Characterization of isomers of oleuropein aglycon in olive oils by rapid-resolution liquid chromatography coupled to electrospray time-of-flight and ion trap tandem mass spectrometry

Monitoring the Phenolic and Terpenic Profile of Olives, Olive Oils and By-Products throughout the Production Process

Olive oil is a food of great importance in the Mediterranean diet and culture. However, during its production, the olive oil industry generates a large amount of waste by-products that can be an important source of bioactive compounds, such as phenolic compounds and terpenes, revalorizing them in the context of the circular economy. Therefore, it is of great interest to study the distribution and abundance of these bioactive compounds in the different by-products. This research is a screening focused on phytochemical analysis, with particular emphasis on the identification and quantification of the phenolic and terpenic fractions. Both the main products of the olive industry (olives, olive paste and produced oil) and the by-products generated throughout the oil production process (leaf, "alpeorujo", liquid and solid residues generated during decanting commonly named "borras" and washing water) were analyzed. For this purpose, different optimized extraction procedures were performed for each matrix, followed by high-performance liquid chromatography coupled with electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF/MS) analysis. Although no phenolic alcohols were quantified in the leaf and the presence of secoiridoids was low, this by-product was notable for its flavonoid (720 ± 20 µg/g) and terpene (5000 ± 300 µg/g) contents. "Alpeorujo" presented a complete profile of compounds of interest, being abundant in phenolic alcohols (900 ± 100 µg/g), secoiridoids (4500 ± 500 µg/g) and terpenes (1200 ± 100 µg/g), among others. On the other hand, while the solid residue of the borras was the most abundant in phenolic alcohols (3700 ± 200 µg/g) and secoiridoids (680 ± 20 µg/g), the liquid fraction of this waste was notable for its content of elenolic acid derivatives (1700 ± 100 µg/mL) and phenolic alcohols (3000 ± 300 µg/mL). Furthermore, to our knowledge, this is the first time that the terpene content of this by-product has been monitored, demonstrating that it is an important source of these compounds, especially maslinic acid (120 ± 20 µg/g). Finally, the phytochemical content in wash water was lower than expected, and only elenolic acid derivatives were detected (6 ± 1 µg/mL). The results highlighted the potential of the olive by-products as possible alternative sources of a wide variety of olive bioactive compounds for their revalorization into value-added products.

Bio-phenols determination in olive oils: Recent mass spectrometry approaches

Extra virgin olive oil (EVOO) is largely used in Mediterranean diet, and it is also worldwide apprised not only for its organoleptic properties but also for its healthy effects mainly attributed to the presence of several naturally occurring phenolic and polyphenolic compounds (bio-phenols). These compounds are characterized by the presence of multiple phenolic groups in more or less complex structures. Their content is fundamental in defining the healthy qualities of EVOO and consequently the analytical methods for their characterization and quantification are of current interest. Traditionally their determination has been conducted using a colorimetric assay based on the reaction of Folin-Ciocalteu (FC) reagent with the functional hydroxy groups of phenolic compounds. Identification and quantification of the bio-phenols in olive oils requires certainly more performing analytical methods. Chromatographic separation is now commonly achieved by HPLC, coupled with spectrometric devices as UV, FID, and MS. This last approach constitutes an actual cutting-edge application for bio-phenol determination in complex matrices as olive oils, mostly on the light of the development of mass analyzers and the achievement of high resolution and accurate mass measurement in more affordable instrument configurations. After a short survey of some rugged techniques used for bio-phenols determination, in this review have been described the most recent mass spectrometry-based methods, adopted for the analysis of the bio-phenols in EVOOs. In particular, the sample handling and the results of HPLC coupled with low- and high-resolution MS and MS/MS analyzers, of ion mobility mass spectrometry and ambient mass spectrometry have been reported and discussed.

Experimental and theoretical evaluations on Oleuropein as a natural origin corrosion inhibitor for copper in acidic environment

Copper corrosion in acidic cleaning solutions is a major worry for heat exchangers. Corrosion inhibitors derived from natural sources might be a viable option. The isolation of Oleuropein compound from olive leaf and investigation of its anticorrosion potential for copper in 1.0 M H₂SO₄ solution are reported here. All experimental results from LC-MS, FT-IR, ¹H and ¹³C-NMR characterizations support the molecular structure of Oleuropein. Electrochemical and gravimetric tests were used to evaluate the corrosion inhibition capabilities of Oleuropein. According to polarization investigation, Oleuropein is a mixed-type inhibitor. Oleuropein's inhibitory efficacy increases with concentration, attaining an optimum value (98.92%) at 100 mg L^-1. At high temperatures, Oleuropein can be considered an efficient inhibitor. Thermodynamic variables for the activation operation and copper dissolution were computed and addressed as well. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) examinations revealed that Oleuropein produced an outer layer on the copper surface, shielding it from severe acid damage. Quantum chemical simulations were employed to propose molecular explanations for Oleuropein's inhibitory actions.

Systematic characterization of the absorbed components of Ligustri Lucidi Fructus and their metabolic pathways in rat plasma by ultra-high-performance liquid chromatography-Q-Exactive Orbitrap tandem mass spectrometry combined with network pharmacology

Ligustri Lucidi Fructus is a dried and mature fruit of Ligustrum lucidum Ait., which has the effects of nourishing liver and kidney. Herein, an accurate and sensitive method was established for the separation and identification of the absorbed constituents and metabolites of Ligustri Lucidi Fructus in rat plasma based on ultra-high-performance liquid chromatography-Q-Exactive Orbitrap tandem mass spectrometry. A total of 73 prototype constituents and 148 metabolites were identified or characterized in administered plasma, and the possible metabolic pathways of constituents mainly involved hydroxylation, sulfation, demethylation, and glucuronidation. Besides, the network pharmacology was further investigated to illuminate its potential mechanism of treatment for liver injury by the biological targets regulating related pathways. Network pharmacological analysis showed that target components through 399 targets regulate 220 pathways. The docking results showed that 36 key target components were closely related to liver injury. Overall, the study clearly presented the metabolic processes of Ligustri Lucidi Fructus and gave a comprehensive metabolic profile of Ligustri Lucidi Fructus in vivo first. Combining with network pharmacology and molecular docking discovered potential drug targets and disclose the biological processes of Ligustri Lucidi Fructus, which will be a viable step toward uncovering the secret mask of study for traditional Chinese medicine.

Bioactive Secoiridoids in Italian Extra-Virgin Olive Oils: Impact of Olive Plant Cultivars, Cultivation Regions and Processing

In the last two decades, phenolic compounds occurring in olive oils known as secoiridoids have attracted a great interest for their bioactivity. Four major olive oil secoiridoids, i.e., oleuropein and ligstroside aglycones, oleacin and oleocanthal, were previously characterized in our laboratory using reversed-phase liquid chromatography with electrospray ionization-Fourier transform-mass spectrometry (RPLC-ESI-FTMS). The same analytical approach, followed by multivariate statistical analysis (i.e., Principal Component Analysis), was applied here to a set of 60 Italian extra-virgin olive oils (EVOO). The aim was to assess the secoiridoid contents as a function of olive cultivars, place of cultivation (i.e., different Italian regions) and olive oil processing, in particular two- vs. three-phase horizontal centrifugation. As expected, higher secoiridoid contents were generally found in olive oils produced by two-phase horizontal centrifugation. Moreover, some region/cultivar-related trends were evidenced, as oleuropein and ligstroside aglycones prevailed in olive oils produced in Apulia (Southern Italy), whereas the contents of oleacin and oleocanthal were relatively higher in EVOO produced in Central Italy (Tuscany, Lazio and Umbria). A lower content of all the four secoiridoids was generally found in EVOO produced in Sicily (Southern Italy) due to the intrinsic low abundance of these bioactive compounds in cultivars typical of that region.

Analysis of chemical variations between raw and wine-processed Ligustri Lucidi Fructus by ultra-high-performance liquid chromatography-Q-Exactive Orbitrap/MS combined with multivariate statistical analysis approach

Ligustri Lucidi Fructus (LLF) is the dried and mature fruit of Ligubtrum lucidum Ait., which has the effect of nourishing the liver and kidney, brightening the eyes and promoting the growth of black hair. Wine-processed LLF is commonly used in traditional Chinese medicine; however, the processing mechanisms are still unclear. Herein, a system data acquisition and mining strategy was designed to investigate the chemical profile differences between the raw and wine-processed LLF, based on high-performance liquid chromatography-Orbitrap high resolution mass spectrometry coupled with multivariate statistical analysis including principal component analysis and partial least square analysis. Afterwars, a total of 55 components were found to be the main contributors to the significant difference between raw and wine-processed LLF by comparison with chromatographic behaviors, intact precursor ions, and characteristic MS fragmentation patterns. In addition, 10 main constituents of raw and wine-processed LLF were simultaneously determined by UHPLC-MS/MS for analyzing the content variations. Some structural transformation mechanisms during wine processing were deduced from the results. The results may provide a scientific foundation for deeply elucidating the wine-processing mechanism of LLF.

Insight into the Storage-Related Oxidative/Hydrolytic Degradation of Olive Oil Secoiridoids by Liquid Chromatography and High-Resolution Fourier Transform Mass Spectrometry

The study of negative effects potentially exerted by the exposure to oxygen and/or light and, thus, also by the type of container on the quality of extra virgin olive oil (EVOO) during its prolonged storage requires an appropriate choice of analytical methods and components to be monitored. Here, reverse-phase liquid chromatography coupled to high-resolution/accuracy Fourier transform mass spectrometry with electrospray ionization was exploited to study oxidative/hydrolytic degradation processes occurring on the important bioactive components of EVOO known as secoiridoids, i.e., oleuropein and ligstroside aglycones, oleacin, and oleocanthal, during storage up to 6 months under controlled conditions. Specifically, isomeric oxidative byproducts resulting from the transformation of a carbonylic group of the original secoiridoids into a carboxylic group and compounds resulting from hydrolysis of the ester linkage of secoiridoids, i.e., elenolic and decarboxymethyl elenolic acids and tyrosol and 3-hydroxytyrosol, were monitored, along with their precursors. Data obtained from EVOO storage at room temperature in glass bottles with/without exposure to light and/or oxygen indicated that, although it was more relevant if a periodical exposure to oxygen was performed, a non-negligible oxidative degradation occurred on secoiridoids also when nitrogen was used to saturate the container headspace. In a parallel experiment, the effects of storage of the same EVOO (250 mL) for up to 6 months in containers manufactured with different materials/shapes were considered. In particular, a square dark glass bottle, a stainless-steel can, and a ceramic jar, typically used for EVOO commercialization, and a clear polyethylene terephthalate bottle, purposely chosen to prompt secoiridoid degradation through exposure to light and oxygen, were compared. Dark glass was found to provide the best combined protection of major secoiridoids from oxidative and hydrolytic degradation, yet the lowest levels of oxidized byproducts were observed when the stainless-steel can was used.

Olive oil varieties and ripening stages containing the antioxidants hydroxytyrosol and derivatives in compliance with EFSA health claim

Virgin olive oils (VOO) and extra virgin olive oils (EVOO) contain a specific fraction of polyphenols (hydroxytyrosol and its derivatives) that produce beneficial physiological effects. The European Food Safety Authority (EFSA) authorised a health claim for olive oil (OO) containing at least 250 mg/Kg of those polyphenols. The specific polyphenol content of twelve varieties of EVOO extracted at three different maturation stages was investigated. The total concentration of specific polyphenols changed depending on the olive oil variety. The varieties showing the highest specific polyphenol content (all above 250 mg/Kg) were Lechín Sevilla (429.5 ± 5), Manzanilla Sevilla (407.6 ± 6) and Cornezuelo (394.0 ± 6) in the green phase; Cornicabra (362.0 ± 8), Nevadillo Negro (326.5 ± 4) and Picual 296.0 ± 6) in the turning phase; and Lechin Granada (382.8 ± 4), Picual (317.7 ± 3), Lechin Sevilla (294.4 ± 5) and Manzanilla Sevilla (278.0 ± 2) in the mature phase. These results could have potential application for the industrial production of a category of healthy antioxidant OO.

Application of High Resolution Mass Spectrometric methods coupled with chemometric techniques in olive oil authenticity studies - A review

Extra Virgin Olive Oil (EVOO), the emblematic food of the Mediterranean diet, is recognized for its nutritional value and beneficial health effects. The main authenticity issues associated with EVOO's quality involve the organoleptic properties (EVOO or defective), mislabeling of production type (organic or conventional), variety and geographical origin, and adulteration. Currently, there is an emerging need to characterize EVOOs and evaluate their genuineness. This can be achieved through the development of analytical methodologies applying advanced "omics" technologies and the investigation of EVOOs chemical fingerprints. The objective of this review is to demonstrate the analytical performance of High Resolution Mass Spectrometry (HRMS) in the field of food authenticity assessment, allowing the determination of a wide range of food constituents with exceptional identification capabilities. HRMS-based workflows used for the investigation of critical olive oil authenticity issues are presented and discussed, combined with advanced data processing, comprehensive data mining and chemometric tools. The use of unsupervised classification tools, such as Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA), as well as supervised classification techniques, including Linear Discriminant Analysis (LDA), Support Vector Machine (SVM), Partial Least Square Discriminant Analysis (PLS-DA), Orthogonal Projection to Latent Structure-Discriminant Analysis (OPLS-DA), Counter Propagation Artificial Neural Networks (CP-ANNs), Self-Organizing Maps (SOMs) and Random Forest (RF) is summarized. The combination of HRMS methodologies with chemometrics improves the quality and reliability of the conclusions from experimental data (profile or fingerprints), provides valuable information suggesting potential authenticity markers and is widely applied in food authenticity studies.

Influence of Horizontal Centrifugation Processes on the Content of Phenolic Secoiridoids and Their Oxidized Derivatives in Commercial Olive Oils: An Insight by Liquid Chromatography-High-Resolution Mass Spectrometry and Chemometrics

Reversed-phase liquid chromatography with electrospray ionization-high-resolution/accuracy Fourier transform mass spectrometry (RPC-ESI-FTMS) and chemometrics were exploited to evaluate the influence of horizontal centrifugation by two- or three-phase decanters on the content of major phenolic secoiridoids in extravirgin olive oils (EVOOs). Despite the occurrence of other potential sources of variability typical of commercial olive oils, horizontal centrifugation was found to play a primary role, with a general increase of secoiridoid content occurring when two-phase decanters were used. As emphasized by principal component analysis (PCA), the increase involved preferentially oleacin and oleocanthal, when oxidative deterioration was purposely minimized during and/or after production, and oleuropein and ligstroside aglycones, when no vertical centrifugation was performed at the end of the productive cycle. The influence of the type of horizontal centrifugation was also emphasized by the elaboration of RPC-ESI-FTMS data based on hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA).

Characterization of bioactive and nutraceutical compounds occurring in olive oil processing wastes

RATIONALE

Several bioactive compounds, including phenolic acids and secoiridoids, are transferred from olive drupes to olive oil during the first stage of production. Here, the characterization of these low molecular weight (LMW) compounds in olive oil and in closely related processing materials, like olive leaves (OL) and olive mill wastewaters (OMW), was faced up, for the first time, by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS).

METHODS

A novel binary matrix composed of 1,8-bis(tetramethylguanidino)naphthalene (TMGN) and 9-aminoacridine (9AA) (1:1 molar ratio), displaying excellent ionization properties at low levels of laser energy, was employed in reflectron negative ion mode by a MALDI TOF/TOF system equipped with a neodymium-doped yttrium lithium fluoride (Nd:YLF) laser (345 nm). MS/MS experiments were performed by using ambient air as the collision gas.

RESULTS

Four major secoiridoids typically present in olive oil, i.e., the aglycones of oleuropein and ligstroside, and oleacein and olecanthal at m/z 377.1, 361.1, 319.1 and 303.1, respectively, were detected in virgin olive oil (VOO) extracts, along with some of their chemical/enzymatic hydrolysis by-products, such as elenolic (m/z 241.1), decarboxymethyl-elenolic acids (m/z 183.1) and hydroxytyrosol (m/z 153.1). Besides oleuropein aglycone and oleacein, hydroxylated derivatives of decarboxymethyl-elenolic acid and hydroxytyrosol were evidenced in OMW.

CONCLUSIONS

While oleuropein was confirmed in OL extracts, several interesting phenolic compounds, including hydroxytyrosol, were recognized in OMW. The proposed approach based on the use of a novel binary matrix for MALDI MS/MS analyses of LMW bioactive compounds can be considered a promising analytical tool for a rapid screening of the phenolic fraction in olive oils and related processing wastes.

Direct determination of phenolic secoiridoids in olive oil by ultra-high performance liquid chromatography-triple quadruple mass spectrometry analysis

In recent years, a large number of biological properties and an important role in the organoleptic characteristics of olive oil have been attributed to phenolic secoiridoids, such as oleacein, oleocanthal, oleuropein aglycone and ligstroside aglycone. Consequently, quantifying them is of great interest for the olive oil sector. Currently, there is no consensus in which analytical method must be use to accurately determine these compounds in olive oil, mainly owing to the lack of reference standards for calibration. In this work, analytical standards of phenolic secoiridoids have been used to develop a quantitative and rapid analytical method by UHPLC-MS/MS, in which sample extraction is not carried out. Simple dilutions of the sample with dry tetrahydrofuran and dry acetonitrile were performed before analysing them. It is worth noting that under these conditions the generation of artefacts such as acetals and hemiacetals of the aldehydic forms is highly reduced. The detection and quantification was performed with a Xevo TQS tandem quadrupole mass spectrometer. The method was validated at four concentration levels and finally applied to six samples of extra virgin olive oil.

Structural characterization of the ligstroside aglycone isoforms in virgin olive oils by liquid chromatography-high-resolution Fourier-transform mass spectrometry and H/Dexchange

A systematic structural characterization of the isomeric forms related to ligstroside aglycone (LA), one of the most relevant secoiridoids contained in virgin olive oils, was performed using reverse phase liquid chromatography with electrospray ionization Fourier-transform single and tandem mass spectrometry, operated in negative ion mode (RPLC-ESI(-)-FTMS and FTMS/MS). The high mass resolution and accuracy provided by the adopted orbital trap mass analyzer enabled the recognition of more than 10 different isomeric forms of LA in virgin olive oil extracts. They were related to four different types of molecular structure, two of which including a dihydropyranic ring bearing one or two aldehydic groups, whereas the others corresponded to dialdehydic open-structure forms, differing just for the position of a C═C bond. The contemporary presence of enolic or dienolic tautomers associated to most of these compounds, stable at room temperature (23°C), was also assessed through RPLC-ESI-FTMS analyses operated under H/D exchange conditions, ie, by using D₂ O instead of H₂ O as co-solvent of acetonitrile in the RPLC mobile phase. As discussed in the paper, the results obtained for LA indicated a remarkable structural similarity with oleuropein aglycone (OA), the most abundant secoiridoid of olive oil, whose isoforms had been previously characterized using the same analytical approach.

A comprehensive study of oleuropein aglycone isomers in olive oil by enzymatic/chemical processes and liquid chromatography-Fourier transform mass spectrometry integrated by H/D exchange

A comprehensive structural characterization of the complex family of isomeric forms related to Oleuropein aglycone (OA) detected in virgin olive oil (VOO) was performed by reverse phase liquid chromatography with electrospray ionization and Fourier-transform mass spectrometry (RPLC-ESI-FTMS), integrated by enzymatic/chemical reactions performed on Oleuropein, the natural precursor of OA. First, some of the OA-related isomers typically observed in VOO extracts were generated upon enzymatic hydrolysis of the glycosidic linkage of Oleuropein. This step mimicked the process occurring during olive drupes crushing in the first stage of oil production. The incubation of the enzymatic reaction mixture at a more acidic pH was subsequently performed, to simulate the conditions of olive paste malaxation during oil production. As a result, further isomeric forms were generated and the complex chromatographic profile typically observed for OA in olive oil extracts, including at least 13 different peaks/bands/groups of peaks, was carefully reproduced. Each of those chromatographic features could be subsequently assigned to specific types of OA-related isomers, belonging to one of four structurally different classes. Specifically, diastereoisomers/geometrical isomers corresponding to two different types of open-structure forms and to as many types of closed-structure, di-hydropyranic forms of OA, characterized by the presence of one or two carbonyl groups, according to the case, were evidenced. In addition, the presence of stable enolic/dienolic tautomers, providing an indirect structural confirmation for some OA isomers, was ascertained through RPLC-ESI-FTMS analyses performed under H/D exchange conditions, i.e. in the presence of deuterated water as one of the mobile phase solvents.

Chromatographic Separation of Phenolic Compounds from Extra Virgin Olive Oil: Development and Validation of a New Method Based on a Biphenyl HPLC Column

Three different high performance liquid chromatography columns were accessed for phenolic compounds (PC) separation in the hydrophilic fraction of extra virgin olive oil (EVOO). Two fully porous C₁₈ bonded silica phases and one partially porous biphenyl column were used. Biphenyl column allowed for an increase of more than 30% in peak capacity (n_c), higher selectivity (α) (1.045), and improved retention (k), with a reduction of 22.1% in the retention time. The higher resolution (R_s) was obtained by using the biphenyl column, with a fair separation of oleuropein aglycone isomers (OAI) and a good identification of caffeic acid (CA). Tyrosol (T), hydroxytyrosol (HT), and dihydroxyphenyl glycol (DHPG) were also well separated and identified. Moreover, the method using a biphenyl column was fully validated according to the requirements for new methods. For all parameters, the method applying the biphenyl column proved to be a reliable, accurate, and robust tool for separation, identification, and quantification of the main PCs in EVOOs.

Quantification of oleacein and oleuropein aglycone in olive oil using deuterated surrogates by normal-phase ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry

An analytical method for the analysis of relevant secoiridoid-based components in olive oil, oleacein and oleuropein aglycone, is described using for the first time deuterated surrogates. 0.2 g of sample was necessary to perform the analysis using liquid-liquid extraction and ultrasound-assisted extraction with a mixture of methanol/water (4:1, v/v). To avoid the formation of by-products, normal-phase ultra high performance liquid chromatography was chosen for the chromatographic separation. The selected mobile phase was a gradient mixture of tetrahydrofurane and hexane, and an ACE Excel 3 CN-ES column as stationary phase. The detection and quantification was performed with a SYNAPT G2-Si mass spectrometer. The calibration curves for oleacein and oleuropein aglycone were linear and quadratic, respectively. The validation was done at three levels of concentration. Relative errors from 0.1 to 10.5% and relative standard deviations lower than 9% were obtained. The method was applied to study different samples of olive oil.

Evaluation of phenolic composition and antioxidant activity changes in olive flowers during development using HPLC/DAD and LC-MS/MS

Olive fruit and leaves have been extensively studied for their chemical compositions and biological activities. However, less attention has been given to its flowers. The present research was achieved on Tunisian olive flowers. It aimed at studying the effects of flower development on phenolic compounds and antioxidant activity. The extracts were analyzed using high performance liquid chromatography coupled to diode array detection (HPLC/DAD) and coupled to mass spectrometry (LC-MS/MS). The HPLC/DAD analysis indicated that oleuropein aglycon (from 1.158 to 3.746 g/kg), followed by hydroxytyrosol (from 0.168 to 1.581 g/kg) and oleoside (from 0.143 to 1.325 g/kg) were the predominant phenolics in olive flowers extracts during development stages. Twenty compounds have been identified, revealing the complex profile of olive flowers, composed, in order of abundance, by secoiridoids, phenolic alcohols, lignans, flavonoids and phenolic acids. Total phenolic contents increased from 2.455 to 8.541 g/kg Gallic acid equivalent per kg of fresh flowers during all steps of the flower development. A correlation between antioxidant activity and total phenolic contents was determined.

Oleuropein and Cancer Chemoprevention: The Link is Hot

Cancer comprises a collection of related diseases characterized by the existence of altered cellular pathways resulting in an abnormal tendency for uncontrolled growth. A broad spectrum, coordinated, and personalized approach focused on targeting diverse oncogenic pathways with low toxicity and economic natural compounds can provide a real benefit as a chemopreventive and/or treatment of this complex disease. Oleuropein, a bioactive phenolic compound mainly present in olive oil and other natural sources, has been reported to modulate several oncogenic signalling pathways. This review presents and critically discusses the available literature about the anticancer and onco-suppressive activity of oleuropein and the underlying molecular mechanisms implicated in the anticarcinogenic and therapeutic effects. The existence of limitations and the promising perspectives of research on this phenolic compound are also critically analyzed and discussed.

Application of UHPLC-ESI-Q-TOF-MS to Identify Multiple Constituents in Processed Products of the Herbal Medicine Ligustri Lucidi Fructus

Ligustri Lucidi Fructus (LLF), the fruit of Ligustrum lucidum Ait. (Oleaceae), has been used as a common herbal medicine in clinical practice in China for nearly 2000 years. In most cases, LLF is prescribed in decoctions in the form of processed products rather than crude drugs. In this study, an ultra-high performance liquid chromatography coupled with electrospray ionization-quadrupole-time of flight-mass spectrometry (UHPLC-ESI-Q-TOF-MS) method was established for rapid separation and identification of multiple constituents in the 80% methanol extract of processed-LLF. A total of 50 compounds (one phenylethanoid, seven phenylethanoid glycosides, seven flavonoids, 25 iridoids, nine triterpenoids and one cyclohexanecarboxylic acid) were either unambiguously identified or tentatively characterized with the aid of authentic standards or published data. Luteolin-7-O-rutinoside, oleoside and secologanoside were detected in LLF for the first time. This study enriches the chemical profiling of processed-LLF and could provide valuable information for the quality control and further investigation of processed-LLF and crude LLF.

Identification of position isomers by energy-resolved mass spectrometry

This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals ((●)OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by (●)OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods.

Phenolic Profiling of Olives and Olive Oil Process-Derived Matrices Using UPLC-DAD-ESI-QTOF-HRMS Analysis

All of the matrices entailed in olive oil processing were screened for the presence of known and new phenol constituents in a single study, combining an ultra high pressure liquid chromatography system with diode array and electrospray ionization quadrupole time-of-flight high resolution mass spectrometry (ESI-QTOF-HRMS) detection. Their trail was followed from the fruit (peel/pulp and stone) to the paste and final products, i.e. pomace, wastewater, and oil, providing important insight into the origin, disappearance, and evolution of each during the operational steps. Eighty different phenols, composed of fruit native representatives and their technologically formed and/or released derivatives, were detected in six olive matrices and fully characterized on the basis of HRMS and UV-vis spectroscopic data. In addition to phenols already known in olive matrices, four new molecular formulas were proposed and three new tentative identities assigned to newly discovered phenols, i.e., β-methyl-OH-verbascoside, methoxynüzhenide, and methoxynüzhenide 11-methyl oleoside.

The seed of the Amazonian fruit Couepia bracteosa exhibits higher scavenging capacity against ROS and RNS than its shell and pulp extracts

Couepia bracteosa is an interesting source of bioactive compounds which may be investigated for protecting human health against oxidative damage.

Dynamic changes in composition of extracts of natural products as monitored by in situ NMR

The direct in situ NMR observation and quantification, based on the aldehyde -CH chemical shift region, of the inter-conversion of secoiridoid derivatives due to temperature and solvent effects is demonstrated in complex extracts of natural products without prior isolation of the individual components. The equilibrium between the aldehyde hydrate form and the dialdehyde form of the oleuropein aglycon of an olive leaf aqueous extract in D(2)O was shown to be temperature dependent. The resulting thermodynamic values of the Van't Hoff plot with ΔH(o)  = -26.34 ± 1.00 kJ mol(-1) and TΔS° (298 K) = -24.70 ± 1.00 kJ mol(-1) demonstrate a significant entropy term which nearly compensates the effect of enthalpy at room temperature. The equilibrium between the two diastereomeric hemiacetal forms and the dialdehyde form of the oleuropein 6-O-β-d-glucopyranoside aglycon of an olive leaf aqueous extract in CD(3) OD was also shown to be strongly temperature dependent again because of the significant entropy term (TΔS° (298 K) = -26.50 ± 1.39 kJ mol(-1)) compared with that of the enthalpy term (ΔH(o)  = -36.64 ± 1.46 kJ mol(-1)). This is the first demonstration of the significant role of the entropy parameter in determining the equilibrium of chemical transformations in complex mixtures of natural products due to solvent and temperature effects.

Polyphenols and the modulation of gene expression pathways: can we eat our way out of the danger of chronic disease?

Plant-derived dietary polyphenols may improve some disease states and promote health. Experimental evidence suggests that this is partially attributable to changes in gene expression. The rational use of bioactive food components may therefore present an opportunity to activate or repress selected gene expression pathways and, consequently, to manage or prevent disease. It remains to be determined whether this use of bioactive food components can be done safely. This article reviews the associated controversies and limitations of polyphenol therapy. There is a paucity of clinical data on the rational use of polyphenols, including a lack of knowledge on effective dosage, actual chemical formulations, bioavailability, distribution in tissues, the effect of genetic variations, differences in gut microflora, the synergistic (or antagonistic) effects observed in extracts, and the possible interaction between polyphenols and lipid domains of cell membranes that may alter the function of relevant receptors. The seminal question of why plants make substances that benefit humans remains unanswered, and there is still much to learn in terms of correlative versus causal effects of human exposure to various nutrients. The available data strongly suggest significant effects at the molecular level that represent interactions with the epigenome. The advent of relatively simple technologies is helping the field of epigenetics progress and facilitating the acquisition of multiple types of data that were previously difficult to obtain. In this review, we summarize the molecular basis of the epigenetic regulation of gene expression and the epigenetic changes associated with the consumption of polyphenols that illustrate how modifications in human nutrition may become relevant to health and disease.

Insight into virgin olive oil secoiridoids characterization by high-resolution mass spectrometry and accurate mass measurements

With the aim to enhance characterization of virgin olive oil (VOO), high resolution mass spectrometry (HRMS) and high resolution tandem mass spectrometry (HRMS/MS), in positive and negative electrospray ionization (ESI) modes, coupled to fused-core reverse phase chromatography, were applied to distinct VOO phenolic extracts after the optimization of chromatographic conditions, ESI and fragmentation parameters. HRMS, but also HRMS/MS resulted fundamental to progress in secoiridoids structural elucidation. The former revealed that the secoiridoid composition of VOO was far more complicated than previously reported, while the latter helped clarify product ion elemental composition allowing new fragmentations, in addition to those reported in the literature, to be put forward. In particular, for the first time, different product ions with the same nominal mass were unequivocally identified in the spectra of secoiridoid compounds, confirming the greater capacity of HRMS/MS to clarify structure than low-resolution MS. Furthermore, and differing from previous studies, the multiple isomers of the main VOO secoiridoids could be differentiated on the basis of their HR product ion spectra in positive mode.

Comparative study of chromatographic medium-associated mass and potential antitumor activity loss with bioactive extracts

Natural product drug discovery programs often rely on the use of silica (Si) gel, reversed-phase media, or size-exclusion resins (e.g., RP-C18, Sephadex LH-20) for compound purification. The synthetic polymer-based sorbent Diaion HP20SS (cross-linked polystyrene matrix) is used as an alternative to prepare purified natural product libraries. To evaluate the impact of chromatographic media on the isolation of biologically active, yet chromatographically unstable natural products, Diaion HP20SS was evaluated side-by-side with normal-phase sorbents for irreversible binding of extract constituents and their effects on bioactivity. An array of chemically diverse natural product-rich extracts was selected as a test panel, and a cell-based reporter assay for hypoxia-inducible factor-1 (HIF-1) was employed to monitor potential change(s) in bioactivity. Silica gel caused significant irreversible binding of three out of 10 extracts. Curcuma longa, Saururus cernuus, and Citrus reticulata extracts showed decreased HIF-1 inhibitory activity after elution through Si gel. An additional nonpolar column wash of HP20SS with EtOAc retained considerable bioactivities of active extracts. In general, Si gel produced the greatest loss of bioactivity. However, HP20SS elution reduced significantly HIF-1 inhibitory activity of certain extracts (e.g., Asimina triloba).

High-performance liquid chromatography-mass spectrometry profiling of phenolic compounds for evaluation of olive oil bitterness and pungency

Bitterness and pungency are important parameters for olive oil quality. Therefore, two instrumental methods for evaluation of these taste attributes were developed. The first one is based on the photometric measurement of total phenolic compounds content, whereas the second one is based on the semiquantitative evaluation of hydrophilic compounds by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Evaluation of total phenolic compounds content was performed by a modified method for the determination of the K(225) value using a more specific detection based on the pH value dependency of absorbance coefficients of phenols at λ = 274 nm. The latter method was not suitable for correct prediction, because no significant correlation between bitterness/pungency and total phenolic compounds content could be found. For the second method, areas of 25 peaks detected in 54 olive oil samples by a HPLC-MS profiling method were correlated with the bitterness and pungency by partial least-squares regression. Six compounds (oleuropein aglycon, ligstroside aglycon, decarboxymethyl oleuropein aglycon, decarboxymethyl ligstroside aglycon, elenolic acid, and elenolic acid methyl ester) show high correlations to bitterness and pungency. The computed model using these six compounds was able to predict bitterness and pungency of olive oil in the error margin of the sensory evaluation (±0.5) for most of the samples.

Wastes generated during the storage of extra virgin olive oil as a natural source of phenolic compounds

Phenolic compounds in extra virgin olive oil (EVOO) have been associated with beneficial effects for health. Indeed, these compounds exert strong antiproliferative effects on many pathological processes, which has stimulated chemical characterization of the large quantities of wastes generated during olive oil production. In this investigation, the potential of byproducts generated during storage of EVOO as a natural source of antioxidant compounds has been evaluated using solid-liquid and liquid-liquid extraction processes followed by rapid resolution liquid chromatography (RRLC) coupled to electrospray time-of-flight and ion trap mass spectrometry (TOF/IT-MS). These wastes contain polyphenols belonging to different classes such as phenolic acids and alcohols, secoiridoids, lignans, and flavones. The relationship between phenolic and derived compounds has been tentatively established on the basis of proposed degradation pathways. Finally, qualitative and quantitative characterizations of solid and aqueous wastes suggest that these byproducts can be considered an important natural source of phenolic compounds, mainly hydroxytyrosol, tyrosol, decarboxymethyl oleuropein aglycone, and luteolin, which, after suitable purification, could be used as food antioxidants or as ingredients in nutraceutical products due to their interesting technological and pharmaceutical properties.

Comparison of different extraction procedures for the comprehensive characterization of bioactive phenolic compounds in Rosmarinus officinalis by reversed-phase high-performance liquid chromatography with diode array detection coupled to electrospray time-of-flight mass spectrometry

In the present work, a comparative study between two environmentally friendly and selective extraction techniques, such as supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE) have been carried out focusing in the bioactive phenolic compounds present in Rosmarinus officinalis. For the analysis of the SFE and PLE extracts, a new methodology for qualitative characterization has been developed, based on the use of reversed-phase high-performance liquid chromatography (RP-HPLC), equipped with two different detection systems coupled in series: diode array detector (DAD) and time of flight mass spectrometry (TOF-MS) detector connected via an electrospray ionization interface (ESI). The use of a small particle size C(18) column (1.8 μm) provided a great resolution and made possible the separation of several isomers. Moreover, UV-visible spectrophotometry is a valuable tool for identifying the class of phenolic compounds, whereas MS data enabled to structurally characterize the compounds present in the extracts. The applied methodology was useful for the determination of many well-known phenolic compounds present in R. officinalis, such as carnosol, carnosic acid, rosmadial, rosmanol, genkwanin, homoplantaginin, scutellarein, cirsimaritin and rosmarinic acid, as well as other phenolic compounds present in other species belonging to Lamiaceae family.

Seasonal variations in metabolite profiling of the fruits of Ligustrum lucidum Ait

The metabolite profiling of fruits of the herb Ligustrum lucidum Ait collected during different months has been performed using ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC/QTOFMS) and multivariate statistical analysis techniques. The markers such as oleuropein acid, neonuezhenide, specnuezhenide, oleuropein and ligustrosidic acid accountable for such variations were identified through the loadings plot of principal component analysis (PCA), and the tentative identification of the markers is completed by comparing the mass spectra and retention times with those of reference compounds and/or tentatively assigned by matching empirical molecular formulae and MS/MS data with those of the known compounds published. Furthermore, one of the chemical markers, such as specnuezhenide, which is water-soluble, biologically active and also the predominant compound in this crude drug, was quantified by ultra-performance liquid chromatography coupled with a tunable UV detector (UPLC-TUV). The developed UPLC method provides good linearity (r(2)=0.9991), repeatability (RSD=2.96%), intra- and inter-day precisions (RSD=0.21%, 0.96%), with accuracies of 99.18-100.26% and a recovery of specnuezhenide of 97.57%. The fruits of L. lucidum Ait collected from August to December were tested. The results clearly show that the fruits of L. lucidum Ait harvested in October have the highest yields of specnuezhenide. It is also noted that the variations of content of specnuezhenide obtained by both methods have a strong correlation. This suggests that the newly proposed strategy is a reliable and simple method for the rapid discrimination of subtle variations, within the same plant species or strains, due to different seasonal collection times.

Qualitative screening of phenolic compounds in olive leaf extracts by hyphenated liquid chromatography and preliminary evaluation of cytotoxic activity against human breast cancer cells

In this work, high-performance liquid chromatography (HPLC) coupled to electrospray time-of-flight mass spectrometry (ESI-TOF-MS) and electrospray ion trap multiple-stage tandem mass spectrometry (ESI-IT-MS(2)) has been applied to screen phenolic compounds in olive leaf extracts. The use of a small particle size C18 column (1.8 micro) provided great resolution and made separation of a lot of isomers possible. The structural characterization was based on accurate mass data obtained by ESI-TOF-MS, and the nature of fragmentation ions were further confirmed by ESI-IT-MS(2) when possible. In addition, we employed tetrazolium salt (MTT)-based assays to assess the effects of olive leaf extracts on the growth of human tumor-derived cells. Upon this approach, we achieved an accurate profile of olive leaf phenolics along with the identification of several important isomers of secoiridoids and flavonoids. This will allow a better understanding of the complete composition of olive-leaf-bioactive compounds as well as their involvement in Olea europaea L. biochemical pathways. Importantly, olive leaf extracts exhibited dose-dependent inhibitory effects on the metabolic status (cell viability) of three breast cancer models in vitro. Since the tumoricidal activity of the extracts should be mainly attributed to the identified olive leaf phenolics, these findings warrant further investigation at the structure-function molecular level to definitely establish the anticancer value of these phytochemicals.

Determination of phenolic compounds in modern and old varieties of durum wheat using liquid chromatography coupled with time-of-flight mass spectrometry

An evaluation of the grain functional components of Italian durum wheat cultivars was conducted. The raw material was obtained from the field trial performed in 2006-2007 at the Experimental Farm of the University of Bologna, (Bologna, Italy). The aim of this study was to define the phytochemical profile of ten varieties, comprised of old and modern durum wheat genotypes, including quantitative and qualitative phenolic and flavonoid content (free and bound forms). The results showed that mean values of total phenolic compound and total flavonoid content in old wheat varieties (878.2+/-19.0 micromol gallic acid equivalent/100g of grain and 122.6+/-25.4 micromol catechin equivalent/100g of grain, respectively) did not differ significantly from those detected in modern genotypes (865.9+/-128.9 micromol gallic acid equivalent/100g and 123.5+/-20.6 micromol catechin equivalent/100g, respectively). However, the HPLC-ESI-TOF-MS analysis highlighted remarkable differences between modern and old cultivars. The interpretation of the mass spectra allowed the identification of 70 phenolic compounds, including coumarins, phenolic acids, anthocyanins, flavones, isoflavones, proanthocyanidins, stilbenes and lignans. The free extracts of ancient wheat varieties showed the presence of a mean number of phenolic compounds and isomer forms (8.7+/-2.5 and 7.7+/-4.7 respectively) significantly higher than in modern genotypes (4.4+/-2.9 and 2.0+/-2.4, respectively). A similar trend was observed also for the bound phenolic fraction. Moreover, the phytochemical profiles showed the presence of unique phenolic compounds in both free and bound fractions of some of the investigated wheat genotypes. Results highlighted that investigated old wheat cultivars may offer unique nutraceutical values for their peculiar contents in bioactive phytochemicals, suggesting their uses into a wide range of regular and specialty products naturally enriched with health-promoting compounds.