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Brown carbon (BrC), the important component of carbonaceous aerosol, attracted much attention for its complex chemical composition which affect its light absorption, fluorescent properties, and atmospheric reactions. In this study, we revealed for the first time the molecular composition of non-polar/low-polar organic matters contributing to fluorescence of Beijing PM 2.5 from 2016 to 2018. Firstly, excitation-emission matrix (EEM) spectra of the 122 PM 2.5 samples were analyzed and supported by gas chromatography-time of flight mass spectrometry (GC-ToF-MS) and partial least squares regression model, 400 BrC molecules associated with fluorescence were screened out among which 44 were the newly ones. Secondly, six chromophores (C1–C6) were identified by applying parallel factor analysis (PARAFAC) model, which represented categories of compounds consistent with the ToF results. Then, the specific molecule composition of each chromophore was achieved by combining GC-ToF-MS and EEM-PARAFAC. For example, indeno[1,2,3- cd ]pyrene is a new fluorescent molecule which contributed high in C3 (high oxygenated humic-like chromophore) and C5 (fluorescein chromophore). The results can, on one side, enrich the database of fluorescent molecular composition, which turns out to be similar as that of light-absorption; on the other side and more importantly, provide chemical characteristics of BrC fluorescent chromophores on the level of molecule. [Display omitted] • Identified fluorescent low-polar molecules in PM 2.5 by applying GC-ToF-MS and PLS model. • Decomposed six fluorescent components of PM 2.5 via EEM-PARAFAC. • Revealed the molecular composition of each chromophore by combining EEM-PARAFAC and GC-ToF-MS. [ABSTRACT FROM AUTHOR]

Zingiber species are members of the Zingiberaceae family, and are widely used for medicinal and food purposes. In this study aboveground and root parts of Zingiber mioga and Zingiber officinale were subjected to metabolite profiling by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) in order to characterize them by species and parts and also to measure bioactivities. Both primary and secondary metabolites showed clear discrimination in the PCA score plot and PLS-DA by species and parts. Tetrahydrocurcumin, diarylheptanoid, 8-gingerol, and 8-paradol were discriminating metabolites between Z. mioga and Z. officinale that were present in different quantities. Eleven flavonoids, six amino acids, six organic acids, four fatty acids, and gingerenone A were higher in the aboveground parts than the root parts. Antioxidant activities were measured and were highest in the root part of Z. officinale. The relatively high contents of tetrahydrocurcumin, diarylheptanoid, and galanganol C in the root part of Z. officinale showed highly positive correlation with bioactivities based on correlation assay. On the basis of these results, we can suggest different usages of structurally different parts of Zingiber species as food plants. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive metabolite profile analysis of doenjang, a fermented soybean paste, at various steps of its industrial 5-step production process was conducted, by combining gas and liquid chromatography-mass spectrometry techniques with multivariate analysis. From the partial least squares discriminant analysis of primary and secondary metabolites, the patterns were clearly distinguishable between the various processing steps (step 1: steaming, step 2: drying, step 3: meju fermentation, step 4: brining, step 5: doenjang aging). Of the primary metabolites, most of the monosaccharides, amino acids, and fatty acids increased in steps 3-5. Isoflavone and soyasaponin derivatives were major secondary metabolites identified during the processing of doenjang. Isoflavone glycosides gradually decreased after step 1, while isoflavone aglycones distinctly increased in steps 4-5. Soyasaponins generally decreased during processing after step 2. Increased isoflavone aglycones, such as daidzein, glycitein, and genistein, were observed in steps 4-5 showed the strongest positive correlation with doenjang's antioxidant potential and total phenolic content. [ABSTRACT FROM AUTHOR]

Until recently, studies reporting the concentrations of polybrominated diphenyl ethers (PBDEs) as well as polybrominated biphenyls (PBBs) are generally scarce in the literature. Consequently, this study was aimed to investigate the occurrence and concentrations of certain PBDE congeners (BDE 28, 47, 100, 99, 154, 153, 183 and 209) and BB 153 in river water samples collected bi-monthly from the Diep River. The routine analyses of the target compounds were performed using a high-capillary GC-microelectron capture detection, while their structural elucidation was assessed using GC-TOF-MS technique. The overall mean concentrations of the sum of the eight PBDE congeners were 2.60, 4.83 and 4.29 ng/L for the upstream, point of discharge and downstream sampling points, respectively. Similarly, the overall mean concentrations of BB 153 were 0.25, 4.85 and 1.56 ng/L for the upstream, point of discharge and downstream sampling points, respectively. BDE 47 was the dominant congener found in these samples contributing between 19 and 26 % to the total PBDEs across the sampling points. The statistical analyses performed on the results obtained showed that all the congeners, except BDE 209 in certain instances, had strong positive correlations with one another, thus suggesting that these contaminants could be emanating from the same source. In this study, potential sources of these pollutants other than WWTP discharges into the investigated river were also identified. However, the relatively high concentrations of the target compounds found at the point of discharge sampling point coupled with the large volume of treated effluent being discharged suggested that the contributions from this source could be very significant over time. [ABSTRACT FROM AUTHOR]

Abstract: In order to determine how plant uptake of a sulfur-rich secondary metabolite, sinalbin, affects the metabolic profile of sulfur-deficient plants, gas chromatography time-of-flight mass spectrometry (GC–TOF-MS), in combination with liquid chromatography–mass spectrometry (LC–MS), was used to survey the metabolome of Arabidopsis seedlings grown in nutrient media under different sulfur conditions. The growth media had either sufficient inorganic sulfur for normal plant growth or insufficient inorganic sulfur in the presence or absence of supplementation with organic sulfur in the form of sinalbin (p-hydroxybenzylglucosinolate). A total of 90 metabolites were identified by GC–TOF-MS and their levels were compared across the three treatments. Of the identified compounds, 21 showed similar responses in plants that were either sulfur deficient or sinalbin supplemented compared to sulfur-sufficient plants, while 12 metabolites differed in abundance only in sulfur-deficient plants. Twelve metabolites accumulated to higher levels in sinalbin-supplemented than in the sulfur-sufficient plants. Secondary metabolites such as flavonol conjugates, sinapinic acid esters and glucosinolates, were identified by LC–MS and their corresponding mass fragmentation patterns were determined. Under sinalbin-supplemented conditions, sinalbin was taken up by Arabidopsis and contributed to the endogenous formation of glucosinolates. Additionally, levels of flavonol glycosides and sinapinic acid esters increased while levels of flavonol diglycosides with glucose attached to the 3-position were reduced. The exogenously administered sinalbin resulted in inhibition of root and hypocotyl growth and markedly influenced metabolite profiles, compared to control and sulfur-deficient plants. These results indicate that, under sulfur deficient conditions, glucosinolates can be a sulfur source for plants. This investigation defines an opportunity to elucidate the mechanism of glucosinolate degradation in vivo. [Copyright &y& Elsevier]

Abstract: A headspace SPME GC–TOF-MS method was developed for the acquisition of metabolite profiles of apple volatiles. As a first step, an experimental design was applied to find out the most appropriate conditions for the extraction of apple volatile compounds by SPME. The selected SPME method was applied in profiling of four different apple varieties by GC–EI-TOF-MS. Full scan GC–MS data were processed by MarkerLynx software for peak picking, normalisation, alignment and feature extraction. Advanced chemometric/statistical techniques (PCA and PLS-DA) were used to explore data and extract useful information. Characteristic markers of each variety were successively identified using the NIST library thus providing useful information for variety classification. The developed HS-SPME sampling method is fully automated and proved useful in obtaining the fingerprint of the volatile content of the fruit. The described analytical protocol can aid in further studies of the apple metabolome. [Copyright &y& Elsevier]

Metabolic footprinting has been applied as a non-invasive approach to study the behaviour and responses of cultured cells to a range of genetic and environmental perturbations. Gas chromatography interfaced with time-of-flight mass spectrometry (GC-ToF-MS) has become a powerful tool for the analysis of metabolome-derived samples. Generally, two data analysis strategies are used to interrogate and understand the biological patterns within the multi-dimensional data. The first strategy, a commoner one, uses multivariate analysis after chromatographic and mass spectral deconvolution, and the second strategy directly employs multivariate analysis of non-deconvoluted data. Here, two strategies have been assessed for the separation and classification of metabolic footprints (exometabolomes) of two strains of Candida albicans grown on three different carbon sources (glycerol, glucose and galactose). We describe a semi-automated approach that simultaneously processes all samples using the chromatographic dimension data with principal components analysis (PCA), which can include data pre-processing before PCA analysis. The preprocessed and non-deconvoluted total ion chromatogram (TIC) data showed good separation of classes defined by growth on different carbon sources and when comparing the two strains grown on the same carbon source separation was achieved for strains grown on glucose and glycerol after preprocessing. The discrimination observed is greater for preprocessed and non-deconvoluted TIC data than for that of preprocessed and non-deconvoluted single ion chromatogram data. The results from the proposed approach with those produced by MZmine were compared. The results from MZmine data depicted separations in PCA space according to carbon source, but no separation was seen when studying strains grown on the same carbon source. Our research showed that the non-deconvoluted strategy is suitable for fast comparison of large sets of GC-MS data although it will not directly provide biological information. The non-deconvoluted strategy can avoid problems of analyzing complex samples using deconvolution software. [ABSTRACT FROM AUTHOR]

Abstract: An important feature relevant to potato (Solanum tuberosum) tuber quality management is the susceptibility to blackspot bruising caused by melanin production after exposure to severe mechanical stress. We analyzed the previously neglected nature and sequence of responses in primary metabolism and compared the cultivars ‘Afra’ and ‘Milva’ that differ in tissue elasticity and susceptibility to blackspot bruising. Mechanical stress application was highly standardized and differential formation of bruising damage and occurrence of small cracks in the outer tuber layers were demonstrated. Concomitant GC–TOF-MS based metabolite profiling revealed characteristic changes in central metabolism, namely in intermediates of the TCA cycle and linked parts of amino acid metabolism, with the clear exception of phenylalanine and tyrosine, the immediate precursor of melanin biosynthesis. We conclude that the initial metabolic responses and the initiation of blackspot formation are distinct, and that melanin biosynthesis is not driven by early precursor accumulation through activation of the aromatic amino acid biosynthesis pathway. [Copyright &y& Elsevier]

Abstract: To investigate the metabolic regulation against inoculum density and stress response to high cell density, comparative metabolomic analysis was employed on Saccharomyces cerevisiae under fermentations with five different inoculum sizes by gas chromatography time-of-flight mass spectrometry. Samples from these fermentations were clearly distinguished by principal components analysis, indicating that inoculum size had a profound effect on the metabolism of S. cerevisiae. Potential biomarkers responsible for the discrimination were identified as glycerol, phosphoric acid, succinate, glycine, isoleucine, proline, palmitoleic acid, myo-inositol and ethanolamine. It indicated that enhanced stress protectants in glycerol biosynthesis and amino acid metabolism, depressed citric acid cycle intermediates, as well as decreased metabolites relating to membrane structure and function were involved as the inoculum size of yeast increased. Furthermore, significantly higher levels of glycerol and proline in yeast cells of higher inoculum size fermentation (40gl−1) revealed that they played important roles in protecting yeast from stresses in high cell density fermentation. These findings provided new insights into characterizing the metabolic regulation and stress response depending on inoculum density during ethanol fermentation. [Copyright &y& Elsevier]

Abstract: A new, simple, gas chromatographic method was developed for the direct analysis of 5-hydroxymethylfurfural (5-HMF), 2-furfural (2-F) and 5-methylfurfural (5-MF) in liquid and water soluble foods, using direct immersion SPME coupled to GC-FID and/or GC–TOF-MS. The fiber (DVB/CAR/PDMS) conditions were optimized: pH effect, temperature, adsorption and desorption times. The method is simple and accurate (RSD<8%), showed good recoveries (77–107%) and good limits of detection (GC-FID: 1.37μgL−1 for 2-F, 8.96μgL−1 for 5-MF, 6.52μgL−1 for 5-HMF; GC–TOF-MS: 0.3, 1.2 and 0.9ngmL−1 for 2-F, 5-MF and 5-HMF, respectively). It was applied to different commercial food matrices: honey, white, demerara, brown and yellow table sugars, and white and red balsamic vinegars. This one-step, sensitive and direct method for the analysis of furfurals will contribute to characterise and quantify their presence in the human diet. [Copyright &y& Elsevier]

Abstract: Pine forests constitute some of the most important renewable resources supplying timber, paper and chemical industries, among other functions. Characterization of the volatiles emitted by different Pinus species has proven to be an important tool to decode the process of host tree selection by herbivore insects, some of which cause serious economic damage to pines. Variations in the relative composition of the bouquet of semiochemicals are responsible for the outcome of different biological processes, such as mate finding, egg-laying site recognition and host selection. The volatiles present in phloem samples of four pine species, P. halepensis, P. sylvestris, P. pinaster and P. pinea, were identified and characterized with the aim of finding possible host-plant attractants for native pests, such as the bark beetle Tomicus piniperda. The volatile compounds emitted by phloem samples of pines were extracted by headspace solid-phase micro extraction, using a 2cm 50/30mm divinylbenzene/carboxen/polydimethylsiloxane table flex solid-phase microextraction fiber and its contents analyzed by high-resolution gas chromatography, using flame ionization and a non polar and chiral column phases. The components of the volatile fraction emitted by the phloem samples were identified by mass spectrometry using time-of-flight and quadrupole mass analyzers. The estimated relative composition was used to perform a discriminant analysis among pine species, by means of cluster and principal component analysis. It can be concluded that it is possible to discriminate pine species based on the monoterpenes emissions of phloem samples. [Copyright &y& Elsevier]

Bladder cancer (BCa) and prostate cancer (PCa) are some of the most common cancers in the world. In both BCa and PCa, the diagnosis is often confirmed with an invasive technique that carries a risk to the patient. Consequently, a non-invasive diagnostic approach would be medically desirable and beneficial to the patient. The use of volatile organic compounds (VOCs) for disease diagnosis, including cancer, is a promising research area that could support the diagnosis process. In this study, we investigated the urinary VOC profiles in BCa, PCa patients and non-cancerous controls by using gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) to analyse patient samples. GC-IMS separated BCa from PCa (area under the curve: AUC: 0.97 (0.93–1.00)), BCa vs. non-cancerous (AUC: 0.95 (0.90–0.99)) and PCa vs. non-cancerous (AUC: 0.89 (0.83–0.94)) whereas GC-TOF-MS differentiated BCa from PCa (AUC: 0.84 (0.73–0.93)), BCa vs. non-cancerous (AUC: 0.81 (0.70–0.90)) and PCa vs. non-cancerous (AUC: 0.94 (0.90–0.97)). According to our study, a total of 34 biomarkers were found using GC-TOF-MS data, of which 13 VOCs were associated with BCa, seven were associated with PCa, and 14 VOCs were found in the comparison of BCa and PCa. [ABSTRACT FROM AUTHOR]

Brunfelsia acuminata is a popular ornamental plant with different colors resulted from the rapid change of color after blooming. The petals at day one (purple), day three (white and purple) and day five (white) were used to analyze the reason of flower color change by a comparative proteomics approach, gas chromatography coupled to a time-of-flight mass analyzer (GC-TOF-MS) and quantitative real-time PCR (qRT-PCR). The results showed that the 52 identified proteins were classified into eight functional groups, 6% of which were related to the anthocyanin metabolic pathway. The expression levels of all anthocyanin proteins from the first day to fifth day were remarkably down-regulated, which was consistent with the changing patterns of the key genes (CHS, CHI and F3′5′H) in petals. Simultaneously, the main floral volatile components including Linalool and 2-Hexenal (E) were identified, and the contents of 2-Hexenal at day five increased dramatically. Moreover, the content of flavonoids and total phenolic increased at day five. The majority of the proteins associated with stress defense and senescence proteins were up-regulated and the activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in the petals at day five were significantly higher than others. It was concluded that the competition in the precursors of metabolic pathways occurs and causes the flow of metabolite to the pathways of floral scent and lignin derived from the shikimate pathway or degrade into others. Therefore, the anthocyanin content significantly decreased, and the petal color changed from deep purple to white. [ABSTRACT FROM AUTHOR]