New insights into the search of meat quality biomarkers assisted by Orbitrap Tribrid untargeted metabolite analysis and chemometrics

Metabolite profiles of normal and defective dry, firm and dark (DFD) meat extracts with known ultimate pH (pHu) values were determined by Orbitrap Tribrid ID-X untargeted analysis coupled to chemometrics. An intelligent MS³ AcquireX^TM workflow firstly approached the unambiguous characterization of detected features that were subsequently quantified by a complementary MS¹ study of biological replicates. Chemometric research revealed how threonylphenylalanine (overexpressed in normal meats) together to tetradecadienoyl- and hydroxydodecanoyl-carnitines (both overexpressed in DFD meats) appropriately grouped meat groups assayed. Robustness of such biomarkers was confirmed through a time-delayed study of a blind set of samples (unknown pHu) and evidenced limitations of pHu as an isolated parameter for accurate meat quality differentiation. Other acyl-carnitines also characterized DFD samples, suggesting interferences induced by pre-slaughter stress (PSS) on lipid catabolism that would explain accumulation of such intermediate metabolites. Results achieved can ease understanding of biochemical mechanisms underlying meat quality defects.

Application of 2-D DIGE to study the effect of ageing on horse meat myofibrillar sub-proteome

Considering the high relevance of meat tenderness for consumer acceptability, the aim of this study was to investigate post-mortem changes in myofibrillar sub-proteome in steaks from longissimus thoracis et lumborum muscle of six Hispano-Bretón horses. Indeed, the ageing process that leads to meat tenderization has been scarcely studied in this species. Steaks (n = 24) were aged (4 °C) in the dark under vacuum for 0, 7, 14 and 21 days and the myofibrillar sub-proteome was extracted. Using 2-D DIGE minimal labelling, 35 spots that were differentially abundant between 0 and 21 days aged meat were detected. Of them, 24 were analysed by LC-MS/MS, identifying a total of 29 equine proteins. These were structural and metabolic proteins, and among them, four (Actin, Troponin T and Myosin binding proteins 1 and 2) were selected for Western blot analysis, reporting changes in their abundance after 0, 7, 14 and 21 days of ageing. Results revealed that they should be further studied as potential protein biomarkers of horse meat tenderization. Additionally, several protein fragments increased after ageing, as was the case of glyceraldehyde-3-phosphate dehydrogenase. Fragments of this protein were present in four protein spots, and their study could be useful for monitoring horse meat tenderization. SIGNIFICANCE: Tenderization during ageing has been widely studied in meat from several farm animal species; however, both research and standardized ageing practices are lacking for the particular case of horse meat. In this regard, this study presents novel proteomic findings related to post-mortem evolution of horse muscle proteins. Acquired knowledge would support the development and optimization of efficient ageing practices by horse meat industry.

Caspase activity in post mortem muscle and its relation to cattle handling practices

BACKGROUND

Animal handling practices are one of the factors majorly affecting animal metabolism prior to slaughter. This phenomenon increases the occurrence of meat quality defects such as dark cutting-beef, causing high economical losses in the meat industry. Under this framework, the assessment of apoptosis onset in post mortem muscle was proposed as a novel approach to reveal biochemical characteristics in several Spanish bovine breeds (Asturiana de los Valles, Retinta and Rubia Gallega) managed under different production systems (intensive versus semi-extensive) and transport/lairage conditions (mixing versus not mixing with unfamiliar animals). To do so, the activities of initiator caspase 9 and executioner caspases 3/7 were determined in Longissimus thoracis et lumborum muscle at three early post mortem times (2, 8, and 24 h).

RESULTS

Breed effect and transport/lairage conditions were the most relevant factors that influenced both caspase activities over post mortem time, showing Rubia Gallega breed a completely different behavior compared to Asturiana de los Valles and Retinta breeds. Moreover, it is postulated that apoptosis cascade is initiated via the activation of caspase 9 under hypoxic or metabolic stress followed by the activation of executioner caspases 3/7.

CONCLUSIONS

Assessment of apoptosis on post mortem muscle can be a novel approach to study the influence of animal handling on muscle metabolism and post mortem cell death and its consequences on meat quality traits. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Protein Biomarkers of Bovine Defective Meats at a Glance: Gel-Free Hybrid Quadrupole-Orbitrap Analysis for Rapid Screening

An understanding of biological mechanisms that could be involved in the stress response of animal cattle prior to slaughter is critical to create effective strategies aiming at the production of high-quality meat. The sarcoplasmic proteome of directly extracted samples from normal and high ultimate pH (pHu) meat groups was studied through a straightforward gel-free strategy supported by liquid chromatography hybrid quadrupole-Orbitrap high-resolution mass spectrometry (LC-HRMS) analysis. A stepped proteomic pipeline combining rapid biomarker hunting supported by qualitative protein Mascot scores followed by targeted label-free peptide quantification revealed 26 descriptors that characterized meat groups assayed. The functional study of the proposed biomarkers suggested their relevant role in metabolic, chaperone/stress-related, muscle contractility/fiber organization, and transport activities. The efficiency, flexibility, rapidity, and easiness of the methodology proposed can positively contribute to the creation of innovative proteomic alternatives addressing meat quality assessment.

Proteomic pipeline for biomarker hunting of defective bovine meat assisted by liquid chromatography-mass spectrometry analysis and chemometrics

A wide variety of factors prior to slaughter may affect the stress status of beef cattle, giving rise to well-known 'dark-cutting' defective meats characterised by a high ultimate pH (pHu). To understand the underlying mechanisms of pHu fluctuations in beef cattle there was studied the proteome changes caused by pre-slaughter stress through a gel-free proteomic approach. Comparative peptidomic analysis was carried out on 12 loin samples at 24 h post-mortem from Longissimus thoracis et lumborum bovine muscle of crossbred animals, previously sorted into two different groups according to their pHu values: normal (pHu < 6.0) and high (pHu ≥ 6.0). Tryptic peptides from direct protein extracts were approached by combining untargeted (intact mass, MS¹) and targeted (Selected Reaction Monitoring, SRM) quantitative LC-MS assays followed by chemometric analysis. Seventeen peptide biomarkers belonging to 10 different proteins appropriately discriminated sample groups assayed. Results may promote the use of this simple and effective methodology towards the creation of new insights in meat quality research. SIGNIFICANCE: The significance of this study was the optimization of an affordable straightforward gel-free proteomic approach addressing the differentiation of the muscle sub-proteome of normal and high pHu meat samples. This strategy allowed the study of tryptic peptides from direct meat protein extracts by combining untargeted MS¹ and targeted SRM quantitative assays performed by conventional LC-MS detection. Affordability, simplicity and robustness of this methodology can facilitate its readily implementation in routine protocols for quality assessment of meat.

Optimization of a fluorogenic assay to determine caspase 3/7 activity in meat extracts

Usefulness of general-purpose fluorogenic assay kits to determine caspase 3/7 activity of biological extracts is highly compromised in meat-based samples due to their scarce enzyme concentration. In the present work, a straightforward protocol is presented with two main purposes: 1) to enhance sensitivity of the fluorogenic approach addressing caspase 3/7 activity in tissues showing scarce enzyme concentration such as skeletal muscle, and 2) to reduce/economize the volume of employed reagents. The enzyme extraction procedure, peptide substrate, dithiothreitol concentration and detection settings were appropriately optimized for use in microtiter-plate fluorometers. As a result, low to high enzyme activity extracts (from 10,000 to 260,000 relative fluorescence units) can be measured under developed sampling and experimental conditions. The fact that enzyme reactions took place in 96-microtiter well plates reduces the consumption of chemical compounds when analysing a high number of samples, thus contributing to environment sustainability.

A straightforward gel-free proteomics pipeline assisted by liquid isoelectric focusing (OFFGEL) and mass spectrometry analysis to study bovine meat proteome

Bovine sarcoplasmic sub-proteome was studied through a straightforward gel-free pipeline supported by liquid isoelectric focusing (OFFGEL) protein fractionation coupled to liquid chromatography-mass spectrometry (LC-MS) analysis. Full-MS and data-dependent MS/MS analyses were simultaneously performed by a conventional three-dimensional ion-trap addressing targeted quantitative and untargeted qualitative research, respectively. There were unambiguously identified 47 proteins distributed along 12 OFFGEL fractions assayed. Regarding intermediate- and high-abundant peptides, bulky quantitative data processing performed by MZmine 2 freeware yielded a satisfactory linearity and coefficient of variation with r2 in the 0.95–0.99 range and about 25%, respectively. Up to 41 peptides from 20 identified proteins were relatively quantified throughout OFFGEL fractions. This reliable, flexible and affordable gel-free proteomic approach could be readily implemented by industry to improve quality assessment of protein-based food products.

Influence of high pressure homogenization and pasteurization on the in vitro bioaccessibility of carotenoids and flavonoids in orange juice

Production of high-quality healthy foods through sustainable methodologies is an urgent necessity. High pressure homogenization (HPH) is an interesting alternative to obtain premium citrus juices, but its effects on bioactive compounds are unclear. There was studied the influence of HPH (150 MPa) and pasteurization (92 °C for 30 s and 85 °C for 15 s) processing on physicochemical properties and in vitro bioaccessibility of carotenoids and flavonoids in orange juices. Regarding fresh juice, physicochemical properties of samples remained unchanged although cloudiness was improved by homogenization. Pasteurization did not affect total carotenoids content and retinol activity equivalents (RAE) of juices whereas homogenization yielded a significant reduction (1.37 and 1.35-fold, respectively). Interestingly, particle size reduction from homogenization drastically enhanced (about 5-fold) bioaccessibility of carotenoids including hardly bioaccessible epoxycarotenoids, finding unaltered rates in pasteurized samples. Bioaccessibility of flavonoids was constant in all cases. Results can promote HPH as an efficient option to obtain health-enhanced foods.

R-MetaboList 2: A Flexible Tool for Metabolite Annotation from High-Resolution Data-Independent Acquisition Mass Spectrometry Analysis

Technological advancements have permitted the development of innovative multiplexing strategies for data independent acquisition (DIA) mass spectrometry (MS). Software solutions and extensive compound libraries facilitate the efficient analysis of MS¹ data, regardless of the analytical platform. However, the development of comparable tools for DIA data analysis has significantly lagged. This research introduces an update to the former MetaboList R package and a workflow for full-scan MS¹ and MS/MS DIA processing of metabolomic data from multiplexed liquid chromatography high-resolution mass spectrometry (LC-HRMS) experiments. When compared to the former version, new functions have been added to address isolated MS¹ and MS/MS workflows, processing of MS/MS data from stepped collision energies, performance scoring of metabolite annotations, and batch job analysis were incorporated into the update. The flexibility and efficiency of this strategy were assessed through the study of the metabolite profiles of human urine, leukemia cell culture, and medium samples analyzed by either liquid chromatography quadrupole time-of-flight (q-TOF) or quadrupole orbital (q-Orbitrap) instruments. This open-source alternative was designed to promote global metabolomic strategies based on recursive retrospective research of multiplexed DIA analysis.

Chemometrics-assisted optimization of liquid chromatography-quadrupole-time-of-flight mass spectrometry analysis for targeted metabolomics

Mass spectrometry-based metabolomics is characterized by a vast number of variables leading to a great degree of complexity. In this work, we aimed to simplify this process with a stepped chemometric optimization of the both funnel technology (funnel exit DC, FDC; funnel RF LP, FLC; funnel RF HP, FRP) and ion source parameters (Octopolo, Oct; and Fragmentor, Frag) of a quadrupole-time of flight (qTOF) for a human urinary metabolites. The workflow comprised a Box-Behnken experimental design with 47 experiments followed by the identification and quantification of a set of metabolites using high-resolution full-scan MS mode and feature extraction with an inclusion list. Metabolite peak areas were grouped according to abundance (high and low) and modeled by Random Forest regression (variance explained >85%). The full three-level factorial design consisting in 243 experiments was predicted and top 10 solutions for desirability function and those comprising the Pareto front were extracted and investigated. To guarantee the quality of results, we compared the Pareto front solutions with those achieved by standard instrumental parameters suggested by the manufacturer. A set of five solutions were identified that increased the mean peak area by 56-59% and 17%, for high- and low-abundance metabolites, respectively. The optimal parameters were determined to be: FLP, 100 V; FDC, 40 and 30 V; Frag, 275 and 400 V; and Oct, 600 and 800 V. The methodology applied throughout this work represents a flexible strategy to optimize instrumental parameters and exploit the performance of a qTOF MS detector.

Deletion of the neural tube defect-associated gene disrupts one-carbon and central energy metabolism in mouse embryos

One-carbon (1C) metabolism is a universal folate-dependent pathway essential for de novo purine and thymidylate synthesis, amino acid interconversion, universal methyl-donor production, and regeneration of redox cofactors. Homozygous deletion of the 1C pathway gene Mthfd1l encoding methylenetetrahydrofolate dehydrogenase (NADP⁺-dependent) 1-like, which catalyzes mitochondrial formate production from 10-formyltetrahydrofolate, results in 100% penetrant embryonic neural tube defects (NTDs), underscoring the central role of mitochondrially derived formate in embryonic development and providing a mechanistic link between folate and NTDs. However, the specific metabolic processes that are perturbed by Mthfd1l deletion are not known. Here, we performed untargeted metabolomics on whole Mthfd1l-null and wildtype mouse embryos in combination with isotope tracer analysis in mouse embryonic fibroblast (MEF) cell lines to identify Mthfd1l deletion-induced disruptions in 1C metabolism, glycolysis, and the TCA cycle. We found that maternal formate supplementation largely corrects these disruptions in Mthfd1l-null embryos. Serine tracer experiments revealed that Mthfd1l-null MEFs have altered methionine synthesis, indicating that Mthfd1l deletion impairs the methyl cycle. Supplementation of Mthfd1l-null MEFs with formate, hypoxanthine, or combined hypoxanthine and thymidine restored their growth to wildtype levels. Thymidine addition alone was ineffective, suggesting a purine synthesis defect in Mthfd1l-null MEFs. Tracer experiments also revealed lower proportions of labeled hypoxanthine and inosine monophosphate in Mthfd1l-null than in wildtype MEFs, suggesting that Mthfd1l deletion results in increased reliance on the purine salvage pathway. These results indicate that disruptions of mitochondrial 1C metabolism have wide-ranging consequences for many metabolic processes, including those that may not directly interact with 1C metabolism.

Erratum: Combinatorial treatment with natural compounds in prostate cancer inhibits prostate tumor growth and leads to key modulations of cancer cell metabolism

[This corrects the article DOI: 10.1038/s41698-017-0024-z.].

RpeakChrom: Novel R package for the automated characterization and optimization of column efficiency in high-performance liquid chromatography analysis

Characterization of chromatographic columns using the traditional van Deemter method is limited by the necessity of calculating extra-column variance, issue particularly relevant when modeling asymmetrical peaks eluted from monolithic columns. A novel R package that implements Parabolic Variance Modified Gaussian approach for accurate peak modeling, van Deemter equation and two alternatives approaches, based on van Deemter, has been developed to calculate the height equivalent to a theoretical plate (HETP). To assess package capabilities conventional packed reverse-phase and monolithic HPLC columns were characterized. Peaks eluted from the monolithic column showed a high value of factor asymmetry due, in part, to the contribution of extra-column factors. Such deviation can be circumvented by the two alternatives approaches implemented in the R-package. Furthermore, increased values of eddy diffusion and mass transfer kinetics terms in HETP were observed for the packed column, while accuracy was below 9% in all cases. These results showed the usefulness of the R-package for both modeling chromatographic peaks and assessing column efficiency. The RpeakChrom package could become a helpful tool for testing new stationary phases during column development and to evaluate column during its lifetime. This R tool is freely available from CRAN (https://CRAN.R-project.org/package=RpeakChrom).

The early metabolomic response of adipose tissue during acute cold exposure in mice

To maintain core body temperature in cold conditions, mammals activate a complex multi-organ metabolic response for heat production. White adipose tissue (WAT) primarily functions as an energy reservoir, while brown adipose tissue (BAT) is activated during cold exposure to generate heat from nutrients. Both BAT and WAT undergo specific metabolic changes during acute cold exposure. Here, we use an untargeted metabolomics approach to characterize the initial metabolic response to cold exposure in multiple adipose tissue depots in mice. Results demonstrate dramatically distinct metabolic responses during cold exposure in BAT and WAT. Amino acids, nucleotide pathways, and metabolites involved in redox regulation were greatly affected 4 hours post-exposure in BAT, while no polar metabolites were observed to significantly change in WAT depots up to 6 hours post exposure. Lipid metabolism was activated early (2 hours) in both BAT and the subcutaneous WAT depots, with the most striking change being observed in the modulation of diglyceride and monoglyceride levels in BAT. Overall, these data provide a timeline of global thermogenic metabolism in adipose depots during acute cold exposure. We have highlighted differences in visceral and subcutaneous WAT thermogenic metabolism and demonstrate the distinct metabolism of BAT during cold exposure.

Combinatorial treatment with natural compounds in prostate cancer inhibits prostate tumor growth and leads to key modulations of cancer cell metabolism

High-throughput screening of a natural compound library was performed to identify the most efficacious combinatorial treatment on prostate cancer. Ursolic acid, curcumin and resveratrol were selected for further analyses and administered in vivo via the diet, either alone or in combination, in a mouse allograft model of prostate cancer. All possible combinations of these natural compounds produced synergistic effects on tumor size and weight, as predicted in the screens. A subsequent untargeted metabolomics and metabolic flux analysis using isotopically labeled glutamine indicated that the compound combinations modulated glutamine metabolism. In addition, ASCT2 levels and STAT3, mTORC1 and AMPK activity were modulated to a greater extent by the combinations compared to the individual compounds. Overall, this approach can be useful for identifying synergistic combinations of natural compounds for chemopreventive and therapeutic interventions.

Effects of Heat Treatment Conditions on Fresh Taste and on Pectinmethylesterase Activity of Chilled Mandarin and Orange Juices

Juices from oranges, mandarins and hybrids were thermally treated in a plate exchanger at different conditions to evaluate the effects of treatment on fresh taste and on residual pectinmethylesterase (PME) activity. Freshness was significantly higher in fresh juices than in samples treated at 70°C or higher temperatures for 10 seconds of retention time, whereas no differences were found among samples heated at temperatures from 70 to 90°C for the same time, however at 95°C fresh taste decreased again. Residual PME activity was about 20% in samples treated at 70°C for 5, 10 and 20 seconds and in those heated at 80°C for 5 and 10 seconds, decreasing to 15%, also at 80°C, when retention time increased to 20 seconds. A drastic reduction to about 3% of residual activity was observed at 85°C for 10 seconds. Minimum activities of 0-1% corresponded to samples treated at 95°C. Considering the results of sensory and residual enzyme analyses, the treatment at 85°C for 10 seconds can be considered suitable. In these conditions fresh taste did not differ from that of juices treated at lower temperatures but residual enzyme activity was clearly smaller and acceptable for chilled juices, products of high quality but short shelf life. On the other hand, a deeper reduction of PME activity increasing the temperature to 95°C does not seem advisable since fresh taste decreases. Mandarin juices pasteurised at 85°C for 10 seconds and pasteurised again at the same conditions did not show a further decrease of fresh taste. Two heat treatments were usually applied when packing plants receive the juice from other factories.

Time Evolution of Exposed Hydrophobicity of Water-Soluble Proteins During their Depolymerisation by Endo-Proteases

During the depolymerisation of a water-soluble protein by an endo-protease, the exposed hydrophobicity of the substrate, that is the hydrophobicity that is accessible to hydrophobic probes, changes with the progress of the reaction. This work describes the depolymerisation of bovine serum albumin, α-casein and β-lactoglobulin using the proteases Alcalase, Flavourzyme, α-chymotrypsin, mercuripapain and trypsin. Time evolution of substrate hydrophobicity was monitored by a flow-injection analysis (FIA) system with fluorescence detection and an aqueous eluant containing p-toluidinylnaphthalene-6-sulfonate (2,6-TNS) as the fluorescent probe. In all cases, the time evolution of the substrate hydrophobicity was fitted using a derived mathematical function containing two adjustable rate constants and two constant parameters. This methodology allowed the determination of protease activities, as well as online monitoring of the depolymerisation process, when using water-soluble proteins as substrate.

Abstract 3: Amino acid profiles indicate dependence on different metabolic pathways between leukemia subtypes

Despite the growing body of evidence that the tumor microenvironment protects leukemia cells from chemotherapeutic stresses (1-3), the effect of many extracellular metabolites remains largely unknown. To explore the influence of extracellular metabolites on different leukemia subtypes, cells were treated for 24 hours in vitro with either a supplemental amino acid or amino acid derivative. From this initial screening, a subset of metabolites were chosen for metabolomics analysis. Mass spectrometry (UPLC-MS/MS) was performed on intracellular fractions to identify metabolic differences that resulted from supplementation. Metabolite profiles were also compared between leukemia cell types, namely AML, pre-B cell ALL, and T cell ALL. Of the metabolites tested, lysine and 4-hydroxyphenylpyruvate, an intermediate of tyrosine and phenylalanine metabolism, had the greatest impact on global amino acid profiles. In AML and T cell ALL cell lines, intracellular glutamate, glutamine, proline, and aspartate were increased relative to their respective controls. These amino acids can enter the tricarboxylic acid (TCA) cycle as either α-ketoglutarate or oxaloacetate, suggesting a central role of the TCA cycle in both AML and T cell ALL metabolism. Interestingly, these metabolites were not significantly increased in pre-B cell ALL, signifying the inverse it true for pre-B cells. This observation provides metabolomics evidence that is consistent with a previous study that reported downregulated expression of TCA cycle related genes in pre-B cell ALL (4). Our findings indicate that uptake and metabolism of amino acids and their derivatives is distinct for different leukemia types. Moreover, supplementation with a single metabolite can result in global changes in intracellular metabolite profiles, suggesting an influence not only as an energy substrate, but on overall metabolic pathway activity. Specifically, we conclude that the TCA cycle is more active in AML and T cell ALL and can be modulated by changing the extracellular environment, while pre-B cells are less sensitive to amino acid modulation.

(1) Meads MB, et al. Clin Cancer Res 2008;14(9):2519-2526.

(2) Ayala F, et al. Leukemia 2009;23:2233-2241.

(3) Konopleva M, et al. Drug Resist Updat 2009;12:103-113.

(4) Boag JM, et al. Leukemia 2006;20:1731-1737.

Citation Format: Shannon R. Sweeney, Enrique Sentandreu, Stefano Tiziani. Amino acid profiles indicate dependence on different metabolic pathways between leukemia subtypes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3.

Rapid screening of low-molecular-weight phenols from persimmon (Diospyros kaki) pulp using liquid chromatography/UV-visible/electrospray mass spectrometry analysis

BACKGROUND

Persimmon fruits have been widely used in traditional medicine owing to their phenolic composition. This research aims to perform a rapid, detailed and affordable study of the profile of low-molecular-weight phenols from persimmon pulp.

RESULTS

Two different HPLC-DAD/ESI-MS(n) analyses were performed using a routine three-dimensional ion trap mass spectrometer to analyze the ethanolic extract of persimmon pulp: (1) an untargeted data-dependent analysis to identify the majority of small phenols that included full MS and MS(2) scan events; (2) a targeted data-dependent analysis to identify polymerized phenols (dimers and formic acid adducts) through a source-induced dissociation analysis that included full MS and MS(2) scan events. Thirty-two low-molecular-weight phenols were detected, comprising gallic acid and its glycoside and acyl derivatives, glycosides of p-coumaric, vanillic and cinnamic acids and different flavone di-C-hexosides, most of them reported for the first time in persimmon.

CONCLUSION

The use of a straightforward and affordable methodology of analysis led to obtain an up-to-date profiling of low-molecular-weight phenols in persimmon. The results can help future actions aimed to expand the understanding of the phenolic metabolome of persimmon cultivars.

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.

Determination of the antiradical activity and kinetics of pomegranate juice using 2,2-diphenylpicyrl-1-hydrazyl as the antiradical probe

Whole fruit pomegranate (Punica granatum L.) juice of the 'Wonderful' cultivar was characterized through the elucidation of its antiradical kinetics and activity using 2,2-diphenyl-1-picrylhydrazyl as the antiradical probe. Time-dependent concentration of 2,2-diphenyl-1-picrylhydrazyl during its reduction by the juice has been adjusted through a non-linear parametric fitting. Determined total antiradical activity was high, able to reduce 84.58 µmol/l of 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), equivalent to a concentration of 42.29 mmol/l of ascorbic acid (or Trolox). Partial antiradical activities due to the fast-, medium- and slow-kinetics were 49.09, 18.16 and 17.33 µmol/l of reduced 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), respectively. The corresponding rate constant for the fast-, medium- and slow-kinetics were κ 1 = 6.03, κ 2 = 0.169 and κ 3 = 0.0094 (μl l)/(ml µmol min), respectively. This methodology allows characterization of samples through the accurate determination of the kinetics of their antiradical features, avoiding the use of empirical approximations that hinder the realistic comparison between extracts independently of their origin.

Volunteer stratification is more relevant than technological treatment in orange juice flavanone bioavailability

The effect of two technological treatments on orange juice flavanone bioavailability in humans was assessed. Processing affected flavanone solubility and particle size of the cloud. Volunteers were stratified in high, medium, and low urinary excretion capabilities. Flavanones from high-pressure homogenized juice showed better absorption than those of conventional pasteurized juice in high excretors. These differences were not observed in medium and low excretors. High flavanone excretors took advantage of the high-pressure homogenization juice attributes (smaller cloud particle size) and showed an improved absorption/excretion. Stratification of the individuals by their excretion capability is more relevant than technological treatments in terms of flavanone bioavailability. This stratification should be considered in clinical studies with citrus juices and extracts as it could explain the large interindividual variability that is often observed.

Oxidative markers in children with severe obesity following low-calorie diets supplemented with mandarin juice

AIM

 To evaluate the effect of supplementing a hypocaloric diet with mandarin juice, a food with a high content of antioxidants (vitamin C, flavonoids and carotenoids), on biomarkers of oxidant/antioxidant status of severe obese children.

METHODS

 Forty obese children were randomized into two groups pair-wise in a 4-week controlled intervention study. Both groups followed a hypocaloric diet. One group received additionally a supplementation of 500mL of 100% mandarin juice daily. Clinical data, anthropometry, dietary intake and fasting blood samples were collected at baseline and after the intervention. Lipid peroxidation was assessed by circulating levels of malondialdehyde, and protein oxidation was determined by the concentration of plasma carbonyl groups. The antioxidant defence was evaluated by red cell-reduced glutathione and plasma levels of α-tocopherol and vitamin C.

RESULTS

 The supplemented group experienced a decrease in the levels of malondialdehyde (-9.6%, p =0.014) and carbonyl groups (-36.1%, p =0.006) and an increase in antioxidants (α-tocopherol +16.1%, p=0.006, glutathione +36.1%, p < 0.0001, and vitamin C + 94.6%, p < 0.0001).

CONCLUSION

  The mandarin juice consumption with a reduced calorie diet positively affects the antioxidant defence and produces a decrease in biomarkers of oxidative stress in obese children.

LC-DAD-ESI/MS(n) determination of direct condensation flavanol-anthocyanin adducts in pressure extracted pomegranate (Punica granatum L.) juice

Pomegranate (Punica granatum L.) juice, obtained by pressure extraction of the whole fruit, has been analyzed for its flavanol-anthocyanin adduct content using reversed-phase liquid chromatography with diode array detection, coupled to mass spectrometry (ion trap) with electrospray ionization (HPLC-DAD-ESI/MS(n)), operating in positive ion mode. A total of 35 dimers have been detected, consisting of mono- and disubstituted hexoside derivatives of the adducts between the flavan-3-ols (epi)gallocatechin, (epi)catechin and (epi)afzelechin and the anthocyanidins delphinidin, cyanidin and pelargonidin. In addition, evidence is given for the presence of additional anthocyanin-flavanol adducts in this juice.

Reduction kinetics of the antiradical probe 2,2-diphenyl-1-picrylhydrazyl in methanol and acetonitrile by the antiradical activity of protocatechuic acid and protocatechuic acid methyl ester

This work evaluates the reduction kinetics of the antiradical probe 2,2-diphenyl-1-picrylhydrazyl (DPPH (*)) in methanol and acetonitrile by the antiradical activity of protocatechuic acid (3,4-dihydroxybenzoic acid, 1) and protocatechuic acid methyl ester ( 2). The reduction kinetics of DPPH (*) in both solvents by the antiradical activity of the p-catechol group in 2 is regular, that is, coincide with the proposed standard kinetic model for the reduction kinetics of DPPH (*) by the antiradical activity of an isolated p-catechol group. Therefore, the antiradical activity of 2 experimentally exhibits two rate-two stoichiometric constants in acetonitrile and three rate--three stoichiometric constants in methanol. In contrast, the reduction kinetics of DPPH (*) in both solvents by the antiradical activity of the p-catechol group in 1 is perturbed, that is, deviate from the proposed standard kinetic model. The deviations arise from the presence of the reactive carboxylic acid function which, in methanol, induces an additional reversible side reaction and, in acetonitrile, turns an irreversible reaction reversible, thus modifying the otherwise regular reduction kinetics of DPPH (*) by the antiradical activity of the p-catechol group in 1. On the other hand, the approximated theoretical kinetic equation that applies for those p-catechol groups whose reduction kinetics is regular and that experimentally exhibit three rate--three stoichiometric constants has been derived and used for fitting.

Kinetic model for the antiradical activity of the isolated p-catechol group in flavanone type structures using the free stable radical 2,2-diphenyl-1-picrylhydrazyl as the antiradical probe

The time evolution of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*) concentration in four solvents (methanol, ethanol, propanol, and acetonitrile) during its reduction by three flavanones containing an isolated p-catechol group (taxifolin, eriodyctiol, and fustin) as well as the time evolution of the mass spectra of the reaction mixture has been determined by spectrophotometry and liquid mass spectrometry, respectively. In alcoholic solvents the reduction curves consisted of an initial short but fast kinetics step followed by a longer slow kinetics step; in contrast, in acetonitrile the reduction curves completely lacked the slow kinetics step. From the results, a kinetic model for the reaction of reduction of the DPPH* by the isolated p-catechol group in flavanone type structures is proposed. According to this model, the p-catechol group rapidly transfers two hydrogen atoms to DPPH*, through a fast rate constant k1, yielding the corresponding o-quinone. Then, the intermediate o-quinone forms an adduct with the alcoholic solvent, through a slow rate constant k2, and regenerates the p-catechol group. The regenerated p-catechol group reduces additional DPPH* through a fast rate constant k3, yielding the corresponding o-quinone, which can form a new adduct with the solvent to regenerate the p-catechol group, and so on. From the kinetics model, two explicit kinetics equations have been derived that fit very well the experimental data points acquired from all assayed compounds in all of the experiments carried out, thus allowing an accurate determination of the corresponding rate and stoichiometric constants.

Pulsed electric fields versus thermal treatment: equivalent processes to obtain equally acceptable citrus juices

Pulsed electric field treatment has been claimed to produce more acceptable chilled citrus juices than those obtained by conventional thermal treatment. The pectin methylesterase activity and the acceptability of nine juices obtained from Clementine mandarins, Valencia oranges, and Ortanique fruits (hybrid of mandarin and orange), untreated, pasteurized (85 degrees C for 10 s), and treated by pulsed electric fields (25 kV/cm for 330 micros), were evaluated. The treatments, selected to reach a similar level of pectin methylesterase inactivation, produced juices that did not differ in acceptability from each other for the three varieties and in all cases were less acceptable than the untreated juice.

Monitoring of chemical and enzymatic hydrolysis of water-soluble proteins using flow-injection analysis with fluorescence detection and an aqueous eluant containing 2-p-toluidinylnaphthalene-6-sulfonate as the fluorescent probe

The exposed hydrophobicity of proteins, which is due to the hydrophobic regions located on their surfaces, enhances the fluorescence intensity of the probe 2-p-toluidinylnaphthalene-6-sulfonate (2,6-TNS) by the formation of a complex. During the hydrolysis of a protein, the average exposed hydrophobicity of the substrate continuously changes with incubation time, and these changes are immediately reflected by a corresponding change in the fluorescence intensity of the 2,6-TNS/substrate complex. Therefore, 2,6-TNS seems to be a good probe to monitor the course of the depolymerization processes of proteins. In this work, bovine serum albumin and alpha-casein have been hydrolyzed both chemically and enzymatically, and the course of the reactions is monitored by using flow-injection analysis (FIA) with fluorescence detection and a buffered aqueous eluant containing 2,6-TNS as the fluorescent probe. Results indicate that the time evolution of the fluorescence intensity of the 2,6-TNS/substrate complex can be correlated with the initial concentration of the parent protein, in mass per unit volume, the hydrolytic activity added, and the time evolution of the mean chain length of the substrate. In addition, because the time elapsed between injection of the sample into the FIA system and measurement of the corresponding fluorescence intensity is only a few seconds, this methodology could be a useful tool for on-line monitoring of processes for the production of protein hydrolysates.