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

Determination of 16 ultraviolet-absorbing compounds in marine invertebrates by using LC-USI-MS/MS coupled with QuEChERS

In this study, we examined multiple endocrine-disrupting ultraviolet-absorbing compounds (UVACs) in marine invertebrates used in personal care products and packaging. Modified QuEChERS and liquid chromatography UniSpray ionization tandem mass spectrometry were used to identify 16 UVACs in marine invertebrates. Matrix-matched calibration curves revealed high linearity (r ≥ 0.9929), with limits of detection and quantification of 0.006-1.000 and 0.020-3.000 ng/g w.w., respectively. In oysters, intraday and interday analyses revealed acceptable accuracy (93%-120%) and precision (≤18%), except for benzophenone (BP) and ethylhexyl 4-(dimethylamino) benzoate. Analysis of 100 marine invertebrate samples revealed detection frequencies of 100%, 98%, 89%, 64%, and 100% for BP, 4-hydroxybenzophenone, 4-methylbenzophenone, 4-methylbenzylidene camphor, and benzophenone-3 (BP-3), respectively. BP and BP-3 were detected at concentrations of 4.40-27.39 and < 0.020-0.560 ng/g w.w., respectively, indicating their widespread presence. Overall, our proposed method successfully detected UVACs in marine invertebrates, raising concerns regarding their potential environmental and health effects.

A New Culture Medium Rich in Phenols Used for Screening Bitter Degrading Strains of Lactic Acid Bacteria to Employ in Table Olive Production

The olive oil industry recently introduced a novel multi-phase decanter with the "Leopard DMF" series, which gives a by-product called pâté, made up of pulp and olive wastewater with a high content of phenolic substances and without pits. This study aims to create a new culture medium, the Olive Juice Broth (OJB), from DMF pâté, and apply it to select bacteria strains able to survive and degrade the bitter substances normally present in the olive fruit. Thirty-five different bacterial strains of Lactiplantibacillus plantarum from the CREA-IT.PE Collection of Microorganisms were tested. Seven strains characterized by ≥50% growth in OJB (B31, B137, B28, B39, B124, B130, and B51) showed a degradation of the total phenolic content of OJB ≥ 30%. From this set, L. plantarum B51 strain was selected as a starter for table olive production vs. spontaneous fermentation. The selected inoculant effectively reduced the debittering time compared to spontaneous fermentation. Hydroxytyrosol, derived from oleuropein and verbascoside degradation, and tyrosol, derived from ligstroside degradation, were produced faster than during spontaneous fermentation. The OJB medium is confirmed to be useful in selecting bacterial strains resistant to the complex phenolic environment of the olive fruit.

The Effect of the Extra Virgin Olive Oil Minor Phenolic Compound 3',4'-Dihydroxyphenylglycol in Experimental Diabetic Kidney Disease

The aim of this study was to analyze the possible nephroprotective effect of 3',4'-dihydroxyphenylglycol (DHPG), a polyphenolic compound of extra virgin olive oil (EVOO), on renal lesions in an experimental model of type 1 diabetes. Rats were distributed as follows: healthy normoglycemic rats (NDR), diabetic rats treated with saline (DR), and DR treated with 0.5 mg/kg/day or 1 mg/kg/day of DHPG. DR showed a significantly higher serum and renal oxidative and nitrosative stress profile than NDR, as well as reduced prostacyclin production and renal damage (defined as urinary protein excretion, reduced creatinine clearance, increased glomerular volume, and increased glomerulosclerosis index). DHPG reduced the oxidative and nitrosative stress and increased prostacyclin production (a 59.2% reduction in DR and 34.7-7.8% reduction in DHPG-treated rats), as well as 38-56% reduction in urinary protein excretion and 22-46% reduction in glomerular morphological parameters (after the treatment with 0.5 or 1 mg/kg/day, respectively). Conclusions: DHPG administration to type 1-like diabetic rats exerts a nephroprotective effect probably due to the sum of its antioxidant (Pearson's coefficient 0.68-0.74), antinitrosative (Pearson's coefficient 0.83), and prostacyclin production regulator (Pearson's coefficient 0.75) effects.

Development of a Chemically Modified Sensor Based on a Pentapeptide and Its Application for Sensitive Detection of Verbascoside in Extra Virgin Olive Oil

In addition to their antioxidant and antimicrobial action in functional foods, beverages, and in some dermato-cosmetic products, olive phenolic compounds are also recognized for their role in the prevention of diabetes and inflammation, treatment of heart disease and, consequently, of the numerous chronic diseases mediated by the free radicals. In recent years, attention has increased, in particular, regarding one of the most important compound in extra virgin olive oil (EVOO) having glycosidic structure, namely verbocoside, due to the existence in the literature of numerous studies demonstrating its remarkable contribution to the prophylaxis and treatment of various disorders of the human body. The purpose of this study was the qualitative and quantitative determination of verbascoside in commercial EVOOs from different regions by means of a newly developed sensor based on a screen-printed carbon electrode (SPCE) modified with graphene oxide (GPHOX), on the surface of which a pentapeptide was immobilized by means of glutaraldehyde as cross-linking agent. The modified electrode surface was investigated using both Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. This newly developed sensor has shown a high sensibility compared to the unmodified electrode, a low detection limit (LOD) of up to 9.38 × 10^-8 M, and a wide linearity range between 0.1 µM and 10.55 µM. The applicability of the modified sensor was confirmed by detecting verbascoside in ten different EVOOs samples using the cyclic voltammetry (CV) method, with very good results. The validation of the electroanalytical method was performed by using the standard addition method with very good recoveries in the range of 97.48-103.77%.

Increasing Antioxidant Activity in Food Waste Extracts by β-Glucosidase

Research background

Food by-products such as onion peels and olive leaves are rich in bioactive compounds applicable as natural and low-cost sources of antioxidants. Still, these compounds mainly exist in glycosylated form. Often, hydrolysis of glycoside compounds increases their antioxidant activity and health benefits. However, not many studies have been done concerning the β-glucosidase effect, specifically from Aspergillus niger, on glycosylated compounds within these by-products. Also, changes in the antioxidant activity of the mentioned by-products under the effect of β-glucosidase have not been reported yet. Therefore, this study considers the effect of A. niger β-glucosidase on glucoside compounds and the antioxidant activity of onion peel and olive leaf extracts.

Experimental approach

The antioxidant activity of the extracts was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Also, glucose, total phenolic and flavonoid contents were measured. Moreover, TLC and HPLC analyses were performed before and after the enzymatic hydrolysis.

Results and conclusions

The obtained results showed an increase in the extract antioxidant activity after treatment. Also, β-glucosidase increased the glucose content of the extracts. The thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) results showed the β-glucosidase efficacy to hydrolyze quercetin glucosides in onion peel extract, and the quercetin concentration increased from (0.48±0.04) mg/mL in the untreated extract to (1.26±0.03) mg/mL in the treated extract (0.5% m/V) after 3 h of enzymatic hydrolysis at 45 °C. Also, the content of quercetin-3-O-glucoside increased considerably from (1.8±0.1) to (54±9) µg/mL following the enzyme treatment. Moreover, oleuropein in olive leaf extract (1% m/V) was hydrolyzed completely from (0.382±0.016) to 0 mg/mL by β-glucosidase for 24 h at 50 °C.

Novelty and scientific contribution

This study showed that A. niger β-glucosidase, as a stable enzyme, hydrolyzed quercetin and oleuropein glycosides in onion peel and olive leaf extracts. Thus, A. niger β-glucosidase is a good candidate for processing the food waste and extracting valuable bioactive compounds. Also, the treated extracts with higher antioxidant and biological activity, and without bitter taste can be applicable as potent, natural and cost-effective antioxidants in the food industry.

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.

α-glucosidase inhibitors from Syzygium polyanthum (Wight) Walp leaves as revealed by metabolomics and in silico approaches

ETHNOPHARMACOLOGICAL RELEVANCE

Syzygium polyanthum (Wight) Walp leaves are traditionally used to cure diabetes in many regions of Indonesia. Traditional use involves boiling the leaves until the water is reduced to half volume, and then the decoction is taken 1-2 times daily. Despite several studies reporting the antidiabetic activity of this plant, bioactive compounds have not been well identified.

AIM OF THE STUDY

Indonesia is one of the countries with the highest diabetes cases, particularly type 2 diabetes mellitus (T2DM). Few people have access to modern medicinal treatment; thus, the role of antidiabetic traditional medicine has become increasingly important. This research aimed to identify α-glucosidase inhibitors from S. polyathum leaves using a metabolomics approach. When the active compounds of S. polyathum are properly identified, the quality of the herb can be more easily controlled.

MATERIALS AND METHODS

The dried leaves of S. polyanthum were extracted by a comprehensive extraction method using a solvent combination of n-hexane, acetone, and water in a gradient, resulting in a total of 42 fractions. All fractions were subjected to an in vitro α-glucosidase inhibition test and chemical profile analysis using Nuclear Magnetic Resonance (NMR) and high performance liquid chromatography (HPLC). Orthogonal projection least square (OPLS) analysis was used to correlate the two data to identify NMR signals, and HPLC chromatogram peaks correlated to the activity. 2D NMR and ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) analyses were also used to give more precise compound identification. The activity of the identified active compounds was confirmed by an in silico technique.

RESULTS AND DISCUSSION

The results of the α-glucosidase activity test showed that the most active fractions were obtained from solvents with medium polarity: Fractions 9 and 10 (F9 and F10), obtained from gradient acetone-water 4:1 and 3:2, respectively. The IC50 values of F9 and F10 were 24.8 and 31.8 μg/mL, respectively. NMR data showed that F9 had more intense and diverse signals in the aromatic region than F10. OPLS analysis results showed that some typical flavonoid signals abundant in F9 positively correlated with α-glucosidase activity. 2D NMR and UHPLC-HRMS analysis of F9 led to the conclusion that these signals could be attributed to myricetin-3-O-rhamnoside (myricitrin) and epigallocatechin-3-gallate (EGCG). In silico analysis confirmed these results, as myricitrin and EGCG had binding energies resembling acarbose as a positive control (-8.47, -8.19, and -10.13, respectively).

CONCLUSIONS

NMR and HPLC-metabolomics successfully identified myricitrin and EGCG as α-glucosidase inhibitors from S. polyanthum leaves, and docking analysis validated their inhibitory activity. The results of this study justified the traditional use of S. polyanthum as an antidiabetes herbal.

Chemical characterization of Echium plantagineum seed oil obtained by three methods of extraction

Echium seed oil has been considered an important alternative source of omega 3 fatty acids (n-3 FA) for human consumption. Considering the oxidative instability of n-3 FA richer oils, the objective of this study was to determine the chemical and sensory parameters of the oil obtained from Echium plantagineum seeds obtained by three extraction methods (hydraulic press: HYD; continuous screw press: PRESS; and solvent technique: SOLV). Stearidonic acid (C18:4, n3), the most important n-3 FA present in the oil, changed from 12.5% to 12.7%. Regarding the minor compounds, PRESS sample showed the highest concentration of gamma-tocopherol (782.24 mg/kg oil), while SOLV samples presented the highest amount of β-sitosterol (73.46 mg/100 g) with no difference of campesterol concentration (159.56 mg/100 g) among the samples. Higher values of total phenolics (19.65 mg GAE/kg oil) and β-carotene (34.83 mg/kg oil) were also found in the SOLV samples, suggesting the influence of hexane in the extraction of these bioactive compounds. High resolution mass spectrometry identified caffeic acid and its derivatives as the main phenolic compounds present in the echium oil. PRESS sample showed the best oxidative stability as measured by PV (0.61 mmol/kg oil) and malondialdehyde (173.13 µmol), probably due to faster time of processing compared to HYD and SOLV samples. Our data showed that the extraction method changed the chemical composition of the minor compounds in the echium oil, but these alterations did not reduce its nutritional quality or sensory acceptability. PRACTICAL APPLICATION: Echium oil represents a great potential source of omega 3 fatty acids, but there is not enough information about its oxidative stability and chemical composition, especially toward minor compounds. Our study characterizes echium oil composition obtained from three extraction methods, contributing to amplify the technical information about this important alternative oil for human consumption.

A liquid chromatography-tandem mass spectrometry method for the analysis of primary aromatic amines in human urine

Aromatic amines are widely used in personal care products and human exposure to this class of chemicals is widespread. Bioanalytical methods to determine trace levels of aromatic amines in human urine are scarce. In this study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine 39 primary aromatic amines (AAs) along with nicotine and cotinine in human urine. Chromatographic separation of the 41 analytes was achieved on an Ultra Biphenyl (100 mm × 2.1 mm, 5 µm) column. Mass spectrometry was operated in electrospray ionization positive ion multiple reaction monitoring (MRM) mode. The method exhibited excellent linear dynamic range (0.1-50 ng/mL) with correlation coefficients (r) > 0.999 for all analytes. Urine samples (2 mL) were hydrolyzed using 10 M NaOH at 95 °C for 15 h and target analytes were extracted using methyl-tert-butyl ether (MTBE). Addition of 15 µL of 0.25 M HCl to the sample extracts improved the recoveries of several target analytes. The method was validated through the analysis of fortified quality control (QC) samples and a certified standard reference material (SRM). Relative recoveries (%) of target analytes fortified in QC samples were in the range of 75-114% for 37 of the 41 analytes while the other analytes exhibited lower recoveries (16-74%). The limits of detection (LOD) and limits of quantification (LOQ) of target analytes were in the range of 0.025-0.20 ng/mL and 0.1-1.0 ng/mL, respectively. Intra-day and inter-day precision of the method assessed through the analysis of fortified urine QC samples at three different concentrations were < 11.7% and < 15.9% (measured as RSD), respectively. The method was applied in the analysis of urine samples from the general population and known smokers; aniline, para-anisidine, para-toluidine, ortho/meta-toluidine, 3-chloroaniline, 4-chloroaniline, 3,4-dichloroaniline, and 4,4'-methylenedianiline were found in all smoker's urine at sum concentrations ranging from 0.04 to 9.16 ng/mL.

Extraction, Radical Scavenging Activities, and Chemical Composition Identification of Flavonoids from Sunflower (Helianthus annuus L.) Receptacles

This study was focused on extraction, radical scavenging activities, and chemical composition identification of total flavonoids in sunflower (Helianthus annuus L.) receptacles (TFSR). We investigated the optimal extract parameters of TFSR using response surface methodology. The highest yield of TFSR was 1.04% with the ethanol concentration 58%, the material-to-liquid ratio 1:20 (v/w), the extraction time 2.6 h, and the extraction temperature 67 °C. The results of radical scavenging activities showed that ethyl acetate fraction (EAF) was the strongest by using 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2’-azino-bis (3-ethylbenzo thiazoline-6-sulfonic acid) (ABTS) and iron ion reducing analysis. The EAF had the highest flavonoids contents. Four fractions A, B, C and D were enrichment from EAF by polyamide resin. Fraction B had the highest flavonoids content. Thirteen chemical components of flavonoids in fraction B were first identified by Ultimate 3000 Nano LC System coupled to a Q Exactive HF benchtop Orbitrap mass spectrometer (UHPLC-HRMS/MS). Among of the thirteen chemical components, isoquercetin and daidzein were identified accurately by comparing with standard samples. Radical scavenging analysis showed that isoquercetin and EAF had strong activities. Therefore, sunflower receptacles can be used as a source of natural flavonoids. TFSR as a natural radical scavenger has potential applications in pharmaceutical industry.

Phenolic Profile Characterization of ‘Galega Vulgar’ and ‘Cobrançosa’ Portuguese Olive Cultivars along the Ripening Stages

The phenolic composition of olive fruits represents a vast and unique source of health beneficial molecules due to the presence of specific phenolic compounds (PCs), such as verbascoside (VERB), oleuropein (OLE) and its derivative molecules. Despite of being some of the most critical compounds regarding olive oil quality, these PCs are mostly abundant in olive fruits and leafs due to their hydrophilic nature. In olives, the phenolic profile suffers a deep and constant change along fruit ripening being the phenolic alcohols, such as hydroxytyrosol (HT), mainly formed by OLE, and/or OLE aglycone molecules degradation. The present work aims to study the maturation evolution of olive fruits from two major traditional Portuguese cultivars, ‘Galega Vulgar’ and ‘Cobrançosa’, in regard to their specific phenolic profile, as well as caliber (C), moisture (H), fat content in dry matter (OPDW) and maturity index (MI). Results show that both cultivars present distinct phenolic profiles along their ripening, with ‘Galega Vulgar’ reaching a high MI and OPDW at a much earlier ripening stage (S3), in agreement with the moment when a maximum OLE accumulation was registered. On the other hand, ‘Cobrançosa’ cultivar reached its higher MI and OPDW at S6 (harvest period), coinciding also with high OLE concentrations. MI may be used as a prediction tool for ’Galega Vulgar’ optimal harvesting time evaluation, associated with higher OLE and VERB concentrations, which will confer an additional protection towards diseases, that normally affect olive orchards.

Lipase-Catalyzed Chemoselective Ester Hydrolysis of Biomimetically Coupled Aryls for the Synthesis of Unsymmetric Biphenyl Esters

Lipases are among the most frequently used biocatalysts in organic synthesis, allowing numerous environmentally friendly and inexpensive chemical transformations. Here, we present a biomimetic strategy based on iron(III)-catalyzed oxidative coupling and selective ester monohydrolysis using lipases for the synthesis of unsymmetric biphenyl-based esters under mild conditions. The diverse class of biphenyl esters is of pharmaceutical and technical relevance. We explored the potency of a series of nine different lipases of bacterial, fungal, and mammalian origin on their catalytic activities to cleave biphenyl esters, and optimized the reaction conditions, in terms of reaction time, temperature, pH, organic solvent, and water–organic solvent ratios, to improve the chemoselectivity, and hence control the ratio of unsymmetric versus symmetric products. Elevated temperature and increased DMSO content led to an almost exclusive monohydrolysis by the four lipases Candida rugosa lipase (CRL), Mucor miehei lipase (MML), Rhizopus niveus lipase (RNL), and Pseudomonas fluorescens lipase (PFL). The study was complemented by in silico binding predictions to rationalize the observed differences in efficacies of the lipases to convert biphenyl esters. The optimized reaction conditions were transferred to the preparative scale with high yields, underlining the potential of the presented biomimetic approach as an alternative strategy to the commonly used transition metal-based strategies for the synthesis of diverse biphenyl esters.