Salvatore, Maria Michela (2020) Study of secondary metabolites produced by fungi from diverse environmental contexts using combined analytical techniques. [Tesi di dottorato]

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Abstract

In the last decades the scientific community has focused on the study of secondary metabolites produced by fungi. In this respect, fungi from diverse habitat and/or associated to organisms are prime targets of a vigorous investigational activity, based on the employment of the most advanced analytical and structure elucidation techniques. In addition to the classic procedure of isolating and identifying bioactive fungal substances, the metabolomic approaches represent emerging tools for metabolite identification in complex samples. In this thesis, robust and comprehensive analytical strategies, essentially based on NMR and mass spectrometry, were employed for the structural and stereostructural elucidations of new and known compounds produced in vitro by fungi. The importance of study the fungal metabolomic profiles is related to the important biological roles of secondary metabolites as virulence factors, chemical defense agents and chemical signals for the communication with other organisms. In fact, many fungi are responsible of severe damages in plants and causing infections in immunocompromised patients. To this end, in this work fungi from the family of Botryospheraceae (i.e. Lasiodiplodia theobromae, Macrophomina phaseolina, Neofusicoccum vitifusiforme) were studied for their capacity to switch with unfavourable environmental conditions from asymptomatic endophytes to virulent pathogens. Their ability to produce lipophilic secondary metabolites (e.g. lasiodiplodins, melleins, botryodiplodins) and the effect of abiotic factors, such as temperature, on the metabolite profile were investigated to better understand the dynamic between host and pathogen. Furthermore, the increasing awareness of the importance to exploit natural resources for the finding of new bioactive products that may be useful in the search for drugs stimulated us to study fungi as potential biosynthetic factories for a plethora of biological active and structurally diverse natural products. Our analytical strategies allowed the identification of biological important and taxonomically informative types of compounds (e.g. thiosilvatins, diketopiperazines, funicones) from marine-derived strains collected in the Naples bay (Trichoderma citrinoviride, Aspergillus niger, Penicillium brevicompactum) and from Talaromyces pinophilus isolated from the rhizosphere of tobacco plant.

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