro­pro­tec­tive effects. 

Oleuropein and Alzheimer’s dis­ease

Numerous in vitro inves­ti­ga­tions have explored the antiox­i­dant and neu­ro­pro­tec­tive attrib­utes of extracts from extra vir­gin olive oil, uncov­er­ing their ther­a­peu­tic poten­tial in com­bat­ing Alzheimer’s dis­ease. 

When admin­is­tered before expo­sure, these extracts have been shown to upreg­u­late key antiox­i­dant enzymes in neu­rob­las­toma cells, mit­i­gat­ing oxida­tive dam­age induced by free rad­i­cals.

Phenolic com­pounds found in extra vir­gin olive oil, such as hydrox­y­ty­rosol and oleu­ropein, have demon­strated the abil­ity to impede the translo­ca­tion of nuclear fac­tor kappa B (NFkB) into the nucleus, lead­ing to dimin­ished pro­duc­tion of pro-inflam­ma­tory agents and thus curb­ing neu­roin­flam­ma­tion dri­ven by microglia. 

Moreover, these com­pounds have been observed to enhance the secre­tion of anti-inflam­ma­tory cytokines while sup­press­ing the pro­duc­tion of pro-inflam­ma­tory cytokines, pre­sent­ing a mul­ti­fac­eted approach to com­bat­ing neu­roin­flam­ma­tion.

In exper­i­ments using neu­rob­las­toma cells, a com­bi­na­tion treat­ment involv­ing oleu­ropein agly­cone and hydrox­y­ty­rosol has exhib­ited the acti­va­tion of autophagic flux, reduc­tion in free rad­i­cal pro­duc­tion, pre­ven­tion of mito­chon­dr­ial dys­reg­u­la­tion and inhi­bi­tion of cel­lu­lar dam­age inflicted by amy­loid-beta plaques. 

Furthermore, inter­ven­tions involv­ing oleu­ropein sup­ple­men­ta­tion have shown promise in enhanc­ing cog­ni­tive func­tions, mem­ory and behav­ioral dis­or­ders in patients with mild Alzheimer’s dis­ease. 

Oleuropein and osteo­poro­sis

Age-related bone den­sity loss is asso­ci­ated with osteoblast insuf­fi­ciency dur­ing the body’s con­tin­u­ous bone remod­el­ing. 

Studies sug­gest that the for­ma­tion of osteoblasts in bone mar­row is closely asso­ci­ated with adi­po­ge­n­e­sis, the for­ma­tion of adipocytes (fat cells) from stem cells and that age-related changes in this rela­tion­ship could be respon­si­ble for the increas­ing adi­pos­ity of bone mar­row asso­ci­ated with osteo­poro­sis.

Puel et al. exam­ined oleu­ropein’s effects on ovariec­tomized rats with and with­out inflam­ma­tion, find­ing pos­i­tive impacts on bone loss only in inflamed rats. 

Oleuropein enhances osteoblast for­ma­tion while reduc­ing adipocyte gen­er­a­tion, sug­gest­ing pre­ven­tive effects against osteo­poro­sis and age-related bone loss. 

Regarding bone resorp­tion, oleu­ropein at vary­ing con­cen­tra­tions decreased the for­ma­tion of osteo­clast-like cells in spleen cell cul­tures. 

In vitro stud­ies by García Martínez et al. also demon­strated that phe­no­lic extracts from Sicilian vir­gin olive oil increased osteoblast cell num­bers, poten­tially aid­ing bone growth.

Phenolic com­pounds have also been shown to mod­u­late gene expres­sion related to bone growth and dif­fer­en­ti­a­tion in MG-63 osteosar­coma cells. These phe­no­lic com­po­nents ben­e­fit bone phys­i­ol­ogy, poten­tially pro­tect­ing against bone dis­eases by influ­enc­ing osteoblast func­tion.

Oleuropein and can­cer

Over the years, the con­sump­tion of oleu­ropein has been asso­ci­ated with aid­ing in can­cer treat­ment. 

This was ini­tially attrib­uted to its antiox­i­dant prop­er­ties, but it is now rec­og­nized that oleu­ropein’s impact on can­cer extends beyond its antiox­i­dant role. It func­tions as both an anti-pro­lif­er­a­tive and apop­totic pro­moter in var­i­ous can­cer cells, demon­strat­ing many anti­cancer prop­er­ties cur­rently under inves­ti­ga­tion.

Oleuropein shows mul­ti­fac­eted effects in can­cer. It induces apop­to­sis (cell death) in cer­vi­cal can­cer cells via JNK acti­va­tion and acti­vates ERK1/2 through GPER in breast can­cer, inhibit­ing cell growth.

Moreover, it mod­u­lates apop­to­sis reg­u­la­tors like BAX, Bcl2 and p53, enhanc­ing apop­totic path­ways and reduc­ing can­cer cell sur­vival.

A wealth of exper­i­men­tal data sup­ports HER2-induced sig­nal­ing as a key player in can­cer pro­gres­sion. HER2 over­ex­pres­sion, par­tic­u­larly in breast can­cer, acti­vates path­ways like PI3K/Akt and MAPK, dri­ving tumor growth. 

While drugs like trastuzumab tar­get HER2, resis­tance often devel­ops. Oleuropein agly­cone syn­er­gizes with trastuzumab in breast can­cer cells, inhibit­ing HER2 pro­te­olytic pro­cess­ing and down­reg­u­lat­ing its expres­sion, offer­ing a promis­ing ther­a­peu­tic approach.

Combining oleu­ropein with AKT inhibitors enhances apop­to­sis, par­tic­u­larly in cells over­ex­press­ing AKT. Oleuropein also impacts ROS lev­els, reduc­ing them in thy­roid can­cer cells while increas­ing them in prostate can­cer cells, sug­gest­ing cell-spe­cific effects. Additionally, it down­reg­u­lates NF-κB and cyclin D1, inhibit­ing onco­genic path­ways in breast can­cer.

Researchers believe that future stud­ies should explore oleu­ropein’s in vivo effects on redox sta­tus across var­i­ous can­cer stages and microen­vi­ron­ments. Understanding these dynam­ics could lead to the devel­op­ment of tar­geted anti­cancer ther­a­pies.

• Scientia Pharmaceutica
• Molecules
• International Journal of Molecular Sciences