Chemometric analysis of NMR and UPLC-qTOF/MS data on extracts from carrots cultivated with organic and conventional agricultural systems

POLITI, M.; DASKO, L.; ALONSO-SALCES, R. M.; SEGEBARTH, N.; MATTARUCCHI, E.; RENIERO, F.; GIORDANO, G.; MAQUET, A.; GUILLOU, C.

Siófok (Hungría)

Conferencia; Conferentia Chemometrica 2009; 2009

Chemometric Section of the Hungarian Chemical Society and Hungarian Academy of Sciences

Following our previous investigations aiming the identification of discriminant metabolites between organically and conventionally grown crops [1], carrots (Daucus carota L.) were studied in this context. Carrots were differentiated on the basis of the agricultural system adopted (organic or conventional) and on the basis of the growing environment (1 or 2). Carrots were grown and collected under controlled conditions during two years (2007 and 2008). Carrot samples of both harvest were dried, lyophilized, and powdered, and some samples of 2008 were directly frozen in the field and then lyophilized and powdered (fresh samples). Then the freeze-dried carrot samples were stored at -80 oC until analysis. Samples were extracted with deuterated methanol in a ultrasonic water bath and then centrifuged. The methanol extracts were directly analyzed by proton Nuclear Magnetic Resonance (NMR) spectroscopy and Ultra-performance Liquid Chromatography coupled with a Quadupole Time of Flight Mass Spectrometry (UPLC-qTOF/MS). The 1H-NMR and MS data acquired were pre-processed in order to extract the data using different softwares, including TopSpin and Amix for NMR data, and MassLynx and MarkerLynx for MS data, as well as others open source informatics tools especially for evaluating the data extraction in LC-MS. Then, the analytical data were analysed by chemometric techniques such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). The exhaustive analysis performed on carrots samples stimulated a wide-ranging discussion about the potential of the proposed approach as a quality control tool for crops cultivated with biological and conventional agricultural systems. The choice of the metabolite extraction strategy is the first step causing an inevitable targeting in the further metabolite analysis. The successive selection of the spectrometer detectors has also a strong targeting effect about the classes of natural products that will be identified. Finally, the data extraction step can deeply affect as well the nature of the final results; care is therefore a must along the entire procedure. However, metabolomics approach appears an optimal strategy for differentiation of biological samples in terms of single chemical entities therein contained.