Application of the INFOGEST Standardized Method to Assess the Digestive Stability and Bioaccessibility of Phenolic Compounds from Galician Extra-Virgin Olive Oil.

The INFOGEST standardized method was applied to assess the potential bioaccessibility and bioaccessibility of the phenolic compounds from a Galician extra-virgin olive oil (EVOO). The in vitro digestion model involves three steps and generates two fractions after each one: an aqueous fraction (namely, water phase (Wp)) and an oily fraction (namely, oily phase (Op)). The results showed that secoiridoids were the most abundant family in the Galician EVOO polar fraction, representing 98% of the total phenolic compounds. After oral digestion, phenolic acids and simple phenols were mainly detected in Wp, while lignans and flavonoids were mostly found in Op. After gastric digestion, extensive hydrolysis of secoiridoids was observed to generate free tyrosol, hydroxytyrosol, and hydroxytyrosol acetate. The instability of secoiridoids after intestinal digestion was again responsible for the release of simple phenols, which were mainly recovered in Wp together with flavonoids. In contrast, lignans were stable to duodenal conditions and remained in Op.

Effect of olive ripening degree on the antidiabetic potential of biophenols-rich extracts of Brava Gallega virgin olive oils.

The diet management is imperative to anticipate risk factors that favour the development of diseases; indeed, the intake of virgin olive oil could be an alternative natural source of α-glucosidase enzyme inhibitors, which delay the digestion rate of carbohydrates. Consequently, the impact of diabetes mellitus (DM) could be diminished. Extra Virgin Olive Oils (EVOO) were elaborated from Galician autochthonous variety 'Brava Gallega' with olives selected at three different degree of ripeness (ripening index, RI: 1.4, 3.0, 5.5) in order to assess the effect of maturation on overall chemical composition, sensory quality, and enzyme inhibition. The phenolic profile of the EVOOs determined by LC-ESI-IT-MS exhibited quantitative differences as ripening advanced; for example oleocanthal, tyrosol, luteolin and apigenin concentrations were higher in the overripe olive oil (RI 5.5). Anyway, the phenolic extracts (from every tested RI) were more active than acarbose. In particular, those obtained from the most mature olives displayed the most powerful inhibitory activity (IC50 value of 143 µg of dry extract/mL). In addition, the significant effect of these compounds (i.e. luteolin, apigenin, tyrosol and oleocanthal) on the inhibitory activity of the olive oil extracts was demonstrated. Our results suggest that, regardless of RI, the inhibitory activity of 'Brava Gallega' olive oils could represent a valuable strategy for reinforcing the health claim of olive oil for phenolic compounds.

The involvement of phenolic-rich extracts from Galician autochthonous extra-virgin olive oils against the α-glucosidase and α-amylase inhibition.

'Brava' and 'Mansa de Figueiredo' extra-virgin olive oils (EVOOs) are two varieties identified from north-western Spain. A systematic phenolic characterization of the studied oils was undertaken by LC-ESI-IT-MS. In addition, the role of dietary polyphenols from these EVOOs has been evaluated against the inhibition of key enzymes (α-glucosidase and α-amylase) in the management of diabetes mellitus (DM). Oleuropein and ligstroside derivatives comprised 83% and 67% of the total phenolic compounds in 'Brava' and 'Mansa de Figueiredo' EVOOs, respectively. The main secoiridoids from oleuropein were DOA (3,4-DHPEA-EDA, 59 and 22 mg kg-1, respectively) and the main isomer of OlAgl (3,4-DHPEA-EA, 74 and 23 mg kg-1). The main secoiridoids from ligstroside were D-LigAgl (p-HPEA-EDA or oleocanthal, 23 and 167 mg kg-1) and the main isomer of LigAgl (p-HPEA-EA, 214 and 114 mg kg-1). For α-glucosidase, both EVOO extracts displayed stronger inhibitory activity (IC50 values of 60 ±â€¯8 and 118 ±â€¯9 µg mL-1, respectively) than the commercial inhibitor acarbose (IC50 = 356 ±â€¯21 µg mL-1). Nevertheless, for α-amylase, only 'Brava' extracts showed anti-α-amylase capacity. A daily VOO intake lower than the requirements of EFSA seem to be enough to reach both 50% for α-glucosidase and 25% for α-amylase inhibition. These findings support the potential health benefits derived from Galician EVOOs that might be probably linked to the outstanding high concentration levels of phenolic acids and flavonoids.

Evaluation of the neuroprotective and antidiabetic potential of phenol-rich extracts from virgin olive oils by in vitro assays.

In this work, phenol-rich extracts from 'Cornicabra' and 'Picual' virgin-olive oils (EVOOs) were examined, for the first time, to establish their capacity to inhibit key enzymes involved in Alzheimer's disease (AD) (acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) and 5-lipoxygenase (LOX)), major depressive disorder (MDD) and Parkinson's disease (PD) (monoamine oxidases: hMAO-A and hMAO-B respectively), and diabetes mellitus (DM) (α-glucosidase and α-amylase). 'Cornicabra' displayed the best inhibitory activity against all enzymes, when compared to 'Picual': BuChE (IC50 = 156 ±â€¯4 and 308 ±â€¯33 mg mL-1), LOX (IC50 = 26 ±â€¯0.5 and 37 ±â€¯3 mg mL-1), hMAO-A (IC50 = 20 ±â€¯2 and 37 ±â€¯0.2 mg mL-1), hMAO-B (IC50 = 131 ±â€¯7 and 215 ±â€¯13 mg mL-1) and α-glucosidase (IC50 = 154 ±â€¯17 and 251 ±â€¯31 mg mL-1), respectively. The behaviour observed can be associated with the higher content of secoiridoids, lignans and phenolic acids in 'Cornicabra' EVOO.

Characterisation of extra virgin olive oils from Galician autochthonous varieties and their co-crushings with Arbequina and Picual cv.

The current trend of the olive oil market is the production of high quality extra from traditional minor olive varieties with peculiar and differentiated characteristics (especially with respect to the aromatic and phenolic composition). In this way, the interest of Galician oil producers (NW Spain) in recovering old autochthonous Local olive fruits has increased substantially in recent years. In order to investigate the potential of the Local olives by either producing high quality monovarietal oils or mixing with the most widespread olives in Galicia (Arbequina and Picual cv.), quality indices, and fatty acid composition as well as volatile and phenolic profiles were determined and compared. All EVOOs studied in this work can be considered as "extra virgin olive oil" due to quality indices fell within the ranges established in legislation. Picual and Local olive oils as well as those resulting from their co-crushing reach values which are required by EU legislation to add the specific health claim on the oil label. Co-crushing Picual:Local (80:20) provided a significant enhancement of grass and apple nuances and a decrease of banana notes with respect to Picual oils. The co-crushing process improved sensory and health properties of Picual extra virgin olive oils. The effect of co-crushing on phenolics, ester volatiles and banana nuances cannot be easily modulated, contrary to quality indices and fatty acid composition, both changing linearly in strict correlation with the fruit mass ratio.

Quality of extra virgin olive oils produced in an emerging olive growing area in north-western Spain.

Systematic studies of physico-chemical and stability-related properties, and chemical composition, of extra virgin olive oils (EVOOs) obtained from drupes cropped in specific regions are of special agricultural interest. This is particularly so with new production areas, where careful selection of the most suitable olive varieties for EVOO production is required. This paper reports the first comprehensive chemical characterisation of EVOOs obtained from three different olive varieties (viz., Picual, Morisca and Manzanilla de Sevilla) grown in a new cultivation area in Galicia (NW Spain). The Morisca variety was that providing the highest industrial oil yield (21%). However, the three types of EVOO exhibited no statistically significant differences in standard quality-related indices other than acidity. Morisca EVOO was that with the lowest content in oleic acid (mean=68%) and highest content in linoleic acid (mean=13%). Also, Morisca EVOO exhibited the highest sterol levels (mean=1,616 mg/kg) and Picual EVOO the lowest (mean=1,160 mg/kg). Picual EVOO contained greater amounts of the phenolic compounds luteolin and pinoresinol than both Morisca and Manzanilla de Sevilla EVOOs. Finally, Manzanilla de Sevilla EVOO exhibited differential attributes, with banana and olive fruit aromatic series prevailing predominantly over bitter-like, pungent-like and leaf series.

Improvements in the malaxation process to enhance the aroma quality of extra virgin olive oils.

The influence of olive paste preparation conditions on the standard quality parameters, as well as volatile profiles of extra virgin olive oils (EVOOs) from Morisca and Manzanilla de Sevilla cultivars produced in an emerging olive growing area in north-western Spain and processed in an oil mill plant were investigated. For this purpose, two malaxation temperatures (20/30 °C), and two malaxation times (30/90 min) selected in accordance with the customs of the area producers were tested. The volatile profile of the oils underwent a substantial change in terms of odorant series when different malaxation parameters were applied.

Ultrasound-assisted emulsification-microextraction for the determination of phenolic compounds in olive oils.

A reliable, sensitive and effective method based on ultrasound-assisted emulsification-microextraction (USAEME) coupled to HPLC-DAD has been developed to identify and quantify several target phenolic compounds from extra virgin olive oils (EVOO). This approach is based on the emulsification of a microvolume of polar organic extractant in a non-polar liquid sample by ultrasound radiation and further separation of both liquid phases by centrifugation. The percentage of methanol/water (v/v) in the extractant, the volume of extractant, and the extraction time as three effective parameters on the extraction were optimised by a central composite design (Box-Behnken response surface) method. The optimised method presented recoveries in EVOO between 91% and 115% for the target analytes (except vanillin with 65%) and a satisfactory precision with relative standard deviations (RSD%) lower than 8.4% for repeatability and reproducibility. The method showed good linearity and limits of detection and quantification were in the range 0.001-0.14 and 0.004-0.47mg/kg, respectively. After method validation, it was successfully applied to the analysis of three EVOO samples. All target compounds were detected in all analysed samples. Tyrosol and hydroxytyrosol were the major phenolic compounds, followed by pinoresinol and luteolin.

Aroma biogenesis and distribution between olive pulps and seeds with identification of aroma trends among cultivars.

The two constitutive parts of four cultivars (Arbequina, Picual, Local and Manzanilla de Sevilla) grown in Spain were separately analysed in order to establish the role of pulp and seed in the biogenesis of extra virgin olive oil (EVOO) aroma through the lipoxygenase (LOX) pathway. C6 and C5 volatile compounds responsible of EVOO aroma were produced by endogenous enzymes in both parts of olive fruits and the differences can be attributed to different enzymes distribution in pulp and seed. According to results, C6 and C5 volatile compounds have mainly their biogenesis in pulp (80-90%) vs. seed (20-10%), independently of the cultivar considered. A linear discriminant analysis was used to establish discriminant aroma compounds between pulp and seed related to the maturity index. A decrease in trans-2-hexen-1-al and an increase in 1-hexanol with ripeness were observed independently of the cultivar considered. Finally, Partial Least Squares (PLS) regression analysis between pulp and seed aroma compounds allowed to establish those volatile compounds that better describe each cultivar.