Characterisation and quantification of phenolic compounds of extra-virgin olive oils according to their geographical origin by a rapid and resolutive LC-ESI-TOF MS method

Identification of compounds from high-fat and extra virgin olive oil-supplemented diets in whole mouse liver extracts and isolated mitochondria using mass spectrometry

Nonalcoholic steatohepatitis (NASH) is a fatty liver disorder that could be improved with extra virgin olive oil (EVOO) supplementation in diet. We propose the monitoring, in whole mouse liver extracts and in isolated mitochondria, of the absorption of compounds from three different diets: standard (CT), high-fat (HFD) and high-fat supplemented with EVOO (HFSO). Male mice were submitted to one of the following three diets: CT or HFD for 16 weeks or HFD for 8 weeks followed by additional 8 weeks with HFSO. Following this period, liver was extracted for histological evaluation, mitochondria isolation and mass spectrometry analyses. Diets, liver extracts and Percoll-purified mitochondria were analyzed using ESI-MS and the lipidomics approach. Morphological, histological and spectrometric results indicated a decrease in NASH severity with EVOO supplementation in comparison with animals maintained with HFD. Spectrometric data also demonstrated that some compounds presented on the diets are absorbed by the mitochondria. EVOO was shown to be a potential therapeutic alternative in food for NASH. Our results are in accordance with the proposition that the major factor that influences different responses to diets is their composition - and not only calories - especially when it comes to studies on obesity.

Comprehensive 3-year study of the phenolic profile of Moroccan monovarietal virgin olive oils from the Meknès region

The phenolic fraction of monovarietal virgin olive oils (VOOs) from the main Moroccan cultivar Picholine marocaine (142 samples from three different subareas of the Meknès region) was studied over three consecutive crop seasons (2011, 2012, and 2013) using a powerful LC-MS methodology. First, LC-ESI-TOF MS was used to get a comprehensive characterization of the phenolic fraction; afterward, LC-ESI-IT MS was utilized for further identification (MS/MS experiments) and quantitation purposes. A total of 28 phenolic compounds (and quinic acid) were determined, revealing the complex profile of Meknès VOO, composed, in order of abundance, by secoiridoids, phenolic alcohols, lignans, flavonoids, and phenolic acids. Tukey's test was applied to ascertain possible significant intraregional and/or interannual variations of the phenolic content of the Meknès VOOs under study. Results showed that the content of phenolic compounds was mainly related to the crop season.

High-resolution mass spectrometry to evaluate the influence of cross-breeding segregating populations on the phenolic profile of virgin olive oils

BACKGROUND

The growing demand for high-quality virgin olive oils (VOOs) has increased the interest in olive breeding programs. Cross-breeding is considered, within these programs, the best strategy to generate new cultivars as an attempt to improve the present cultivars. In this research, the phenolic profile of VOOs from target crosses (Arbequina × Arbosana, Picual × Koroneiki and Sikitita × Arbosana) and their corresponding genitors (Arbequina, Arbosana, Koroneiki, Picual and Sikitita) has been evaluated using a targeted metabolomics approach.

RESULTS

The phenolic profiles were obtained by liquid chromatographic-hybrid quadrupole time-of-flight mass spectrometric targeted analysis of 37 phenols or compounds involved in the main pathways for their biosynthesis. Statistical multivariate analysis by principal component analysis was applied to study the influence of genotype on phenol composition. Phenolic compounds with the highest contribution to explain the observed variability associated to genotype were identified through fold change algorithms (cut-off > 2.0) and t-test analysis.

CONCLUSION

A total of nine phenols (viz. quercetin, ligstroside aglycon (p-HPEA-EA), demethyl oleuropein aglycon, oleuropein aglycon (3,4-DHPEA-EA), hydroxypinoresinol, hydroxytyrosol and phenolic acids such as p-coumaric acid, ferulic acid and protocatechuic acid) contributed to explain the observed variability with 99% confidence (P<0.01).

Characterization of monovarietal virgin olive oils by phenols profiling

The phenolic profiles of seven monovarietal virgin olive oils (VOOs) - viz. Arbequina, Arbosana, Cornicabra, FS-17, Hojiblanca, Picual and Sikitita - were characterized by using a quantitative strategy based on LC-MS/MS and the selected reaction monitoring (SRM) mode. Data dependent methods, based on precursor ion scanning, product ion scanning and neutral loss scanning, were developed for confirmatory analysis of secoiridoid derivatives. The observed phenolic profiles were used to find correlation between pairs of phenols and similarity trends among the monovarietal VOOs. A Pearson analysis revealed several correlations among phenols with p-value<0.01 and correlation coefficient (R)>0.75 in the seven monovarietal VOOs. Cluster analysis showed two main clusters between VOOs, formed by Arbequina/Hojiblanca/Cornicabra/Picual and Sikitita/Arbosana/FS-17. High correlations (R>0.7) were observed for the following pairs of VOOs: Arbequina/Hojiblanca (R=0.77), essentially supported on levels of hydroxytyrosol acetate (3,4-DHPEA-AC) and dialdehydic forms of secoiridoids; Cornicabra/FS-17 (R=0.81) and Picual/FS-17 (R=0.79), by correlation of flavonoids and secoiridoid derivatives in general. The highest correlation was observed for the pair Picual/Cornicabra (R=0.99). This preliminary study allowed setting similarities and dissimilarities between monovarietal VOOs by analysis of the phenolic profile. The observed connections between phenols for different varieties have been tentatively interpreted according to the main pathways for phenols biosynthesis.

Characterisation of phenolic compounds by HPLC-TOF/IT/MS in buds and open flowers of 'Chemlali' olive cultivar

INTRODUCTION

Plant phenolics are secondary metabolites that constitute one of the most widely occurring groups of phytochemicals that play several important functions in plants. In olive (Olea europaea L), there is not enough information about the occurrence of these compounds in buds and flowers.

OBJECTIVE

To conduct a comprehensive characterisation of buds and open flowers from the olive cultivar 'Chemlali'.

METHODS

The polar fraction of buds and open flowers was extracted using solid-liquid extraction with hydro-alcoholic solvent. Then extracts were analysed using high performance liquid chromatography (HPLC) coupled to electrospray ionisation time-of-flight mass spectrometry (ESI/TOF/MS) and electrospray ionisation ion-trap tandem mass spectrometry (ESI/IT/MS²) operating in negative ion mode.

RESULTS

Phenolic compounds from different classes including secoiridoids, flavonoids, simple phenols, cinnamic acid derivatives and lignans were tentatively identified in both extracts. Qualitatively, no significant difference was observed between flower buds and open flowers extracts. However, quantitatively the secoiridoids presented higher percentage of total phenols in open flowers (41.7%) than in flower buds (30.5%) in contrast to flavonoids, which decreased slightly from 38.1 to 26.7%. Cinnamic acid derivatives and simple phenols did not show any change. Lignans presented the lowest percentage in both extracts with an increase during the development of the flower bud to open flower.

CONCLUSION

The HPLC-TOF/IT/MS allowed the characterisation, for the first time, of the phenolic profile of extracts of 'Chemlali' olive buds and open flowers, proving to be a very useful technique for the characterisation and structure elucidation of phenolic compounds.

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.

Characterization of phenolics of Sarcandra glabra by non-targeted high-performance liquid chromatography fingerprinting and following targeted electrospray ionisation tandem mass spectrometry/time-of-flight mass spectrometry analyses

In this study, we successfully characterised the phenolic profiles of Sarcandra glabra (Thunb.) Nakai by high-performance liquid chromatography (HPLC) fingerprinting analyses and mass spectrometry (MS) identification. We first established a specific and valid HPLC approach for fingerprint analysis of S. glabra based on HPLC-UV detection. Using several chemometric methods such as similarity evaluation and principal components analysis, we determined herb-markers peaks from many HPLC peaks. The structures of these herb-markers were further identified targetedly by electrospray ionisation tandem mass spectrometry (ESI-MS/MS)/time-of-flight mass spectrometry (TOF-MS) analyses. As results, four phenolics, including chlorogenic acid, caffeic acid, 4-O-glucopyranosyl rosmarinic acid and rosmarinic acid, were characterised as major herb-markers for the stems of S. glabra, while another three phenolics, including kaempferol-3-O-β-d-glucuronic acid, chlorogenic acid and rosmarinic acid, were characteristic components for the leaves. The compounds may be very useful for further phenolome analysis.

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.

New filtration systems for extra-virgin olive oil: effect on antioxidant compounds, oxidative stability, and physicochemical and sensory properties

The purpose of this work was to evaluate some new filtration systems in relation to the quality of extra-virgin olive oil (EVOO). Filtration processes were undertaken using a polypropylene filter bag and two different inert gas flows as filter aids (argon and nitrogen). Qualitative and quantitative variations of the glyceride composition, antioxidant and pro-oxidant compounds, and water content were correlated with the oxidative stability to establish the effect on EVOO shelf life. The influence on physicochemical and sensorial properties was also evaluated. After filtration, the oxidative stability was reduced. The behavior of the polyphenols and water content on the filtration process could explain the lowest oxidative stability of filtered EVOO. Moreover, the results of the sensorial analysis confirmed that filtration using inert gases did not decrease the intensity of the main positive sensory attributes. The results could help olive-oil producers to improve EVOO quality and establish optimal storage conditions.