Taxonomy and discovery of bioactive metabolites from selected helotiales

Name: Kunthida Phutthacharoen

Address: 333 Moo1, Thasud, Muang, Chiang Rai 57100

Organization : Mae Fah Luang University

Email : library@mfu.ac.th

keyword: Secondary Metabolites

MeSH: Fungi

Classification :.DDC: e-thesis

; Taxonomy

MeSH: Discomycetes -- 223455

MeSH: Helotiales -- 310947

MeSH: Metabolites

MeSH: Morphology

MeSH: Biology -- Classification -- 59923

LCSH: Fungi

LCSH: Discomycetes -- 223455

LCSH: Helotiales -- 310947

LCSH: Metabolites

LCSH: Morphology

Abstract: This thesis presents an extensive taxonomic and chemical study of various fungal species within the order Helotiales, particularly focusing on samples collected from Italy and Thailand. Through the integration of morphological, molecular, and chemical analyses, this work not only contributes to resolving the taxonomic relationships within certain families of Helotiales but also leads to the discovery of several novel compounds with notable biological activities. The study addresses a critical gap in fungal biodiversity research and explores the potential of these species as sources of bioactive secondary metabolites. The taxonomic investigation primarily focused on families such as Heterosphaeriaceae, Helotiaceae and Ploettnelulaceae. Molecular data derived from multi-gene phylogenetic analyses (using LSU and ITS) were combined with detailed morphological characterizations to reassess and describe new species. In Heterosphaeriaceae, we identified Heterosphaeria linariae, which showed distinct morphological features, including larger ellipsoidal ascospores compared to previously reported strains, and a broader host range than previously known, suggesting potential ecological diversity. Similarly, the genus Dicephalospora was expanded, with the introduction of three novel species: Dicephalospora chiangraiensis, D. inthanonensis, and D. irregularis. These new species were identified based on unique morphological characteristics such as the structure of their apothecia and distinctive ascospores dimensions. Molecular phylogenetics provided strong statistical support, confirming these species as distinct from known members of the genus. In the Ploettnerulaceae family, five new species were identified within the genera Pyrenopeziza and Rhexocercosporidium. These species exhibit unique morphological features, such as diverse spore shapes and sizes, as well as the ability to colonize a range of plant hosts, including previously unreported species. The newly introduced taxa were confirmed through phylogenetic studies, enhancing our understanding of species diversity within the family. In addition, taxonomic notes were provided for Cadophora and Rhynchosporium, expanding the known range and ecological roles of these genera. These taxonomic advancements not only improve the clarity of Helotiales classification but also shed light on the ecological roles of these fungi. Several species described in this thesis are endophytes, saprobes or pathogens, reflecting their functional diversity in various ecosystems. The revision of these groups highlights the significant under-explored fungal biodiversity in both temperate and tropical regions, emphasizing the need to sustain mycological research. The chemical aspect of this study resulted in the isolation and characterization of eight new compounds from the genus Lachnum, particularly from the strain L. carneolum DSM 116717. Among the newly identified compounds were two unusual polyketides, diaporphasines E and F, which exhibited potent biological activity. These polyketides were found to be effective inhibitors of Staphylococcus aureus biofilms, with minimum inhibitory concentrations (MIC) of 31.25 µg/mL indicating strong antibiofilm properties. Additionally, six previously undescribed ambuic acid derivatives named lachnuoic acids (A−F) were isolated and characterized from the polar fraction of the same L. carneolum DSM 116717 extract. These compounds showed a range of antimicrobial activities against both gram-positive and gram-negative bacteria, with significant inhibition observed against Escherichia coli and Bacillus subtilis. The chemical structures of these acids characterized using NMR spectroscopy (¹H, ¹³C, HSQC, HMBC, and COSY) and mass spectrometry revealed novel structural motifs that could serve as promising templates for the development of new antibiotics. This thesis provides significant contributions to both the taxonomic and chemical understanding of Helotiales. The discovery of new species and novel bioactive compounds enhances our knowledge of fungal biodiversity and underscores the pharmaceutical potential of these organisms. The novel polyketides and depsipeptides show great promise in combating antimicrobial resistance and as potential anticancer agents. Future research will focus on the further exploration of fungal secondary metabolites and the ecological roles of these newly described species in their natural environments.

LCSH: Biology -- Classification -- 59923

Mae Fah Luang University. Learning Resources and Educational Media Centre

Address: CHIANG RAI

Email: library@mfu.ac.th

Name: Hyde Kevin David

Role: Advisor

Created: 2024

Modified: 2024-12-17

Issued: 2024-12-17

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: e-thesis

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Biological Sciences

Grantor: Mae Fah Luang University

©copyrights Mae Fah Luang University

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