Antioxidant and Biological Activities of Hydroxytyrosol and Homovanillic Alcohol Obtained from Olive Mill Wastewaters of Extra-Virgin Olive Oil Production

Modular cascade with engineered HpaB for efficient synthesis of hydroxytyrosol

Hydroxytyrosol, a naturally occurring chemical with antioxidant and antiviral properties, is widely used in the nutrition, pharmaceutical, and cosmetic industries. In the present study, a modularized cascade composed of Modules 1 and 2 was designed and implemented to convert l-tyrosine to hydroxytyrosol. Module 1 was a four-enzymatic cascade for converting l-tyrosine to tyrosol. Engineering Module 1 by fine-tuning the expression of the desired enzymes resulted in a robust whole-cell catalyst, BL21 (M1-13), which converted l-tyrosine to tyrosol at high substrate loading. Module 2 involved a 4-hydroxyphenylacetate 3-monooxygenase (HpaBC)-catalyzed reaction to hydroxylate tyrosol to form hydroxytyrosol. The rational design of the HpaB subunit led to a positive variant, HpaB-Mu (T292S/R474A), which was subsequently applied to Module 2 for tyrosol hydroxylation, yielding a robust whole-cell catalyst, BL21 (M2-05). The two designed modules were merged for one-pot conversion of l-tyrosine to hydroxytyrosol by adjusting the ratio and total amount of whole-cell catalyst loading, capable of converting 40 mM of l-tyrosine to 35.8 mM of hydroxytyrosol with a high space-time yield (1.38 g/L/h). The current study proved that engineering HpaB at the substrate tunnel was a feasible way to boost its activity and proposed an effective method for synthesizing hydroxytyrosol from low-cost substrates, which has great economic potential.

Selective Lipophilization of Natural Phenolic Alcohols Induced by In Situ Choline Chloride-Based Natural Deep Eutectic Solvents

In this scientific work, a novel and green method for selective lipophilization of EVOO's bioactive phenolic alcohols (PAs), namely, tyrosol, hydroxytyrosol, and its metabolite homovanillyl alcohol as fatty acid esters, is elucidated. The PAs have been employed as hydrogen bond donors in the formation of natural deep eutectic solvents (NADES) with choline chloride (ChCl). The fast and cheap esterification method by in situ formation of choline chloride-based deep eutectic solvents promotes the derivatization of PAs with various fatty acids as acylating agents in the absence of organic solvents and catalysts. Furthermore, given the growing interest in the application of NADES formed by bioactive molecules in the pharmacological and cosmetic fields, we analyzed the activity of antioxidant enzymes, superoxide dismutase, and glutathione S-transferase of three chemical formulations obtained after the formation of PA-oleate in the H2O2-treated HaCat human keratinocytes cell line, assessing also their toxicity via the MTT assay.

Use of Oleuropein and Hydroxytyrosol for Cancer Prevention and Treatment: Considerations about How Bioavailability and Metabolism Impact Their Adoption in Clinical Routine

The fact that the Mediterranean diet could represent a source of natural compounds with cancer-preventive and therapeutic activity has been the object of great interest, especially with regard to the mechanisms of action of polyphenols found in olive oil and olive leaves. Secoiridoid oleuropein (OLE) and its derivative hydroxytyrosol (3,4-dihydroxyphenylethanol, HT) have demonstrated anti-proliferative properties against a variety of tumors and hematological malignancies both in vivo and in vitro, with measurable effects on cellular redox status, metabolism, and transcriptional activity. With this review, we aim to summarize the most up-to-date information on the potential use of OLE and HT for cancer treatment, making important considerations about OLE and HT bioavailability, OLE- and HT-mediated effects on drug metabolism, and OLE and HT dual activity as both pro- and antioxidants, likely hampering their use in clinical routine. Also, we focus on the details available on the effects of nutritionally relevant concentrations of OLE and HT on cell viability, redox homeostasis, and inflammation in order to evaluate if both compounds could be considered cancer-preventive agents or new potential chemotherapy drugs whenever their only source is represented by diet.

Anti-Inflammatory Effects of Nutritionally Relevant Concentrations of Oleuropein and Hydroxytyrosol on Peripheral Blood Mononuclear Cells: An Age-Related Analysis

Immunosenescence and inflammaging facilitate the insurgence of chronic diseases. The Mediterranean diet is a non-invasive intervention to improve the chronic low-grade inflammatory status associated with aging. Olive oil oleuropein (OLE) and hydroxytyrosol (HT) demonstrated a controversial modulatory action on inflammation in vitro when tested at concentrations exceeding those detectable in human plasma. We studied the potential anti-inflammatory effects of OLE and HT at nutritionally relevant concentrations on peripheral blood mononuclear cells (PBMCs) as regards cell viability, frequency of leukocyte subsets, and cytokine release, performing an age-focused analysis on two groups of subjects: Adult (age 18-64 years) and Senior (age ≥ 65 years). OLE and HT were used alone or as a pre-treatment before challenging PBMCs with lipopolysaccharide (LPS). Both polyphenols had no effect on cell viability irrespective of LPS, but 5 µM HT had an LPS-like effect on monocytes, reducing the intermediate subset in Adult subjects. OLE and HT had no effect on LPS-triggered release of TNF-α, IL-6 and IL-8, but 5 µM HT reduced IL-10 secretion by PBMCs from Adult vs. Senior group. In summary, nutritionally relevant concentrations of OLE and HT elicit no anti-inflammatory effect and influence the frequency of immune cell subsets with age-related different outcomes.

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.

The Effect of a Hydroxytyrosol-Rich, Olive-Derived Phytocomplex on Aerobic Exercise and Acute Recovery

There is current scientific interest in naturally sourced phenolic compounds and their potential benefits to health, as well as the effective role polyphenols may provide in an exercise setting. This study investigated the chronic effects of supplementation with a biodynamic and organic olive fruit water phytocomplex (OliPhenolia® [OliP]), rich in hydroxytyrosol (HT), on submaximal and exhaustive exercise performance and respiratory markers of recovery. Twenty-nine recreationally active participants (42 ± 2 yrs; 71.1 ± 2.1 kg; 1.76 ± 0.02 m) consumed 2 × 28 mL∙d−1 of OliP or a taste- and appearance-matched placebo (PL) over 16 consecutive days. Participants completed a demanding, aerobic exercise protocol at ~75% maximal oxygen uptake (V˙O2max) for 65 min 24 h before sub- and maximal performance exercise tests prior to and following the 16-day consumption period. OliP reduced the time constant (τ) (p = 0.005) at the onset of exercise, running economy (p = 0.015) at lactate threshold 1 (LT1), as well as the rating of perceived exertion (p = 0.003) at lactate turnpoint (LT2). Additionally, OliP led to modest improvements in acute recovery based upon a shorter time to achieve 50% of the end of exercise V˙O2 value (p = 0.02). Whilst OliP increased time to exhaustion (+4.1 ± 1.8%), this was not significantly different to PL (p > 0.05). Phenolic compounds present in OliP, including HT and related metabolites, may provide benefits for aerobic exercise and acute recovery in recreationally active individuals. Further research is needed to determine whether dose-response or adjunct use of OliP alongside longer-term training programs can further modulate exercise-associated adaptations in recreationally active individuals, or indeed support athletic performance.

Wnt/β-Catenin Pathway in Experimental Model of Fibromyalgia: Role of Hidrox®

Fibromyalgia (FM) is a chronic condition characterized by persistent widespread pain that negatively affects the quality of life of patients. The WNT/β-catenin signaling pathway seems to be involved in central sensitization and different pain states. The objective of this study was to investigate the beneficial effects of a new compound called Hidrox^® (HD), containing 40-50% hydroxytyrosol, in counteracting the pain associated with FM. An FM-like model was induced in rats by subcutaneous injections of reserpine (1 mg/kg) for three consecutive days. Later, HD (10 mg/kg) was administered orally to the animals for seven days. Reserpine injections induced WNT/β-catenin pathway activation, release of pro-inflammatory mediators as well as a significant increase in oxidative stress. Daily treatment with HD was able to modulate the WNT/β-catenin and Nrf2 pathways and consequently attenuate the behavioral deficits and microglia activation induced by reserpine injection. These results indicate that nutritional consumption of HD can be considered as a new therapeutic approach for human FM.

Antioxidant Properties of Olive Mill Wastewater Polyphenolic Extracts on Human Endothelial and Vascular Smooth Muscle Cells

This work aims to analyze the chemical and biological evaluation of two extracts obtained by olive mill wastewater (OMW), an olive oil processing byproduct. The exploitation of OMW is becoming an important aspect of development of the sustainable olive oil industry. Here we chemically and biologically evaluated one liquid (L) and one solid (S) extract obtained by liquid–liquid extraction followed by acidic hydrolysis (LLAC). Chemical characterization of the two extracts indicated that S has higher phenol content than L. Hydroxytyrosol and tyrosol were the more abundant phenols in both OMW extracts, with hydroxytyrosol significantly higher in S as compared to L. Both extracts failed to induce cell death when challenged with endothelial cells and vascular smooth muscle cells in cell viability experiments. On the contrary, the higher extract dosages employed significantly affected cell metabolic activity, as indicated by the MTT tests. Their ability to counteract H₂O₂-induced oxidative stress and cell death was assessed to investigate potential antioxidant activities of the extracts. Fluorescence measurements obtained with the reactive oxygen species (ROS) probe H₂DCF-DA indicated strong antioxidant activity of the two OMW extracts in both cell models, as indicated by the inhibition of H₂O₂-induced ROS generation and the counteraction of the oxidative-induced cell death. Our results indicate LLAC-obtained OMW extracts as a safe and useful source of valuable compounds harboring antioxidant activity.

Oxidative Stress Is Increased in Combined Oral Contraceptives Users and Is Positively Associated with High-Sensitivity C-Reactive Protein

Information concerning the mechanisms underlying oxidative stress and low-grade inflammation in young healthy women predisposing eventually to future diseases is scarce. We investigated the relationship of oxidative stress and high-sensitivity C-reactive protein (hsCRP) in fertile-age women by oral combined contraceptive (OC) use. Caucasian Italian healthy non-obese women (n = 290; 100 OC-users; 190 non-OC-users; mean age 23.2 ± 4.7 years) were analyzed. Blood hydroperoxides, as oxidative stress biomarkers, were assessed by Free Oxygen Radical Test (FORT). Serum hsCRP was determined by an ultra-sensitive method (hsCRP). Markedly elevated oxidative stress (≥400 FORT Units) was found in 77.0% of OC-users and 1.6% of non-OC-users, odds ratio (OR) = 209, 95% CI = 60.9–715.4, p < 0.001. Elevated hsCRP levels ≥ 2.0 mg/L, considered risky for cardiovascular diseases (CVDs), were found in 41.0% of OC-users and 9.5% of non-OC-users, OR = 6.6, 95%CI 3.5–12.4, p < 0.001. Hydroperoxides were strongly positively correlated to hsCRP in all women (r_s = 0.622, p < 0.001), in OC-users (r_s = 0.442, p < 0.001), and in non-OC-users (r_s = 0.426, p < 0.001). Women with hydroperoxides ≥ 400 FORT Units were eight times as likely to have hsCRP ≥ 2 mg/L. In non-OC-users only, hydroperoxides values were positively correlated with weight and body mass index, but negatively correlated with red meat, fish and chocolate consumption. Our research is the first finding a strong positive correlation of serum hydroperoxides with hsCRP, a marker of low-grade chronic inflammation, in young healthy women. Further research is needed to elucidate the potential role of these two biomarkers in OC-use associated side-effects, like thromboembolism and other CVDs.