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NMR based Metabolomics in Food Chemistry
Get PDFMetabolomics is defined as the systematic analysis of hundreds or thousands of small metabolites present in a living system. It has emerge as an important field of study along with other, already established ‘omics’ sciences, i.e., genomics, proteomics and transcriptomics. Metabolomics is well established in the field of medicine, drug toxicity and disease diagnosis. Among the existing analytical techniques, NMR is a fast, reproducible and non-destructive technique to construct an informative snapshot of the metabolites under certain conditions. NMR data give metabolic signature information of the samples when it is combined with data preprocessing and chemometric tools, such as multivariate statistical techniques. NMR-based metabolomics is still expanding in the field of the food chemistry. In this context, this Ph.D. thesis is focused on two major aspects, which show applications of NMR-based metabolomics in food chemistry.
1. Many nutraceutical products possess powerful antioxidant activity as demonstrated in many chemical in vitro tests and in several in vivo trials. Nevertheless, the mechanism of their activity is not completely studied in detail. Due to their poor bioavailability and fast metabolism, studies on the in vivo antioxidant effects are still needed. We performed longitudinal experiments on Sprague Dawley (SD) rats using two commonly available nutraceutical antioxidant products, namely, Curcumin (chapter 2) and Resveratrol (chapter 3). The effects of different doses of orally administered standardized antioxidant extracts in healthy rats were investigated by untargeted metabolomic analysis based on LC-MS and NMR spectrometry. The experiments were carried out over different periods of time for different antioxidants. Changes in the urinary metabolome were evaluated by monitoring the 24-hour urine composition by 1H-NMR and HPLC-MS. The two different approaches were able to detect variations in the urinary levels of antioxidant markers, leading to the observation of different metabolites thus proving the complementarity of these two analytical techniques for metabolomic purposes. Analytical tools such as MS and NMR spectroscopy in combination with chemometrics can profile the impact of time, stress, nutritional status, and environmental perturbations on hundreds of metabolites simultaneously. This results in complex, massive data sets that must be analyzed through a careful statistical protocol. Our strategy included data preprocessing, data analysis and validation of statistical models. After several data processing steps, principal component analysis (PCA) and partial least-squares (PLS) were used to identify urine biomarkers. The PLS models were validated by permutation tests and critically important variables were validated through univariate analysis.
2. The second part of this thesis (chapters 4 and 5) describe the use of NMR-based metabolomics as a fast, convenient, and effective tool for origin discrimination and biomarker discovery in food analysis. Traditionally, the determination of the floral origin of honey is made from palynological analysis. The method is based on the identification of pollen by microscopic inspection. However, melissopalynological analysis needs expertise and also it is not a very reliable technique for the discrimination of botanical origin of some types of honey. Also, honey regulation in the EU (Codex Alimentarius Commission 2001; European Commission 2002) emphasizes that the botanical and geographical origins of the product must be printed on the label in order to avoid the fraud such as adulteration with industrial sugar, selling product under false name or mixing the honey of different floral origin. Therefore, there is need to establish a method to discriminate honey from different origin. The aim of this work was to develop an NMR-based metabolomic approach that used multivariate statistical analysis to discriminate the botanical (chapter 4) and entomological (chapter 5) origin of different types of honey. Multivariate statistical analysis helped us to identify the most relevant signals to differentiate honey botanically and entomologically. The obtained data sets were useful in the search of markers responsible for the discrimination of different honey samples from different botanical species and produced by different bee species
Entomological Origin of Honey Discriminated by NMR Chloroform Extracts in Ecuadorian Honey
Get PDFHoneys are produced by Apis mellifera and stingless
bees (Meliponini) in Ecuador. We studied honey produced in
beeswax combs by Apis mellifera, and honey produced in pots by
Geotrigona and Scaptotrigona bees. Chloroform extracts of honey
were obtained for fast NMR spectra. The 1D spectra were acquired at
298 K, with a 600 MHz NMR Bruker instrument, using a modified
double pulsed field gradient spin echoes (DPFGSE) sequence.
Signals of 1H NMR spectra were integrated and used as inputs for
PCA, PLS-DA analysis, and labelled sets of classes were successfully
identified, enhancing the separation between the three groups of
honey according to the entomological origin: A. mellifera,
Geotrigona and Scaptotrigona. This procedure is therefore
recommended for authenticity test of honey in Ecuador
Evaluation of hidden H2-consuming pathways using metabolic flux-based analysis for a fermentative side-stream dynamic membrane bioreactor using untreated seed sludge
No full textObjective Definition of Monofloral and Polyfloral Honeys Based on NMR Metabolomic Profiling
No full textIn this paper, a remarkably precise, simple, and objective definition of monofloral and polyfloral honey based on
NMR metabolomics is proposed. The spectra of organic extracts of 983 samples of 16 botanical origins were used to derive oneversus-
all OPLS-DA classification models. The predictive components of the statistical models reveal not only the principal but
also the secondary floral origins present in a sample of honey, a novel feature with respect to the methods present in the literature
that are able to confirm the authenticity of monofloral honeys but not to characterize a mixture of honey types. This result
descends from the peculiar features of the chloroform spectra that show diagnostic resonances for almost each botanical origin,
making these NMR spectra suitable fingerprints. The reliability of the method was tested with an additional 120 samples, and the
class assignments were compared with those obtained by traditional analysis. The two approaches are in excellent agreement in
identifying the floral species present in honeys and in the botanical classification. Therefore, this NMR method may prove to be a
valid solution to the huge limitations of traditional classification, which is very demanding and complex
Studying the effects of natural extracts with metabolomics: A longitudinal study on the supplementation of healthy rats with Polygonum cuspidatum Sieb. et Zucc
No full textBackground A longitudinal study was performed to evaluate the effects of Polygonum cuspidatum extract (standardized at 20% resveratrol) supplementation on healthy rats. The effects were explored by monitoring urinary metabolome changes using UPLC-HRMS and 1H NMR-based approaches. The aim of the study was to explore the effects of P. cuspidatum supplementation on a healthy animal model using metabolomics, in order to determine possible modes of action and obtain information on bioactivity. Methods Healthy Sprague-Dawley rats were orally supplemented with 100 mg/kg of dried P. cuspidatum extract for 49 days and 24-h urinary outputs were collected. Samples were analysed by untargeted UPLC-HRMS and 1H NMR approaches and the obtained data sets were modelled by an adaptation of post-transformation of PLS2 to longitudinal studies. Putative markers were discovered by a stability selection procedure and specific oxidative stress markers were monitored by a targeted HPLC–MS/MS analysis to assess the in vivo antioxidant activity of P. cuspidatum extract. Results UPLC-HRMS and 1H NMR platforms showed two different but complementary patterns of metabolites describing the changes ascribable to P. cuspidatum supplementation and using both approaches, a comprehensive resveratrol metabolism and urinary excretion could be observed. Markers of P. cuspidatum supplementation effects identified by UPLC-HRMS were mainly related to its antioxidant activity and to a possible “adaptogenic” activity. Urinary changes observed by 1H NMR were mainly related to energy metabolism. UPLC-HRMS and 1H NMR metabolomics approaches allowed the effects of a prolonged supplementation with P. cuspidatum on healthy rats to be observed. The statistical models built from both data sets showed metabolic changes in urines related to rat aging
New findings on the in vivo antioxidant activity of Curcuma longa extract by an integrated 1H NMR and HPLC-MS metabolomic approach
Get PDFCurcuminoids possess powerful antioxidant activity as demonstrated in many chemical in vitro tests and in several in vivo trials. Nevertheless, the mechanism of this activity is not completely elucidated and studies on the in vivo antioxidant effects are still needed. Metabolomics may be used as an attractive approach for such studies and in this paper, we describe the effects of oral administration of a Curcuma longa L. extract (150 mg/kg of total curcuminoids) to 12 healthy rats with particular attention to urinary markers of oxidative stress. The experiment was carried out over 33 days and changes in the 24-h urine samples metabolome were evaluated by H-1 NMR and HPLC-MS. Both techniques produced similar representations for the collected samples confirming our previous study. Modifications of the urinary metabolome lead to the observation of different variables proving the complementarity of 1H NMR and HPLC-MS for metabolomic purposes. The urinary levels of allantoin, m-tyrosine, 8-hydroxy-2'-deoxyguanosine, and nitrotyrosine were decreased in the treated group thus supporting an in vivo antioxidant effect of the oral administration of Curcuma extract to healthy rats. On the other hand, urinary TMAO levels were higher in the treated compared to the control group suggesting a role of curcumin supplementation on microbiota or on TMAO urinary excretion. Furthermore, the urinary levels of the sulphur containing compounds taurine and cystine were also changed suggesting a role for such constituents in the biochemical pathways involved in Curcuma extract bioactivity and indicating the need for further investigation on the complex role of antioxidant curcumin effects
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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