Anti-proliferative and pro-apoptotic activities of hydroxytyrosol on different tumour cells: the role of extracellular production of hydrogen peroxide

Impact of pharmacokinetic enhancement strategies on the antimicrobial and antioxidant activities of hydroxytyrosol

Hydroxytyrosol (HTyr), a plant-derived phenolic compound found in Olea europaea L. products and by-products, is well-known for its antioxidant activity and a wide range of biological effects, including anti-inflammatory, anticancer, antiviral, cardioprotective, neuroprotective, and antibacterial properties. However, due to its high hydrophilicity, HTyr exhibits unfavorable pharmacokinetic properties, preventing its potential therapeutic use. Various strategies can be employed to address these limitations. In this study, we evaluated the effect of two specific approaches on the HTyr antimicrobial and antioxidant activities: chemical modification of HTyr by lipophilization of the alcoholic moiety and encapsulation in liposomes. Based on our experience in the synthesis and biological activities of HTyr derivatives, the attention was focused on HTyr oleate (HTyr-OL), having a C-18 unsaturated alkylic chain responsible for an increased lipophilicity compared to HTyr. This structural feature enhanced antimicrobial activity against both tested strains of S. aureus, ATCC 25923 (wild-type strain) and ATCC 33591 (MRSA), and comparable antioxidant activity against two different radicals, Galvinoxyl radical and 1,1-diphenyl-2-picrylhydrazyl radical. Moreover, liposomes as delivery systems for HTyr and HTyr-OL were developed using both natural and synthetic amphiphiles, and the impact of encapsulation on their activities was further investigated. The experimental results showed that the antimicrobial properties of HTyr and HTyr-OL against S. aureus strains were not enhanced after encapsulation in liposomes, while the high antioxidant activity of HTyr-OL was preserved when conveyed in liposomes.

Exploring the Biological Potential of Hydroxytyrosol and Derivatives: Synthetic Strategies and Evaluation of Antiproliferative, Antioxidant, and Antimicrobial Activities

Phenolic compounds found in Extra Virgin Olive Oil (EVOO) have been associated with various health benefits. Bioavailability studies indicate that the phase I and II metabolites of these phenolic compounds can be detected in human urine and plasma following EVOO consumption. To contribute to the understanding of the biological potential of these phenolic compounds and their metabolites, this study delves into the synthesis, stability, and biological activities of hydroxytyrosol (HT), tyrosol (Tyr), and homovanillic alcohol (HVA), as well as their glucuronide, sulfate, and acetylated metabolites. For the first time, an effective synthesis was developed to allow the selective obtention of 3'- and 4'-glucuronides, as well as sulfates of HT. HT and its acetylated derivative emerged as the most potent compounds across antioxidant assessments, antiproliferative studies against human colorectal adenocarcinoma cell lines, and antimicrobial assays.

Hydroxytyrosol isolation, comparison of synthetic routes and potential biological activities

Hydroxytyrosol (HT) is a polyphenol found in the olive plant (Olea europaea) that has garnered attention from the food, feed, supplement, and pharmaceutical industries. HT has evolved from basic separation and extraction to chemical and biocatalytic synthesis. The yield of HT can reach 1.93 g/L/h through chemical synthesis and 7.7 g/L/h through biocatalysis; however, both methods are subject to inherent limitations. Furthermore, the potential health benefits associated with HT have been highlighted, including its ability to act as an antioxidant, reduce inflammation, combat cancer and obesity, and exert antibacterial and antiviral effects. Its neuroprotective effects, skin protection, and wound healing capabilities are also discussed. Given these remarkable biological properties, HT stands out as one of the most extensively investigated natural phenols. This review highlights future methods and pathways for the synthesis of HT, providing insights based on its bioactivity characteristics, health benefits, and potential future applications.

Generation of Hydrogen Peroxide in Cancer Cells: Advancing Therapeutic Approaches for Cancer Treatment

Cancer cells show altered antioxidant defense systems, dysregulated redox signaling, and increased generation of reactive oxygen species (ROS). Targeting cancer cells through ROS-mediated mechanisms has emerged as a significant therapeutic strategy due to its implications in cancer progression, survival, and resistance. Extensive research has focused on selective generation of H2O2 in cancer cells for selective cancer cell killing by employing various strategies such as metal-based prodrugs, photodynamic therapy, enzyme-based systems, nano-particle mediated approaches, chemical modulators, and combination therapies. Many of these H2O2-amplifying approaches have demonstrated promising anticancer effects and selectivity in preclinical investigations. They selectively induce cytotoxicity in cancer cells while sparing normal cells, sensitize resistant cells, and modulate the tumor microenvironment. However, challenges remain in achieving selectivity, addressing tumor heterogeneity, ensuring efficient delivery, and managing safety and toxicity. To address those issues, H2O2-generating agents have been combined with other treatments leading to optimized combination therapies. This review focuses on various chemical agents/approaches that kill cancer cells via H2O2-mediated mechanisms. Different categories of compounds that selectively generate H2O2 in cancer cells are summarized, their underlying mechanisms and function are elucidated, preclinical and clinical studies as well as recent advancements are discussed, and their prospects as targeted therapeutic agents and their therapeutic utility in combination with other treatments are explored. By understanding the potential of these compounds, researchers can pave the way for the development of effective and personalized cancer treatments.

Beneficial Effect of Olive Oil and Its Derivates: Focus on Hematological Neoplasm

Olive oil (Olea europaea) is one of the major components of the Mediterranean diet and is composed of a greater percentage of monounsaturated fatty acids, such as oleic acid; polyunsaturated fatty acids, such as linoleic acid; and minor compounds, such as phenolic compounds, and particularly hydroxytyrosol. The latter, in fact, are of greater interest since they have found widespread use in popular medicine. In recent years, it has been documented that phenolic acids and in particular hydroxytyrosol have anti-inflammatory, antioxidant, and antiproliferative action and therefore interest in their possible use in clinical practice and in particular in neoplasms, both solid and hematological, has arisen. This work aims to summarize and analyze the studies present in the literature, both in vitro and in vivo, on the possible use of minor components of olive oil in some hematological neoplasms. In recent years, in fact, interest in nutraceutical science has expanded as a possible adjuvant in the treatment of neoplastic pathologies. Although it is worth underlining that, regarding the object of our study, there are still few preclinical and clinical studies, it is, however, possible to document a role of possible interest in clinical practice.

Anti-Cancer, Anti-Angiogenic, and Anti-Atherogenic Potential of Key Phenolic Compounds from Virgin Olive Oil

The Mediterranean diet, renowned for its health benefits, especially in reducing cardiovascular risks and protecting against diseases like diabetes and cancer, emphasizes virgin olive oil as a key contributor to these advantages. Despite being a minor fraction, the phenolic compounds in olive oil significantly contribute to its bioactive effects. This review examines the bioactive properties of hydroxytyrosol and related molecules, including naturally occurring compounds (-)-oleocanthal and (-)-oleacein, as well as semisynthetic derivatives like hydroxytyrosyl esters and alkyl ethers. (-)-Oleocanthal and (-)-oleacein show promising anti-tumor and anti-inflammatory properties, which are particularly underexplored in the case of (-)-oleacein. Additionally, hydroxytyrosyl esters exhibit similar effectiveness to hydroxytyrosol, while certain alkyl ethers surpass their precursor's properties. Remarkably, the emerging research field of the effects of phenolic molecules related to virgin olive oil on cell autophagy presents significant opportunities for underscoring the anti-cancer and neuroprotective properties of these molecules. Furthermore, promising clinical data from studies on hydroxytyrosol, (-)-oleacein, and (-)-oleocanthal urge further investigation and support the initiation of clinical trials with semisynthetic hydroxytyrosol derivatives. This review provides valuable insights into the potential applications of olive oil-derived phenolics in preventing and managing diseases associated with cancer, angiogenesis, and atherosclerosis.

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.

Next-generation sequencing reveals altered gene expression and enriched pathways in triple-negative breast cancer cells treated with oleuropein and oleocanthal

Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by poor prognosis and limited treatment options. Oleuropein and oleocanthal are bioactive chemicals found in extra-virgin olive oil; they have been shown to have anti-cancer potential. In this study, we examined the inhibitory effects of these two natural compounds, on MDA-MB-231 and MDA-MB-468 TNBC cell lines. The human TNBC MDA-MB-231 and MDA-MB-468 cell lines were treated with oleuropein or oleocanthal at ranging concentrations for 48 h. After determining the optimum concentration to reach IC50, using the sulforhodamine B assay, total RNA was extracted after 12, 24, and 48 h from treated and untreated cells. Poly(A)-RNA selection was conducted, followed by library construction and RNA sequencing. Differential gene expression (DEG) analysis was performed to identify DEGs between treated and untreated cells. Pathway analysis was carried out using the KEGG and GO databases. Oleuropein and oleocanthal considerably reduced the proliferation of TNBC cells, with oleocanthal having a slightly stronger effect than oleuropein. Furthermore, multi-time series RNA sequencing showed that the expression profile of TNBC cells was significantly altered after treatment with these compounds, with temporal dynamics and groups of genes consistently affected at all time points. Pathway analysis revealed several significant pathways associated with TNBC, including cell death, apoptotic process, programmed cell death, response to stress, mitotic cell cycle process, cell division, and cancer progression. Our findings suggest that oleuropein and oleocanthal have potential therapeutic benefits for TNBC and can be further investigated as alternative treatment options.

Inhibition of Endothelial Inflammatory Response by HT-C6, a Hydroxytyrosol Alkyl Ether Derivative

Hydroxytyrosol (HT) is a bioactive phenolic compound naturally present in olives and extra virgin olive oil (EVOO) which is described as an antioxidant, antitumoral and antiangiogenic molecule. Previous studies of semi-synthetic HT-derivatives presented the hydroxytyrosyl alkyl ether HT-C6 as one of the most potent derivatives studied in the context of antioxidant, anti-platelet and antiangiogenic assays, but its direct effect on inflammation was not reported. In this work, we use RT-qPCR measure of gene expression, protein analysis by Western-blot and immunofluorescence techniques, adhesion and migration functional assays and single-cell monitoring of reactive oxygen species (ROS) in order to explore in vitro the ability of HT-C6 to interfere in the inflammatory response of endothelial cells (ECs). Our results showed that HT-C6 strongly reduces the TNF-α-induced expression of vascular cell adhesion molecule 1 (VCAM1), intercellular cell adhesion molecule 1 (ICAM1), E-selectin (SELE), C-C motif chemokine ligand 2 and 5 (CCL2 and CCL5) in HUVECs, impairing the chemotactic and adhesion potential of these cells towards THP-1 monocytes in vitro. In this work, we define a mechanism of action underlying the anti-inflammatory effect of HT-C6, which involves the abrogation of nuclear factor kappa B (NF-κB) pathway activation in ECs. These results, together with the ability of HT-C6 to reduce ROS formation in ECs, point to this compound as a promising HT-derivative to be tested in the treatment of atherosclerosis.

Hydroxytyrosol-rich extract from olive juice as an additive in gilthead sea bream juveniles fed a high-fat diet: Regulation of somatic growth

The dietary inclusion of plant-based products in fish feeds formulation is required for the sustainable development of aquaculture. Moreover, considering functional diets, hydroxytyrosol, one of the major phenolic compounds found in olives (Olea europaea), has been identified as a potential candidate to be used in the aquafeeds industry due to its health promoting abilities. The aim of this study was to evaluate the effects of the inclusion of an olive juice extract rich in hydroxytyrosol as an additive (0.52 g HT/kg feed) in a high-fat (24% lipids) diet in gilthead sea bream (Sparus aurata) juveniles. Moreover, the experimental diets, with or without the extract, were administered daily at a standard (3% of total biomass in the tank) or restricted ration (40% reduction) for 8–9 weeks. Growth and biometric parameters, insulin-like growth factor 1 (IGF-1) plasma levels and growth hormone/IGF axis-, myogenic- and osteogenic-related genes expression in liver, white muscle and/or bone were analyzed. Moreover, in vitro cultures of vertebra bone-derived cells from fish fed the diets at a standard ration were performed at weeks 3 and 9 to explore the effects of hydroxytyrosol on osteoblasts development. Although neither body weight or any other biometric parameter were affected by diet composition after 4 or 8 weeks, the addition of the hydroxytyrosol-rich extract to the diet increased IGF-1 plasma levels, regardless of the ration regime, suggesting an anabolic condition. In muscle, the higher mRNA levels of the binding protein igfbp-5b and the myoblast fusion marker dock5 in fish fed with the hydroxytyrosol-rich diet suggested that this compound may have a role in muscle, inducing development and a better muscular condition. Furthermore in bone, increased osteogenic potential while delayed matrix mineralization after addition to the diet of the olive juice extract was supported by the upregulated expression of igf-1 and bmp4 and reduced transcript levels of osteopontin. Overall, this study provides new insights into the beneficial use of hydroxytyrosol as a dietary additive in gilthead sea bream functional diets to improve muscle-skeletal condition and, the aquaculture industry.

Valorization of an Underutilized Waste from Olive Oil Production by Recovery of Hydroxytyrosol

Hydroxytyrosol (HT) is one of the most powerful natural antioxidants, mainly contained in olive oil and its by-products. Here, a procedure for the preparation of an HT-enriched sample is described. An acidic aqueous extract (pH 1.25) from Olive Oil Dregs (OOD), a by-product from oil mills, was prepared by incubation at 37 °C for 1 h. The total phenolic content and HT amount were 6.24 ± 0.10 mg gallic acid equivalent/g OOD and 532.98 ± 5.78 μg/g OOD, respectively. Amberlite XAD16N and XAD7HP resins were used for the recovery of HT from the raw extract. Several elution conditions were tested with both resins, and elution with 25% ethanol provided the highest HT recovery (92.50% from XAD7HP). Antioxidant activities were assessed in the pool containing the highest quantity of HT. The results were compared with those of the raw extract. Ferric reducing antioxidant power values were comparable (95.71 ± 2.50 and 96.64 ± 13.47 μg ascorbic acid equivalent/mg for HT-enriched pool and raw extract, respectively), while the radical scavenging activity was higher for the pool (92.83% ± 0.44 and 44.12% ± 1.82, respectively). The results reported here demonstrate that HT can be recovered with a high yield from OOD, providing a preparation with high radical scavenging power. In addition, it is proved that this by-product, poorly considered up to now, can be usefully exploited.

Involvement of the PI3K/AKT Intracellular Signaling Pathway in the AntiCancer Activity of Hydroxytyrosol, a Polyphenol from Olea europaea, in Hematological Cells and Implication of HSP60 Levels in Its Anti-Inflammatory Activity

Hydroxytyrosol (HT), the main representative of polyphenols of olive oil, has been described as one of the most powerful natural antioxidants, also showing anti-inflammatory, antimicrobial, cardioprotective and anticancer activity in different type of cancers, but has been little studied in hematological neoplasms. The objective of this work was to evaluate the anticancer potential of HT in acute human leukemia T cells (Jurkat and HL60) and the anti-inflammatory potential in murine macrophages (Raw264.7). For this, cytotoxicity tests were performed for HT, showing IC₅₀ values, at 24 h, for Jurkat, HL60 and Raw264.7 cells, of 27.3 µg·mL⁻¹, 109.8 µg·mL⁻¹ and 45.7 µg·mL⁻¹, respectively. At the same time, HT caused cell arrest in G₀/G₁ phase in both Jurkat and HL60 cells by increasing G₀/G₁ phase and significantly decreasing S phase. Apoptosis and cell cycle assays revealed an antiproliferative effect of HT, decreasing the percentage of dividing cells and increasing apoptosis. Furthermore, HT inhibited the PI3K signaling pathway and, consequently, the MAPK pathway was activated. Inflammation tests revealed that HT acts as an anti-inflammatory agent, reducing NO levels in Raw264.7 cells previously stimulated by lipopolysaccharide (LPS). These processes were confirmed by the changes in the expression of the main markers of inflammation and cancer. In conclusion, HT has an anticancer and anti-inflammatory effect in the cell lines studied, which were Raw264.7, Jurkat, and HL60, and could be used as a natural drug in the treatment of liquid cancers, leukemias, myelomas and lymphomas.

Nutraceutical Role of Polyphenols and Triterpenes Present in the Extracts of Fruits and Leaves of Olea europaea as Antioxidants, Anti-Infectives and Anticancer Agents on Healthy Growth

There is currently a worldwide consensus and recognition of the undoubted health benefits of the so-called Mediterranean diet, with its intake being associated with a lower risk of mortality. The most important characteristics of this type of diet are based on the consumption of significant amounts of fruit, vegetables, legumes, and nuts, which provide, in addition to some active ingredients, fiber and a proportion of vegetable protein, together with extra virgin olive oil (EVOO) as the main sources of vegetable fat. Fish and meat from poultry and other small farm animals are the main sources of protein. One of the main components, as already mentioned, is EVOO, which is rich in monounsaturated fatty acids and to a lesser extent in polyunsaturated fatty acids. The intake of this type of nutrient also provides an important set of phytochemicals whose health potential is widely spread and agreed upon. These phytochemicals include significant amounts of anthocyanins, stilbenes, flavonoids, phenolic acids, and terpenes of varying complexities. Therefore, the inclusion in the diet of this type of molecules, with a proven healthy effect, provides an unquestionable preventive and/or curative activity on an important group of pathologies related to cardiovascular, infectious, and cancerous diseases, as well as those related to the metabolic syndrome. The aim of this review is therefore to shed light on the nutraceutical role of two of the main phytochemicals present in Olea europaea fruit and leaf extracts, polyphenols, and triterpenes, on healthy animal growth. Their immunomodulatory, anti-infective, antioxidant, anti-aging, and anti-carcinogenic capabilities show them to be potential nutraceuticals, providing healthy growth.

Influence of Olive Oil and Its Components on Breast Cancer: Molecular Mechanisms

Breast cancer is the most frequent malignant neoplasia and a leading cause of mortality in women worldwide. The Mediterranean diet has been proposed as a healthy dietary pattern with protective effects in several chronic diseases, including breast cancer. This diet is characterized by the consumption of abundant plant foods and olive oil as the principal source of fat, which is considered one of the main components with potential antioxidant, anti-inflammatory and anticancer effects. Extra-virgin olive oil (EVOO) has several bioactive compounds, mainly including monounsaturated fatty acids, triterpenes and polyphenols, such as phenolic alcohols (e.g., hydroxytyrosol), secoiridoids (e.g., oleuropein and oleocanthal), lignans (e.g., pinoresinol) or flavonoids (e.g., luteolin). While epidemiological evidence is still limited, experimental in vivo and in vitro data have shown a protective effect of this oil and its compounds on mammary carcinogenesis. Such effects account through complex and multiple mechanisms, including changes in epigenetics, transcriptome and protein expression that modulate several signaling pathways. Molecular targets of EVOO compounds have a role in the acquisition of cancer hallmarks. Although further research is needed to elucidate their beneficial effects on human prevention and progression of the disease, evidence points to EVOO in the context of the Mediterranean diet as a heathy choice, while EVOO components may be promising adjuvants in anticancer strategies.

Potential of olive oil and its phenolic compounds as therapeutic intervention against colorectal cancer: a comprehensive review

Colorectal cancer (CRC) is one of the major causes of death across the world and incidence rate of CRC increasing alarmingly each passing year. Diet, genomic anomalies, inflammation and deregulated signalling pathways are among the major causes of CRC. Because of numerous side effects of CRC therapies available now, researchers all over the world looking for alternative treatment/preventive strategy with lesser/no side effects. Olive oil which is part of Mediterranean diet contains numerous phenolic compounds that fight against free radicals and inflammation and also well-known for protective role against CRC. The current review focused on the recent evidences where olive oil and its phenolic compounds such as hydroxytyrosol, oleuropein and oleocanthal showed activities against CRC as well to analyse the cellular and molecular signalling mechanism through which these compounds act on. These compounds shown to combat CRC by reducing proliferation, migration, invasion and angiogenesis through regulation of numerous signalling pathways including MAPK pathway, PI3K-Akt pathway and Wnt/β-catenin pathway and at the same time, induce apoptosis in different CRC model. However, further research is an absolute necessity to establish these compounds as nutritional supplements and develop therapeutic strategy in CRC.

Discovery of hydroxytyrosol as thioredoxin reductase 1 inhibitor to induce apoptosis and G1/S cell cycle arrest in human colorectal cancer cells via ROS generation

Colorectal cancer (CRC) is one of the most common cancer types and a leading cause of cancer-associated mortality in China. Increased thioredoxin reductase 1 (TrxR1) levels have been previously identified as possible target for CRC. The present study revealed that the natural product hydroxytyrosol (HT), which exhibits a polyphenol scaffold, is a potent inhibitor of TrxR1. Inhibition of TrxR1 was indicated to result in accumulation of reactive oxygen species, inhibit proliferation and induce apoptosis and G1/S cell cycle arrest of CRC cells. Using a C-terminal mutant TrxR1 enzyme activity assay, TrxR1 RNA interference assay and HT binding model assay, the present study demonstrated the core character of the selenocysteine residue in the interaction between HT and TrxR1. HT can serve as polyphenol scaffold to develop novel TrxR1 inhibitors for CRC treatment in the future.

Potential Effects of Phenolic Compounds That Can Be Found in Olive Oil on Wound Healing

The treatment of tissue damage produced by physical, chemical, or mechanical agents involves considerable direct and indirect costs to health care systems. Wound healing involves a series of molecular and cellular events aimed at repairing the defect in tissue integrity. These events can be favored by various natural agents, including the polyphenols in extra virgin olive oil (EVOO). The objective of this study was to review data on the potential effects of different phenolic compounds that can also be found in EVOO on wound healing and closure. Results of in vitro and animal studies demonstrate that polyphenols from different plant species, also present in EVOO, participate in different aspects of wound healing, accelerating this process through their anti-inflammatory, antioxidant, and antimicrobial properties and their stimulation of angiogenic activities required for granulation tissue formation and wound re-epithelialization. These results indicate the potential usefulness of EVOO phenolic compounds for wound treatment, either alone or in combination with other therapies. Human studies are warranted to verify this proposition.

Potential Uses of Olive Oil Secoiridoids for the Prevention and Treatment of Cancer: A Narrative Review of Preclinical Studies

The Mediterranean diet (MD) is a combination of foods mainly rich in antioxidants and anti-inflammatory nutrients that have been shown to have many health-enhancing effects. Extra-virgin olive oil (EVOO) is an important component of the MD. The importance of EVOO can be attributed to phenolic compounds, represented by phenolic alcohols, hydroxytyrosol, and tyrosol, and to secoiridoids, which include oleocanthal, oleacein, oleuropein, and ligstroside (along with the aglycone and glycosidic derivatives of the latter two). Each secoiridoid has been studied and characterized, and their effects on human health have been documented by several studies. Secoiridoids have antioxidant, anti-inflammatory, and anti-proliferative properties and, therefore, exhibit anti-cancer activity. This review summarizes the most recent findings regarding the pharmacological properties, molecular targets, and action mechanisms of secoiridoids, focusing attention on their preventive and anti-cancer activities. It provides a critical analysis of preclinical, in vitro and in vivo, studies of these natural bioactive compounds used as agents against various human cancers. The prospects for their possible use in human cancer prevention and treatment is also discussed.

Beneficial effects of olive oil and Mediterranean diet on cancer physio-pathology and incidence

Virgin olive oil is a characteristic component and the main source of fat of the Mediterranean diet. It is a mix of high-value health compounds, including monounsaturated fatty acids (mainly oleic acid), simple phenols (such as hydroxytyrosol and tyrosol), secoiridoids (such as oleuropein, oleocanthal), flavonoids, and terpenoids (such as squalene). Olive oil consumption has been shown to improve different aspects of human health and has been associated with a lower risk of cancer. However, the underlying cellular mechanisms involved in such effects are still poorly defined, but seem to be related to a promotion of apoptosis, modulation of epigenetic patterns, blockade of cell cycle, and angiogenesis regulation. The aim of this review is to update the current associations of cancer risk with the Mediterranean diet, olive oil consumption and its main components. In addition, the identification of key olive oil components involved in anticarcinogenic mechanisms and pathways according to experimental models is also addressed.

The Hydroxytyrosol Induces the Death for Apoptosis of Human Melanoma Cells

Melanoma is the most aggressive form of skin cancer and one of the most treatment-refractory malignancies. In metastatic melanoma cell lines, we analysed the anti-proliferative and pro-apoptotic potentials of a phenolic component of olive oil, the hydroxytyrosol. In particular, through MTS assay, DeadEnd™ Colorimetric TUNEL assay, Annexin V binding and PI uptake, western blot experiment, intracellular reactive oxygen species (ROS) analysis, and the cell colony assay, we showed that the hydroxytyrosol treatment remarkably reduces the cell viability inducing the death for apoptosis of melanoma cells. Moreover, we showed that the hydroxytyrosol treatment of melanoma cells leads to a significant increase of p53 and γH2AX expression, a significant decrease of AKT expression and the inhibition of cell colony formation ability. Finally, we propose that the increased amount of intracellular reactive oxygen species (ROS) that may be related to the regulation of the pathways involved in the activation of apoptosis and in the inhibition of melanoma growth could be the strategy used by hydroxytyrosol to exert its functions in melanoma. Therefore, for its role in melanoma growth inhibition, the hydroxytyrosol treatment could deeply interfere with melanoma progression as a promising therapeutic option for the treatment of this highly invasive tumour.

An Industrial and Sustainable Platform for the Production of Bioactive Micronized Powders and Extracts Enriched in Polyphenols From Olea europaea L. and Vitis vinifera L. Wastes

In the last few years, literature data have reported that health status is related to the consumption of foods rich in polyphenols, bioactive compounds found in the plant world, in particular in vegetables and fruit. These pieces of scientific evidence have led to an increase in the demand for functional foods and drinks enriched in polyphenols, so that plant materials are more and more requested. The availability of food and agricultural wastes has adverse effects on the economy, environment, and human health. On the other hand, these materials are a precious source of bioactive compounds as polyphenols. Their recovery and reuse from wastes are according to the circular economy strategy, which has introduced the “zero waste concept.” However, the process is convenient from an economic and environmental point of view only if the final products are standardized and obtained using sustainable and industrial technologies. In this panorama, this paper describes an industrial and sustainable platform for the production of micronized powders and extracts enriched in polyphenols from Olea europaea L. and Vitis vinifera L. wastes that are useful for food, cosmetics, and pharmaceuticals sectors. The platform is based on drying plant materials, extraction of polyphenols through membrane technologies with water, and, when necessary, the concentration of the final fractions under vacuum evaporation. All powders and extracts were characterized by high-performance liquid chromatography–diode array detector–mass spectrometry analysis to define the qualitative and quantitative content of bioactive compounds and insure their standardization and reproducibility. The chromatographic profiles evidenced the presence of secoiridoids, flavones, flavonols, anthocyanins, hydroxycinnamic acids, catechins, and condensed tannins. An overview of the biological activities of the main polyphenols present in Olea europaea L. and Vitis vinifera L. powders and extracts is reported because of biomedical applications.

A glucotolerant β-glucosidase from the fungus Talaromyces amestolkiae and its conversion into a glycosynthase for glycosylation of phenolic compounds

Background

The interest for finding novel β-glucosidases that can improve the yields to produce second-generation (2G) biofuels is still very high. One of the most desired features for these enzymes is glucose tolerance, which enables their optimal activity under high-glucose concentrations. Besides, there is an additional focus of attention on finding novel enzymatic alternatives for glycoside synthesis, for which a mutated version of glycosidases, named glycosynthases, has gained much interest in recent years.

Results

In this work, a glucotolerant β-glucosidase (BGL-1) from the ascomycete fungus Talaromyces amestolkiae has been heterologously expressed in Pichia pastoris, purified, and characterized. The enzyme showed good efficiency on p-nitrophenyl glucopyranoside (pNPG) (K_m= 3.36 ± 0.7 mM, k_cat= 898.31 s⁻¹), but its activity on cellooligosaccharides, the natural substrates of these enzymes, was much lower, which could limit its exploitation in lignocellulose degradation applications. Interestingly, when examining the substrate specificity of BGL-1, it showed to be more active on sophorose, the β-1,2 disaccharide of glucose, than on cellobiose. Besides, the transglycosylation profile of BGL-1 was examined, and, for expanding its synthetic capacities, it was converted into a glycosynthase. The mutant enzyme, named BGL-1-E521G, was able to use α-d-glucosyl-fluoride as donor in glycosylation reactions, and synthesized glucosylated derivatives of different pNP-sugars in a regioselective manner, as well as of some phenolic compounds of industrial interest, such as epigallocatechin gallate (EGCG).

Conclusions

In this work, we report the characterization of a novel glucotolerant 1,2-β-glucosidase, which also has a considerable activity on 1,4-β-glucosyl bonds, that has been cloned in P. pastoris, produced, purified and characterized. In addition, the enzyme was converted into an efficient glycosynthase, able to transfer glucose molecules to a diversity of acceptors for obtaining compounds of interest. The remarkable capacities of BGL-1 and its glycosynthase mutant, both in hydrolysis and synthesis, suggest that it could be an interesting tool for biotechnological applications.

Hydroxytyrosol: A natural compound with promising pharmacological activities

Hydroxytyrosol is a phenolic phytochemical with antioxidant properties in vitro. It is a natural compound that can be found in olive leaves and oil. The main dietary source of hydroxytyrosol is extra virgin olive oil. Due to its bioavailability, chemical properties and easy formulation along with its lack of toxicity, hydroxytyrosol is considered an excellent food supplement by the nutraceutical and food industries. The purpose of this review is to discuss the potential therapeutic effects of hydroxytyrosol in vivo. To do so, we conducted an electronic search in PubMed and other literature databases using "hydroxytyrosol", "beneficial effect/s", "pharmacology" as key-words. From this search, we found that hydroxytyrosol has anti-inflammatory, anti-tumor, antiviral, antibacterial and antifungal properties. Hydroxytyrosol also improves endothelial dysfunction, decreases oxidative stress, and is neuro- and cardio-protective. Due to all these biological properties, hydroxytyrosol is currently the most actively investigated natural phenol. The evidence presented in this review suggests that hydroxytyrosol has great pharmacological potential.

Anticancer effects of olive oil polyphenols and their combinations with anticancer drugs

Cancer presents one of the leading causes of death in the world. Current treatment includes the administration of one or more anticancer drugs, commonly known as chemotherapy. The biggest issue concerning the chemotherapeutics is their toxicity on normal cells and persisting side effects. One approach to the issue is chemoprevention and the other one is the discovery of more effective drugs or drug combinations, including combinations with polyphenols. Olive oil polyphenols (OOPs), especially hydroxytyrosol (HTyr), tyrosol (Tyr) and their derivatives oleuropein (Ole), oleacein and oleocanthal (Oc) express anticancer activity on different cancer models. Recent studies report that phenolic extract of virgin olive oil may be more effective than the individual phenolic compounds. Also, there is a growing body of evidence about the combined treatment of OOPs with various anticancer drugs, such as cisplatin, tamoxifen, doxorubicin and others. These novel approaches may present an advanced strategy in the prevention and treatment of cancer.

Hydroxytyrosol encapsulated in biocompatible water-in-oil microemulsions: How the structure affects in vitro absorption

Over the last years, the incorporation of natural antioxidants in food and pharmaceutical formulations has gained attention, delaying or preventing oxidation phenomena in the final products. In order to take full advantage of their properties, protection in special microenvironments is of great importance. The unique features of the natural phenolic compound hydroxytyrosol (HT) - including antioxidant, anti-inflammatory, antiproliferative and cardioprotective properties - have been studied to clarify its mechanism of action. In the present study novel biocompatible water-in-oil (W/O) microemulsions were developed as hosts for HT and subsequently examined for their absorption profile following their oral uptake. The absorption of HT in solution was compared with the encapsulated one in vitro, using a coculture model (Caco-2/TC7 and HT29-MTX cell lines). The systems were structurally characterized by means of Dynamic Light Scattering (DLS) and Electron Paramagnetic Resonance (EPR) techniques. The diameter of the micelles remained unaltered after the incorporation of 678 ppm of HT but the interfacial properties were slightly affected, indicating the involvement of the HT molecules in the surfactant monolayer. EPR was used towards a lipophilic stable free radial, namely galvinoxyl, indicating a high scavenging activity of the systems and encapsulated HT. Finally, after the biocompatibility study of the microemulsions the intestinal absorption of the encapsulated HT was compared with its aqueous solution in vitro. The higher the surfactants' concentration in the system the lower the HT concentration that penetrated the constructed epithelium, indicating the involvement of the amphiphiles in the antioxidant's absorption and its entrapment in the mucus layer.

Transglycosylation products generated by Talaromyces amestolkiae GH3 β-glucosidases: effect of hydroxytyrosol, vanillin and its glucosides on breast cancer cells

Background

Transglycosylation represents one of the most promising approaches for obtaining novel glycosides, and plant phenols and polyphenols are emerging as one of the best targets for creating new molecules with enhanced capacities. These compounds can be found in diet and exhibit a wide range of bioactivities, such as antioxidant, antihypertensive, antitumor, neuroprotective and anti-inflammatory, and the eco-friendly synthesis of glycosides from these molecules can be a suitable alternative for increasing their health benefits.

Results

Transglycosylation experiments were carried out using different GH3 β-glucosidases from the fungus Talaromyces amestolkiae. After a first screening with a wide variety of potential transglycosylation acceptors, mono-glucosylated derivatives of hydroxytyrosol, vanillin alcohol, 4-hydroxybenzyl alcohol, and hydroquinone were detected. The reaction products were analyzed by thin-layer chromatography, high-pressure liquid chromatography, and mass spectrometry. Hydroxytyrosol and vanillyl alcohol were selected as the best options for transglycosylation optimization, with a final conversion yield of 13.8 and 19% of hydroxytyrosol and vanillin glucosides, respectively. NMR analysis confirmed the structures of these compounds. The evaluation of the biological effect of these glucosides using models of breast cancer cells, showed an enhancement in the anti-proliferative capacity of the vanillin derivative, and an improved safety profile of both glucosides.

Conclusions

GH3 β-glucosidases from T. amestolkiae expressed in P. pastoris were able to transglycosylate a wide variety of acceptors. Between them, phenolic molecules like hydroxytyrosol, vanillin alcohol, 4-hydroxybenzyl alcohol, and hydroquinone were the most suitable for its interesting biological properties. The glycosides of hydroxytyrosol and vanillin were tested, and they improved the biological activities of the original aglycons on breast cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s12934-019-1147-4) contains supplementary material, which is available to authorized users.

Hydroxytyrosol, Tyrosol and Derivatives and Their Potential Effects on Human Health

The Mediterranean diet and olive oil as its quintessential part are almost synonymous with a healthy way of eating and living nowadays. This kind of diet has been highly appreciated and is widely recognized for being associated with many favorable effects, such as reduced incidence of different chronic diseases and prolonged longevity. Although olive oil polyphenols present a minor fraction in the composition of olive oil, they seem to be of great importance when it comes to the health benefits, and interest in their biological and potential therapeutic effects is huge. There is a growing body of in vitro and in vivo studies, as well as intervention-based clinical trials, revealing new aspects of already known and many new, previously unknown activities and health effects of these compounds. This review summarizes recent findings regarding biological activities, metabolism and bioavailability of the major olive oil phenolic compounds—hydroxytyrosol, tyrosol, oleuropein, oleocanthal and oleacein—the most important being their antiatherogenic, cardioprotective, anticancer, neuroprotective and endocrine effects. The evidence presented in the review concludes that these phenolic compounds have great pharmacological potential, however, further studies are still required.

Effects of hydroxytyrosol dose on the redox status of exercised rats: the role of hydroxytyrosol in exercise performance

Background

Hydroxytyrosol (HT) is a polyphenol found in olive oil that is known for its antioxidant effects. Here, we aimed to describe the effects of a low and high HT dose on the physical running capacity and redox state in both sedentary and exercised rats.

Methods

Male Wistar rats were allocated into 6 groups: sedentary (SED; n = 10); SED consuming 20 mg/kg/d HT (SED20; n = 7); SED consuming 300 mg/kg/d HT (SED300; n = 7); exercised (EXE; n = 10); EXE consuming 20 mg/kg/d HT (EXE20; n = 10) and EXE consuming 300 mg/kg/d HT (EXE300; n = 10). All the interventions lasted 10 weeks; the maximal running velocity was assessed throughout the study, whereas daily physical work was monitored during each training session. At the end of the study, the rats were sacrificed by bleeding. Hemoglobin (HGB) and hematocrit (HCT) were measured in the terminal blood sample. Moreover, plasma hydroperoxide (HPx) concentrations were quantified as markers of lipid peroxidation.

Results

In sedentary rats, HT induced an antioxidant effect in a dose-dependent manner without implications on running performance. However, if combined with exercise, the 300 mg/kg/d HT dosage exhibited a pro-oxidant effect in the EXE300 group compared with the EXE and EXE20 groups. The EXE20 rats showed a reduction in daily physical work and a lower maximal velocity than the EXE and EXE300 rats. The higher physical capacity exhibited by the EXE300 group was achieved despite the EXE300 rats expressing lower HGB levels and a lower HCT than the EXE20 rats.

Conclusions

Our results suggest that a high HT dose induces a systemic pro-oxidant effect and may prevent the loss of performance that was observed with the low HT dose.

Hydroxytyrosol and the Colonic Metabolites Derived from Virgin Olive Oil Intake Induce Cell Cycle Arrest and Apoptosis in Colon Cancer Cells

After the sustained consumption of virgin olive oil (VOO), the unabsorbed native phenols (mainly hydroxytyrosol (HT)) are transformed into its catabolites in the intestine by microbials. The role of these catabolites in preventing colon cancer has not been sufficiently investigated. This work aims to study the antiproliferative and apoptotic activities in colon (Caco-2; HT-29) cancer cell lines of the main catabolites detected in human feces (phenylacetic, phenylpropionic, hydroxyphenylpropionic, and dihydroxyphenylpropionic acids and catechol), after the sustained VOO intake. Additionally, an assessment of the ability of these colonic cells to metabolize the studied compounds was performed. The results showed that HT and phenylacetic and hydroxyphenylpropionic acids produce cell cycle arrest and promote apoptosis. HT-29 cells were more sensitive to phenol treatments than Caco-2. In synthesis, the results of the present study represent a good starting point for understanding the potential apoptotic and antiproliferative effects of VOO phenolic compounds and their colonic metabolites.

High doses of hydroxytyrosol induce apoptosis in papillary and follicular thyroid cancer cells

PURPOSE

Recent evidences indicates that hydroxytyrosol, one of the main olive oil phenols, possess antitumor effects because of its pro-oxidant properties and the capacity to inhibit proliferation and to promote apoptosis in several tumor cell lines, although most of the results were obtained for breast and digestive systems cancers.

METHODS

In this study, we evaluated the activities of hydroxytyrosol against papillary (TPC-1, FB-2) and follicular (WRO) thyroid cancer cell lines.

RESULTS

Cellular viability revealed that high doses of hydroxytyrosol reduced cancer cells viability concomitantly with a reduction of cyclin D1 expression and an up-regulation of cell cycle key modulator p21 levels. In the same experimental conditions, Annexin V-PI staining and DNA laddering revealed that hydroxytyrosol exerts proapoptotic effects on papillary and follicular cancer cells. Furthermore, by Western blot analysis, we observed that hydroxytyrosol treatment reduced thyroid cancer cells viability by promoting apoptotic cell death via intrinsic pathway.

CONCLUSIONS

Collectively, our results demonstrated for the first time that in thyroid cancer cells hydroxytyrosol promoted apoptosis at higher doses with respect to other cancer cells lines. Therefore, further studies will reveal the mechanisms by which thyroid cancer cells are more resistant to the proapoptotic effect exerted by hydroxytyrosol as well as the potential application as novel target therapeutic in thyroid cancer.

Nutrigenomics of extra-virgin olive oil: A review

Nutrigenomics data on the functional components of olive oil are still sparse, but rapidly increasing. Olive oil is the main source of fat and health-promoting component of the Mediterranean diet. Positive effects have been observed on genes involved in the pathobiology of most prevalent age- and lifestyle-related human conditions, such as cancer, cardiovascular disease and neurodegeneration. Other effects on health-promoting genes have been identified for bioactive components of olives and olive leafs. Omics technologies are offering unique opportunities to identify nutritional and health biomarkers associated with these gene responses, the use of which in personalized and even predictive protocols of investigation, is a main breakthrough in modern medicine and nutrition. Gene regulation properties of the functional components of olive oil, such as oleic acid, biophenols and vitamin E, point to a role for these molecules as natural homeostatic and even hormetic factors with applications as prevention agents in conditions of premature and pathologic aging. Therapeutic applications can be foreseen in conditions of chronic inflammation, and particularly in cancer, which will be discussed in detail in this review paper as major clinical target of nutritional interventions with olive oil and its functional components. © 2016 BioFactors, 43(1):17-41, 2017.

In vitro chemo-preventive activities of hydroxytyrosol: the main phenolic compound present in extra-virgin olive oil

The co-incubation in the culture medium with hydroxytyrosol [3,4-dihydroxyphenyl ethanol (3,4-DHPEA)], the main phenolic compound present in extra-virgin olive oil, and H₂O₂reduces the oxidative DNA damage in peripheral blood mononuclear cells (PBMC).

The hydroxytyrosol-dependent increase of TNF-α in LPS-activated human monocytes is mediated by PGE2 and adenylate cyclase activation

An accurate regulation of PGE2 and TNF-α production is an important event for a physiological inflammation process. We have recently reported that in LPS-activated human monocytes hydroxytyrosol, the main phenol present in extra virgin olive oil reduced both the COX-2 gene expression and PGE2 secretion while it increased the TNF-α accumulation in the culture medium. Here we have investigated whether these effects were related to each other, clarifying the possible mechanisms involved. We found that hydroxytyrosol (100 μM) increased the TNF-α mRNA level in LPS-activated human monocytes as evaluated by both RT-PCR and real time PCR (qPCR). Exogenous PGE2 reduced both TNF-α mRNA and TNF-α secretion (EIA assay) while the activation of adenylate cyclase by forskolin decreased only the TNF-α secretion but did not influence the TNF-α mRNA level. Acting similarly to non steroidal anti-inflammatory drugs (NSAIDs), the hydroxytyrosol could be used to develop innovative drugs for the control of inflammation and immune response. The decrease of TNF mediated by forskolin, moreover, could suggest that the pharmacological regulation of cAMP production may represent a strategy to control the side effects of NSAIDs.

Hydroxytyrosol and potential uses in cardiovascular diseases, cancer, and AIDS

Hydroxytyrosol is one of the main phenolic components of olive oil. It is present in the fruit and leaf of the olive (Olea europaea L.). During the past decades, it has been well documented that this phenolic compound has health benefits and a protective action has been found in preclinical studies against several diseases. Here, we review its bioavailability in human beings and several assays showing significant results related with cardiovascular diseases, cancer, and acquired immunodeficiency syndrome (AIDS). Mechanisms of action include potent anti-oxidant and anti-inflammatory effects, among others. The importance of hydroxytyrosol in protection of low-density lipoproteins and consequently its implication in the reduction of cardiovascular disease risk has been highlighted by the European Food Safety Authority, concluding that 5 mg of hydroxytyrosol and its derivatives should be consumed daily to reach this effect at physiological level. We discuss the potential uses of this compound in supplements, nutraceutic foods, or topical formulations in the disease risk reduction. Finally, we conclude that more studies are needed to sustain or reject many other health claims not yet fully documented and to validate these newly available hydroxytyrosol-based products, because it seems to be a good candidate to reduce the risk of diseases mentioned.

Recovering bioactive compounds from olive oil filter cake by advanced extraction techniques

The potential of by-products generated during extra-virgin olive oil (EVOO) filtration as a natural source of phenolic compounds (with demonstrated bioactivity) has been evaluated using pressurized liquid extraction (PLE) and considering mixtures of two GRAS (generally recognized as safe) solvents (ethanol and water) at temperatures ranging from 40 to 175 °C. The extracts were characterized by high-performance liquid chromatography (HPLC) coupled to diode array detection (DAD) and electrospray time-of-flight mass spectrometry (HPLC-DAD-ESI-TOF/MS) to determine the phenolic-composition of the filter cake. The best isolation procedure to extract the phenolic fraction from the filter cake was accomplished using ethanol and water (50:50, v/v) at 120 °C. The main phenolic compounds identified in the samples were characterized as phenolic alcohols or derivatives (hydroxytyrosol and its oxidation product), secoiridoids (decarboxymethylated and hydroxylated forms of oleuropein and ligstroside aglycones), flavones (luteolin and apigenin) and elenolic acid derivatives. The PLE extraction process can be applied to produce enriched extracts with applications as bioactive food ingredients, as well as nutraceuticals.

Beneficial effects of the olive oil phenolic components oleuropein and hydroxytyrosol: focus on protection against cardiovascular and metabolic diseases

The overall health beneficial action of olive oil phenolic components is well established. Recent studies have elucidated the biological effects of two isolated compounds, namely oleuropein and hydroxytyrosol, with particular attention on their antioxidant activity. Thus, a protective action has been demonstrated in preclinical studies against several diseases, especially cardiovascular and metabolic disorders.

The present review will describe the biological effects of oleuropein and hydroxytyrosol, with particular attention on the molecular mechanism underlying the protective action on cardiovascular and metabolic alterations, as demonstrated by in vitro and in vivo experimental studies performed with the isolated compounds.

Role of the inhibition of oxidative stress and inflammatory mediators in the neuroprotective effects of hydroxytyrosol in rat brain slices subjected to hypoxia reoxygenation

The aim of this study was to analyze the mechanism of the neuroprotective effect of hydroxytyrosol (HT) in an experimental model of hypoxia-reoxygenation in rat brain slices. After reoxygenation the increase in lactate dehydrogenase efflux was inhibited by HT in a concentration-dependent manner and dose-dependent inhibition after oral administration to rats for 7 days (1, 5 and 10 mg/kg per day). Maximum inhibition was 57.4% in vitro and 38.7% ex vivo. Hydroxytyrosol reduced oxidative stress parameters: it inhibited lipid peroxidation and increased enzymatic activities related with the glutathione system both in vitro and after oral administration to rats. The increase in prostaglandin E2 and interleukin 1β after reoxygenation were inhibited after incubation of brain slices with HT and after oral administration. The accumulation of nitric oxide in brain slices was reduced in a concentration-dependent manner. In conclusion, HT exerts a neuroprotective effect in a model of hypoxia-reoxygenation in rat brain slices, both in vitro and after 7 days of oral administration to rats. HT exerts an antioxidant activity and lowered some inflammatory markers in this model.

Hydroxytyrosol induces apoptosis in human colon cancer cells through ROS generation

Cancer cells are usually under higher levels of oxidative stress compared to normal cells.

Biological Activities of Phenolic Compounds of Extra Virgin Olive Oil

Over the last few decades, multiple biological properties, providing antioxidant, anti-inflammatory, chemopreventive and anti-cancer benefits, as well as the characteristic pungent and bitter taste, have been attributed to Extra Virgin Olive Oil (EVOO) phenols. In particular, growing efforts have been devoted to the study of the antioxidants of EVOO, due to their importance from health, biological and sensory points of view. Hydrophilic and lipophilic phenols represent the main antioxidants of EVOO, and they include a large variety of compounds. Among them, the most concentrated phenols are lignans and secoiridoids, with the latter found exclusively in the Oleaceae family, of which the drupe is the only edible fruit. In recent years, therefore, we have tackled the study of the main properties of phenols, including the relationships between their biological activity and the related chemical structure. This review, in fact, focuses on the phenolic compounds of EVOO, and, in particular, on their biological properties, sensory aspects and antioxidant capacity, with a particular emphasis on the extension of the product shelf-life.

Effect of olive oil phenols on the production of inflammatory mediators in freshly isolated human monocytes

Recent in vitro and in vivo studies suggest that the anti-inflammatory properties of extra virgin olive oil may be involved in the prevention of chronic degenerative diseases. In this study, the ability of olive oil phenols to influence the release of superoxide anions (O2-), prostaglandin E2 (PGE2) and tumor necrosis factor α (TNFα) and the expression of cyclooxygenase2 (COX2) in human monocytes, freshly isolated from healthy donors, was investigated. O2- were measured by superoxide dismutase-inhibitable cytochrome c reduction and PGE2 and TNFα production were determined in culture medium with appropriate enzyme immunoassay kits. COX2 mRNA and protein were evaluated by quantitative reverse transcription-polymerase chain reaction and Western immunoblotting, respectively. Treatment of monocytes for 24 h with 100 μM of hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and their secoiridoid derivatives (3,4-DHPEA and p-HPEA linked to the dialdehydic form of elenolic acid: 3,4-DHPEA-EDA and p-HPEA-EDA, respectively) significantly (P<.05) inhibited the production of O2(-) as follows: 3,4-DHPEA (40%,), p-HPEA (9%), 3,4-DHPEA-EDA (25%) and p-HPEA-EDA (36%). Hydroxytyrosol also considerably reduced the expression of COX2 at both the mRNA and protein level (P<.05) and caused a clear dose-dependent reduction of PGE2 released into the culture medium (45% and 71% at 50 and 100 μM, respectively, P<.05). The COX2 mRNA was also efficiently inhibited by the secoiridoids. Moreover, it was shown that hydroxytyrosol increased the monocytes TNFα production. In addition to other chemopreventive properties, these results suggest that the health effects of olive oil phenols may be related to their ability to modulate the production of pro-inflammatory molecules, a property common to non-steroidal anti-inflammatory drugs.

Enhanced chemopreventive activity of hydroxytyrosol on HL60 and HL60R cells by chemical conversion into thio derivatives

Thio derivatives of hydroxytyrosol containing thiol, thioacetate and disulfide functionalities were synthesized from natural hydroxytyrosol (3,4-DHPEA) via 3,4-dihydroxyphenethyl halides. These compounds, containing the combination of catechol moiety and divalent sulfur functions, were tested for the pro-apoptotic and anti-proliferative activities on both parental HL60 and multi-drug resistant HL60R cells. It was found that all synthesized compounds were more effective than 3,4-DHPEA in inducing apoptosis on HL60R cells, and that the hydroxytyrosol disulfide was the most active pro-apoptotic and anti-proliferative compound on both HL60 and HL60R cells. Different from 3,4-DHPEA, all thio derivatives of hydroxytyrosol induced apoptosis by a mechanism not involving the release of H(2)O(2) in the culture medium. The data on HL60R cells suggest that these compounds could be able to reverse the resistance toward the most common drugs in cancer therapy.