L'objectif de cette thèse est d'évaluer les modifications du métabolisme secondaire des plantes contaminées aux éléments trace métalliques (ETM) et leurs conséquences sur les communautés bactériennes rhizosphériques associées incluant des bactéries présentant des phénotypes de MultiDrug Résistance (MDR). This manuscript provides an overview of the metabolomics toolbox available for the discovery of novel bioactive compounds and the integration of these tools in the bioprospection and drug discovery workflows. Technical developments in instrumentation and data processing have fostered the development of the field of metabolomics which provides a wealth of tools with the huge potential for application in the process of drug/bioactive discovery from plant tissues. The resolution of these challenges relied extensively on the use of hyphenated mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based analytical technologies for the structural elucidation and annotation of novel compounds. The contribution of natural products (such as plant-derived) to the modern pharmacopeia is indeed significant however, the process of identifying novel bioactive compounds from biological sources has been a central challenge in the discovery of natural products. These properties have been exploited by traditional and modern medicine providing important sources of healthcare to this day. Plants and crops contain a staggering diversity of compounds, many of which have pharmacological activity towards a variety of diseases. Hence, we argue that the VOC profile of Koji is largely determined by the rational choice of inocula, which modifies the primary metabolomes in Koji substrates, potentially shaping its volatolome as well as the aroma characteristics. Alternatively, malty flavor compounds (2-methylpropanal, 2-methylbutanal, 3-methylbutanal) and sweet flavor compounds (monosaccharides and maltol) were relatively abundant in Aspergillus-fermented Koji (Aspergillus Koji, AK). Furthermore, the umami taste engendered by 2-methoxyphenol, (E,E)-2,4-decadienal, and glutamic acid was primarily detected in Bacillus Koji. A cheesy and rancid flavor was characteristic of Bacillus Koji, which is attributable to high content of typical 'off-flavor' compounds. In particular, alcohols, ketones, and furans were mainly detected in Bacillus-fermented Koji (Bacillus Koji, BK), potentially due to the increased levels of lipid oxidation. The VOCs and primary metabolites were analyzed using headspace solid phase microextraction (HS-SPME) followed by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). Herein, we performed comparative metabolomic analyses of volatile organic compounds (VOCs) and primary metabolites for Koji samples fermented individually with Bacillus amyloliquefaciens and Aspergillus oryzae. Production of good Koji primarily depends upon the selection of substrate materials and fermentative microflora, which together influence the characteristic flavor and aroma. The current study suggests that the LC-MS-based untargeted metabolomics strategy can be used to illuminate subtle metabolic disparities as well as compounds associated with bioactivities. aspera, while isorhamnetin O-glucuronide and procyanidin dimer were the primary antioxidants in Z. As a result, quercetin O-sophoroside was determined as the main antioxidant in A. Further, we performed preparative high-performance liquid chromatography (prep-HPLC) analysis coupled with the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) assay to validate their functional correlations. These metabolites were clearly distinguished in pathway map and displayed strong positive correlations with antioxidant activity. aspera, whereas quercetin, isorhamnetin O-glucuronides, and procyanidin dimer were relatively higher in Z. Examining the metabolite compositions of the 40% SPE extracts, we observed relatively higher abundances of quercetin, kaempferol, and isorhamnetin O-glucosides for A.

Further, we chose 40% solid-phase extraction (SPE) extracts of the two species displaying the highest antioxidant activities coupled with distinct PCA patterns.

Firstly, we selected Aphananthe aspera and Zelkova serrata (Family: Ulmaceae) from 16 Korean plant species based on their distinct principal component analysis (PCA) patterns in LC-MS datasets and antioxidant activity assays. Liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomics implies that annotated metabolites can serve as potential markers of the associated bioactivities of plant extracts.

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