A nuclear magnetic resonance (1H and 13C) and isotope ratio mass spectrometry (delta13C, delta2H and delta18O) study of Andalusian olive oils

Fingerprinting of monovarietal olive oils from Argentina and Uruguay via stable isotope, fatty acid profile, and chemometric analyses

Tracing methods of non-European EVOOs commercialized worldwide are becoming crucial for effective authenticity controls. Limited analytical studies of these oils are available on a global scale, similar to those of European EVOOs. We report for the first time the fatty acid concentrations, bulk-oil 2H/1H, 13C/12C, and 18O/16O ratios and fatty acid 13C/12C ratios of 43 authentic monovarietal EVOOs from different geographical regions in Argentina and Uruguay. The samples were obtained from a wide range of latitudes and altitudes along an E-W profile, from lowlands near the Atlantic Ocean to the pre-Andean highlands near the Pacific Ocean. Principal component scores were used to cluster EVOOs into three groups- central-western Argentina, central Argentina, and Uruguay-based on nine stable isotope ratios and the oleic-linoleic acid concentration ratio. The bulk 2H/1H and 18O/16O values and 13C/12C of palmitoleic and linoleic acids provide good tools for differentiating these oils via linear discriminant analysis.

Contrast Agents Based on Human Serum Albumin and Nitroxides for 1H-MRI and Overhauser-Enhanced MRI

In cancer diagnostics, magnetic resonance imaging (MRI) uses contrast agents to enhance the distinction between the target tissue and background. Several promising approaches have been developed to increase MRI sensitivity, one of which is Overhauser dynamic nuclear polarization (ODNP)-enhanced MRI (OMRI). In this study, a macromolecular construct based on human serum albumin and nitroxyl radicals (HSA-NIT) was developed using a new synthesis method that significantly increased the modification to 21 nitroxide residues per protein. This was confirmed by electron paramagnetic resonance (EPR) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight (MALDI ToF) mass spectrometry. Gel electrophoresis and circular dichroism showed no significant changes in the structure of HSA-NITs, and no oligomers were formed during modification. The cytotoxicity of HSA-NITs was comparable to that of native albumin. HSA-NITs were evaluated as potential "metal-free" organic radical relaxation-based contrast agents for 1H-MRI and as hyperpolarizing contrast agents for OMRI. Relaxivities (longitudinal and transversal relaxation rates r1 and r2) for HSA-NITs were measured at different magnetic field strengths (1.88, 3, 7, and 14 T). Phantoms were used to demonstrate the potential use of HSA-NIT as a T1- and T2-weighted relaxation-based contrast agent at 3 T and 14 T. The efficacy of 1H Overhauser dynamic nuclear polarization (ODNP) in liquids at an ultralow magnetic field (ULF, B0 = 92 ± 0.8 μT) was investigated for HSA-NIT conjugates. The HSA-NITs themselves did not show ODNP enhancement; however, under the proteolysis conditions simulating cancer tissue, HSA-NIT conjugates were cleaved into lower-molecular-weight (MW) protein fragments that activate ODNP capabilities, resulting in a maximum achievable enhancement |Emax| of 40-50 and a radiofrequency power required to achieve half of Emax, P1/2, of 21-27 W. The HSA-NIT with a higher degree of modification released increased the number of spin probes upon biodegradation, which significantly enhanced the Overhauser effect. Thus, HSA-NITs may represent a new class of MRI relaxation-based contrast agents as well as novel cleavable conjugates for use as hyperpolarizing contrast agents (HCAs) in OMRI.

Deep Learning-Based Quantitative Assessment of Melamine and Cyanuric Acid in Pet Food Using Fourier Transform Infrared Spectroscopy

Melamine and its derivative, cyanuric acid, are occasionally added to pet meals because of their nitrogen-rich qualities, leading to the development of several health-related issues. A nondestructive sensing technique that offers effective detection must be developed to address this problem. In conjunction with machine learning and deep learning technique, Fourier transform infrared (FT-IR) spectroscopy was employed in this investigation for the nondestructive quantitative measurement of eight different concentrations of melamine and cyanuric acid added to pet food. The effectiveness of the one-dimensional convolutional neural network (1D CNN) technique was compared with that of partial least squares regression (PLSR), principal component regression (PCR), and a net analyte signal (NAS)-based methodology, called hybrid linear analysis (HLA/GO). The 1D CNN model developed for the FT-IR spectra attained correlation coefficients of 0.995 and 0.994 and root mean square error of prediction values of 0.090% and 0.110% for the prediction datasets on the melamine- and cyanuric acid-contaminated pet food samples, respectively, which were superior to those of the PLSR and PCR models. Therefore, when FT-IR spectroscopy is employed in conjunction with a 1D CNN model, it serves as a potentially rapid and nondestructive method for identifying toxic chemicals added to pet food.

The Leaf Essential Oil of Gynoxys buxifolia (Kunth) Cass. (Asteraceae): A Good Source of Furanoeremophilane and Bakkenolide A

The present study describes the chemical and enantiomeric composition of a new essential oil, distilled from the dry leaves of Gynoxys buxifolia (Kunth) Cass. The chemical analysis was conducted by GC-MS and GC-FID, on two orthogonal capillary columns. A total of 72 compounds were detected and quantified with at least one column, corresponding to about 85% by weight of the whole oil mass. Of the 72 components, 70 were identified by comparing the respective linear retention indices and mass spectra with data from the literature, whereas the two main constituents were identified by preparative purification and NMR experiments. The quantitative analysis was carried out calculating the relative response factor of each compound according to their combustion enthalpy. The major constituents of the EO (≥3%) were: furanoeremophilane (31.3-28.3%), bakkenolide A (17.6-16.3%), caryophyllene oxide (6.0-5.8%), and (E)-β-caryophyllene (4.4%). Additionally, the hydrolate was also analyzed with respect to the dissolved organic phase. About 40.7-43.4 mg/100 mL of organic compounds was detected in solution, of which p-vinylguaiacol was the main component (25.4-29.9 mg/100 mL). Finally, the enantioselective analysis of some chiral terpenes was carried out, with a capillary column based on β-cyclodextrin chiral stationary phase. In this analysis, (1S,5S)-(-)-α-pinene, (1S,5S)-(-)-β-pinene, (S)-(+)-α-phellandrene, (S)-(+)-β-phellandrene, and (S)-(-)-terpinen-4-ol were detected as enantiomerically pure, whereas (S)-(-)-sabinene showed an enantiomeric excess of 69.2%. The essential oil described in the present study is a good source of two uncommon volatile compounds: furanoeremophilane and bakkenolide A. The former lacks bioactivity information and deserves further investigation, whereas the latter is a promising selective anticancer product.

Metabolic profiles and fingerprints for the investigation of the influence of nitisinone on the metabolism of the yeast Saccharomyces cerevisiae

Nitisinone (2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione, NTBC) is considered a potentially effective drug for the treatment of various metabolic diseases associated with disorders of L-tyrosine metabolism however, side-effects impede its widespread use. This work aimed to broaden the knowledge of the influence of NTBC and its metabolites 2-amino-4-(trifluoromethyl)benzoic acid (ATFA), 2-nitro-4-(trifluoromethyl)benzoic acid (NTFA), and cyclohexane-1,3-dione (CHD) on the catabolism of L-tyrosine and other endogenous compounds in Saccharomyces cerevisiae. Based on a targeted analysis performed by LC-ESI-MS/MS, based on multiple reaction monitoring, it was found that the dissipation kinetics of the parent compound and its metabolites are compatible with a first-order reaction mechanism. Moreover, it has been proven that formed NTBC metabolites, such as CHD, cause a decrease in L-tyrosine, L-tryptophan, and L-phenylalanine concentrations by about 34%, 59% and 51%, respectively, compared to the untreated model organism. The overall changes in the metabolism of yeast exposed to NTBC or its derivatives were evaluated by non-targeted analysis via LC-ESI-MS/MS in the ion trap scanning mode. Based on principal components analysis, a statistically significant similarity between metabolic responses of yeast treated with ATFA or NTFA was observed. These findings facilitate further studies investigating the influence of NTBC on the human body and the mechanism of its action.

Synthesis and Characterization of Nanoformulation of the Broad-Spectrum Enzyme Inhibitor Mancozeb by Polyethylene Glycol Capping and Its Dissipation Kinetics in Water Using TiO2 Nanoparticles

The poly(ethylene) glycol (PEG) capped mancozeb nanoformulation was prepared by the ultrasonic method using a 1% mancozeb solution and 20% capping agent, PEG-4000. The synthesized nanoformulation was characterized using UV-visible, FTIR, SEM and TEM techniques. The photolytic and photo catalytic experiments were carried out in a Borosil glass bottle in the presence of sunlight, varying the pH proportions at a single fortification level (1.0 g/mL) in ground water, under sunlight. The optimal catalyst concentration for complete degradation was observed to be 0.1 percent. The mancozeb nanoformulation in water was determined using the HPLC-PDA method, and the rate constant and the 50% degradation (DT50) values were calculated based on the results. The photolytic results show that there is no significant loss of residues due to adsorption. Titanium dioxide (TiO2) was discovered to be an excellent decontaminating catalyst in a variety of water samples. The compound survives for several days in the absence of a catalyst.

Antioxidant Content and Antioxidant Capacity of the Protein-Rich Powdered Beverages Enriched with Flax Seeds Gum

Powdered beverages produced from dried fruit and vegetables are new products whose properties may be tailored by adding efficient nutrients and functional ingredients. The analyses of low-molecular antioxidants and antioxidant properties as well as nutrient content and digestibility were tested in beverages enriched with lentil proteins (AGF) and flaxseed gum (FSG). A replacement of sprouted lentil flour with the AGF deteriorated the phenolic content. As a main source of phenolics and vitamin C, lyophilized parsley leaves and broccoli sprouts were recognized. (There was no clear effect of the FGS.) The highest content of phenolics was determined in the beverages with these additives without the AGS (c.a. 125 μg/g). The AGF significantly improved the ability to quench ABTS radicals and reduce power. The best results were for the beverages without the FSG. (The effect was enhanced by lyophilized fruit and green vegetables.) The lowest chelating power and ability to quench hydroxyl radicals were in the beverages based on the AGF (improvement by the FSG and green vegetables). The tailoring of beverages' recipes significantly increased protein content and did not affect nutrient digestibility. The modifications allow obtaining the beverages exhibiting multidirectional antioxidant properties, being a source of easily bioaccessible starch and proteins.

Metabolomics-driven determination of targets for salicylic acid and ibuprofen in positive electrospray ionization using LC-HRMS

Due to the large number of basic therapeutic and illicit drugs, systematic toxicological analysis has widely been performed with liquid chromatography coupled to mass spectrometry using positive electrospray ionization. However, there exists a smaller number of drugs, typically acidic drugs, which require the use of negative electrospray ionization either via a separate injection or polarity switching. Here, targets relating to salicylic acid and ibuprofen in positive electrospray ionization were determined through a metabolomics-driven retrospective investigation of forensic casework. Samples were previously screened using liquid chromatography coupled with high-resolution mass spectrometry with quantification of target analytes performed using liquid chromatography with tandem mass spectrometry. Of the 1717 whole-blood samples submitted between 2014 and 2019, 48 were positive for salicylic acid (1.1-1400 mg/kg) and 78 for ibuprofen (1-46 mg/kg). Based on the retrospective analysis, 19 and 90 targets were identified for salicylic acid and ibuprofen, respectively. For targets of salicylic acid, the protonated adduct of salicyluric acid ([M+H]⁺ , m/z 196.0605) was present in 89.6% (n = 32) of the salicylic acid positive cases while the [M+HCOOH+CH₃ CN+Ca-H]⁺ adduct (m/z 264.0179) of salicylic acid was present in all positive samples with concentrations above 66 mg/kg salicylic acid. Similarly, the [M + 2Na - H]⁺ adduct (m/z 251.1018) of ibuprofen was present in 98.7% (n = 77) of positive cases and was present in all samples with concentrations above 3 mg/kg ibuprofen.

MALDI Matrices for the Analysis of Low Molecular Weight Compounds: Rational Design, Challenges and Perspectives

The analysis of low molecular weight (LMW) compounds is of great interest to detect small pharmaceutical drugs rapidly and sensitively, or to trace and understand metabolic pathways. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) plays a central role in the analysis of high molecular weight (bio)molecules. However, its application for LMW compounds is restricted by spectral interferences in the low m/z region, which are produced by conventional organic matrices. Several strategies regarding sample preparation have been investigated to overcome this problem. A different rationale is centred on developing new matrices which not only meet the fundamental requirements of good absorption and high ionization efficiency, but are also vacuum stable and "MALDI silent", i. e., do not give matrix-related signals in the LMW area. This review gives an overview on the rational design strategies used to develop matrix systems for the analysis of LMW compounds, focusing on (i) the modification of well-known matrices, (ii) the search for high molecular weight matrices, (iii) the development of binary, hybrid and nanomaterial-based matrices, (iv) the advance of reactive matrices and (v) the progress made regarding matrices for negative or dual polarity mode.

Combination of Stable Isotope Analysis and Chemometrics to Discriminate Geoclimatically and Temporally the Virgin Olive Oils from Three Mediterranean Countries

The knowledge of the isotopic composition of virgin olive oil (VOO) allows the evaluation of authenticity and geographical origin, being an important tool against fraud. This study aimed to assess if VOOs produced in three Mediterranean regions could be discriminated on the basis of multivariate statistical analysis of geoclimatic and isotopic data. A total of 138 geo-referenced VOO samples from Portugal, France and Turkey from two different cultivation years were collected. The isotopic composition (δ13C, δ2H and δ18O) of VOOs was obtained using an elemental analyzer coupled to an isotope ratio mass spectrometer (EA-IRMS). One-way analysis of variance for δ13C, δ2H and δ18O showed some significant differences either between crop years or geoclimatic conditions. Based on multiple regression analyses using meteorological and geographical parameters, a meteoric water line for olive oil from Portugal, France and Turkey, in two harvest years, were created to assess the impact of climate change on their δ2H and δ18O values. Principal component analysis and Linear Discriminant Analysis, used to sort samples according to geoclimatic origin, performed best for French and Portuguese olive oils. In light of the results, multivariate isotopic analysis of VOO samples may discriminate not only between geoclimatic regions but also among cultivation years.

Bulk C, H, O, and fatty acid C stable isotope analyses for purity assessment of vegetable oils from the southern and northern hemispheres

RATIONALE

The carbon, hydrogen and oxygen stable isotope composition (δ¹³ C, δ² H, and δ¹⁸ O values) of plants and their products is linked to photosynthetic fractionation, environmental factors and agricultural practices. Therefore, they contribute to determining the purity of commercial vegetable oils and may provide information on their geographical origin.

METHODS

Maize, olive, sunflower, groundnut, soybean and rice oils differing in sites of growth in the southern and northern hemispheres were characterized by bulk oil stable isotope ratios (δ¹³ C_bulk , δ² H_bulk , and δ¹⁸ O_bulk values), fatty acid (FA) concentrations and δ¹³ C_FA values using elemental analysis/isotope ratio mass spectrometry, gas chromatography/mass spectrometry, gas chromatography/flame ionization detection and gas chromatography/combustion/isotope ratio mass spectrometry. Principal component analysis was applied to examine the inherent structure of the data.

RESULTS

The δ¹³ C_bulk values of maize oils (-18.4 to -14.9 ‰) are typical for C₄ plants, and those of olive (-30.2 to -28.2 ‰), sunflower (-30.2 to -29.2 ‰), groundnut (-29.3 ‰), soybean (-30.6 ‰), and rice (-34.5 ‰) oils are typical for C₃ plants. The δ² H_bulk values vary from -161 to -132 ‰ for maize oils and -171 to -109 ‰ for C₃ oils. The δ¹⁸ O_bulk values of all oils vary between 15.2 and 38.9 ‰. The major δ¹³ C_FA differences (>5 ‰) within plant species render the inter-C₃ -species comparison difficult. These differences are explained in terms of variations in the lipid biosynthetic pathways and blend of vegetable oils of different FA composition and δ¹³ C_FA values. The samples from the southern hemisphere are generally enriched in ¹³ C compared with those from the northern hemisphere. Differences between the southern and northern hemispheres were observed in δ² H (p < 0.001) and δ¹⁸ O_bulk (p = 0.129) values for all C₃ oils, and in δ¹³ C_18:1 (p = 0.026) and δ¹⁸ O_bulk (p = 0.160) values for maize oils.

CONCLUSIONS

The results of this study show that combining bulk and molecular stable isotope ratios, FA compositions and their statistical analysis helps the characterization of the geographic origin of oils. This methodology can be used to detect and source impurities in valuable vegetable oils commercialized worldwide. Copyright © 2016 John Wiley & Sons, Ltd.

Fatty acid composition and δ13 C of bulk and individual fatty acids as marker for authenticating Italian PDO/PGI extra virgin olive oils by means of isotopic ratio mass spectrometry

European Regulation (EEC) 2568/91 has been setting the minimum requirements in order to allow labeling of oil as extra virgin. These general requirements, are based on physical-chemical and organoleptic parameters directly linked to the freshness and quality of the product. Isotope ratio mass spectrometry (IRMS) was demonstrated to be a useful tool for the discrimination of the origin of unknown samples, because the obtained data are practically independent of the cultivar employed and the production technique. In this work, the evaluation of the composition of fatty acid methyl esters (FAME) alongside with the determination of stable isotope ratio of C in bulk oils and in main FAME constituents have been investigated as a tool to improve geographical discrimination of Italian Protected Designation of Origin/Protected Geographical Indication (PDO/PGI) samples. For this purpose, authentic PDO/PGI extra virgin olive oils were sampled at oil mills and grouped into different sets according to their areas of provenience. The use of principal component analysis and partial least squares discriminant analysis multivariate analysis techniques demonstrated that discrimination of olive oil samples can be done using geographical and pedoclimatic parameters predominantly by using δ(13) C results of bulk and individual fatty acids. Results showed that δ(13) C values are a more reliable marker of origin with respect to fatty acid composition.