Desenvolvimento de procedimentos analíticos para avaliação ionômica e metabolômica em manjericão (Ocimum basilicum L. grecco a palla) exposto ao Cádmio

Abstract

In this study, basil (Ocimum basilicum L. grecco a palla) was cultivated in 5% v-1 Hoagland nutrient solution and exposed to different concentrations of CdII. An ultrasound-assisted microextraction (MUS) procedure was optimized (2% v v-1 HNO3, 100 μL H2O2, 50% amplitude and 5 min extraction time), validated and applied to leaf, stem and root for multielemental determination by inductively coupled plasma mass spectrometry (ICP-MS). The detection and quantification limits of the procedure ranged from 0.022 to 5.33 μg g-1 (Be and K) and from 0.066 to 20.1 μg g-1 (Be and Ca), respectively. From the results obtained, an ionomic evaluation was performed indicating that Cd preferentially accumulated in the roots and translocated to the aerial part causing serious damage to plants, including effects on the uptake and translocation of essential elements. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) discriminated leaves, stems, and roots by ionomic profile for the different Cd((II) supplementations. In metabolomics studies, Paper Spray Mass Spectrometry (PS-MS) was used to identify glutathione (GSH), phytochelatins and their derivatives, besides Cd complexes in roots that were cultivated for 7 and 14 days. In seedlings exposed to Cd, iso-PC2(Cys), des-Gly-PC3, iso-PC3(Asn or Ser or Gln or Glu) and different Cd complexes formed by the plant as a defense mechanism to intoxication were identified. By Desorption Electrospray Ionization Mass Spectrometry Imaging (DESI-MSI), leaf imprint (0; 1.0; 3.6; 5.0; 25.0 and 50.0 μM of CdII) and root imprint (0 and 25.0 μM of CdII) were analysed and a direct analysis of leaves submitted to different concentrations of CdII (0; 1.0; 3.6; 10.0; 25.0; 50.0 and 100.0 μM) was also performed for untarget metabolomic evaluation. The images showed that Cd interfered in the basil metabolome by inhibition/stimulation in metabolite synthesis, including biological signaling of 24, 20 and 8 potential biomarkers from leaves, root and both organs, respectively. The results proved to be effective for target and untarget ionomic and metabolomic analysis in leaves and roots and they are promising for further studies involving defense mechanisms of plants exposed to different toxic metals.