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Accueil du site → Doctorat → Allemagne → Novel natural products from endophytic fungi of Egyptian medicinal plants : chemical and biological characterization

Heinrich-Heine Universität Düsseldorf (2007)

Novel natural products from endophytic fungi of Egyptian medicinal plants : chemical and biological characterization

Hassan, Amal E. H. A.

Titre : Novel natural products from endophytic fungi of Egyptian medicinal plants : chemical and biological characterization

Auteur : Hassan, Amal E. H. A.

Université de soutenance : Heinrich-Heine Universität Düsseldorf

Grade : Doktorgrade 2007

Description
Being poorly investigated, endophytes are obviously a rich and reliable source of bioactive and chemically novel compounds with huge medicinal and agricultural potential. The aim of this study was the purification of endophytic fungal strains from Egyptian medicinal plants, the isolation, characterization and structure elucidation of biologically active secondary metabolites from the extracts of these endophytic fungal strains, and the preliminary evaluation of their pharmaceutical potential. Four endophytic fungi, Alternaria sp., Ampelomyces sp., Stemphylium botryosum and Chaetomium sp., were subjected as biological sources of the study. In order to isolate the secondary metabolites, the fungi were grown in static liquid Wickerham medium as well as solid rice medium at room temperature. The cultures were allowed to grow for 3-4 weeks, followed by harvesting and subsequent extraction with organic solvents. The obtained raw extracts were then fractionated and separated using various chromatographic techniques and their fractions were analysed by HPLC-DAD for their purity and ESI-LC/MS for their molecular weight and fragmentation patterns. The pure compounds were submitted to state-of-the-art one- and two-dimensional NMR techniques for structure elucidation. In addition, selected compounds were derivatized in order to determine their absolute stereochemistry. Furthermore, fractions and pure compounds were subjected to selected bioassays to determine their pharmaceutical potential. Thus, antimicrobial activity was studied using the agar diffusion assay as well as the biofilm test, whereas cytotoxicity was studied in vitro using mouse lymphoma (L5178Y) cell line. Moreover, fractions and pure compounds were also tested for their protein kinase inhibitory activity. The latter three assays were conducted in cooperation with Prof. U. Hentschel, Würzburg, Prof. W. E. G. Müller, Mainz, and ProQinase, Freiburg, respectively. Finally, extracts were prepared from the corresponding host plants and fractionated, and the obtained fractions were analyzed by HPLC and LC/MS for the presence of the identified fungal metabolites. The samples were then reanalyzed parallel to the pure substances and retention times as well as MS/MS spectra were compared.

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Page publiée le 25 mars 2008, mise à jour le 11 janvier 2019