Lipase-Produced Hydroxytyrosyl Eicosapentaenoate is an Excellent Antioxidant for the Stabilization of Omega-3 Bulk Oils, Emulsions and Microcapsules

Bioaccessible Phenolic Alkyl Esters of Wine Lees Decrease COX-2-Catalyzed Lipid Mediators of Oxidative Stress and Inflammation in a Time-Dependent Manner

Lipophenols, phenolic compounds esterified with fatty alcohols or fatty acids, provide greater health benefits upon dietary ingestion of plant-based foods than unesterified (poly)phenols. Based on this premise, the present study aimed to demonstrate the role of gastrointestinal enzymes (pepsin, pancreatin, and pancreatic lipase) in releasing alkyl gallates and trans-caffeates from wine lees, providing bioactive compounds with enhanced capacities against oxidative stress (OS) and para-inflammation. The UHPLC-ESI-QqQ-MS/MS-based analysis revealed ethyl gallate and ethyl trans-caffeate as the most prominent compounds (1.675 and 0.872 μg/g dw, respectively), while the bioaccessibility of the derivatives of gallic and caffeic acids was dependent on the alkyl chain properties. The de novo formation of alkyl gallates during gastric and intestinal digestion resulted from intestinal enzyme activity. Moreover, the in vitro capacity of bioaccessible alkyl esters of gallic and trans-caffeic acids to reduce cyclooxygenase-2 concentration and modulate oxilipins related to OS (8-iso-PGF2α) and inflammation (PGF2α and PGE2) was demonstrated in a time-dependent manner. In conclusion, the presence of alkyl esters of gallic and trans-caffeic acids in wine lees and their subsequent formation during digestion of this byproduct emphasize their value as a source of antioxidant and anti-inflammatory compounds, encouraging the consideration of wine lees as a valuable ingredient for health-promoting coproducts.

The Inhibitory Effects of Hydroxytyrosol, α-Tocopherol and Ascorbyl Palmitate on Lipid Peroxidation in Deep-Fat Fried Seafood

This study aimed to investigate the inhibitory effects of hydroxytyrosol, α-tocopherol and ascorbyl palmitate on lipid peroxidation in squid, hoki and prawn during deep-fat frying and refrigerated storage. Fatty acid analysis using gas chromatography (GC) showed that the seafood had a high omega-3 polyunsaturated fatty acid (n-3 PUFAs) content, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The total content of n-3 fatty acids in their lipids was 46% (squid), 36% (hoki) and 33% (prawn), although they all had low lipid contents. The oxidation stability test results showed that deep-fat frying significantly increased the peroxide value (POV), p-anisidine value (p-AV) and the value of thiobarbituric acid reactive substances (TBARS) in squid, hoki and prawn lipids. Meanwhile, antioxidants delayed the lipid oxidation in fried seafood and sunflower oil (SFO) used for frying, albeit in different ways. The least effective of all the antioxidants was α-tocopherol, as the POV, p-AV and TBARS values obtained with this antioxidant were significantly higher. Ascorbyl palmitate was better than α-tocopherol but was not as effective as hydroxytyrosol in suppressing lipid oxidation in the frying medium (SFO) and in the seafood. However, unlike the ascorbyl palmitate-treated oil, hydroxytyrosol-treated oil could not be used for multiple deep-fat frying of seafood. Hydroxytyrosol appeared to be absorbed in the seafood during multiple frying, thus leaving a low concentration in the SFO and making it susceptible to oxidation.

Advances in enzyme biocatalysis for the preparation of functional lipids

Functional lipids, mainly ω-3 polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic (DHA; 22:6n-3), are known to have a variety of health benefits. Lipases and phospholipases are widely used to prepare different forms of structured lipids, since biocatalytic methods can be carried out under mild conditions, preserving the quality of the products. On the other hand, many processes still are conducted at high temperatures and with organic solvents, which are conditions unfavorable for the production of nutritional products. This article gives an updated overview of enzyme biocatalysis methods for the preparation of different derivatives containing n-3 PUFAs, including specific reactions, enzyme immobilization research for high-efficiency catalysis, and enzyme engineering technologies (higher selectivity, stability, and activity). Furthermore, advanced control strategies of biocatalytic processes and reactors are presented. The future prospect and opportunities for marine functional lipids are also discussed. Therefore, the obtainment of enzymes endowed with superior properties and the development of optimized processes, still have to be pursued to achieve greener bio-catalyzed processes.

The Tower of Babel of Pharma-Food Study on Extra Virgin Olive Oil Polyphenols

Much research has been conducted to reveal the functional properties of extra virgin olive oil polyphenols on human health once EVOO is consumed regularly as part of a balanced diet, as in the Mediterranean lifestyle. Despite the huge variety of research conducted, only one effect of EVOO polyphenols has been formally approved by EFSA as a health claim. This is probably because EFSA’s scientific opinion is entrusted to scientific expertise about food and medical sciences, which adopt very different investigative methods and experimental languages, generating a gap in the scientific communication that is essential for the enhancement of the potentially useful effects of EVOO polyphenols on health. Through the model of the Tower of Babel, we propose a challenge for science communication, capable of disrupting the barriers between different scientific areas and building bridges through transparent data analysis from the different investigative methodologies at each stage of health benefits assessment. The goal of this work is the strategic, distinctive, and cost-effective integration of interdisciplinary experiences and technologies into a highly harmonious workflow, organized to build a factual understanding that translates, because of trade, into health benefits for buyers, promoting EVOOs as having certified health benefits, not just as condiments.

Catalytic Routes to Produce Polyphenolic Esters (PEs) from Biomass Feedstocks

Polyphenolic esters (PEs) are valuable chemical compounds that display a wide spectrum of activities (e.g., anti-oxidative effects). As a result, their production through catalytic routes is an attractive field of research. The present review aims to discuss recent studies from the literature regarding the catalytic production of PEs from biomass feedstocks, namely, naturally occurred polyphenolic compounds. Several synthetic approaches are reported in the literature, mainly bio-catalysis and to a lesser extent acid catalysis. Immobilized lipases (e.g., Novozym 435) are the preferred enzymes thanks to their high reactivity, selectivity and reusability. Acid catalysis is principally investigated for the esterification of polyphenolic acids with fatty alcohols and/or glycerol, using both homogeneous (p-toluensulfonic acid, sulfonic acid and ionic liquids) and heterogeneous (strongly acidic cation exchange resins) catalysts. Based on the reviewed publications, we propose some suggestions to improve the synthesis of PEs with the aim of increasing the greenness of the overall production process. In fact, much more attention should be paid to the use of new and efficient acid catalysts and their reuse for multiple reaction cycles.

Recent advances in the enzymatic synthesis of lipophilic antioxidant and antimicrobial compounds

Due to the increase in the consumption of highly processed food in developed countries, as well as, a growing number of foodborne diseases, exploration of new food additives is an issue focusing on scientific attention and industrial interest. Functional compounds with lipophilic properties are remarkably desirable due to the high susceptibility to the deterioration of lipid-rich food products. This paper in a comprehensive manner provides the current knowledge about the enzymatic synthesis of lipophilic components that could act as multifunctional food additives. The main goal of enzymatic lipophilization of compounds intentionally added to food is to make these substances soluble in lipids and/or to obtain environmentally friendly surfactants. Moreover, lipase-catalyzed syntheses could result in changes in the antioxidant and antimicrobial activities of phenolic compounds, carbohydrates, amino acids (oligopeptides), and carboxylic acids. The review describes also the implementation of a new trend in green chemistry, where apart from simple and uncomplicated chemical compounds, the modifications of multi-compound mixtures, such as phenolic extracts or essential oils have been carried out.

Fatty Acid Hydroxytyrosyl Esters of Olive Oils Are Bioaccessible According to Simulated In Vitro Gastrointestinal Digestion: Unraveling the Role of Digestive Enzymes on Their Stability

Recently, new bioactive compounds were identified in olive oil, lipophenols, which are composed of a fatty acid (FA) and a phenolic core, such as HT (HT-FA). However, their bioaccessibility remains unknown. Thus, the present study uncovers the impact of the separate phases of gastrointestinal digestion on the release and stability of HT-FAs from oily matrices under in vitro simulated conditions. Accordingly, it was found that the bioaccessibility of HT derivatives is largely dependent on the type of FA that esterifies HT, as well as the food matrix. Also, the generation of HT-FAs during intestinal digestion was observed, with pancreatin being the enzyme responsible, to a higher extent, for the de novo formation of lipophenolic derivatives. These findings prompt us to identify new applications to oily matrices and their byproducts as potential functional ingredients for the promotion of health, where the possible formation of new lipophenols during digestion should be taken into consideration.

Lipase Assisted (S)-Ketoprofen Resolution from Commercially Available Racemic Mixture

Ketoprofen is a commercially available drug sold as a racemic mixture that belongs to the family of non-steroidal anti-inflammatory drugs known as profens. It has been demonstrated (in vitro) that (S)-ketoprofen is around 160 times more potent than its enantiomer (R)-ketoprofen, while accumulation of (R)-ketoprofen can cause serious side effects, such as dyspepsia, gastrointestinal ulceration/bleeding, pain, salt and fluid retention, and hypertension. In this work, four commercially available lipases were systematically assessed. Parameters such as conversion, enantiomeric excess, and enantioselectivity were considered. Among them, and by evaluating lipase load, temperature, solvent, and alcohol, Candida rugosa lipase exhibited the best results in terms of enantioselectivity E = 185 ((S)-enantiopreference) with esterification conversions of c = 47% (out of 50%) and enantiomeric excess of 99%. The unreacted (R)-enantiomer was recovered by liquid-liquid extraction and racemized under basic media, which was recycled as starting material. Finally, the (S)-alkyl ketoprofen ester was successfully enzymatically hydrolyzed to the desired (S)-ketoprofen with c = 98.5% and 99% ee. This work demonstrated the benefit and efficiency of using Candida rugosa lipase to kinetically resolve racemic ketoprofen by an environmentally friendly protocol and with the recycling of the undesired (R)-ketoprofen.

A comprehensive review on polarity, partitioning, and interactions of phenolic antioxidants at oil-water interface of food emulsions

There has been a growing interest in developing effective strategies to inhibit lipid oxidation in emulsified food products by utilization of natural phenolic antioxidants owing to their growing popularity over the past decades. However, due to the complexity of emulsified systems, the inhibition mechanism of phenolic antioxidants against lipid oxidation is rather complicated and not yet fully understood. In order to highlight the importance of polarity of phenolic antioxidants in emulsified systems according to the polar paradox, this review covers the recent progress on chemical, enzymatic, and chemoenzymatic lipophilization techniques used to modify the polarity of antioxidants. The partitioning behavior of phenolic antioxidants at the oil-water interface, which can be influenced by the presence of synthetic surfactants and/or antioxidant emulsifiers (e.g., polysaccharides, proteins, and phospholipids), is discussed. In addition, the emerging phenolic antioxidants among phenolic acids, flavonoids, tocopherols, and stilbenes applied in food emulsions are elaborated. As well, the interactions of polar-nonpolar antioxidants are stressed as a promising strategy to induce synergistic interactions at oil-water interface for improved oxidative stability of emulsions.

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.

Fish Oil Microcapsules as Omega-3 Enrichment Strategy: Changes in Volatile Compounds of Meat Products during Storage and Cooking

This work aims to analyze the effects of processing and storage on the volatile compound profile of different meat products enriched in ω-3 polyunsaturated fatty acids (PUFA). Monolayered (Mo) and multilayered (Mu) microcapsules of fish oil were tested. The profiles of volatile compounds were analyzed by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The enrichment with Mo significantly increases the abundance of volatile compounds from lipid oxidation and markers of ω-3 PUFA oxidation, which may be related to the multilayer structure of chitosan–maltodextrin in Mu that achieves greater fish oil protection than the simple coating of maltodextrin in Mo. Besides, the changes in volatile compounds during storage depends on the type of fish oil microcapsules and the meat products, having an increased abundance of ω-3 PUFA oxidation markers in dry-cured sausages added with Mo. However, the enrichment of these meat products with Mo and Mu does not modify the usual variations in the volatile compound profile during culinary cooking. Thus, the addition of multilayer fish oil microcapsules may be a suitable option for enrichment of meat products in ω-3 PUFA without modifying the abundance of volatile compounds, including oxidation markers.

Green Synthesized Magnetic Nanoparticles as Effective Nanosupport for the Immobilization of Lipase: Application for the Synthesis of Lipophenols

In this work, hybrid zinc oxide-iron oxide (ZnOFe) magnetic nanoparticles were synthesized employing Olea europaea leaf aqueous extract as a reducing/chelating and capping medium. The resulting magnetic nanoparticles were characterized by basic spectroscopic and microscopic techniques, namely, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fourier-transform infrared (FTIR) and atomic force microscopy (AFM), exhibiting a spherical shape, average size of 15-17 nm, and a functionalized surface. Lipase from Thermomyces lanuginosus (TLL) was efficiently immobilized on the surface of ZnOFe nanoparticles through physical absorption. The activity of immobilized lipase was found to directly depend on the enzyme to support the mass ratio, and also demonstrated improved pH and temperature activity range compared to free lipase. Furthermore, the novel magnetic nanobiocatalyst (ZnOFe-TLL) was applied to the preparation of hydroxytyrosyl fatty acid esters, including derivatives with omega-3 fatty acids, in non-aqueous media. Conversion yields up to 90% were observed in non-polar solvents, including hydrophobic ionic liquids. Different factors affecting the biocatalyst performance were studied. ZnOFe-TLL was reutilized for eight subsequent cycles, exhibiting 90% remaining esterification activity (720 h of total operation at 50 °C). The green synthesized magnetic nanoparticles, reported here for the first time, are excellent candidates as nanosupports for the immobilization of enzymes with industrial interest, giving rise to nanobiocatalysts with elevated features.

Revisiting the scope and applications of food enzymes from extremophiles

Microorganisms from extreme environments tend to undergo various adaptations due to environmental conditions such as extreme pH, temperature, salinity, heavy metals, and solvents. Thus, they produce enzymes with unique properties and high specificity, making them useful industrially, particularly in the food industries. Despite these enzymes' remarkable properties, only a few instances can be reported for actual exploitation in the food industry. This review's objectives are to highlight the properties of these enzymes and their prospects in the food industry. First, an introduction to extremophilic organisms is presented, followed by the categories and application of food enzymes from extremophiles. Then, the unique structural features of extremozymes are shown. This review also covers the prospective applications of extremozymes in the food industry in a broader sense, including degradation of toxins, deconstruction of polymers into monomers, and catalysis of multistep processes. Finally, the challenges in bioprocessing of extremozymes and applications in food are presented. PRACTICAL APPLICATIONS: Enzymes are important players in food processing and preservation. Extremozymes, by their nature, are ideal for a broad range of food processing applications, particularly those that require process conditions of extreme pH, temperature, and salinity. As the global food industry grows, so too will grow the need to research and develop food products that are diverse, safe, healthy, and nutritious. There is also the need to produce food in a sustainable way that generates less waste or maximizes waste valorization. We anticipate that extremozymes can meet some of the research and development needs of the food industry.

The Versatility of Antioxidant Assays in Food Science and Safety-Chemistry, Applications, Strengths, and Limitations

Currently, there is a growing interest in screening and quantifying antioxidants from biological samples in the quest for natural and effective antioxidants to combat free radical-related pathological complications. Antioxidant assays play a crucial role in high-throughput and cost-effective assessment of antioxidant capacities of natural products such as medicinal plants and food samples. However, several investigators have expressed concerns about the reliability of existing in vitro assays. Such concerns arise mainly from the poor correlation between in vitro and in vivo results. In addition, in vitro assays have the problem of reproducibility. To date, antioxidant capacities are measured using a panel of assays whereby each assay has its own advantages and limitations. This unparalleled review hotly disputes on in vitro antioxidant assays and elaborates on the chemistry behind each assay with the aim to point out respective principles/concepts. The following critical questions are also addressed: (1) What make antioxidant assays coloured? (2) What is the reason for working at a particular wavelength? (3) What are the advantages and limitations of each assay? and (4) Why is a particular colour observed in antioxidant–oxidant chemical reactions? Furthermore, this review details the chemical mechanism of reactions that occur in each assay together with a colour ribbon to illustrate changes in colour. The review ends with a critical conclusion on existing assays and suggests constructive improvements on how to develop an adequate and universal antioxidant assay.

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.

New Dihydroxytyrosyl Esters from Dicarboxylic Acids: Synthesis and Evaluation of the Antioxidant Activity In Vitro (ABTS) and in Cell-Cultures (DCF Assay)

New dihydroxytyrosyl esters 2a, 2c–2j of dicarboxylic acids were synthesized from methyl orthoformate protected hydroxytyrosol 3 and diacyl chlorides. New compounds were characterized (HRMS, FT-IR, ¹H- and ¹³C-NMR), and tested for antioxidant activity both in vitro (ABTS) and on L6 myoblasts and THP1 leukemic monocytes cell culture by DCF assay. According to the ABTS assay, compounds 2a, 2c–2j showed a TEAC value of antioxidant capacity up to twice that of Trolox. Very high or complete ROS protections were obtained in the cell environment where lipophilicity and rigidity of dicarboxylic structure seem to facilitate the antioxidant effect. MTT assay and proliferation test were used for assessment of cell viability. These compounds can be envisaged as a new class of preservatives for food or cosmetic products.

Fish oil/lycopene microcapsules as a source of eicosapentaenoic and docosahexaenoic acids: a case study on spreads

BACKGROUND

The consumption of omega-3 fatty acids has many beneficial effects for human health, but the intake of foods rich in these fatty acids is not enough to achieve the recommended quantity per person and per day, and their direct addition in foods cause oxidation and unacceptable rancidity and off-flavor. Taking account of all these aspects, this study was aimed to develop stable microcapsules of fish oil (omega-3 polyunsaturated fatty acids) and lycopene (antioxidant) and to investigate their effect on different spreads.

RESULTS

The inclusion of different proportions of lycopene in fish oil did not show great benefits in the quality characteristics of emulsions and microcapsules. After the addition of fish oil and fish oil + lycopene microcapsules to dry-cured ham and cheese spreads, no significant differences were found in the proximal composition and oxidative stability, whereas fatty acids composition and sensory analysis were influenced. The eicosapentaenoic and docosahexaenoic acids content increased with the fish oil content in both products, but it decreased significantly after storage in the cheese spreads. Addition of microcapsules did not significantly influence on quantitative-descriptive and acceptability sensory analyses in dry-cured spreads, but it negatively affected the flavor of cheese spreading creams.

CONCLUSION

There is no need to add antioxidants to improve the stability of the fish oil microcapsules in the present study, which are appropriate as eicosapentaenoic acid and docosahexaenoic acid vehicles to enrich meat-derived spreading creams. © 2019 Society of Chemical Industry.

Evaluating the use of fish oil microcapsules as omega-3 vehicle in cooked and dry-cured sausages as affected by their processing, storage and cooking

This work evaluated the use of monolayered (Mo) and multilayered (Mu) fish oil microcapsules as vehicles of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in cooked and dry-cured meat products as affected by the storage and culinary heating or dry-cured processing. Proximate composition, oxidation, EPA and DHA quantity, acceptability and morphology were evaluated. Mo and Mu microcapsules increased the quantity of EPA and DHA, leading to cooked and dry-cured products susceptible to be labeled as "source of omega-3 fatty acids", without influencing physico-chemical characteristics, oxidative stability, acceptability or usual changes that take place during the culinary heating or dry-cured processing. The storage at refrigeration influenced on usual modifications on lipid oxidation and hedonic scores, but overall quality of the meat products enriched seems not to be impaired after storing. Thus, it could be indicated the viability of Mo and Mu as vehicles to enrich meat products subjected to low and high temperature for manufacturing, storage at refrigeration and culinary heating.

Polydatin-fatty acid conjugates are effective antioxidants for stabilizing omega 3-containing bulk fish oil and fish oil emulsions

Candida antarctica lipase B-catalysed synthesis of lipophilic esters of polydatin was investigated along with their antioxidant activities. The effects of synthesis parameters such as solvent, substrate molar ratio, enzyme concentration, addition of molecular sieves, reaction temperature and time on the production of ester were studied and optimised. The highest production of esters was obtained with acetone as the reaction solvent. The antioxidant activities of the esters were compared with those of commercial butylated hydroxytoluene (BHT) and α-tocopherol. All polydatin esters inhibited the oxidative destruction of β-carotene more effectively than did BHT and α-tocopherol. Results of thiobarbituric acid tests showed that in bulk fish oil, all esters were more effective than α-tocopherol at 2 mmol/kg concentration but were not as effective as BHT. In fish oil-emulsions, all esters were more effective than both BHT and α-tocopherol at 2 mmol/kg concentration. The synthesized polydatin esters are promising antioxidants for oil/fat-based foods.

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.

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.