engleski

Biologically active phenolic compounds in extra virgin olive oil and olive fruit from Croatia

Introduction. Traditional Mediterranean diet, characterized by high intake of olive oil, fruit, nuts, vegetables, cereals and a moderate intake of fish and wine, is widely recognized and approved as beneficial for human health. Olive oil has been the subject of numerous studies, as valuable source of bioactive phenols and possible use in prevention/treatment of cardiovascular and neurodegenerative diseases, cancer, diabetes mellitus, metabolic syndrome. The composition and the level of the phenolic compounds in the olive oil are affected by a number of factors as cultivar, climate and other agro-ecological factors. Olive fruit, even richer in phenolic compounds, presents an interesting and possibly not enough exploited source of these bioactive molecules. The aim of this study was to evaluate and to compare the content of phenolic compounds in the olive oil and the olive fruit, particularly those characteristic for olive species, with prominent biological activity (hydroxytyrosol, HOTyr ; tyrosol, Tyr ; oleuropein, Ole ; decarboxymethyl-oleuropein aglycon, 3, 4-DHPEA-EDA). Materials and methods. Fresh and health olive fruits of Oblica cultivar (Ugljan island, Croatia) have been picked carefully. One part of the fruits was kept frozen until analysis, while the other one was used for the extraction of olive oil, using the centrifugal line OLIOMIO 350. Extraction of phenolic compounds from extra virgin olive oil (EVOO) and de-stoned olive fruits (dsOF) was carried out using the ultrasound-assisted liquid-liquid extraction method according to the literature, with some modifications. The total phenol (TP) content was determined by the Folin-Ciocalteu method. The concentration of o-diphenols was determined with the sodium molybdate assay. The phenolic compounds content (OHTyr, Tyr, Ole and 3, 4- DHPEA-EDA) has been determined following the HPLC-DAD analysis performed in essence by applying the previously used procedure. Results. The determined TPs in EVOO and dsOF in cultivar Oblica (Ugljan) were 507±63 mg gallic acid equivalent (GAE)/kg EVOO and 3102±608 mg GAE/kg dsOF, respectively. The o-diphenols were 241±58 mg GAE/kg EVOO and 2190±593 mg GAE/kg dsOF. Following the HPLC-DAD analysis, the content of OHTyr, Tyr, Ole and 3, 4-DHPEA-EDA in EVOO and dsOF, as well as the relationship between the content in EVOO and dsOF were determined. The dsOF showed roughly tenfold greater content of HOTyr and Tyr, while the EVOO showed higher content of 3, 4-DHPEA-EDA. Conclusion. The content of the total phenols, o-diphenols, HOTyr, Tyr, Ole is roughly tenfold greater in the olive fruit than in the olive oil. The determined relationship between the content in the olive oil and the olive fruit could be useful in recognition of the “fruits” which should give the oil with the best content of certain phenolic compounds. Furtherly, olive fruit itself could be used as a potential source of biologically active phenolic compounds.

Olive fruit, olive oil, phenolic compound

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