An easy and green tool for olive oils labelling according to the contents of hydroxytyrosol and tyrosol derivatives: Extraction with a natural deep eutectic solvent and direct spectrophotometric analysis

Alternative Assisted Extraction Methods of Phenolic Compounds Using NaDESs

A renewed understanding of eco-friendly principles is moving the industrial sector toward a shift in the utilization of less harmful solvents as a main strategy to improve manufacturing. Green analytical chemistry (GAC) has definitely paved the way for this transition by presenting green solvents to a larger audience. Among the most promising, surely DESs (deep eutectic solvents), NaDESs (natural deep eutectic solvents), HDESs (hydrophobic deep eutectic solvents), and HNaDESs (hydrophobic natural deep eutectic solvents), with their unique features, manifest a wide-range of applications, including their use as a means for the extraction of small bioactive compounds. In examining recent advancements, in this review, we want to focus our attention on some of the most interesting and novel 'solvent-free' extraction techniques, such as microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) in relation to the possibility of better exploiting DESs and NaDESs as plausible extracting solvents of the phenolic compounds (PCs) present in different matrices from olive oil components, such as virgin olive pomace, olive leaves and twigs, virgin and extra virgin olive oil (VOO and EVOO, respectively), and olive cake and olive mill wastewaters (OMWW). Therefore, the status of DESs and NaDESs is shown in terms of their nature, efficacy and selectivity in the extraction of bioactive phytochemicals such as secoiridoids, lignans, phenolic acids and alcohols. Related studies on experimental design and processes' optimization of the most promising DESs/NaDESs are also reviewed. In this framework, an extensive list of relevant works found in the literature is described to consider DESs/NaDESs as a suitable alternative to petrochemicals in cosmetics, pharmaceutical, or food applications.

Recent Progress on Green New Phase Extraction and Preparation of Polyphenols in Edible Oil

With the proposal of replacing toxic solvents with non-toxic solvents in the concept of green chemistry, the development and utilization of new green extraction techniques have become a research hotspot. Phenolic compounds in edible oils have good antioxidant activity, but due to their low content and complex matrix, it is difficult to achieve a high extraction rate in a green and efficient way. This paper reviews the current research status of novel extraction materials in solid-phase extraction, including carbon nanotubes, graphene and metal-organic frameworks, as well as the application of green chemical materials in liquid-phase extraction, including deep eutectic solvents, ionic liquids, supercritical fluids and supramolecular solvents. The aim is to provide a more specific reference for realizing the green and efficient extraction of polyphenolic compounds from edible oils, as well as another possibility for the future research trend of green extraction technology.

A Critical Appraisal of the Separation Protocols Proposed for the Implementation of the Health Claim on “Olive Oil Polyphenols” (EC Regulation 432/2012)

The analysis of the secoiridoid type of phenolic compounds present in virgin olive oil has become a challenging area of research since the first evidence of their presence in the polar fraction of the oil. Separation techniques, mainly liquid chromatographic ones, prevailed over the years of application toward elucidation of their structure, content determination and collection of evidence on cultivar, origin, processing and storage conditions dependence. One of the latest challenges in their analysis was related to the need to address the requirement set by EC Regulation 432/2012 for the implementation of the health claim on ‘olive oil polyphenols’. The present work considers in a chronological order the original articles, viewpoints, review articles and other published efforts that appeared in the literature after the issuing of the relevant EFSA scientific opinion in 2011. The EFSA health claim created a lot of expectations among producers of virgin olive oil and boosted research for the development of a ‘fit for the purpose’ analytical protocol. Emphasis is given to the dedicated separation protocols that have been developed in the last 10 years and to the progress in their validation in comparison to the features of the method that were recently adopted by the International Olive Council.

Deep Eutectic Liquids as Tailorable Extraction Solvents: A Review of Opportunities and Challenges

Deep Eutectic Liquids (DELs) fall among the rapidly evolving discoveries of the 21st century, and these liquids are considered as alternative solvents to toxic and volatile organic liquids. Nevertheless, the emerging trend regarding the use of DELs in every field of physical and biological sciences, a lot of ambiguities and misconceptions exist about their formation, mechanism, and efficiencies observed or projected. A review of available technical data makes it obvious that these liquids have the potential to revolutionize the underdeveloped areas of analytical chemistry particularly the extraction/enrichment of analytes. To ensure the green and sustainable use of DELs, the researchers need to have a thorough understanding of DELs, their classification, chemistry, the nature and strength of molecular entanglements, and their tailorable features. Many researchers have declared these liquids recyclable but more attentive trials are needed to develop an authentic and straightforward DELs recycling methodology. The present review covers sound background knowledge and expert opinions about the technical definition of DELs, their classification, formation, recyclability, and tailorable features for their application as extraction solvent/sorbent in analytical chemistry.

Natural Deep Eutectic Solvent-Based Dispersive Liquid-Liquid Microextraction Coupled with Direct Analysis in Real Time Mass Spectrometry: A Green Temperature-Mediated Analytical Strategy

Green analytical chemistry (GAC) represents a rapidly growing research field that aims at developing novel analytical approaches with minimal consumption of hazardous reagents and solvents. The current study reports on a GAC methodology exploiting the unique physicochemical properties of natural deep eutectic solvents (NADESs), a supposedly environmentally friendly class of solvents. Based on a temperature-mediated strategy, the NADESs were manipulated to undergo multiple phase transitions for favorable functionality and performance. As proof-of-concept demonstrations, both hydrophobic and hydrophilic NADESs were prepared for the extraction and analysis of eight phthalate esters in aqueous samples (food simulants) and three aflatoxins in oily samples (edible oils), respectively. NADES-based dispersive liquid-liquid microextraction (DLLME) was employed to achieve high-efficiency sample pretreatment. Afterward, the NADESs were transformed from liquids into solids by tuning the peripheral temperature for a convenient phase separation from the sample matrices. The solidified NADES extracts were melted and vaporized at elevated temperatures by transmission-mode direct analysis in real time (DART) for further quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS) analysis. The developed protocol was validated, achieving good repeatability with relative standard deviations (RSDs) of less than 9% and satisfactory sensitivity with limits of detection (LODs) and quantitation (LOQs) ranging from 0.1 to 0.8 and 0.2 to 2.0 μg/kg, respectively. The greenness of the analytical methodology was assessed with the calculated scores of 0.66 and 0.57 for the hydrophobic and hydrophilic NADES-based protocols, respectively. The method was applied to marketed samples, highlighting the great potential for green chemical analysis.

Influence of the extraction method on the recovery of bioactive phenolic compounds from food industry by-products

Agro-foodindustries generate colossal amounts of non-edible waste and by-products, easily accessible as raw materials for up-cycling active phytochemicals. Phenolic compounds are particularly relevant in this field given their abundance in plant residues and the market interest of their functionalities (e.g. natural antioxidant activity) as part of nutraceutical, cosmetological and biomedical formulations. In "bench-to-bedside" achievements, sample extraction is essential because valorization benefits from matrix desorption and solubilization of targeted phytocompounds. Specifically, the composition and polarity of the extractant, the optimal sample particle size and sample:solvent ratio, as well as pH, pressure and temperature are strategic for the release and stability of mobilized species. On the other hand, current green chemistry environmental rules require extraction approaches that eliminate polluting consumables and reduce energy needs. Thus, the following pages provide an update on advanced technologies for the sustainable and efficient recovery of phenolics from plant matrices.

Deep Eutectic Solvents Application in Food Analysis

Current trends in Analytical Chemistry are focused on the development of more sustainable and environmentally friendly procedures. However, and despite technological advances at the instrumental level having played a very important role in the greenness of the new methods, there is still work to be done regarding the sample preparation stage. In this sense, the implementation of new materials and solvents has been a great step towards the development of "greener" analytical methodologies. In particular, the application of deep eutectic solvents (DESs) has aroused great interest in recent years in this regard, as a consequence of their excellent physicochemical properties, general low toxicity, and high biodegradability if they are compared with classical organic solvents. Furthermore, the inclusion of DESs based on natural products (natural DESs, NADESs) has led to a notable increase in the popularity of this new generation of solvents in extraction techniques. This review article focuses on providing an overview of the applications and limitations of DESs in solvent-based extraction techniques for food analysis, paying especial attention to their hydrophobic or hydrophilic nature, which is one of the main factors affecting the extraction procedure, becoming even more important when such complex matrices are studied.

Bioactive compounds and antioxidant activities in the agro-industrial residues of acerola (Malpighia emarginata L.), guava (Psidium guajava L.), genipap (Genipa americana L.) and umbu (Spondias tuberosa L.) fruits assisted by ultrasonic or shaker extraction

The aim of this study was to analyze the residue powders of Malpighia emarginata L., Psidium guajava L., Genipa americana L. and Spondias tuberosa L. regarding their total phenolic compounds contents, antioxidant activity (ABTS, DPPH and FRAP), soluble sugars, carotenoids, organic acids by HPLC-DAD/RID and individual phenolic compounds by the UPLC-QDa-MS system. The genipap residue had a high content of soluble sugars (422.72 ± 19.15 mg.g^-1 DW), with a higher content of sucrose (170.83 ± 10.89 mg.g^-1 DW). Nystose was found in the residues of guava (6.59 ± 0.56 mg.g^-1 DW) and umbu (65.61 ± 2.31 mg.g^-1 DW). The residues of acerola and umbu showed contents of β-carotene of 5.84 ± 0.01 mg.g^-1 DW and 0.10 ± 0.05 mg.g^-1 DW, respectively while high concentration (1116.00 ± 2.00 mg.100 g^-1 DW) of tartaric acid was found in acerola residue and quinic acid (6340 ± 104.00 mg.100 g^-1 DW) in umbu residue. Acetone (80%) and ultrasonic extraction were the best conditions for the residues of acerola, guava and genipap, however, for the umbu residue, extraction with shaker showed better results. The acerola and umbu residues showed higher yields of total phenolics, the values being 378.69-444.05 mg GAE.100 g^-1 DW and 326.14-404.36 mg GAE.100 g^-1 DW, respectively, as well as antioxidant activity. Naringenin was the individual phenolic compound with the highest concentration in the residue of acerola and genipap, vanillin in guava and rutin in umbu. Thus, residues powders from acerola, guava, genipap and umbu constitute potential sources of bioactive compounds, which could be used in the food, pharmaceutical and cosmetic industries.

Paving the Way to Food Grade Analytical Chemistry: Use of a Natural Deep Eutectic Solvent to Determine Total Hydroxytyrosol and Tyrosol in Extra Virgin Olive Oils

Extra virgin olive oil (EVOO) is well known for containing relevant amounts of healthy phenolic compounds. The European Food Safety Authority (EFSA) allowed a health claim for labelling olive oils containing a minimum amount of hydroxytyrosol (OHTyr) and its derivatives, including tyrosol (Tyr). Therefore, harmonized and standardized analytical protocols are required in support of an effective application of the health claim. Acid hydrolysis performed after extraction and before chromatographic analysis has been shown to be a feasible approach. Nevertheless, other fast, green, and easy methods could be useful for on-site screening and monitoring applications. In the present research, a natural deep eutectic solvent (NADES) composed of lactic acid and glucose was used to perform a liquid/liquid extraction on EVOO samples, followed by UV-spectrophotometric analysis. The spectral features of the extracts were related with the content of total OHTyr and Tyr, determined by the acid hydrolysis method. The second derivative of spectra allowed focusing on three single wavelengths (i.e., 299 nm, 290 nm, and 282 nm) significantly related with total OHTyr, total Tyr, and their sum, respectively. In particular, the sum of OHTyr and Tyr could be determined with a root mean square error of prediction of 29.5 mg kg⁻¹, while the limits of quantitation and detection were respectively 11.8 and 4.9 mg kg⁻¹. The proposed method, therefore, represents an easy screening tool, with the use of a green, food-derived solvent, and could be considered as an attempt to pave the way for food grade analytical chemistry.

A comprehensive review on different classes of polyphenolic compounds present in edible oils

Edible oils are used as a frying medium and in the preparation of several food products. They are mainly constituting triacylglycerols as major components, while other compounds are classified as minor constituents, which include polyphenols. This class of compounds plays an important role in the thermal stability and quality attributes of the finished industrial food products. In addition to other antioxidants, the desired thermal stability of edible is achieved by either fortification or mixing of edible oils. This comprehensive review was therefore aimed to review the different classes of polyphenolic compounds present in commonly consumed edible oils. The edible oils reviewed include soybean, olive, rapeseed, canola, sunflower, flaxseed, sesame, cottonseed, palm, almond, peanut, chestnut, coconut, and hazelnut oils. The identified classes of polyphenolic compounds such as simple phenols, hydroxybenzoic acids, phenylethanoids, hydroxycinnamic acid, esters of hydroxycinnamic acids, coumarins & chromans, stilbenes, flavonoids, anthocyanins, and lignans were discussed. It was observed that a single edible from different origins showed the varied composition of the different classes of phenolic compounds. Among the oils, soybean, sunflower, olive, and brassica oils received higher attention in terms of polyphenol composition. Some classes of phenolic compounds were either not reported or absent in one edible oil, while present in others. Among the different classes of phenolics, hydroxybenzoic acids, hydroxycinnamic acid and flavonoids were the most widely present compounds. Phenolic compounds in edible oils possess several health benefits such as antioxidant, antibacterial, anti-viral, anti-inflammatory, anti-tumour, antioxidants, cardioprotective, neuroprotective, anti-diabetic properties and anti-obesity.

The Potential of Apulian Olive Biodiversity: The Case of Oliva Rossa Virgin Olive Oil

In this study, the drupes and virgin olive oils extracted from the Oliva Rossa landrace are characterized. Oliva Rossa is an old landrace part of the autochthonous Apulian olive germplasm for which only few data have been reported till now. During the study, the maturity patterns of the drupes had been followed. Four samplings per year were planned, one every 14 days starting from the middle of October. The pigmentation index, the oil content and the total phenolic content of the drupes were measured. Simultaneously, virgin olive oils were extracted at the lab scale and analyzed for the fatty acid composition, the basic quality parameters and the content of minor compounds. The pigmentation pattern of the drupes was different among the years and, despite this trend, at the third sampling time the stage of maximum oil accumulation was always over. The extracted virgin olive oils had a medium to high level of oleic acid. With colder temperatures, a higher level of monounsaturated fatty acids, oleic/linoleic ratio and antioxidants was observed. The phenolic profile was dominated by 3,4-DPHEA-EDA and p-HPEA-EDA while the volatile profile by (E)-2-hexenal and 3-ethyl-1,5-octadiene.

Innovative Extraction Techniques Using Deep Eutectic Solvents and Analytical Methods for the Isolation and Characterization of Natural Bioactive Compounds from Plant Material

The growing interest of the food, pharmaceutical and cosmetics industries in naturally occurring bioactive compounds or secondary plant metabolites also leads to a growing demand for the development of new and more effective analysis and isolation techniques. The extraction of bioactive compounds from plant material has always been a challenge, accompanied by increasingly strict control requirements for the final products and a growing interest in environmental protection. However, great efforts have been made in this direction and today a considerable number of innovative extraction techniques have been developed using green, environmentally friendly solvents. These solvents include the deep eutectic solvents (DES) and their natural equivalents, the natural deep eutectic solvents (NADES). Due to their adjustable physical-chemical properties and their green character, it is expected that DES/NADES could be the most widely used solvents in the future, not only in extraction processes but also in other research areas such as catalysis, electrochemistry or organic synthesis. Consequently, this review provided an up-to-date systematic overview of the use of DES/NADES in combination with innovative extraction techniques for the isolation of bioactive compounds from various plant materials. The topicality of the field was confirmed by a detailed search on the platform WoS (Web of Science), which resulted in more than 100 original research papers on DES/NADES for bioactive compounds in the last three years. Besides the isolation of bioactive compounds from plants, different analytical methods are presented and discussed.

A Review of the Use of Eutectic Solvents, Terpenes and Terpenoids in Liquid–liquid Extraction Processes

Diverse and abundant applications of the eutectic solvents have appeared in the last years. Their promising tunable properties, eco-friendly character and the possibility of being prepared from numerous compounds have led to the publication of numerous papers addressing their use in different areas. Terpenes and terpenoids have been employed in the formulation of eutectic solvents, though they also have been applied as solvents in extraction processes. For their hydrophobic nature, renewable character, low environmental impact, cost and being non-hazardous, they have also been proposed as possible substitutes of conventional solvents in the separation of organic compounds from aqueous streams, similarly to hydrophobic eutectic solvents. The present work reviews the application of eutectic solvents in liquid–liquid extraction and terpenes and terpenoids in extraction processes. It has been made a research in the current state-of-the-art in these fields, describing the proposed applications of the solvents. It has been highlighted the scale-up feasibility, solvent regeneration and reuse procedures and the comparison of the performance of eutectic solvents, terpenes and terpenoids in extraction with conventional organic solvents or ionic liquids. Ultimately, it has been also discussed the employ of predictive methods in extraction, the reliability of thermodynamic models in correlation of liquid–liquid equilibria and simulation of liquid–liquid extraction processes.

Deep eutectic solvents (DES) as green extraction media for antioxidants electrochemical quantification in extra-virgin olive oils

A new electroanalytical method has been developed for the determination of polar antioxidant compounds in extra virgin olive oils. This method is based on the extraction of polar antioxidant compounds from extra-virgin olive oils by means of a deep eutectic solvent and their determination by a modified screen-printed electrode platform. The platform sensitivity was increased by modifying the working electrode with MWCNT and TiO₂ nanoparticles as modifiers and Nafion as a binder. The platform showed very good sensitivity in detecting polar antioxidant compounds in extra-virgin olive oils in a fairly wide range of concentrations. The measurements were performed by using square wave voltammetry. The extraction was performed without using organic solvents, making the method environmentally friendly. The proposed method has been compared with a common spectrophotometric one, the results appeared in good agreement. The method is sufficiently easy and quick to be used for screening analyses of polar antioxidant compounds in extra-virgin olive oils on the field.

Application of Deep Eutectic Solvents in Food Analysis: A Review

Deep eutectic solvents (DESs) have emerged recently as new and green solvents. DESs can be used for extraction and separation of both inorganic metallic components and organic compounds such as phenolic compounds, flavonoids, sugars, and aromatic amines from food samples. DESs possess a tunable property simply by adjusting the ratio of hydrogen bond acceptors to the hydrogen bond donors. As a green extraction medium, DESs have various applications in the pretreatment process and improve the efficiency of different food analyses. This review summarizes the findings of recent studies on the development, production, application, and efficacy of DESs in the pretreatment process of various food analyses.

Vinyl Phosphate-Functionalized, Magnetic, Molecularly-Imprinted Polymeric Microspheres' Enrichment and Carbon Dots' Fluorescence-Detection of Organophosphorus Pesticide Residues

The rapid detection of organophosphorus pesticide residues in food is crucial to food safety. One type of novel, magnetic, molecularly-imprinted polymeric microsphere (MMIP) was prepared with vinyl phosphate and 1-octadecene as a collection of dual functional monomers, which were screened by Gaussian09W molecular simulation. MMIPs were used to enrich organic phosphorus, which then detected by fluorescence quenching in vinyl phosphate-modified carbon dots (CDs@VPA) originated from anhydrous citric acid. MMIPs and CDs@VPA were characterized by TEM, particle size analysis, FT-IR, VSM, XPS, adsorption experiments, and fluorescence spectrophotometry in turn. Through the fitting data from experiment and Gaussian quantum chemical calculations, the molecular recognition properties and the mechanism of fluorescence detection between organophosphorus pesticides and CDs@VPA were also investigated. The results indicated that the MMIPs could specifically recognize and enrich triazophos with the saturated adsorption capacity 0.226 mmol g^-1, the imprinting factor 4.59, and the limit of recognition as low as 0.0006 mmol L^-1. Under optimal conditions, the CDs@VPA sensor has shown an extensive fluorescence property with a LOD of 0.0015 mmol L^-1 and the linear range from 0.0035 mmol L^-1 to 0.20 mmol L^-1 (R² = 0.9988) at 390 nm. The mechanism of fluorescence detection of organic phosphorus with CDs@VPA sensor might be attributable to hydrogen bonds formed between heteroatom O, N, S, or P, and the O-H group, which led to fluorescent quenching. Meanwhile, HN-C=O and Si-O groups in CDs@VPA system might contribute to cause excellent blue photoluminescence. The fluorescence sensor was thorough successfully employed to the detection of triazophos in cucumber samples, illustrating its tremendous value towards food sample analysis in complex matrix.

Nutraceutical polyphenols: New analytical challenges and opportunities

Nowadays, the research for secondary metabolites with health promoting effects in countering or slowing-down chronic and degenerative diseases (e.g. cancer, cardiovascular, and neurodegenerative diseases) identify phenols and polyphenols, widespread and mostly copious in dietary plant sources, as beneficial for human health. These compounds, as intrinsically antioxidant, are claimed as nutraceuticals with preventive efficacy in offsetting oxidant species over-genesis in normal cells, and with the potential ability to halt or reverse oxidative stress-related diseases. In this context, pure (poly)phenols and/or their herbal/food complexes were found to exert both anti- and pro-oxidant activities, suggesting also a promising chemopreventive efficacy. In fact, different evidence further highlights their ability to induce apoptosis, growth arrest, DNA synthesis inhibition and/or modulation of signal transduction pathways. Indeed, a full understanding of the phenolic and polyphenolic composition of plant species, which still now represent their inestimable and worth exploring source, is an important challenge, which today can and must be favourably pursued in the consciousness that the bioactivity of a plant extract is always in its chemistry. To reach this purpose a number of new and advanced techniques are available for extraction, purification and structural identification purposes, but, taking into account how, when and where (poly)phenols are biosynthesized, their use must be highly rationalized. This is particularly true for mass spectrometry techniques which, although representing one of the most powerful tools and in continuous evolution in this era, often suffer from an automatism that does not give justice to the chemical goodness of a plant species and particularly those of nutraceutical interest. This review will deepen into polyphenol research, focusing on biosynthesis, analytical approaches for a conscious exploitability of nutraceutical plant extracts rich in antioxidant and anti-inflammatory polyphenols and/or pure isolated polyphenols.