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Obtention de composés azotés bioactifs d'origine naturelle : étude de biotransformation par des bactéries associées aux lichens

Abstract : New advances in anti-cancer therapeutic are today more than necessary. It is also well establish that amongst bioactive natural compounds, nitrogen compounds are widely represented and that, in all therapeutic classes. Thus, these works are focused on obtaining bioactive nitrogen compounds from natural sources targeting cytotoxic products. This work is divided in three parts. First of all, we chose to study bacterial strains associated with lichen. Indeed, lichens are a complex symbiotic network of great interest for the discovery of new bacterial strains. Especially for strains with a great biotechnological potential particularly in the production of compounds of interest. At first, culture conditions of an Actinobacteria, Nocardia sp, isolated from a lichen, Collema auriforme, were optimised in order to produce cytotoxic compounds. Secondly, the study of the secondary metabolites patterns of this strain allows the isolation of 13 nitrogen compounds, including 2 brominated diketopiperazines which are newly described, along with purine and pyrimidine derivatives. Finally, a targeting work of bioactive compounds was realised by establishing molecular networking and multivariate analysis of mass spectrometry data, highlighting molecules potentially responsible for activity. The second part of this work bring some answers about the nature of the relationship between bacteria and lichen, by observing effect of some lichen compounds on bacterial growth and metabolism as well as studying the biotransformation potential of three lichen-associated bacteria (a Firmicutes, an beta-proteobacteria and an Actinobacteria). All selected strains showed ability for the biotransformation of tested lichen compounds (usnic acid and methyl-beta-orcinolcarboxylate). Finally, the third part of this work describes a new method for obtaining bioactive nitrogen compounds by a synthetic way. Thus, a novel synthesis method of bgugaine, coniine and tylophorine was studied and led to N-Boc-2-heptylpyrrolidine, showing the possibility to synthesize pyrrolidine alkaloids and to consider the synthesis of selected targets.
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Alba Noël. Obtention de composés azotés bioactifs d'origine naturelle : étude de biotransformation par des bactéries associées aux lichens. Sciences pharmaceutiques. Université Rennes 1, 2017. Français. ⟨NNT : 2017REN1S127⟩. ⟨tel-01809512⟩

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