From Green Technology to Functional Olive Oils: Assessing the Best Combination of Olive Tree-Related Extracts with Complementary Bioactivities

Oleocanthal - Characterization, production, safety, functionality and in vivo evidences

Oleocanthal, OC, 2-(4-Hydroxyphenyl)ethyl(3S,4E)-4-formyl-3-(2-oxoethyl)hex-4-enoate, is a natural organic compound exclusively found in Olea europaea L. (Oleoaceae), such as extra virgin olive oil (EVOO). Chemically, it is considered a monophenolic secoiridoid, taking part of the validated antioxidants naturally occurring in some plant-based foods. In this review, the aim is to summarize the identity and characteristics of this molecule, where it can be obtained (isolation from the natural source or chemical synthesis), as well as the use as food component. Then, the bioavailability, safety and studies aiming to demonstrate the potential health benefits, including in vitro and in vivo animal and human studies were also discussed.

Towards a circular economy in virgin olive oil production: Valorization of the olive mill waste (OMW) "alpeorujo" through polyphenol recovery with natural deep eutectic solvents (NADESs) and vermicomposting

Virgin olive oil (VOO) production generates large amounts of a harmful by-product, olive mill waste (OMW) or alpeorujo, which has a strong environmental impact and that must be recycled to adapt VOO production to a circular economy model. Here, the valorization of OMW was studied by considering three consecutive stages: Stage 1 involves the generation of OMW; Stage 2 the recovery of bioactive phenolic compounds from the fresh OMW using natural deep eutectic solvents (NADESs), generating a valuable phenolic extract and a new by-product, a dephenolized OMW named "alpeoNADES"; and Stage 3 involves vermicomposting alpeoNADES with Eisenia fetida earthworms. Six NADES were formulated and tested, selecting a NADES composed of citric acid and fructose (CF) derived from food grade and biodegradable substances. CF was the most effective solvent to obtain phenolic extracts for nutraceutical and agronomical purposes, extracting 3988.74 mg/kg of polyphenols from fresh OMW. This alpeoNADES is a non-palatable substrate for E. fetida earthworms, as the residual CF gives it an acidic pH (pH 2). Its palatability was improved by mixing it with horse manure and straw for vermicomposting, in a 1:1 and 3:1 dry weight ratio. When these substrates were precomposted for 3 weeks they reached pH 5.5-6 and they could then be vermicomposted for 23 weeks (using OMW as a control). The best substrate for vermicomposting was determined by the worm biomass, growth rate, carbon to nitrogen (C:N) ratio, and N and P content. AlpeoNADES and manure 3:1 produced the highest quality vermicompost in the shortest time, generating a product that complied with European standards for organic fertilizers. Hence, alpeoNADES was recycled to a low-cost, organic balanced fertilizer in Stage 3, enabling the olive oil industry to transition to sustainable production through this integrated circular economy design.

Neuroprotective Effect of 3',4'-Dihydroxyphenylglycol in Type-1-like Diabetic Rats-Influence of the Hydroxytyrosol/3',4'-dihydroxyphenylglycol Ratio

The aim of this study was to assess the possible neuroprotective effect of 3′,4′-dihydroxyphenylglycol (DHPG), a polyphenol from extra virgin olive oil (EVOO), in an experimental model of diabetes and whether this effect is modified by the presence of another EVOO polyphenol, hydroxytyrosol (HT). The neuroprotective effect was assessed in a hypoxia–reoxygenation model in brain slices and by quantifying retinal nerve cells. The animals were distributed as follows: (1) normoglycemic rats (NDR), (2) diabetic rats (DR), (3) DR treated with HT (5 mg/kg/day p.o.), (4) DR treated with DHPG (0.5 mg/kg/day), or (5) with 1 mg/kg/day, (6) DR treated with HT plus DHPG 0.5 mg/kg/day, or (7) HT plus 1 mg/kg/day p.o. DHPG. Diabetic animals presented higher levels of oxidative stress variables and lower numbers of neuronal cells in retinal tissue. The administration of DHPG or HT reduced most of the oxidative stress variables and brain lactate dehydrogenase efflux (LDH) as an indirect index of cellular death and also reduced the loss of retinal cells. The association of DHPG+HT in the same proportions, as found in EVOO, improved the neuroprotective and antioxidant effects of both polyphenols.

From Low-Quality Olive Oils to Valuable Bioactive Compounds: Obtaining Oleacein and Oleocanthal from Olive Oils Intended for Refining

The aim of this work was to recover phenolic compounds such as oleacein and oleocanthal from low commercial value olive oils destined for refining [lampante olive oil (LOO)]. For this, the ability of three extraction systems of phenols from oils was evaluated. A new quick and simple extraction method (NM) for obtaining phenols was developed, consisting of the acidified mixture MeOH/H₂O (50:50) (v/v) 0.1% formic acid, and it was compared to a conventional method (CM) widely used for the analytical determination of phenolic compounds in olive oil using MeOH: H₂O (80:20) (v/v). NM showed a higher yield for the extraction of oleacein with an increase of 14% compared to CM; no significant differences were observed in the extraction of oleocanthal between the two methods. The third method, using two formulations of deep eutectic solvents (DESs) based on ChCl, showed higher extractive efficiency for the two secoiridoids than CM and NM when DES consisted of ChCl and xylitol. On the other hand, the concentrations of oleacein and oleocanthal were determined in 14 samples of blended oils that were previously classified as extra virgin olive oil and LOO according to EU regulation. LOO contained amounts up to 109.89 and 140.16 mg/kg of oleacein and oleocanthal, respectively. Oleacein (>98%) and oleocanthal (>95%) were successfully recovered from phenolic extracts obtained from LOO oils through chromatographic separation and purification by semipreparative high-performance liquid chromatography. Therefore, these low-quality oils are an inexpensive source of bioactive substances.

Synergistic Effect of 3',4'-Dihidroxifenilglicol and Hydroxytyrosol on Oxidative and Nitrosative Stress and Some Cardiovascular Biomarkers in an Experimental Model of Type 1 Diabetes Mellitus

The objective of this study was to assess a possible synergistic effect of two extra-virgin olive oil polyphenols, 3,4,-dyhydroxyphenylglycol (DHPG) and hydroxytyrosol (HT), in an experimental model of type 1 diabetes. Seven groups of animals were studied: (1) Nondiabetic rats (NDR), (2) 2-month-old diabetic rats (DR), (3) DR treated with 5 mg/kg/day p.o. HT, (4) DR treated with 0.5 mg/kg/day p.o. DHPG, (5) DR treated with 1 mg/kg/day p.o. DHPG, (6) DR treated with HT + DHPG (0.5), (7) DR treated with HT + DHPG (1). Oxidative stress variables (lipid peroxidation, glutathione, total antioxidant activity, 8-isoprostanes, 8-hydroxy-2-deoxyguanosine, and oxidized LDL), nitrosative stress (3-nitrotyrosine), and some cardiovascular biomarkers (platelet aggregation, thromboxane B₂, prostacyclin, myeloperoxidase, and vascular cell adhesion protein 1 (VCAM-1)) were analyzed. The diabetic animals showed an imbalance in all of the analyzed variables. HT exerted an antioxidant and downregulatory effect on prothrombotic biomarkers while reducing the fall of prostacyclin. DHPG presented a similar, but quantitatively lower, profile. HT plus DHPG showed a synergistic effect in the reduction of oxidative and nitrosative stress, platelet aggregation, production of prostacyclin, myeloperoxidase, and VCAM-1. This synergism could be important for the development of functional oils enriched in these two polyphenols in the proportion used in this study.