Antioxidant properties of tyrosol and hydroxytyrosol saturated fatty acid esters

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

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

Controlled dual release of phenol compounds from phospholipid complexes of short-chain lipophenols

Ethanol evaporation method was applied to synthesize phospholipid complexes from phosphatidylcholine (PC) and short-chain alkyl gallates (A-GAs, a typical representative of lipophenols) including butyl-, propyl- and ethyl gallates. 1H NMR, UV and FTIR showed that A-GAs were interacted with PC through weak physical interaction. Through the analysis of concentrations of A-GAs and gallic acid (GA) by an everted rat gut sac model coupled with HPLC-UV detection, phospholipid complexes were found to gradually release A-GAs. These liberated A-GAs were further hydrolyzed by intestinal lipases to release GA. Both of GA and A-GAs could cross intestinal membrane. Especially, the transmembrane A-GAs could also be hydrolyzed to produce GA. Undoubtedly, the dual release of phenol compounds from phospholipid complexes of short-chain lipophenols will be effective to extend the in vivo residence period of phenol compounds. More importantly, such behavior is easily adjusted by changing the acyl chain lengths of lipophenols in phospholipid complexes.

Synthesis of lipophilic antioxidant tyrosol laurate using imidazolium ionic liquid [Bmim]HSO4 as a catalyst

Tyrosol is a natural phenolic compound with potent antioxidant properties in the field of food manufacturing. However, the low lipophilicity of tyrosol limited its application. Therefore, the construction of tyrosol laurate (Tyr-L) could effectively overcome the limitations of tyrosol. In this work, four ionic liquids (ILs) were applied for TYr-L preparation. Among them, the 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) showed the best catalytic performance. The maximum TYr-L yield was achieved (94.24 ± 1.23 %) under the optimal conditions (reaction temperature 119 °C, substrate ratio 1:6.7, IL dosage 9.2 %, and reaction time 12 h). The kinetic and thermodynamic parameters were also evaluated and it was found that Ea, ΔH, ΔS, and ΔG were 80.81 kJ·mol-1, 77.63 kJ·mol-1, -82.08 J·(mol·K)-1, and 109.89 kJ·mol-1, respectively. The acidic [Bmim]HSO4 demonstrated excellent reusability and stability, even after 6 cycles. Furthermore, TYr-L showed superior ABTS radical scavenging ability, which could be further applied in various industrial processes.

High Tyrosol and Hydroxytyrosol Intake Reduces Arterial Inflammation and Atherosclerotic Lesion Microcalcification in Healthy Older Populations

Aging is an important risk factor for cardiovascular diseases and convincing data have shown that chronic low-grade inflammation, which develops with advanced age, contributes significantly to cardiovascular risk. The present study aimed to use 18F-FDG/18F-NaF-PET/CT imaging to, respectively, gauge arterial inflammation and microcalcification in a healthy elderly population and to assess the potential benefits of a tyrosol- and hydroxytyrosol-rich diet on these two markers of atherosclerotic plaque fragility. Eleven healthy participants (mean age 75 ± 5.67 years) were supplemented for 6 months with high polyphenol-rich extra virgin olive oil (HP-EVOO), extra virgin olive oil (EVOO), or refined olive oil (ROO). The participants underwent PET/CT imaging with 18F-FDG and 18F-NaF radiotracers at baseline and after 6 months. 18F-FDG and 18F-NaF uptakes were quantified using standardized uptake values (SUV) and were categorized based on artery calcification and olive oil type. A total of 324 slices of the aortas of the imaged participants were analyzed for arterial inflammation and 327 slices were analyzed for microcalcification. 18F-FDG uptake was significantly higher in the non-calcified segments than in the calcified segments (SUVmax = 2.70 ± 0.62 and SUVmax = 2.54 ± 0.44, respectively, p < 0.042). Conversely, the non-calcified segments displayed significantly lower 18F-NaF uptake than the calcified segments (SUVmax = 1.90 ± 0.37 and 2.09 ± 0.24, respectively, p < 0.0001). The 6-month supplementation with HP-EVOO induced a significant reduction in 18F-FDG uptake in both the non-calcified (2.93 ± 0.23 to 2.75 ± 0.38, p < 0.004) and calcified segments of the aortas (2.25 ± 0.29 to 2.15 ± 0.19, p < 0.02). 18F-NaF uptake was also significantly lower in patients supplemented with HP-EVOO (SUVmax = 1.98 ± 0.33 at baseline compared to 1.85 ± 0.28, after the 6-month supplementation, p < 0.004), whereas no significant effect was observed with EVOO. Conversely, participants supplemented with ROO displayed a significant increase in 18F-NaF uptake (SUVmax = 1.78 ± 0.34 to 1.95 ± 0.34, p < 0.0001). The present study confirmed that a phenolic-compound-rich diet reduces both arterial inflammation and atherosclerotic lesion microcalcification and demonstrated that 18F-FDG/18F-NaF-PET/CT imaging is a valuable approach for assessing age-related arterial damage.

Lipase-mediated flow synthesis of nature-inspired phenolic carbonates

A facile and convenient lipase-catalyzed flow approach for the chemoselective synthesis of tyrosol and hydroxytyrosol methyl carbonates has been developed in neat dimethylcarbonate. The products were obtained in quantitative yield with high catalyst productivity. The biocatalytic approach was then exploited for the preparation of value-added symmetrical tyrosol and hydroxytyrosol carbonates.

Oral administration of nano-tyrosol reversed the diabetes-induced liver damage in streptozotocin-induced diabetic rats

Objectives

The present study was designed to evaluate the effects of Tyrosol and Nano-tyrosol on the cellular arrangement, collagen disposition, protein level of insulin receptor (INSR), and superoxide dismutase (SOD) activity in both control and streptozotocin-induced diabetic rats.

Methods

Type 2 Diabetes (T2D) was induced in rats by a single intraperitoneal injection of streptozotocin (50 mg/kg). Experimental rats were administered Tyrosol and Nano-tyrosol 1 ml intra-gastrically at a dose of 20 mg/kg once a day for 30 days. Then, rats were sacrificed according to ethical principles. Livers were removed and processed for histological studies using the paraffin technique. Furthermore, non-paraffin sections were used for the INSR-1 western blot technique.

Results

At the end of the experiments, the rats in diabetic control and plain niosome groups exhibited a significant increase in collagen disposition (p < 0.001), and apoptotic cells (p < 0.001), as well as decreased total protein levels of INSR (p < 0.001), and SOD activity (p < 0.001) in the hepatic cells. Oral administration of Tyrosol and Nano-tyrosol to diabetic rats reversed all the above-mentioned parameters to near normal levels (p < 0.001). Nano-tyrosol showed the highest significant effect rather than Tyrosol.

Conclusion

The results of the present study suggested the beneficial effects of Tyrosol and especially Nano-tyrosol on decreasing the adverse effects of diabetes.

Enzymatic lipophilization of bioactive compounds with high antioxidant activity: a review

Food products contain bioactive compounds such as phenolic and polyphenolic compounds and vitamins, resulting in a myriad of biological characteristics such as antimicrobial, anticarcinogenic, and antioxidant activities. However, their application is often restricted because of their relatively low solubility and stability in emulsions and oil-based products. Therefore, chemical, enzymatic, or chemoenzymatic lipophilization of these compounds can be achieved by grafting a non-polar moiety onto their polar structures. Among different methods, enzymatic modification is considered environmentally friendly and may require only minor downstream processing and purification steps. In recent years, different systems have been suggested to design the synthetic reaction of these novel products. This review presents the new trends in this area by summarizing the essential enzymatic modifications in the last decade that led to the synthesis of bioactive compounds with attractive antioxidative properties for the food industry by emphasizing on optimization of the reaction conditions to maximize the production yields. Lastly, recent developments regarding characterization, potential applications, emerging research areas, and needs are highlighted.

Enzymatic continuous-flow preparation of nature-inspired phenolic esters as antiradical and antimicrobial agents

A collection of nature-inspired lipophilic phenolic esters have been prepared by an enzymatic synthesis under flow conditions, using the immobilized lipase B from Candida antarctica (Novozyme 435®) as a catalyst in cyclopentyl methyl ether (CPME), a non-conventional and green solvent. Their antimicrobial activity against four selected bacterial strains together with their efficiency as radical scavengers were evaluated. The obtained compounds were characterized by enhanced lipophilicity in comparison with the parent non-esterified compounds, which increased the possibility of their use as additives in the food industry.

Gastrointestinal Distribution of Tyrosol Acyl Esters in Orally Infected Mice and Their Hydrolysis by Lactobacillus Species Isolated from the Feces of Mice

Phenolipids, which have been widely used as food antioxidants, are also a potential functional ingredient. However, their characteristics of gastrointestinal distribution and microbial hydrolysis remain unexplored. In this study, an in vivo mouse model and an in vitro anaerobic fermentation model were used to evaluate the above characteristics of tyrosol acyl esters (TYr-Es) with fatty acids (FAs) of C12:0, C18:0, and C18:2. HPLC-UV measurements indicated that oral TYr-Es were remarkably stable in the stomach environment of mice. However, TYr-Es were hydrolyzed to free TYr by lipase in the small intestine, which showed a sustained-release behavior. Specially, TYr was rapidly and almost completely absorbed in the small intestine. By contrast, detectable amounts of TYr-Es were found in the cecum and colon and could be further hydrolyzed to free TYr and FAs by Lactobacillus. These TYr and FAs can participate in regulating the composition of the intestinal microorganisms, which may lead to some health benefits.

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.

Identification of Tyrosyl Oleate as a Novel Olive Oil Lipophenol with Proliferative and Antioxidant Properties in Human Keratinocytes

Lipophenols are an emerging subclass of phenolic compounds characterized by the presence of a lipid moiety. Recently, hydroxytyrosyl oleate (HtyOle), a derivative of hydroxytyrosol, has been identified in olive oil and by-products. Furthermore, HtyOle possesses anti-inflammatory, antioxidant, and tissue regenerating properties. In this work, the potential occurrence of tyrosyl oleate (TyOle) in olive oil was investigated based on the hypothesis that its precursors tyrosol and oleic acid, both present in relatively high amount can be coupled together. Moreover, TyOle effects have been investigated in human keratinocytes to verify its proliferative and antioxidant properties. The quantitative determination of TyOle was carried out by the external standard method in liquid chromatography coupled with mass spectrometry (LC/MS), in negative mode using multiple reaction monitoring (MRM). The proliferative properties of TyOle on immortalized human keratinocytes (HaCat) were evaluated by 3-(4,5-dimethylthiasol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Morphological changes were observed by fluorescent staining with phalloidin (for F-actin) or 4,6-diamidino-2-phenylindole (DAPI, for chromatin) dye. The antioxidant activity was assessed at the level of production of mitochondrial reactive oxygen species (ROS) induced with UV exposure. TyOle was identified in all the oil samples investigated. Interestingly, TyOle concentration was higher in defective or low-quality oils than in extra virgin oils. The formation of TyOle likely occurs during the crushing and kneading processes and its concentration is related to the increase of rancidity and of the concentration of free precursors. Herein we show that TyOle induced an increase in the viability of HaCat cells and cytoskeletal remodeling.

Quercetin and its ester derivatives inhibit oxidation of food, LDL and DNA

Quercetin was esterified with fatty acids (FA) in order to expand its application in a wide range of food and biological systems. The antioxidant potential of the esters were examined using hydroxyl radical scavenging activity, antioxidation in oil-in-water emulsion and bulk oil, inhibition of low-density lipoprotein (LDL) oxidation and deoxyribonucleic acid (DNA) scission. Except for oil-in-water emulsion system, quercetin derivatives demonstrated similar and/or better antioxidant activity than quercetin itself in bulk oil (quercetin with C18:1 and C22:6), hydroxyl radical scavenging assay (quercetin with C3:0-C8:0), DNA scission (quercetin with C3:0-C8:0), and LDL oxidation (quercetin with C14:0-C22:6, except C18:0). These results suggest that esterification did not compromise the antioxidant activity of the parent compound and quercetin derivatives might be useful as possible antioxidants in food and biological systems.

Graphene-Based Sensors for the Detection of Bioactive Compounds: A Review

Over the last years, different nanomaterials have been investigated to design highly selective and sensitive sensors, reaching nano/picomolar concentrations of biomolecules, which is crucial for medical sciences and the healthcare industry in order to assess physiological and metabolic parameters. The discovery of graphene (G) has unexpectedly impulsed research on developing cost-effective electrode materials owed to its unique physical and chemical properties, including high specific surface area, elevated carrier mobility, exceptional electrical and thermal conductivity, strong stiffness and strength combined with flexibility and optical transparency. G and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), are becoming an important class of nanomaterials in the area of optical and electrochemical sensors. The presence of oxygenated functional groups makes GO nanosheets amphiphilic, facilitating chemical functionalization. G-based nanomaterials can be easily combined with different types of inorganic nanoparticles, including metals and metal oxides, quantum dots, organic polymers, and biomolecules, to yield a wide range of nanocomposites with enhanced sensitivity for sensor applications. This review provides an overview of recent research on G-based nanocomposites for the detection of bioactive compounds, providing insights on the unique advantages offered by G and its derivatives. Their synthesis process, functionalization routes, and main properties are summarized, and the main challenges are also discussed. The antioxidants selected for this review are melatonin, gallic acid, tannic acid, resveratrol, oleuropein, hydroxytyrosol, tocopherol, ascorbic acid, and curcumin. They were chosen owed to their beneficial properties for human health, including antibiotic, antiviral, cardiovascular protector, anticancer, anti-inflammatory, cytoprotective, neuroprotective, antiageing, antidegenerative, and antiallergic capacity. The sensitivity and selectivity of G-based electrochemical and fluorescent sensors are also examined. Finally, the future outlook for the development of G-based sensors for this type of biocompounds is outlined.

Strategies to Broaden the Applications of Olive Biophenols Oleuropein and Hydroxytyrosol in Food Products

Oleuropein (OLE) and hydroxytyrosol (HT) are olive-derived phenols recognised as health-promoting agents with antioxidant, anti-inflammatory, cardioprotective, antifungal, antimicrobial, and antitumor activities, providing a wide range of applications as functional food ingredients. HT is Generally Recognised as Safe (GRAS) by the European Food Safety Authority (EFSA) and the Food and Drug Administration (FDA), whereas OLE is included in EFSA daily consumptions recommendations, albeit there is no official GRAS status for its pure form. Their application in food, however, may be hindered by challenges such as degradation caused by processing conditions and undesired sensorial properties (e.g., the astringency of OLE). Among the strategies to overcome such setbacks, the encapsulation in delivery systems and the covalent and non-covalent complexation are highlighted in this review. Additionally, the synthesis of OLE and HT derivatives are studied to improve their applicability. All in all, more research needs however to be carried out to investigate the impact of these approaches on the sensory properties of the final food product and its percussions at the gastrointestinal level, as well as on bioactivity. At last limitations of these approaches at a scale of the food industry must also be considered.

Semi-synthesis as a tool for broadening the health applications of bioactive olive secoiridoids: a critical review

Covering: 2005 up to 2020Olive bioactive secoiridoids are recognized as natural antioxidants with multiple beneficial effects on human health. Nevertheless, the study of their biological activity has also disclosed some critical aspects associated with their application. Firstly, only a few of them can be extracted in large amounts from their natural matrix, namely olive leaves, drupes, oil and olive mill wastewater. Secondly, their application as preventive agents and drugs is limited by their low membrane permeability. Thirdly, the study of their biological fate after administration is complicated by the absence of pure analytical standards. Accordingly, efficient synthetic methods to obtain natural and non-natural bioactive phenol derivatives have been developed. Among them, semi-synthetic protocols represent efficient and economical alternatives to total synthesis, combining efficient extraction protocols with efficient catalytic conversions to achieve reasonable amounts of active molecules. The aim of this review is to summarize the semi-synthetic protocols published in the last fifteen years, covering 2005 up to 2020, which can produce natural olive bioactive phenols scarcely available by extractive procedures, and new biophenol derivatives with enhanced biological activity. Moreover, the semi-synthetic protocols to produce olive bioactive phenol derivatives as analytical standards are also discussed. A critical analysis of the advantages offered by semi-synthesis compared to classical extraction methods or total synthesis protocols is also performed.

Antiglycative and anti-inflammatory effects of lipophilized tyrosol derivatives

Abstract

To expand the application of tyrosol, a series of lipophilized tyrosol derivatives were synthesized via esterification of tyrosol with fatty acids of different chain lengths. The antiglycative activity of tyrosol esters so prepared was subsequently examined in the bovine serum albumin/glucose system. A quasi-parabolic shape was observed when the activity was plotted against alkyl chain length. Additionally, the anti-inflammatory effects of these derivatives were evaluated against methylglyoxal-induced inflammation in RAW264.7 cells. The same trend on anti-inflammatory activity was found as in the antiglycation study. The results showed that tyrosol esters with C12:0 and C14:0 were two most efficient ones among all the tested derivatives. Thus, some lipophilized tyrosol derivatives were stronger antiglycative and anti-inflammatory agents compared to the parent compound, tyrosol.

Graphical abstract

Homogeneous distribution of fatty ester-based active cosmetic ingredients in hydrophilic thin films by means of nanodispersion

OBJECTIVE

Cosmetic films and patches are interesting forms to promote skin penetration of active ingredients as they ensure their long stay on the treated zone of the skin. Nevertheless, currently developed films and patches are most of all hydrophilic and are not adapted to the hydrophobic molecules. The aim of this study was to establish whether nanodispersion of fatty acid-based active cosmetic ingredients (ACI) could be a manner to introduce high concentrations of those ACI in hydrophilic films.

METHODS

Punica granatum seed oil hydroxyphenethyl esters (PHE) constitute a commercialized lipolytic cosmetic ingredient obtained by enzymatic conjugation of tyrosol to long-chain fatty acids and to enhance its skin diffusion. Nanodispersions of PHE were prepared by a green emulsion-solvent evaporation process and dispersed in polyvinyl alcohol films. Raman imaging coupled to multivariate analysis was used to study the distribution of PHE in the films.

RESULTS

Nanodispersions of PHE combined with antioxidant vitamin E and stabilized by Pluronic® F127 were successfully prepared. The nanodispersions show a spherical shape and a hydrodynamic diameter close to 100 nm. Raman images analysis with multivariate approaches showed a very homogeneous distribution of PHE nanodispersions in the films compared to free PHE introduced as an ethanol solution.

CONCLUSION

Nanodispersions of hydrophobic fatty acid-based ingredients seem to be relevant method to introduce this type of ingredient in hydrophilic film matrix. The co-suspension with vitamin E limits their degradation in time.

Phytochemical Profile, Mineral Content, and Bioactive Compounds in Leaves of Seed-Propagated Artichoke Hybrid Cultivars

The globe artichoke (Cynara cardunculus L. subsp. Scolymus (L.) Hegi) is a multi-year species rich in various classes of phytochemicals with known nutritional and pharmacological properties, such as polyphenols, sesquiterpene lactones, and terpenoids. Over the last decade, hybrids cultivars are transforming the artichoke market for their higher uniformity and stability over the traditional landraces, further increasing the potential of the artichoke as a source of commercial extracts and bioactive molecules. Our aim was to investigate the mineral and phytochemical profiles of leaves from seven seed-propagated hybrids by using an untargeted metabolomic approach based on ultra-high-pressure liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry. Metabolomics identified several compounds in the tested varieties, namely 98 polyphenols, 123 sesquiterpene lactones, and 221 other metabolites. The phenolic content ranged from 3.01 mg Eq./g fw (for 'Opera') to 4.71 mg Eq./g fw (for 'Opal'). Sesquiterpene lactones were, on average, 2.11 mg Eq./g fw. Multivariate statistics (HCA, PCA and OPLS-DA) highlighted the main metabolomics differences among cultivars, which weakly correlated with their agronomic classification. The seven cultivars showed distinctive metabolomics profiles, with 'Opal' and 'Istar' being the most valuable hybrids. The 3-hydroxyphenyl-valeric acid (a medium-chain fatty acid) and the 6-Gingesulfonic acid (a methoxyphenol) were the most discriminant markers. Our findings illustrated the quantitative and qualitative variation of several classes of phytochemicals in seed-propagated artichoke cultivars and allowed identifying distinctive metabolic signatures for both phenolic compounds and sesquiterpene lactones. This work supports the exploitation of the artichoke leaves from hybrid cultivars as a rich source of bioactive phytochemicals.

Transrutinosylation of tyrosol by flower buds of Sophora japonica

Dried flower buds of Japanese sophora (Sophora japonica) comprising rutinosidase activity were tested in rutinosylation of tyrosol via transglycosylation process from rutin. Optimal conditions for transrutinosylation of tyrosol were 49 mM rutin and 290 mM tyrosol, giving maximum conversion up to 66.4% and 24% yield of isolated and purified rutinoside. The rutinosylation proceeded exclusively on the primary hydroxyl of tyrosol, thus forming rhamnosylated derivative of salidroside. This strict regioselectivity differentiates the sophora biocatalyst from microbial rutinosidases.

Delivery Systems for Hydroxytyrosol Supplementation: State of the Art

This review aims to highlight the benefits and limitations of the main colloid-based available delivery systems for hydroxytyrosol. Hydroxytyrosol is a phenolic compound with clear biological activities for human wellness. Olive fruits, leaves and extra-virgin oil are the main food sources of hydroxytyrosol. Moreover, olive oil mill wastewaters are considered a potential source to obtain hydroxytyrosol to use in the food industry. However, recovered hydroxytyrosol needs adequate formulations and delivery systems to increase its chemical stability and bioavailability. Therefore, the application of hydroxytyrosol delivery systems in food sector is still a fascinating challenge. Principal delivery systems are based on the use of colloids, polymers able to perform gelling, thickening and stabilizing functions in various industrial sectors, including food manufacturing. Here, we review the recipes for the available hydroxytyrosol systems and their relative production methods, as well as aspects relative to system characteristics and hydroxytyrosol effectiveness.

Antioxidant properties of two novel lipophilic derivatives of hydroxytyrosol

Two novel lipophilic derivatives of the natural olive oil phenol, hydroxytyrosol (HT), were synthesized using 3,4-dihydroxyphenylacetic acid as starting material. Their antioxidant activities and kinetics compared to HT and TBHQ were assessed by Rancimat, Schaal Oven, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and deep-frying methods. All experiments, including kinetic data analysis based on the Arrhenius equation, utilized in assessing antioxidant activity except the DPPH assay revealed that the new lipophilic HT derivatives exhibited much stronger antioxidant activity than hydroxytyrosol. Tert-butylhydroquinone exhibited stronger antioxidant activity in bulk oil at 65 °C than the new HT derivatives, but showed much lower activity at higher temperatures (>110 °C). This demonstrates that the introduction of bulky alkyl moiety to the ortho-diphenolic structure of HT increased its antioxidant activity. It can be concluded that the new lipophilic HT derivatives satisfy industrial demands for bioactive compounds with strong antioxidant potential at high temperatures.

Isolation of tyrosine derived phenolics and their possible beneficial role in anti-inflammatory and antioxidant potential of Tithonia tubaeformis

The methanolic extract of aerial parts of Tithonia tubaeformis showed significant antioxidant activity in DPPH assay. It was subjected to bioassay guided fractionation affording more active ethyl acetate fraction which on further purification led to the isolation and identification of a series of bioactive phenolic compounds having important biosynthetic relationship. Of these, 4-hydroxyphenethyl henicosanoate (tithonoid) is a new compound. Moreover, in the carrageenan induced paw edema test, significant attenuation of inflammation was also produced by the extract at 50-200 mg/kg. The structures of all the constituents were determined through spectroscopic methods. It is the first systematic biological and chemical investigation on T. tubaeformis, which showed that phenolics may play an important role in the antioxidant and anti-inflammatory activity of the plant, probably through synergism.

Preparation of Quercetin Esters and Their Antioxidant Activity

Quercetin, a polyphenolic compound, is widely distributed in plants and has numerous health benefits. However, its hydrophilicity can compromise its use in lipophilic systems. For this reason, quercetin was esterified with 12 different fatty acids as their acyl chlorides with varying chain lengths and degrees of unsaturation. Two monoesters (Q-3'-O-monoester and Q-3-O-monoester) and four diesters (Q-7,3'-O-diester, Q-3',4'-O-diester, Q-3,3'-O-diester, and Q-3,4'-O-diester) were the major products as was shown by HPLC-MS and ¹H-NMR data. The lipophilicity of quercetin derivatives was calculated; this was found to increase with fatty acid chain length. The antioxidant potential of quercetin and its derivatives was evaluated by using DPPH radical and ABTS radical cation scavenging activity; quercetin showed the highest radical scavenging activity among all tested samples. Despite the decrease of antioxidant activity in this study, the derivatives may show better antioxidant activity in lipophilic media and display improved absorption and bioavailability in the body once consumed.

Hydroxytyrosyl Oleate: Improved Extraction Procedure from Olive Oil and By-Products, and In Vitro Antioxidant and Skin Regenerative Properties

Recently, we identified hydroxytyrosyl oleate (HtyOle) in the by-products of olive oil, pomace and olive mill waste water (OMWW). Herein, we report that HtyOle is more accurately quantified by extracting the phenolic fraction from both matrices by using aqueous methanol (80%). By applying this method, HtyOle was also detected in extra virgin olive oil (EVOO). Since olive oil is used in the preparation of many cosmetic formulations, we explored the antioxidant capacity of HtyOle in human keratinocytes. Formation of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as activity of Glutathione-S-transferase (GST) and superoxide dismutase (SOD) were decreased by HtyOle. In addition to that, microRNAs (miRs) involved in both redox status balance and skin regeneration potential were also tested. The following miRs, hsa-miR-21 and hsa-miR-29a, were increased while has-miR-34a was not affected by HtyOle.

Synthesis of Lipophilic Esters of Tyrosol, Homovanillyl Alcohol and Hydroxytyrosol

Low-molecular weight phenols such as tyrosol, homovanillyl alcohol and hydroxytyrosol are valuable compounds that exhibit a high number of health-promoting effects such as antioxidant, anti-inflammatory and anticancer activity. Despite these remarkable properties, their applications such as dietary supplements and stabilizers of foods and cosmetics in non-aqueous media are limited for the hydrophilic character. With the aim to overcome this limitation, the paper describes a simple and low-cost procedure for the synthesis of lipophilic esters of tyrosol, homovanillyl alcohol and hydroxytyrosol. The reactions were carried out under mild and green chemistry conditions, at room temperature, solubilizing the phenolic compounds in dimethyl carbonate, an eco-friendly solvent, and adding a little excess of the appropriate C2-C18 acyl chloride. The final products were isolated in good yields. Finally, according to the "circular economy" strategy, the procedure was applied to hydroxytyrosol-enriched extracts obtained by Olea europaea by-products to prepare a panel of lipophilic extracts that are useful for applications where solubility in lipid media is required.

Differential metabolic signatures in naturally and lactic acid bacteria (LAB) fermented ting (a Southern African food) with different tannin content, as revealed by gas chromatography mass spectrometry (GC-MS)-based metabolomics

Fermented whole grain (WG) sorghum food products including WG-ting can be obtained from different sample sources and fermentation conditions, leading subsequently to variations in the molecular composition of the products. There is however, a lack of detailed understanding and description of differential molecular profiles of these food products. Thus, the current study is a nontargeted gas chromatography-mass spectrometry (GC-MS)-based metabolomics approach to descriptively elucidate metabolic profiles of two WG-sorghum types [high tannin (HT) and low tannin (LT)] and their derived WG-ting products obtained via fermentation. Metabolites were extracted with 80% aqueous methanol and analyzed on a gas chromatography high resolution time of flight mass spectrometry (GC-HRTOF-MS) system. Chemometric methods such as principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA) were applied to mine the generated data. Our results showed that tannin contents influenced the composition of the raw sorghum and derived WG-ting samples. Metabolite signatures that differentiated raw HT- and LT-sorghum included cyclic compounds, pesticides, 2,4-di-tert-butylphenol, fatty acid esters, and sugar derivatives. Furthermore, fermentation of the HT- and LT-sorghum into WG-ting led to an increase in the levels of fatty acids, fatty acid esters and some other compounds which are vital from a dietary and health context. Equally observed were reduction of some phenols, cyclic compounds, a pesticide and ketone. Thus, the results demonstrated that the inherent metabolic composition of raw sorghum would lead to differential metabolic changes in the fermented products such as WG-ting, with subsequent dietary and health implications. Fermenting ting with Lactobacillus fermentum FUA 3321 was most desirable as relevant metabolites were observed in both HT- and LT-ting samples. Furthermore, the study highlights the applicability of GC-MS metabolomics in understanding WG-ting fermentation.

Chemical characterization of liposomes containing nutraceutical compounds: Tyrosol, hydroxytyrosol and oleuropein

Tyrosol, hydroxytyrosol and oleuropein are among the major phenolic compounds in fruits, leaves and oils from Olea europaea L. These natural antioxidants molecules revealed several beneficial effects on human health, but a low bioavailability and accessibility to targeted site. Liposomes are drug/nutraceutical delivery carriers, used for driving bioactive molecules to desired target tissues, decreasing potential side effects and protecting the encapsulated molecule from enzymatic metabolic processes. In this study, zwitterionic liposomes containing tyrosol, hydroxytyrosol and oleuropein were synthesized and characterized for their size and surface charge. Particular attention was devoted to the determination of encapsulation efficiency (EE%), quantifying the loaded Tyr, HTyr and Ole amount, by using three different techniques: direct UV spectrophotometry, High Performance Liquid Chromatography and Trolox Equivalent Antioxidant Capacity assay. The results revealed higher EE% for oleuropein. Cyto-toxicity and cyto-compatibility of liposomes were also tested on human chondrocyte cells.

Identification of hydroxytyrosyl oleate, a derivative of hydroxytyrosol with anti-inflammatory properties, in olive oil by-products

Hydroxytyrosyl esters with short, medium and long acyl chains were evaluated for their ability to reduce nitric oxide (NO) production by lipopolysaccharide-stimulated RAW264.7 macrophages. Among the compounds tested, C18 esters, namely hydroxytyrosyl stearate (HtySte) and hydroxytyrosyl oleate (HtyOle), were found to decrease NO production in a concentration-dependent manner, while the other compounds, including the parent hydroxytyrosol, were ineffective in the tested concentration range (0.5-5 μM). Further study of the potential immune-modulating properties of HtyOle revealed a significant and concentration-dependent suppression of prostaglandin E₂ production. At a transcriptional level, HtyOle inhibited the expression of inducible NO synthase, cyclooxygenase-2 and interleukin-1β. Moreover, HtyOle was identified for the first time in olive oil by-products by means of high performance liquid chromatography coupled with mass spectrometry. By contrast, HtyOle was not found in intact olives. Our results suggest that HtyOle is formed during oil processing and represents a significant form in which hydroxytyrosol occurs.

Hydroxytyrosol protects against myocardial ischemia reperfusion injury by inhibiting mitochondrial permeability transition pore opening

Hydroxytyrosol (HT), a phenolic compound extracted from olive oil, is reported to protect against myocardial ischemia reperfusion injury (MIRI), but its mechanism has not been fully elucidated. The mitochondria permeability transition pore (MPTP) is an important therapeutic target for MIRI. The present study aimed to investigate the role of MPTP in the cardioprotection of HT. Isolated rat hearts were mounted on a Langendorff apparatus and subjected to 30 min of ischemia followed by 120 min of reperfusion to mimic a MIRI model. Isolated hearts were pretreated with different doses of HT (10, 100 and 1,000 µM) for 10 min prior to ischemia. Myocardial infarct size was detected using TTC staining. Changes in myocardial cell structure were observed using hematoxylin and eosin staining. MPTP opening was detected spectrophotometrically. Myocardial cell apoptosis was observed with terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assays. The expression of apoptosis-associated proteins was measured by western blot analysis. The data revealed that HT (100 and 1,000 µM) treatment significantly alleviated pathological damage in ischemic myocardium and reduced myocardial infarct size compared with the untreated control. However, no significant difference was observed in the 10 µM HT treatment group compared with the untreated control. It was further revealed that HT decreased the B cell lymphoma-2 (Bcl-2)-like protein 4 (Bax)/Bcl-2 ratio, suppressed MPTP opening and subsequently decreased the expression of cytochrome c, cleaved caspase-9 and -3, thereby inhibiting apoptosis. Additionally, the beneficial effects of HT on MIRI were reversed by atractyloside, which induces MPTP opening. In conclusion, the present study demonstrated that HT inhibited MPTP opening, partially via modulation of Bax and Bcl-2, thereby protecting against MIRI and thereby providing a pharmacological basis for future research and treatment of MIRI.