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- Establishment of the varietal profile of Vitis vinifera L. grape varieties from different geographical regions based on HS-SPME/GC–qMS combined with chemometric toolsPublication . Perestrelo, Rosa; Barros, António S.; Rocha, Sílvia M.; Câmara, José S.The varietal volatile profiles of pulp and skin fractions from the main red and white Vitis vinifera L. grape varieties used in the production of Madeira wine (Portugal) were established by headspace solid phase microextraction (SPME) combined with gas chromatography–quadrupole mass spectrometry (GC–qMS) tandem with chemometric tools. A total of 60 varietal volatile compounds — 27 in pulp and 42 in skin of V. vinifera L. grapes studied, were identified, including 27 monoterpenic, 26 sesquiterpenic and 7 C13 norisoprenoid compounds. Principal Component Analysis (PCA) and Hierarchical Clusters Analysis (HCA) results demonstrated that, independently of grape fractions, a distribution by grape variety (white and red) as well as by Terroir effect, was attained using the varietal volatiles from skin grape fraction. Bual, Malvasia Cândida and Malvasia Branca (white varieties) exhibited different varietal volatile profiles, independently of grape fractions, skin or pulp. This difference could be explained by the highest sesquiterpenic level found in Bual grape variety, and monoterpenic level found in Malvasia Cândida and Malvasia Branca grape varieties. The obtained data suggests that climatic factors, such as altitude, temperature and humidity influenced the varietal profile from the target varieties, as the varietal profile of grapes cultivated at Estreito de Câmara de Lobos (32°39′50.59″N; 16°58′48.28″W) and Jardim da Serra (32°41′42.36″N; 16°59′37.32″W) showed qualitative and quantitative differences (expressed as GC peak area) when compared to varietal profile of grapes cultivated at Estreito da Calheta (32°44′0.09″N; 17°11′14.80″W), independently of the grape fractions (pulp or skin). Moreover, the cultivation of recommended grapes to produce Madeira wines — Malvasia Branca, Terrantez and Bastardo, should be promoted as their varietal volatile profile is quite similar to that found in noble varieties (Malvasia Cândida and Sercial, respectively).
- Allergic asthma exhaled breath metabolome: a challenge for comprehensive two-dimensional gas chromatographyPublication . Caldeira, M.; Perestrelo, Rosa Maria de Sá; Barros, António S.; Bilelo, M. J.; Morête, A.; Câmara, J. S.; Rocha, Sílvia M.Allergic asthma represents an important public health issue, most common in the paediatric population, characterized by airway inflammation that may lead to changes in volatiles secreted via the lungs. Thus, exhaled breath has potential to be a matrix with relevant metabolomic information to characterize this disease. Progress in biochemistry, health sciences and related areas depends on instrumental advances, and a high throughput and sensitive equipment such as comprehensive two-dimensional gas chromatography–time of flight mass spectrometry (GC × GC–ToFMS) was considered. GC × GC–ToFMS application in the analysis of the exhaled breath of 32 children with allergic asthma, from which 10 had also allergic rhinitis, and 27 control children allowed the identification of several hundreds of compounds belonging to different chemical families. Multivariate analysis, using Partial Least Squares-Discriminant Analysis in tandem with Monte Carlo Cross Validation was performed to assess the predictive power and to help the interpretation of recovered compounds possibly linked to oxidative stress, inflammation processes or other cellular processes that may characterize asthma. The results suggest that the model is robust, considering the high classification rate, sensitivity, and specificity. A pattern of six compounds belonging to the alkanes characterized the asthmatic population: nonane, 2,2,4,6,6-pentamethylheptane, decane, 3,6-dimethyldecane, dodecane, and tetradecane. To explore future clinical applications, and considering the future role of molecular-based methodologies, a compound set was established to rapid access of information from exhaled breath, reducing the time of data processing, and thus, becoming more expedite method for the clinical purposes.
- In-depth search focused on furans, lactones, volatile phenols, and acetals as potential age markers of Madeira wines by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry combined with solid phase microextractionPublication . Perestrelo, Rosa Maria de Sá; Barros, António S.; Câmara, José S.; Rocha, Sílvia M.The establishment of potential age markers of Madeira wine is of paramount significance as it may contribute to detect frauds and to ensure the authenticity of wine. Considering the chemical groups of furans, lactones, volatile phenols, and acetals, 103 volatile compounds were tentatively identified; among these, 71 have been reported for the first time in Madeira wines. The chemical groups that could be used as potential age markers were predominantly acetals, namely, diethoxymethane, 1,1-diethoxyethane, 1,1-diethoxy-2-methyl-propane, 1-(1-ethoxyethoxy)-pentane, trans-dioxane and 2-propyl-1,3-dioxolane, and from the other chemical groups, 5-methylfurfural and cis-oak-lactone, independently of the variety and the type of wine. GC × GC-ToFMS system offers a more useful approach to identify these compounds compared to previous studies using GC−qMS, due to the orthogonal systems, that reduce coelution, increase peak capacity and mass selectivity, contributing to the establishment of new potential Madeira wine age markers. Remarkable results were also obtained in terms of compound identification based on the organized structure of the peaks of structurally related compounds in the GC × GC peak apex plots. This information represents a valuable approach for future studies, as the ordered-structure principle can considerably help the establishment of the composition of samples. This new approach provides data that can be extended to determine age markers of other types of wines.
- Profiling allergic asthma volatile metabolic patterns using a headspace-solid phase microextraction/gas chromatography based methodologyPublication . Caldeira, M.; Barros, António S.; Bilelo, M. J.; Parada, A.; Câmara, J. S.; Rocha, Sílvia M.Allergicasthmarepresentsanimportantpublichealthissuewithsignificantgrowthovertheyears,especially in the paediatric population. Exhaled breath is a non-invasive, easily performed and rapid method forobtainingsamplesfromthelowerrespiratorytract.Inthepresentmanuscript,themetabolicvolatile profiles of allergic asthma and control children were evaluated by headspace solid-phase microextraction combined with gas chromatography–quadrupole mass spectrometry (HS-SPME/GC–qMS). The lack ofstudiesinbreathofallergicasthmaticchildrenbyHS-SPMEledtothedevelopmentofanexperimental design to optimize SPME parameters. To fulfil this objective, three important HS-SPME experimental parameters that influence the extraction efficiency, namely fibre coating, temperature and time extractions were considered. The selected conditions that promoted higher extraction efficiency corresponding to the higher GC peak areas and number of compounds were: DVB/CAR/PDMS coating fibre, 22◦C and 60min as the extraction temperature and time, respectively. The suitability of two containers, 1L Tedlar® bags and BIOVOC®, for breath collection and intra-individual variability were also investigated. The developed methodology was then applied to the analysis of children exhaled breath with allergicasthma(35),fromwhich13hadalsoallergicrhinitis,andhealthycontrolchildren(15),allowing to identify 44 volatiles distributed over the chemical families of alkanes (linear and ramified) ketones, aromatic hydrocarbons, aldehydes, acids, among others. Multivariate studies were performed by Partial LeastSquares–DiscriminantAnalysis(PLS–DA)usingasetof28selectedmetabolitesanddiscrimination between allergic asthma and control children was attained with a classification rate of 88%. The allergic asthma paediatric population was characterized mainly by the compounds linked to oxidative stress, such as alkanes and aldehydes. Furthermore, more detailed information was achieved combining the volatile metabolic data, suggested by PLS–DA model, and clinical data.
- Optimisation of solid-phase microextraction combined with gas chromatography–mass spectrometry based methodology to establish the global volatile signature in pulp and skin of Vitis vinifera L. grape varietiesPublication . Perestrelo, Rosa Maria de Sá; Barros, António S.; Rocha, Sílvia M.; Câmara, José S.The volatiles (VOCs) and semi-volatile organic compounds (SVOCs) responsible for aroma are mainly present in skin of grape varieties. Thus, the present investigation is directed towards the optimisation of a solvent free methodology based on headspace-solid-phase microextraction (HS-SPME) combined with gas chromatography–quadrupole mass spectrometry (GC–qMS) in order to establish the global volatile composition in pulp and skin of Bual and Bastardo Vitis vinifera L. varieties. A deep study on the extraction-influencing parameters was performed, and the best results, expressed as GC peak area, number of identified compounds and reproducibility, were obtained using 4 g of sample homogenised in 5 mL of ultra-pure Milli-Q water in a 20 mL glass vial with addition of 2 g of sodium chloride (NaCl). A divinylbenzene/carboxen/polydimethylsiloxane fibre was selected for extraction at 60 °C for 45 min under continuous stirring at 800 rpm. More than 100 VOCs and SVOCs, including 27 monoterpenoids, 27 sesquiterpenoids, 21 carbonyl compounds, 17 alcohols (from which 2 aromatics), 10 C13 norisoprenoids and 5 acids were identified. The results showed that, for both grape varieties, the levels and number of volatiles in skin were considerably higher than those observed in pulp. According to the data obtained by principal component analysis (PCA), the establishment of the global volatile signature of grape and the relationship between different part of grapes—pulp and skin, may be an useful tool to winemaker decision to define the vinification procedures that improves the organoleptic characteristics of the corresponding wines and consequently contributed to an economic valorization and consumer acceptance.