Oleuropein Derivatives Research Articles

Management of the olive decline disease complex caused by Xylella fastidiosa subsp. pauca and Neofusicoccum spp. in Apulia, Italy

Xylella fastidiosa subsp. pauca (Xfp) is associated with olive quick decline syndrome (OQDS), a severe disease affecting the olive groves of Salento (Apulia, Italy). Through a series of interdisciplinary studies, an effective management strategy aimed at maintaining the traditional olive germplasm has been developed and evaluated. Specifically, a systemic biocomplex formulation containing zinc (4%), copper (2%) and citric acid, is sprayed on the tree canopy once per month from spring to early autumn. The strategy also includes sustainable vector control through agronomical techniques as well as regular tree pruning and soil fertilization. Quantitative real-time PCR assessments performed in a mid- and long-term studies showed a significant reduction in the Xfp concentration in the leaf xylem tissue upon treatment, improving olive tree yield. Both 1H-NMR metabolomic and mass spectrometric lipidomic analyses of leaf extracts revealed the occurrence of biomarkers linked to disease or tree restoration. The effects of mannitol and oleuropein derivatives, 13-oxylipins/DOX-oxylipins and 9-oxylipins appear to be related to the attenuation of disease symptoms. Both techniques indicate rapid reprogramming of metabolic tree activity upon spray treatment to regain tree health. Multiscale satellite imagery monitoring through high-resolution Sentinel-2, very high-resolution Pleiades and vegetation indices confirmed the robustness of the strategy over several years in both experimental and productive olive groves. Currently, this strategy is applied in many infected olive groves in Salento. Notably, some aggressive fungal species belonging to the Neofusicoccum genus have been recently found to be associated with olive trees that show symptoms similar to those induced by Xfp. Coinfections between this bacterium and fungi have also been frequently observed, suggesting the need for a more in-depth assessment of the epidemiology and management of OQDS.

Non-Targeted Spectranomics for the Early Detection of Xylella fastidiosa Infection in Asymptomatic Olive Trees, cv. Cellina di Nardò.

Olive quick decline syndrome (OQDS) is a disease that has been seriously affecting olive trees in southern Italy since around 2009. During the disease, caused by Xylella fastidiosa subsp. pauca sequence type ST53 (Xf), the flow of water and nutrients within the trees is significantly compromised. Initially, infected trees may not show any symptoms, making early detection challenging. In this study, young artificially infected plants of the susceptible cultivar Cellina di Nardò were grown in a controlled environment and co-inoculated with additional xylem-inhabiting fungi. Asymptomatic leaves of olive plants at an early stage of infection were collected and analyzed using nuclear magnetic resonance (NMR), hyperspectral reflectance (HSR), and chemometrics. The application of a spectranomic approach contributed to shedding light on the relationship between the presence of specific hydrosoluble metabolites and the optical properties of both asymptomatic Xf-infected and non-infected olive leaves. Significant correlations between wavebands located in the range of 530-560 nm and 1380-1470 nm, and the following metabolites were found to be indicative of Xf infection: malic acid, fructose, sucrose, oleuropein derivatives, and formic acid. This information is the key to the development of HSR-based sensors capable of early detection of Xf infections in olive trees.

A theoretical study of oleuropein derivatives as drugs

Oleuropein is a natural product revealing a large variety of biological activity. The natural products are functionalized to increase the activity in the pharmaceutical industry. Theoretical calculations were carried out for oleuropein derivatives to display the target compound exhibiting the most biological effects. Hence, synthetic chemists are able to get inspired to synthesize the most active oleuropein derivatives. The chemical properties of oleuropein derivatives have been investigated theoretically. Gaussian method was used for quantum calculations of these compounds. The properties of compounds were presented and the utilization of these compounds in pharmaceutical industries was investigated. The quantum calculations revealed that 2H-oleuropein (3) and 4-aminobutyl-2-oleuropein (2) were unstable and were prone to react to the radical compounds.

Use of High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry for Structural Characterization of Bioactive Compounds in the Olive Root Bark and Wood of Chemlali Cultivar.

This report aims to provide complete knowledge on the polyphenol composition and biological activities of the olive tree. The extraction of the root bark and wood of Olea europaea. L (Chemlali cultivar) was realized by solid–liquid ethanolic extraction, whose analysis was conducted via high-performance liquid chromatography equipped with photodiode array detection and mass spectrometry (HPLC-ESI-DAD and MS/MS). Moreover, radical scavenging and antibacterial activities were determined. The results present a total of 14 phenolic compounds belonging mainly to secoiridoid and flavonoid subclasses. Oleuropein was found to be the most abundant compound at an amount of up to 7000 mg/kg followed by ligstroside and oleuropein derivatives. In addition, we found oleocanthal at a great amount (2115 mg/kg). Higher individual polyphenolic concentrations were recorded in root wood extracts compared to bark ones, except for the flavonoid group. Likewise, the total phenolic compound contents increased in the olive root wood. This trend was reflected in biological activities. In fact, root wood extracts exert more important antioxidant and antibacterial activities than bark extracts due to their high bioactive compounds.

Investigation on the Effects of a Pulsed Electric Field (PEF) Continuous System Implemented in an Industrial Olive Oil Plant.

The aim of this study was to investigate how the treatment of olive paste of the Picholine variety with pulsed electric fields (PEF) under real operating conditions in a large-scale olive oil extraction plant affects the extractability, chemical composition and sensory profile of the oils. The application of pulsed electric fields (PEF) as a non-thermal food processing technology is interesting for many food extraction processes. The results of this study show that pulsed electric fields can be used as a pretreatment before oil separation to increase the extractability of the process and improve the content of functional components. The application of pulsed electric field (PEF) treatment (2.4 kV/cm, 4 kJ/kg, 6 µs pulse width) to olive paste through a continuous system significantly increased the extractability and total concentration of phenols (especially oleuropein derivatives) compared to the control. In addition, the volatile compounds, α-tocopherol, the fatty acid profile and the main legal quality parameters of extra virgin olive oil (EVOO), including free acidity, peroxide values, extinction indices and sensory analysis, were evaluated. The pulsed electric fields (PEF) treatment did not modify these EVOO quality parameters, neither the α-tocopherol content nor the volatile profile. The sensory properties of EVOO were not affected as well as the PEF treatment showed a similar intensity of fruity and pungent attributes without any off-flavor according to the European Union legal standards. An increase in the bitter taste attribute was observed in the PEF oils. Consequently, this study demonstrates that pulsed electric fields (PEF) processing could be implemented in olive oil processing as pretreatment for improving the efficiency of the process.

In Vitro Activity of Water Extracts of Olive Oil against Planktonic Cells and Biofilm Formation of Arcobacter-like Species.

Extra-virgin olive oils contain many bioactive substances that are phenolic compounds. The survival of Arcobacter-like strains in non-buffered (WEOO) and buffered (BEOO) extracts of olive oils were studied. Time kill curves of different strains were measured in the environment of olive oil extracts of different grades. The activity of the extracts was also monitored for biofilm formation using the Christensen method. In vitro results revealed that extra-virgin olive oil extracts exhibited the strongest antimicrobial effects, especially non-buffered extracts, which exhibited strain inhibition after only 5 min of exposure. The weakest inhibitory effects were observed for olive oil extracts. A decrease in biofilm formation was observed in the environment of higher WEOO concentrations, although at lower concentrations of extracts, increased biofilm formation occurred due to stress conditions. The dialdehydic forms of oleuropein derivatives, hydroxytyrosol, and tyrosol were the main compounds detected by HPLC-CoulArray. The results indicate that not all olive oils had a similar bactericidal effect, and that bioactivity primarily depended on the content of certain phenolic compounds.

Olive leaf phenolic extract from two Portuguese cultivars –bioactivities for potential food and cosmetic application

Olea europaea L. is historically one of the most important trees of the Mediterranean countries. A second-order polynomial models were used to optimize the recovery of polyphenols from olive leaves from two typically produced Portuguese cultivars ‘Negrinha do Freixo’ and ‘Cornicabra’. The model obtained produced a satisfactory fit for both cultivars for total polyphenols, total flavonoids, and antioxidant activity. At the best conditions (6 h, 50% ethanol and 1:20 w-v), extracts with a higher level of phenolics were obtained for the cultivar ‘Negrinha do Freixo’ (40.14 ± 4.35 mg GAE g-1 dry leaves) followed by ‘Cornicabra’ (27.10 ± 1.29 mg GAE g-1 dry leaves). The predominant phenolic acids were oleuropein derivatives accounting for a total amount of 58.81 and 23.49 mg g-1 dry leaf followed by oleosides with 45.16 and 32.09 mg g-1 dry leaf in ‘Negrinha’ and ‘Cornicabra’ respectively. Extracts had a strong potential as an antiaging ingredient and cosmetic/food preservative exhibiting antioxidant activity, capacity to inhibit elastase (82.5% and 87.5%), collagenase (98.7% and 50%) and tyrosinase (50% and 33%) for ‘Negrinha do Freixo’ and ‘Cornicabra’, respectively at a concentration of 5 mg mL-1. The ‘Negrinha do Freixo’ had the highest potential as an antimicrobial agent at 50 mg mL-1 being the minimum inhibitory concentration for E. coli, S. enterica and S. aureus and exhibited an inhibition of 70% and 67% for P. aeruginosa and B. cereus, respectively.

Phenolic and lipophilic metabolite adjustments in Olea europaea (olive) trees during drought stress and recovery

The frequency of combined stress events is increasing due to climate change and represents a new threat to olive (Olea europaea) culture. How olive plants modulate their profile of metabolites under multiple stressing agents remains to unveil, although several metabolites affect plants' resilience, and olive production and quality. Young olive plants were exposed to a water deficit (WD) for 30 days and then exposed to a shock of heat and high UVB-radiation (WDHS+UVB treatment) for 2 days. Then, plants were re-watered and grown under optimal conditions (recovery) for 30 days. Leaves were collected after stress and recovery, analysed by liquid and gas chromatography, and the lipophilic and phenolic profiles were characterized. Except for the oleuropein derivatives, the qualitative metabolite profile was similar during stress and recovery. Metabolite increases or decreases in response to stress were stronger when WD was followed by WDHS+UVB treatment. Phenolic compounds (luteolin-7-O-glucoside, quercetin-3-O-rutinoside, apigenin-7-O-glucoside, chrysoeriol-7-O-glucoside, kaempferol derivatives, oleuropein, and lucidumoside C) were the most involved after WD and WDHS+UVB, possibly acting as reactive oxygen species (ROS) scavengers. Lipophilic compounds were more relevant during the recovery period. The catabolism of fatty acids and carbohydrates may provide the necessary energy for plant performance reestablishment, and sterols, long-chain alkanes, and terpenes metabolic pathways may be shifted for the production of compounds with a more important stress protection role. This work highlights for the first time that tolerance mechanisms activated by WD in olive plants are related to metabolite changes, that are adjusted when other stressors are overlapped (WDHS+UVB), and also help the plants recover. This metabolites’ plasticity represents an essential contribution to understanding how dry-farming olive orchards may deal with drought combined with high UV-B or heat.

Extra Virgin Olive Oil Phenolic Extract on Human Hepatic HepG2 and Intestinal Caco-2 Cells: Assessment of the Antioxidant Activity and Intestinal Trans-Epithelial Transport.

In the framework of research aimed at promoting the nutraceutical properties of the phenolic extract (BUO) obtained from an extra virgin olive oil of the Frantoio cultivar cultivated in Tuscany (Italy), with a high total phenols content, this study provides a comprehensive characterization of its antioxidant properties, both in vitro by Trolox equivalent antioxidant capacity, oxygen radical absorbance capacity, ferric reducing antioxidant power, and 2,2-diphenyl-1-picrylhydrazyl assays, and at the cellular level in human hepatic HepG2 and human intestinal Caco-2 cells. Notably, in both cell systems, after H2O2 induced oxidative stress, the BUO extract reduced reactive oxygen species, lipid peroxidation, and NO overproduction via modulation of inducible nitric oxide synthase protein levels. In parallel, the intestinal transport of the different phenolic components of the BUO phytocomplex was assayed on differentiated Caco-2 cells, a well-established model of mature enterocytes. The novelty of our study lies in having investigated the antioxidant effects of a complex pool of phenolic compounds in an extra virgin olive oil (EVOO) extract, using either in vitro assays or liver and intestinal cell models, rather than the effects of single phenols, such as hydroxytyrosol or oleuropein. Finally, the selective trans-epithelial transport of some oleuropein derivatives was observed for the first time in differentiated Caco-2 cells.

Phenolic compounds and fatty acids content of some West Algerian olive oils

Olive represents the most widespread fruit cultivated in Algeria. Olive oil is the primary source of added fat in the Mediterranean diet with health benefits of which have been verified for millennia. Interest in phenolic compounds in olive oil has increased due to its antioxidant activity, which plays a very important role in human health. The present study is carried out to study the phenolic compounds and fatty acids profile of some olive oils from western Algeria. The quality parameters (acidity, peroxide value, K232, K270), tocopherol analysis, fatty acid composition and phenolic profile were determined by High performance chromatography (HPLC). The results showed that chemlal oil (SBA) recorded the highest level of tocopherol-α with 228.12 mg/Kg. Regarding the fatty acid composition, oleic acid was the most dominant, oil Oleaster (Bensekrane) records the highest percentage (72.80%) of oleic acid. The quantitative data on the phenolic content of the seven samples revealed that chemlal oil (SBA) had the highest level of polyphenols (328.99 mg/Kg). However, Sigoise oil (Sebra1) was characterized by the highest levels of tyrosol and hydroxytyrosol (15.89 mg/kg and 22.42 mg/kg, respectively). The highest concentrations of oleuropein derivatives and ligstroside derivatives were observed in chemlal oil (SBA) and the recoreded values were 105.97 mg/Kg and 83.49 mg/Kg, respectively. Chemlal oil (SBA) was characterized by the highest amount of lignans (35.93 mg/Kg), luteolin (10.16 mg/Kg) and apigenin (5.44 mg/Kg). Oleocanthal was found in all the tested samples and it was higher in Chemlal oil (102.43 mg/kg).

Quality evolution of extra-virgin olive oils according to their chemical composition during 22 months of storage under dark conditions

The quality evolution of 14 extra-virgin olive oils (EVOOs), with different initial polyphenol and oleic acid (64.6–77.7%) levels, was determined during real-time storage in dark conditions at room temperature for 22 months. EVOOs with low (<20–200 mg/kg), medium (450–700 mg/kg), and high polyphenolic levels (750–1400 mg/kg) were used. We found high correlations among peroxide values, K232, K270, and storage time. Oleuropein derivatives decreased by 98%, 89%, and 85% in EVOOs with low, medium, and high polyphenolic levels, respectively, with the highest depletion occurring in those with the lowest initial concentrations. Besides having higher α-tocopherol protection from oxidative phenomena, EVOOs with the highest phenolic fractions showed lower head space accumulations of off-flavour volatile substances and thus demonstrated the best retention of sensory and health benefits. We propose that the shelf life of EVOOs can be determined from their initial levels of oleuropein derivatives.

An Optimized Method for Extraction and Characterization of Phenolic Compounds in Dendranthema indicum var. aromaticum Flower

Dendranthema indicum var. aromaticum plant has been widely used as herbal medicine in China, however, the material basis responsible for the therapeutic benefits remains largely unclear. This study aimed to provide an optimized method for extracting and characterizing phenolic compounds in D. indicum var. aromaticum flower. Firstly, an ultrasound-assisted method combined with central composite circumscribed (CCC) design was applied to optimize phenolic compound extraction. Ethanol-acetic acid (70%:2%, v/v) was selected as solvent, and the optimal extraction condition was: extraction temperature, 57 °C; solid/liquid ratio, 1:30 g/mL; extraction time, 20 min. Secondly, an effective and economic HPLC-PDA-ESI-MSn method was established and validated for phenolic compound characterization and quantification. As a result, 14 phenolic compounds were identified, including 8 phenolic acids and 6 flavonoids, and for the first time, oleuropein derivatives, chrysoeriol, and tricin are reported in D. indicum var. aromaticum flower. The content of phenolics identified by HPLC-MSn was 6.42 ± 0.32 mg/g DW. The optimized method for extraction and characterization of phenolic compounds has significant meaning to future pharmaceutical and medicinal research on D. indicum var. aromaticum, and the results in this study can provide references for herbal research.

Effect of storage on quality parameters and phenolic content of Italian extra-virgin olive oils

The quality of extra virgin olive oils is affected mainly by hydrolytic and oxidative reactions. The present paper investigated the changes of major and minor components and oxidation indices of three monovarietal extra virgin olive oils after 18 months of storage at room temperature and in dark glass bottles conditions. After storage, the basic quality parameters such as free acidity, peroxide values, extinction coefficients, fatty acids composition, chlorophyll and carotenoid content, did not exceed the upper limits set by European Community Regulations for extra-virgin olive oils. Given the importance of the phenolic fraction, UHPLC-HESI-MS metodology was used. A decrease in 3,4-DHPEA-EDA (oleacin) and p-HPEA-EDA (oleochantal) was detected whereas, an increase of tyrosol and hydroxytyrosol was measured as a consequence of degradation of ligstroside and oleuropein derivatives. Based on the results it is possible to observe the high nutritional value of the studied oils even after 18 months of conservation.

Oleuropein derivatives from olive fruit extracts reduce α-synuclein fibrillation and oligomer toxicity

Aggregation of α-synuclein (αSN) is implicated in neuronal degeneration in Parkinson's disease and has prompted searches for natural compounds inhibiting αSN aggregation and reducing its tendency to form toxic oligomers. Oil from the olive tree (Olea europaea L.) represents the main source of fat in the Mediterranean diet and contains variable levels of phenolic compounds, many structurally related to the compound oleuropein. Here, using αSN aggregation, fibrillation, size-exclusion chromatography-multiangle light scattering (SEC-MALS)-based assays, and toxicity assays, we systematically screened the fruit extracts of 15 different olive varieties to identify compounds that can inhibit αSN aggregation and oligomer toxicity and also have antioxidant activity. Polyphenol composition differed markedly among varieties. The variety with the most effective antioxidant and aggregation activities, Koroneiki, combined strong inhibition of αSN fibril nucleation and elongation with strong disaggregation activity on preformed fibrils and prevented the formation of toxic αSN oligomers. Fractionation of the Koroneiki extract identified oleuropein aglycone, hydroxyl oleuropein aglycone, and oleuropein as key compounds responsible for the differences in inhibition across the extracts. These phenolic compounds inhibited αSN amyloidogenesis by directing αSN monomers into small αSN oligomers with lower toxicity, thereby suppressing the subsequent fibril growth phase. Our results highlight the molecular consequences of differences in the level of effective phenolic compounds in different olive varieties, insights that have implications for long-term human health.

Evaluating the reliability of specific and global methods to assess the phenolic content of virgin olive oil: Do they drive to equivalent results?

Despite the huge number of different published methodologies, there is an open debate regarding which one is the most convenient analytical strategy for the determination of phenolic compounds from virgin olive oils. Diverse technical issues together with the disparity of criteria regarding results expression cause a lot of confusion. Herewith, a systematic comparison between specific (a powerful and LC–MS method) and global methodologies (the Folin-Ciocalteau (FC) colorimetric assay, the International Olive Council (IOC) method and hydrolysis plus HPLC-DAD) has been carried out. Thus, these strategies have been applied to the analysis of 50 extra virgin olive oils (covering all the possible quantitative ranges of these substances). This is the first time in which the individual LC–MS quantification of so many phenolic substances is included in this kind of comprehensive comparison. The outcomes of all the strategies have been thoroughly confronted and their equivalence (or divergence) has been carefully evaluated, establishing possible correspondence factors.The LC–MS individual determination with the pure standard of every analyte represented the ideal situation; when only the commercially available standards were used, a drastic change was observed in the absolute concentrations of oleuropein derivatives (in terms of hydroxytyrosol). Total phenolic content (summing individual levels) proved to be higher (1.9–3.0 times when data was expressed in mg/kg) than the values given by the three non-specific methods (with R2 from 0.84 to 0.90). In any case, the IOC method, the FC assay and the hydrolysis approach could be considered as feasible strategies when a global value is pursued. Good correlations between their results were found (R2 > 0.89), with the following equivalence factors: FC(mg caffeic acid/kg) ≈ 0.60 IOC(mg TY/kg); IOC(mg TY/kg) ≈ 1.27 Sum acid hydrolysis(mg TY+HTY/kg); FC(mg HTY/kg) ≈ 1.04 Sum acid hydrolysis(mg TY+HTY/kg).

Brain uptake of hydroxytyrosol and its main circulating metabolites: Protective potential in neuronal cells

Hydroxytyrosol (HT) and oleuropein derivatives are the main phenolic compounds in virgin olive oil (VOO). After VOO intake, HT is extensively metabolized being hydroxytyrosol-sulphate (HT-S) and hydroxytyrosol-acetate sulphate (HT-AC-S) the main circulating metabolites detected in human plasma. The brain uptake and accumulation of HT and its metabolites were observed after 21 days of rat diet supplementation (5 mg/kg rat/day) of HT in its native form or through oleuropein derivatives. To establish their neuroprotective potential HT-S and HT-AC-S were chemically synthetized and their protective effects against oxidative stress at physiological concentrations (10 μM) in neuroblastoma (SH-SY5Y) and dopaminergic (LUHMES) neuronal cells were observed. The sulpho-conjugated HT structures showed a lower protective effect than native HT. Results showed brain accumulation of HT and HT-S, suggesting their neuroprotective activity by the reduction of the oxidative stress at neuronal level.

Influence of irrigation treatments on the yield and quality of ‘Istrska belica’ olive oil

In recent years, Slovenian olive growers and producers have faced problems in achieving constant yields and quality of olive oil due to extreme weather conditions, especially because of the more frequent occurrence of drought. A technically accomplished pilot automatic irrigation system for olive trees was established. In 2015, the impact of different irrigation treatments (0, 15, 33, 40 and 100% ETc (crop evapotranspiration)) on olive cultivar 'Istrska belica' were studied to determine the minimum amount of added water that has a positive effect on the yield and quality of the extra virgin olive oil produced. The study results showed that the quantity of applied water equal to 100% ETc had a significant effect on yield of olive fruits. The average fruit mass of the trees grown under full irrigation (100% ETc) was significantly higher than that of those given rain-fed and deficit irrigation treatments (15, 33 and 40% ETc), with no significant differences found between these treatments. The fatty acid contents showed the highest amount of oleic acid (75.61%) at 100% ETc and the lowest amount (74.69%) at 15% ETc, while the highest amount of linoleic acid (6.52%) was determined at 15% ETc and the lowest (5.98%) at 100% ETc. Total biophenol content and biophenol composition was determined. The 40% ETc irrigation system produced the highest amounts of total biophenols, total oleuropein and total ligstroside derivatives (1076, 562 and 388 mg kg-1, respectively), while the lowest results (883, 477 and 299 mg kg-1, respectively) were determined in the control system (0% ETc). The organoleptic assessment of the olive samples showed that the positive sensory attributes of fruity, bitter and pungent were more intensive at 33% ETc and were graded highest. Olive oil from non-irrigated trees (0% ETc) received the lowest sensory score.

A two-phase olive mill by-product (pâté) as a convenient source of phenolic compounds: Content, stability, and antiaging properties in cultured human fibroblasts

Pâté is a new olive mill by-product potentially suitable for human consumption. This work aimed to characterize the phenolic profile of pâté samples from four crop seasons (2013–2016) in fresh, dried and stored samples, applying HPLC-DAD-MS-TOF, and to evaluate the antiaging effect in a cell senescence model. The dried pâté contains high levels of hydroxytyrosol, oleuropein derivatives and other phenolic compounds and is stable for several months. A diluted hydroalcoholic extract showed antiaging effects in vitro, comparable to those of pure hydroxytyrosol. Pâté can thus be proposed as an additional economical and environment-friendly source of olive bioactive phenolic compounds, particularly hydroxytyrosol: 1 g of pâté provides a daily intake comparable to that derived from 200 g of a typical virgin olive oil. This work lays the basis for a possible use of this food by-product as a natural ingredient for innovative foods or food supplements, contributing to a healthier lifestyle.

Bioactive compounds from extra virgin olive oils: Correlation between phenolic content and oxidative stress cell protection

When compared with other edible vegetable oils, the extra virgin olive oil (EVOO) exhibits excellent nutritional properties due to the presence of biophenolic compounds. Although they constitute only a very small amount of the unsaponifiable fraction of EVOO, biophenols strongly contribute to the sensorial properties of this precious food conferring it, for example, the bitter or pungent taste. Furthermore, it has been found that biophenols possess beneficial effects against many human pathologies such as oxidative stress, inflammation, cardiovascular diseases, cancer and aging-related illness. In the present work, the biophenolic content of 51 Italian and Spanish EVOOs was qualitatively and quantitatively identified and their antioxidant ability analyzed by oxygen radical absorbance capacity (ORAC) assay. Results indicated that the maximum relationship can be found if the ORAC value is correlated with the concentration of the large family composed by ligstroside and oleuropein derivatives together with their degradation products, hydroxytyrosol and tyrosol. Then, selected biophenolic extracts were tested in NIH-3T3 cell line to verify their ability in the recovery of the oxidative stress revealed by DCFH-DA assay. Results were linearly correlated with the concentration of ligstroside aglycone (aldehyde and hydroxyl form).

Olive oil enrichment in phenolic compounds during malaxation in the presence of olive leaves or olive mill wastewater extracts

A combined study was performed to determine the effect of olive leaf aqueous extract (OLE), olive mill wastewater (OMWW) or water addition during the malaxation step on total phenolic content (TPC), antioxidant activity, virgin olive oil composition and quality parameters of olive oil. For these purposes, the Folin‐Ciocalteu assay, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay, and HPLC‐ESI‐TOF/MS were employed. The experiments were carried out at semi‐industrial scale in a cold extraction olive oil mill using olives of Koroneiki cultivar. Olive oil produced by olive paste which was malaxed without adding water, OMWW, or OLE was employed as control. The use of OMWW and OLE allowed obtaining oils with higher significant TPC compared to that malaxed with water (146.2 and 151.8 vs. 132.8 μg Eq GAE/g oil, respectively). The antioxidant activity followed the same trend. The use of OMWW and OLE enabled an oil enrichment in oleuropein derivatives, especially in 3,4‐DHPEA‐EDA. Despite the fact that acidity and oxidation (K270 and K232 values) were higher in the aforementioned oils compared to the oil extracted with water, all values were under the European Union commission parameters for extra virgin olive oil (EVOO) denomination. However, only the oil extracted using OLE presented slightly higher fruity, bitter, and pungent positive attributes compared to the control and to the oil extracted with water, thus, making OLE a promising by‐product for improving olive oils.Practical applications: This research provides new insight for the improvement of olive oil extraction process in order to obtain high‐phenol EVOO which could be useful for the olive oil, nutraceuticals, and cosmeceuticals industries. Besides, this study could serve as a starting point for improving the olive oil production process, while reducing the impact of its by‐products.The addition of Olive mil wastewater (OMWW) and olive leaf extract during malaxation, allowed obtaining enriched oils with a higher content in total phenolics, and antioxidant activity compared to those obtained adding water. These enriched oils presentes higher quantities of oleuropein derivatives and specifically of 3,4‐DHPEA‐EDA.