Wide Biological Role of Hydroxytyrosol: Possible Therapeutic and Preventive Properties in Cardiovascular Diseases

The hydroxytyrosol-typed phenylpropanoidglycosides: A phenylpropanoid glycoside family with significant biological activity

Hydroxytyrosol-typed phenylpropanoid glycosides (HPGs), composed of phenylethanol and various complex oligosaccharides, are widespread and abundant in different plant, and have a diverse range of biological activities. All HPGs reported previously have been isolated from natural sources, and most of them showed significant bioactivities, such as anti-inflamatory, anti-cancer, cytoprotection, neuro-protective effects, enzyme-inhibitory, anti-microbial effects, and cardiovascular activity. The goal of this review is to summarize the structures of HPGs reported over the past few decades, as well as to introduce their pharmacological effects. We also introduce the possible relationship between the structures of HPGs and their source plants, as well as the structure-activity relationships of some important activities. This review will serve as a resource for future research into this class of compounds, and demonstrate their potential value.

Enhancement of the biological activity of hydroxytyrosol through its oxidation by laccase from Trametes versicolor

The laccase-catalyzed oxidation of hydroxytyrosol (HT) towards the formation of its bioactive oligomer derivatives was investigated. The biocatalytic oligomerization was catalyzed by laccase from Trametes versicolor in aqueous or various water-miscible organic solvents and deep eutectic solvent (DES)-based media. Mass Spectroscopy and Nuclear Magnetic Resonance were used for the characterization of the products. The solvent system used significantly affects the degree of HT oligomerization. The use of 50 % v/v methanol favored the production of the HT dimer, while other organic solvents as well as DESs led to the formation of hydroxytyrosol trimer and other oligomers. In vitro studies showed that the HT dimer exhibits 3- to 4-fold enhanced antibacterial activity against Gram-positive and Gram-negative bacteria compared to the parent compound. Moreover, the ability of HT dimer to inhibit the activity of soybean lipoxygenase and Candida rugosa lipase was 1.5-fold higher than HT, while molecular docking supported these results. Furthermore, HT dimer showed reduced cytotoxicity against HEK293 cells and exhibited a strong ability to inhibit ROS formation. The enhanced bioactivity of HT dimer indicates that this compound could be considered for use in cosmetics, skin-care products, and nutraceuticals.

Hydroxytyrosol Alleviates Methotrexate-Induced Pulmonary Fibrosis in Rats: Involvement of TGF-β1, Tissue Factor, and VEGF

Methotrexate (MTX) is an indispensable drug used for the treatment of many autoimmune and cancerous diseases. However, its clinical use is associated with serious side effects, such as lung fibrosis. The main objective of this study is to test the hypothesis that hydroxytyrosol (HT) can mitigate MTX-induced lung fibrosis in rats while synergizing MTX anticancer effects. Pulmonary fibrosis was induced in the rats using MTX (14 mg/kg/week, per os (p.o.)). The rats were treated with or without HT (10, 20, and 40 mg/kg/d p.o.) or dexamethasone (DEX; 0.5 mg/kg/d, intraperitoneally (i.p.)) for two weeks concomitantly with MTX. Transforming growth factor beta 1 (TGF-β1), interleukin-4 (IL-4), thromboxane A2 (TXA2), vascular endothelial growth factor (VEGF), 8-hydroxy-2-deoxy-guanosine (8-OHdG), tissue factor (TF) and fibrin were assessed using enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and RT-PCR. Pulmonary fibrosis was manifested by an excessive extracellular matrix (ECM) deposition and a marked increase in TGF-β1 and IL-4 in lung tissues. Furthermore, cotreatment with HT or dexamethasone (DEX) significantly attenuated MTX-induced ECM deposition, TGF-β1, and IL-4 expression. Similarly, HT or DEX notably reduced hydroxyproline contents, TXA2, fibrin, and TF expression in lung tissues. Moreover, using HT or DEX downregulated the gene expression of TF. A significant decrease in lung contents of VEGF, IL-8, and 8-OHdG was also observed in HT + MTX- or DEX + MTX -treated animals in a dose-dependent manner. Collectively, the results of our study suggest that HT might represent a potential protective agent against MTX-induced pulmonary fibrosis.

Protective effects of macromolecular polyphenols, metals (zinc, selenium, and copper) - Polyphenol complexes, and different organs with an emphasis on arsenic poisoning: A review

For the potential health benefits and nutritional value, polyphenols are one of the secondary metabolites of plants that have received extensive research. It has anti-inflammatory and cytotoxicity-reducing properties in addition to a high antioxidant content. Macromolecular polyphenols and polysaccharides are biologically active natural polymers with antioxidant and anti-inflammatory potential. Arsenic is an ecologically toxic metalloid. Arsenic in drinking water is the most common way people come into contact with this metalloid. While arsenic is known to cause cancer, it is also used to treat acute promyelocytic leukemia (APL). The treatment's effectiveness is hampered by the adverse effects it can cause on the body. Oxidative stress, inflammation, and the inability to regulate cell death cause the most adverse effects. Polyphenols and other macromolecules like polysaccharides act as neuroprotectants by mitigating free radical damage, inhibiting nitric oxide (NO) production, lowering A42 fibril formation, boosting antioxidant levels, and controlling apoptosis and inflammation. To prevent the harmful effects of toxins, polyphenols and pectin lower oxidative stress, boost antioxidant levels, improve mitochondrial function, control apoptosis, and suppress inflammation. Therefore, it prevents damage to the heart, liver, kidneys, and reproductive system. This review aims to identify the effects of the polyphenols in conjugation with polysaccharides as an ameliorative strategy for arsenic-induced toxicity in various organs.

The Short-Term Effect of Olive Oil Extract Enriched with Hydroxytyrosol on Cardiovascular Function

Olive is rich in polyphenols such as hydroxytyrosol (HT) that have antioxidative and anti-inflammatory effects. In this study, we examined the short-term effects of olive oil extract (OE) enriched with HT on left atrial function, left ventricular (LV) function, and arterial elastic properties in patients with chronic coronary artery disease (CAD). Sixty-one patients with chronic CAD were enrolled. This randomized study had a two-period, two-sequence crossover (AB/BA) design. Group AB (n = 32) initially received OE capsules (500 mg) enriched with HT (5 mg) (two capsules/day) for 30 days, and after a wash out of 48 h, placebo for another 30 days. The opposite occurred in Group BA (n = 29). Exclusion criteria included age >70 years, diabetes, anemia, hypertension, liver and thyroid disease, malignancy, autoimmune disease, kidney disease, use of corticosteroids, weight loss, excessive exercise dietary intervention, and use of antioxidant vitamins. Patients underwent echocardiography/Doppler and applanation tonometry applied to radial artery at the beginning and end of the study. No significant change regarding Vmax, Vp, Vmin, E wave, A wave, deceleration time, LV ejection fraction, central aortic systolic and pulse pressure, and augmentation index. However, a trend toward improvement of E/e' (P = .062) and pulse wave velocity (P = .091) was observed. Use of OE enriched with HT for a limited time period was associated with a trend toward improvement of LV diastolic function and aortic elastic properties in chronic CAD patients. Studies of longer duration are needed to delineate the effect of this promising agent on cardiovascular function and outcomes in chronic CAD.

From antiquity to contemporary times: how olive oil by-products and waste water can contribute to health

Since antiquity, numerous advantages of olive oil and its by-products have been recognized in various domains, including cooking, skincare, and healthcare. Extra virgin olive oil is a crucial component of the Mediterranean diet; several of its compounds exert antioxidant, anti-proliferative, anti-angiogenic and pro-apoptotic effects against a variety of cancers, and also affect cellular metabolism, targeting cancer cells through their metabolic derangements. Numerous olive tree parts, including leaves, can contribute metabolites useful to human health. Olive mill waste water (OMWW), a dark and pungent liquid residue produced in vast amounts during olive oil extraction, contains high organic matter concentrations that may seriously contaminate the soil and surrounding waters if not managed properly. However, OMWW is a rich source of phytochemicals with various health benefits. In ancient Rome, the farmers would employ what was known as amurca, a mulch-like by-product of olive oil production, for many purposes and applications. Several studies have investigated anti-angiogenic and chemopreventive activities of OMWW extracts. The most prevalent polyphenol in OMWW extracts is hydroxytyrosol (HT). Verbascoside and oleuperin are also abundant. We assessed the impact of one such extract, A009, on endothelial cells (HUVEC) and cancer cells. A009 was anti-angiogenic in several in vitro assays (growth, migration, adhesion) and inhibited angiogenesis in vivo, outperforming HT alone. A009 inhibited cells from several tumors in vitro and in vivo and showed potential cardioprotective effects mitigating cardiotoxicity induced by chemotherapy drugs, commonly used in cancer treatment, and reducing up-regulation of pro-inflammatory markers in cardiomyocytes. Extracts from OMWW and other olive by-products have been evaluated for biological activities by various international research teams. The results obtained make them promising candidates for further development as nutraceutical and cosmeceutical agents or dietary supplement, especially in cancer prevention or even in co-treatments with anti-cancer drugs. Furthermore, their potential to offer cardioprotective benefits opens up avenues for application in the field of cardio-oncology.

Modulation of mi-RNA25/Ox-LDL/NOX4 signaling pathway by polyphenolic compound Hydroxytyrosol as a new avenue to alleviate cisplatin-induced acute kidney injury, a mechanistic study in rats

Acute kidney injury (AKI) caused by Cis is considered one of the most severe adverse effects, which restricts its use and efficacy. This study seeks to examine the potential reno-protective impact of phenolic compound Hydroxytyrosol (HT) against Cis-induced AKI and the possible involvement of the mi-RNA25/Ox-LDL/NOX4 pathway elucidating the probable implicated molecular mechanisms. Forty rats were placed into 5 groups. Group I received saline only. Group II received Cis only. Group III, IV, and V received 20, 50, and 100 mg/kg b.w, of HT, respectively, with Cis delivery. NOX4, Ox-LDL, and gene expression of mi-RNA 25, TNF-α, and HO-1 in renal tissue were detected. HT showed reno-protective effect and significantly upregulated mi-RNA 25 and HO-1 as well as decreased the expression of NOX4, Ox-LDL, and TNF-α. In conclusion, HT may be promising in the fight against Cis-induced AKI through modulation of mi-RNA25/Ox-LDL/NOX4 pathway.

Hydroxytyrosol produced by engineered Escherichia coli strains activates Nrf2/HO-1 pathway: An in vitro and in vivo study

This study explores the biological effects of hydroxytyrosol (HT), produced by the metabolic engineering of Escherichia coli, in a series of in vitro and in vivo experiments. In particular, a metabolically engineered Escherichia coli strain capable of producing HT was constructed and utilized. HEK293 and HeLa cells were exposed to purified HT to determine non-toxic doses that can offer protection against oxidative stress (activation of Nrf2/HO-1 signaling pathway). Male CD-1 mice were orally supplemented with HT to evaluate (1) renal and hepatic toxicity, (2) endogenous system antioxidant response, and (3) activation of Nrf2/HO-1 system in the liver. HT protected cells from oxidative stress through the activation of Nrf2 regulatory network. Activation of Nrf2 signaling pathway was also observed in the hepatic tissue of the mice. HT supplementation was safe and produced differential effects on mice's endogenous antioxidant defense system. HT biosynthesized from genetically modified Escherichia coli strains is an alternative method to produce high-quality HT that exerts favorable effects in the regulation of the organism's response to oxidative stress. Nonetheless, further investigation of the multifactorial action of HT on the antioxidant network regulation is needed.

Positive contribution of hydroxytyrosol-enriched wheat bread to HbA1c levels, lipid profile, markers of inflammation and body weight in subjects with overweight/obesity and type 2 diabetes mellitus

PURPOSE

The aim of the present study was to assess the impact of the daily consumption of bread enriched with hydroxytyrosol on HbA₁c and blood lipid levels, inflammatory markers and weight loss.

METHODS

Sixty adults with overweight/obesity and type 2 diabetes mellitus (29 male, 31 female) participated in a 12-week dietary intervention based on the Mediterranean diet and consumed daily 60 g of conventional whole wheat bread (WWB) or whole wheat bread enriched with hydroxytyrosol (HTB). Anthropometric characteristics were measured and venous blood samples were collected at baseline and at the end of the intervention.

RESULTS

Both groups experienced significant weight loss, body fat and waist circumference decrease (p < 0.001). Nonetheless, a greater body fat mass decrease was observed in the HTB group compared to the WWB group (14.4 ± 1.6 vs 10.2 ± 1.1%, p = 0.038). Significant reductions were also reported in fasting glucose, HbA₁c and blood pressure in both groups (p < 0.05). Regarding glucose and HbA₁c, greater decreases were observed in the intervention group (101.4 ± 19.9 vs. 123.2 ± 43.4 mg/dL, p = 0.015 and 6.0 ± 0.6 vs. 6.4 ± 0.9%, p = 0.093, respectively). At HTB group, significant reductions in blood lipid, insulin, TNF-αand adiponectin levels (p < 0.05) and a marginally significant reduction in leptin levels (p = 0.081) were also reported.

CONCLUSION

Enrichment of bread with HT resulted in significant body fat mass reduction and positive effects on fasting glucose, insulin and HbA₁c levels. It also contributed to reductions in inflammatory markers and blood lipid levels. Incorporation of HT in staple foods, like bread, may improve their nutritional profile and, in terms of a balanced diet, may contribute to the management of chronic diseases.

TRIAL REGISTRATION

The study was prospectively registered in clinicaltrials.gov (24th May 2021).

CLINICALTRIALS

gov Identifier: NCT04899791.

Hydroxytyrosol Interference with Inflammaging via Modulation of Inflammation and Autophagy

Inflammaging refers to a chronic, systemic, low-grade inflammation, driven by immune (mainly macrophages) and non-immune cells stimulated by endogenous/self, misplaced or altered molecules, belonging to physiological aging. This age-related inflammatory status is characterized by increased inflammation and decreased macroautophagy/autophagy (a degradation process that removes unnecessary or dysfunctional cell components). Inflammaging predisposes to age-related diseases, including obesity, type-2 diabetes, cancer, cardiovascular and neurodegenerative disorders, as well as vulnerability to infectious diseases and vaccine failure, representing thus a major target for anti-aging strategies. Phenolic compounds-found in extra-virgin olive oil (EVOO)-are well known for their beneficial effect on longevity. Among them, hydroxytyrosol (HTyr) appears to greatly contribute to healthy aging by its documented potent antioxidant activity. In addition, HTyr can modulate inflammation and autophagy, thus possibly counteracting and reducing inflammaging. In this review, we reference the literature on pure HTyr as a modulatory agent of inflammation and autophagy, in order to highlight its possible interference with inflammaging. This HTyr-mediated activity might contribute to healthy aging and delay the development or progression of diseases related to aging.

A novel strategy against hepatitis B virus: Glycyrrhetnic acid conjugated multi-component synergistic nano-drug delivery system for targeted therapy

It is well known that Glycyrrhetnic acid (GA) has significant liver-targeting and anti-inflammatory effects. Syringopicroside (SYR) and Hydroxytyrosol (HT), the active components of the Chinese herb Syringa oblata Lindl, have earned great reputation for their potential in preventing or treating viral hepatitis type B. Therefore, we loaded SYR and HT into GA-conjugated PEG-PLGA, so that they could target the liver in additional to exerting their own pharmacological effects in a synergistic. However, the in vivo targeting and the low bioavailability of SYR and HT pose a huge challenge. Therefore, we synthesized GA-conjugated multi-component nano-drug delivery system (SH-GPP). SH-GPP had a regular spherical shape with a uniform size distribution of 110.5 ± 3.18 nm. We further evaluated the effects of SH-GPP in vitro and in vivo. In the in vivo experiment, we evaluated the following parameters: the serum ALT and AST values; liver tissue homogenate MDA and SOD; HE staining of the pathological liver sections; and the liver coefficient. In the in vitro studies, the following parameters were evaluated: cellular uptake of SH-GPP; wound healing/scratch assay; cellular apoptosis; cell cycle; HBsAg; and HBeAg content. SH-GPP had better anti-hepatitis B effect than Syringopicroside and hydroxytyrosol (SH) and NPP alone. The targeting ability of GA enabled HT and SYR in GPP to reach the liver accurately, and played a synergistic role to maximize their therapeutic effects. This study provides a novel strategy against hepatitis B virus, and also provides a feasible scheme for improving the low bioavailability of the active components of traditional Chinese medicine.

The Pharmaceutical Formulation Plays a Pivotal Role in Hydroxytyrosol Pharmacokinetics

Current evidence supports the use of extra virgin olive oil (EVOO) and its minor components such as hydroxytyrosol or 3,4-dihydroxyphenyl ethanol (DOPET), to improve cardiovascular and metabolic health. Nevertheless, more intervention studies in humans are needed because some gaps remain in its bioavailability and metabolism. The aim of this study was to investigate the DOPET pharmacokinetics on 20 healthy volunteers by administering a hard enteric-coated capsule containing 7.5 mg of bioactive compound conveyed in EVOO. The treatment was preceded by a washout period with a polyphenol and an alcohol-free diet. Blood and urine samples were collected at baseline and different time points, and free DOPET and metabolites, as well as sulfo- and glucuro-conjugates, were quantified by LC-DAD-ESI-MS/MS analysis. The plasma concentration versus time profiles of free DOPET was analyzed by a non-compartmental approach, and several pharmacokinetic parameters (Cmax, Tmax, T1/2, AUC0–440 min, AUC0–∞, AUCt–∞, AUCextrap_pred, Clast and Kel) were calculated. Results showed that DOPET Cmax (5.5 ng/mL) was reached after 123 min (Tmax), with a T1/2 of 150.53 min. Comparing the data obtained with the literature, the bioavailability of this bioactive compound is about 2.5 times higher, confirming the hypothesis that the pharmaceutical formulation plays a pivotal role in the bioavailability and pharmacokinetics of hydroxytyrosol.

Effects of Hydroxytyrosol in Endothelial Functioning: A Comprehensive Review

Pharmacologists have been emphasizing and applying plant and herbal-based treatments in vascular diseases for decades now. Olives, for example, are a traditional symbol of the Mediterranean diet. Hydroxytyrosol is an olive-derived compound known for its antioxidant and cardioprotective effects. Acknowledging the merit of antioxidants in maintaining endothelial function warrants the application of hydroxytyrosol in endothelial dysfunction salvage and recovery. Endothelial dysfunction (ED) is an impairment of endothelial cells that adversely affects vascular homeostasis. Disturbance in endothelial functioning is a known precursor for atherosclerosis and, subsequently, coronary and peripheral artery disease. However, the effects of hydroxytyrosol on endothelial functioning were not extensively studied, limiting its value either as a nutraceutical supplement or in clinical trials. The action of hydroxytyrosol in endothelial functioning at a cellular and molecular level is gathered and summarized in this review. The favorable effects of hydroxytyrosol in the improvement of endothelial functioning from in vitro and in vivo studies were scrutinized. We conclude that hydroxytyrosol is capable to counteract oxidative stress, inflammation, vascular aging, and arterial stiffness; thus, it is beneficial to preserve endothelial function both in vitro and in vivo. Although not specifically for endothelial dysfunction, hydroxytyrosol safety and efficacy had been demonstrated via in vivo and clinical trials for cardiovascular-related studies.

Oxidized-Multiwalled Carbon Nanotubes as Non-Toxic Nanocarriers for Hydroxytyrosol Delivery in Cells

Carbon nanotubes (CNTs) possess excellent physicochemical and structural properties alongside their nano dimensions, constituting a medical platform for the delivery of different therapeutic molecules and drug systems. Hydroxytyrosol (HT) is a molecule with potent antioxidant properties that, however, is rapidly metabolized in the organism. HT immobilized on functionalized CNTs could improve its oral absorption and protect it against rapid degradation and elimination. This study investigated the effects of cellular oxidized multiwall carbon nanotubes (oxMWCNTs) as biocompatible carriers of HT. The oxidation of MWCNTs via H₂SO₄ and HNO₃ has a double effect since it leads to increased hydrophilicity, while the introduced oxygen functionalities can contribute to the delivery of the drug. The in vitro effects of HT, oxMWCNTS, and oxMWCNTS functionalized with HT (oxMWCNTS_HT) were studied against two different cell lines (NIH/3T3 and Tg/Tg). We evaluated the toxicity (MTT and clonogenic assay), cell cycle arrest, and reactive oxygen species (ROS) formation. Both cell lines coped with oxMWCNTs even at high doses. oxMWCNTS_HT acted as pro-oxidants in Tg/Tg cells and as antioxidants in NIH/3T3 cells. These findings suggest that oxMWCNTs could evolve into a promising nanocarrier suitable for targeted drug delivery in the future.

Hydroxytyrosol Reduces Foam Cell Formation and Endothelial Inflammation Regulating the PPARγ/LXRα/ABCA1 Pathway

Cholesterol accumulation in macrophages leads to the formation of foam cells and increases the risk of developing atherosclerosis. We have verified whether hydroxytyrosol (HT), a phenolic compound with anti-inflammatory and antioxidant properties, can reduce the cholesterol build up in THP-1 macrophage-derived foam cells. We have also investigated the potential mechanisms. Oil Red O staining and high-performance liquid chromatography (HPLC) assays were utilized to detect cellular lipid accumulation and cholesterol content, respectively, in THP-1 macrophages foam cells treated with HT. The impact of HT on cholesterol metabolism-related molecules (SR-A1, CD36, LOX-1, ABCA1, ABCG1, PPARγ and LRX-α) in foam cells was assessed using real-time PCR (RT-qPCR) and Western blot analyses. Finally, the effect of HT on the adhesion of THP-1 monocytes to human vascular endothelial cells (HUVEC) was analyzed to study endothelial activation. We found that HT activates the PPARγ/LXRα pathway to upregulate ABCA1 expression, reducing cholesterol accumulation in foam cells. Moreover, HT significantly inhibited monocyte adhesion and reduced the levels of adhesion factors (ICAM-1 and VCAM-1) and pro-inflammatory factors (IL-6 and TNF-α) in LPS-induced endothelial cells. Taken together, our findings suggest that HT, with its ability to interfere with the import and export of cholesterol, could represent a new therapeutic strategy for the treatment of atherosclerotic disease.

Hydroxytyrosol: Its role in the prevention of cardiovascular diseases

In recent years, non-pharmacology treatments and their effectiveness have gained popularity due to their beneficial properties in the prevention of cardiovascular diseases. Phenolic compounds intake provides a natural means of improving in vivo antioxidant status. Thus, the purpose of this review is to discuss the potential benefits of hydroxytyrosol (HT), a phenolic compound with powerful antioxidant and anti-inflammatory properties, in preventing and reducing cardiovascular risk factors, concretely atherosclerosis. Closer inspection of the studies showed a significant improvement of lipid profile, antioxidant capacity and inflammatory state. A note of caution is due in vitro studies because the lack of validated approaches difficult the goodness of fit with the in vivo and clinical research. However, animal and clinical studies were very encouraging, determining HT supplementation useful on inflammation, oxidative stress, endothelial function and cardiovascular diseases in general.

Phenylboronic Acid-Grafted Chitosan Nanocapsules for Effective Delivery and Controllable Release of Natural Antioxidants: Olive Oil and Hydroxytyrosol

Olives and virgin olive oil (VOO) are a staple of Mediterranean diets and are rich in several beneficial phenolic compounds, including hydroxytyrosol (HT). Therefore, VOO was extracted from Koroneiki olive fruits, and its volatile as well as phenolic components were identified. Meanwhile, in order to upgrade the pharmaceutical capabilities of VOO and HT, a new conjugate phenylboronic acid-chitosan nanoparticles (PBA-CSNPs, NF-1) was fabricated and applied as nanocapsules for implanting high loading and efficient delivery of VOO and HT nanoformulations (NF-2 and NF-3). Due to the H-bonding interactions and boronate ester formation between the hydroxyl groups of the phenolic content of VOO or HT and the PBA groups in the nanocapsules (NF-1), VOO and HT were successfully loaded into the PBA-CSNPs nanocapsules with high loading contents and encapsulation efficacies. The NF-2 and NF-3 nanoformulations demonstrated physicochemical stability, as revealed by their respective zeta potential values, and pH-triggered drug release characteristics. The in vitro studies demonstrated that the nascent nanocapsules were almost completely nontoxic to both healthy and cancer cells, whereas VOO-loaded (NF-2) and HT-loaded nanocapsules (NF-3) showed efficient anti-breast cancer efficiencies. In addition, the antimicrobial and antioxidant potentials of VOO and HT were significantly improved after nanoencapsulation.

Mitochondrial Aging and Senolytic Natural Products with Protective Potential

Living organisms do not disregard the laws of thermodynamics and must therefore consume energy for their survival. In this way, cellular energy exchanges, which aim above all at the production of ATP, a fundamental molecule used by the cell for its metabolisms, favor the formation of waste products that, if not properly disposed of, can contribute to cellular aging and damage. Numerous genes have been linked to aging, with some favoring it (gerontogenes) and others blocking it (longevity pathways). Animal model studies have shown that calorie restriction (CR) may promote longevity pathways, but given the difficult application of CR in humans, research is investigating the use of CR-mimetic substances capable of producing the same effect. These include some phytonutrients such as oleuropein, hydroxytyrosol, epigallo-catechin-gallate, fisetin, quercetin, and curcumin and minerals such as magnesium and selenium. Some of them also have senolytic effects, which promote the apoptosis of defective cells that accumulate over the years (senescent cells) and disrupt normal metabolism. In this article, we review the properties of these natural elements that can promote a longer and healthier life.

Sensitive Detection of Hydroxytyrosol in Extra Virgin Olive Oils with a Novel Biosensor Based on Single-Walled Carbon Nanotubes and Tyrosinase

Hydroxytyrosol (HT) is an important marker for the authenticity and quality assessment of extra virgin olive oils (EVOO). The aim of the study was the qualitative and quantitative determination of hydroxytyrosol in commercial extra virgin olive oils of different origins and varieties using a newly developed biosensor based on a screen-printed electrode modified with single-layer carbon nanotubes and tyrosinase (SPE-SWCNT-Ty). The enzyme was immobilized on a carbon-based screen-printed electrode previously modified with single-layer carbon nanotubes (SPE-SWCNT-Ty) by the drop-and-dry method, followed by cross-linking with glutaraldehyde. The modified electrode surface was characterized by different methods, including electrochemical (cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS)) and spectrometric (Fourier transform infrared (FTIR) spectroscopy) methods. Cyclic voltammetry was used for the quantitative determination of HT, obtaining a detection limit of 3.49 × 10⁻⁸ M and a quantification limit of 1.0 × 10⁻⁷ M, with a wide linearity range (0.49–15.602 µM). The electrochemical performance of the SPE-SWCNT-Ty biosensor was compared with that of the modified SPE-SWCNT sensor, and the results showed increased selectivity and sensitivity of the biosensor due to the electrocatalytic activity of tyrosinase. The results obtained from the quantitative determination of HT showed that commercial EVOOs contain significant amounts of HT, proving the high quality of the finished products. The determination of the antiradical activity of HT was carried out spectrophotometrically using the free reagent galvinoxyl. The results showed that there is a very good correlation between the antiradical capacity of EVOOs, the voltammetric response and implicitly the increased concentration of HT. SPE-SWCNT-Ty has multiple advantages such as sensitivity, selectivity, feasibility and low cost and could be used in routine analysis for quality control of food products such as vegetable oils.

Hydroxytyrosol Alleviated Hypoxia-Mediated PC12 Cell Damage through Activating PI3K/AKT/mTOR-HIF-1α Signaling

Background

Hypoxia exerts pressure on cells and organisms, and this pressure can occur under both pathological and nonpathological conditions. There are many reports confirmed that hydroxytyrosol has good in vitro antioxidant activity, while the research about hydroxytyrosol on hypoxia-mediated cell damage is still unclear.

Purpose

The aim of this study was to investigate the effect and mechanism of hydroxytyrosol on hypoxia-mediated cell damage.

Methods

We studied the effects of hydroxytyrosol on the content of reactive oxygen species, the change of antioxidant enzymes activity of SOD, CAT, and GSH-Px and the content of oxidation products MDA and GSH, and the changes of cell membrane potential and effect on PI3K/AKT/mTOR-HIF-1α signaling pathway under hypoxia-mediated PC12 cell.

Results

PC12 cell treated with hydroxytyrosol abated the cell apoptosis and alleviated the oxidative stress through scavenging of reactive oxygen species, improving the enzyme activity and changing the content of oxidation products and alleviating mitochondria damage. Western blotting confirmed that the mechanism maybe related to the PI3K/AKT/mTOR-HIF-1α signaling pathway. The inhibition experiment confirmed that hydroxytyrosol takes part in the expression of protein PI3K and p-mTOR.

Conclusion

Hydroxytyrosol reduced the oxidative stress and resisted the inhibition of PI3K/AKT/mTOR-HIF-1α signaling pathway caused by hypoxia, improved cell apoptosis, and ameliorated the antihypoxia ability of PC12 cells under hypoxia.

Availability and Metabolic Fate of Olive Phenolic Alcohols Hydroxytyrosol and Tyrosol in the Human GI Tract Simulated by the In Vitro GIDM-Colon Model

Hydroxytyrosol (HTyr) and tyrosol (Tyr) are the most well studied phenolic alcohols of olive oil and olive products demonstrating numerous and significant beneficial health effects. However, their activity in the human organism as food bioactives is strongly associated with their bioavailability and metabolism, while manifested through their metabolites. Nevertheless, there are limited studies investigating their biotransformation and mainly catabolism by gut microflora under a holistic interpretation close to the human organism. Thus, in the present study, the GastroIntestinal Dialysis (GIDM)-colon model, a continuous flow in vitro dialysis system mimicking physiological conditions during human gastrointestinal digestion, was used to explore the metabolism of HTyr and Tyr as pure compounds. The GIDM-colon model simulates absorption from the lumen to the mucosa, followed by the colon phase using pooled human fecal suspensions. Samples were collected at different time points and analyzed via LC-Orbitrap MS. An integrated approach combining Multivariate Data Analysis (MVA) and thorough dereplication procedures led to the identification of HTyr and Tyr metabolites in different phases (gastric, small intestine, and colon), yielding also valuable information about metabolites kinetics. To our knowledge, this is the first study reporting full spectrometric data of HTyr and Tyr metabolites along with possible transformation mechanisms in the GI tract.

An Olive-Derived Extract 20% Rich in Hydroxytyrosol Prevents β-Amyloid Aggregation and Oxidative Stress, Two Features of Alzheimer Disease, via SKN-1/NRF2 and HSP-16.2 in Caenorhabditis elegans

Olive milling produces olive oil and different by-products, all of them very rich in different bioactive compounds like the phenolic alcohol hydroxytyrosol. The aim of the present study was to investigate the effects of an olive fruit extract 20% rich in hydroxytyrosol on the molecular mechanisms associated with Alzheimer disease features like Aβ- and tau- induced toxicity, as well as on oxidative stress in Caenorhabditis elegans. Moreover, characterization of the extracts, regarding the profile and content of phenolics, as well as total antioxidant ability, was investigated. The study of lethality, growth, pharyngeal pumping, and longevity in vivo demonstrated the lack of toxicity of the extract. One hundred μg/mL of extract treatment revealed prevention of oxidative stress and a delay in Aβ-induced paralysis related with a lower presence of Aβ aggregates. Indeed, the extract showed the ability to avoid a certain degree of proteotoxicity associated with aggregation of the tau protein. According to RNAi tests, SKN-1/NRF2 transcription factor and the overexpression of HSP-16.2 were mechanistically associated in the observed effects.

Angioprevention of Urologic Cancers by Plant-Derived Foods

The number of cancer cases worldwide keeps growing unstoppably, despite the undeniable advances achieved by basic research and clinical practice. Urologic tumors, including some as prevalent as prostate, bladder or kidney tumors, are no exceptions to this rule. Moreover, the fact that many of these tumors are detected in early stages lengthens the duration of their treatment, with a significant increase in health care costs. In this scenario, prevention offers the most cost-effective long-term strategy for the global control of these diseases. Although specialized diets are not the only way to decrease the chances to develop cancer, epidemiological evidence support the role of certain plant-derived foods in the prevention of urologic cancer. In many cases, these plants are rich in antiangiogenic phytochemicals, which could be responsible for their protective or angiopreventive properties. Angiogenesis inhibition may contribute to slow down the progression of the tumor at very different stages and, for this reason, angiopreventive strategies could be implemented at different levels of chemoprevention, depending on the targeted population. In this review, epidemiological evidence supporting the role of certain plant-derived foods in urologic cancer prevention are presented, with particular emphasis on their content in bioactive phytochemicals that could be used in the angioprevention of cancer.

Production of biologically active hydroxytyrosol rich extract via catalytic conversion of tyrosol

An effective and economical process was established to produce hydroxytyrosol, a naturally occurring orthodiphenolic antioxidant molecule found in olive oil from its monophenolic precursor tyrosol. The approach proposed in the present work presents an environment-friendly method based on wet hydrogen peroxide catalytic oxidation with montmorillonite KSF as an inexpensive and environmentally benign solid acid at room temperature. The influence of the principal operating parameters including concentration of tyrosol, H₂O₂, and catalyst used were studied. The antioxidant activity was realized by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. High antioxidant activity was detected according to the high hydroxytyrosol production (IC₅₀ = 0.7 μg mL⁻¹). The bactericidal and fungicidal properties of hydroxytyrosol rich extract were investigated using the NCCLS broth dilution and EN 1276 standard methods. Positive bactericidal and fungicidal effects of concentrations ranging between 1–0.5 g L⁻¹ and 4–2 g L⁻¹ were obtained.

An effective and economical process was established to produce hydroxytyrosol, a natural antioxidant molecule.

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.

Nutrigenomic Effect of Hydroxytyrosol in Vascular Endothelial Cells: A Transcriptomic Profile Analysis

Hydroxytyrosol (HT), a peculiar olive and olive oil phenolic antioxidant, plays a significant role in the endothelial and cardiovascular protection associated with olive oil consumption. However, studies examining the effects of HT on the whole-genome expression of endothelial cells, which are prominent targets for vasculo-protective effects of olive oil polyphenols, have been lacking. This study aims to comprehensively evaluate the genomic effects exerted by HT, at the transcriptional level, in endothelial cells under resting or proinflammatory conditions. Human umbilical vein endothelial cells (HUVECs) were treated with 10 µmol/L HT for 1 h and then stimulated with 5 ng/mL interleukin (IL)-1β for 3 h. Total RNA was extracted, and gene expression profile assessed with microarray analysis. Functional enrichment analysis and pathway analysis were performed by Ingenuity Pathways Analysis. Microarray data were validated by qRT-PCR. Fixing a significance threshold at 1.5-fold change, HT affected the expression of 708 and 599 genes, respectively, in HUVECs under resting and IL-1β-stimulated conditions; among these, 190 were common to both conditions. Unfolded protein response (UPR) and endoplasmic reticulum stress resulted from the two top canonical pathways common between HT and HT-IL-1β affected genes. IL-17F/A signaling was found in the top canonical pathways of HT modified genes under resting unstimulated conditions, whereas cardiac hypertrophy signaling was identified among the pathways affected by HT-IL-1β. The transcriptomic analysis allowed pinpointing immunological, inflammatory, proliferative, and metabolic-related pathways as the most affected by HT in endothelial cells. It also revealed previously unsuspected genes and related gene pathways affected by HT, thus broadening our knowledge of its biological properties. The unbiased identification of novel genes regulated by HT improves our understanding of mechanisms by which olive oil prevents or attenuates inflammatory diseases and identifies new genes to be enquired as potential contributors to the inter-individual variation in response to functional food consumption.

Metabolic engineering of Saccharomyces cerevisiae for hydroxytyrosol overproduction directly from glucose

Hydroxytyrosol (HT) is one of the most powerful dietary antioxidants with numerous applications in different areas, including cosmetics, nutraceuticals and food. In the present work, heterologous hydroxylase complex HpaBC from Escherichia coli was integrated into the Saccharomyces cerevisiae genome in multiple copies. HT productivity was increased by redirecting the metabolic flux towards tyrosol synthesis to avoid exogenous tyrosol or tyrosine supplementation. After evaluating the potential of our selected strain as an HT producer from glucose, we adjusted the medium composition for HT production. The combination of the selected modifications in our engineered strain, combined with culture conditions optimization, resulted in a titre of approximately 375 mg l⁻¹ of HT obtained from shake‐flask fermentation using a minimal synthetic‐defined medium with 160 g l⁻¹ glucose as the sole carbon source. To the best of our knowledge, this is the highest HT concentration produced by an engineered S. cerevisiae strain.

Beneficial effects of dietary supplementation with olive oil, oleic acid, or hydroxytyrosol in metabolic syndrome: Systematic review and meta-analysis

BACKGROUND AND AIMS

Olive oil and components might have a beneficial effect on Metabolic Syndrome (MetS). The aim of this review and meta-analysis was to assess whether those effects are related to hydroxytyrosol or oleic acid contents, or the combination of them as olive oil, and how powerful is this effect.

METHODS

A systematic literature search was performed in MEDLINE via Pubmed, Web of Science (WOS) core collection, and Virtual Health Library (VHL) via LILACS and IBECS (Spain). MeSH terms used were "obesity", "body weight", "body mass index", "adipose tissue", "lipid metabolism", "LDL", "HDL", "VLDL", "insulin resistance", "glucose", "insulin", "hypertension", "arterial pressure", "olive oil", "oleic acid", and other (non-MeSH) terms: "total antioxidant capacity", "total antioxidant status", "hydroxytyrosol" (PROSPERO ID: CRD42021247614). Results of the included studies were meta-analyzed with the RevMan 5.3 program, assuming a random effects model.

RESULTS

76 articles (67 different trials) were identified. Hydroxytyrosol had no effect on MetS [combined standardized mean differences (SMD) = 0.01 (CI 95%: [-0.23, 0.25], I² = 83%; p = 0.920)]. Oleic acid had no significant beneficial effect on MetS [SMD = 0.03 (CI 95%: [-0.01, 0.07], I² = 0%); p = 0.150], but it improved lipid profile [SMD = 0.06 (CI 95%: [-0.00, 0.12], I² = 0%); p = 0. 050]. Olive oil had no effect on MetS [SMD = -0.01 (CI 95%: [-0.05, 0.03]), I² = 55%; p = 0.550)]. The supplementation with hydroxytyrosol, oleic acid or olive oil showed a beneficial effect on antioxidant capacity related to components of MetS [SMD = 0.31 (CI 95%: [-0.34, 0.95], I² = 81%)]; p = 0.35).

CONCLUSION

Most articles compared olive oil and oleic acid with other strategies specially designed for MetS management. Our findings suggest that olive oil or oleic acid consumption are as good as the other strategies to manage MetS.

Evaluation of Polyphenol Content and Antioxidant Capacity of Aqueous Extracts from Eight Medicinal Plants from Reunion Island: Protection against Oxidative Stress in Red Blood Cells and Preadipocytes

Background—Medicinal plants are traditionally used as infusions or decoctions for their antioxidant, anti-inflammatory, hypolipidemic and anti-diabetic properties. Purpose—The aim of the study was to define the polyphenol composition and to assess the antioxidant capacity of eight medicinal plants from Reunion Island referred to in the French Pharmacopeia, namely Aphloia theiformis, Ayapana triplinervis, Dodonaea viscosa, Hubertia ambavilla, Hypericum lanceolatum, Pelargonium x graveolens, Psiloxylon mauritianum and Syzygium cumini. Methods—Polyphenol content was assessed by biochemical assay and liquid chromatography coupled to mass spectrometry. Antioxidant capacity was assessed by measuring DPPH reduction and studying the protective effects of herbal preparation on red blood cells or preadipocytes exposed to oxidative stress. Results—Polyphenol content ranged from 25 to 143 mg gallic acid equivalent (GAE)/L for infusions and 35 to 205 mg GAE/L for decoctions. Liquid chromatography coupled to mass spectrometry analysis showed the presence of major bioactive polyphenols, such as quercetin, chlorogenic acid, procyanidin and mangiferin. Antioxidant capacity assessed by different tests, including DPPH and Human red blood cell (RBC) hemolysis of herbal preparations, demonstrated a dose-dependent effect whatever the extraction procedure. Our data suggest that decoction slightly improved polyphenol extraction as well as antioxidant capacity relative to the infusion mode of extraction (DPPH test). However, infusions displayed a better protective effect against oxidative stress-induced RBC hemolysis. Conclusion—Traditional preparations of medicinal plant aqueous extracts (infusions and decoctions) display antioxidant properties that limit oxidative stress in preadipocytes and red blood cells, supporting their use in the context of metabolic disease prevention and treatment.