Abstract
Microorganisms associated with plants are highly diverse and can produce a large number of secondary metabolites, with antimicrobial, anti-parasitic and cytotoxic activities. We are particularly interested in exploring endophytes from medicinal plants found in the Pantanal, a unique and widely unexplored wetland in Brazil. In a bio-prospecting study, strains LGMF1213 and LGMF1215 were isolated as endophytes from Vochysia divergens, and by morphological and molecular phylogenetic analyses were characterized as Phaeophleospora vochysiae sp. nov. The chemical assessment of this species reveals three major compounds with high biological activity, cercoscosporin (1), isocercosporin (2) and the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone (3). Besides the isolation of P. vochysiae as endophyte, the production of cercosporin compounds suggest that under specific conditions this species causes leaf spots, and may turn into a pathogen, since leaf spots are commonly caused by species of Cercospora that produce related compounds. In addition, the new compound 3-(sec-butyl)-6-ethyl-4,5-dihydroxy-2-methoxy-6-methylcyclohex-2-enone showed considerable antimicrobial activity and low cytotoxicity, which needs further exploration.
Highlights
Cataloguing microorganisms from unexplored biomes is an effective strategy to discover new species, often producers of new secondary metabolites
The Bayesian phylogenetic analysis of internal transcribed spacer region (ITS) region showed strains LGMF1213 and LGMF1215 are in the same clade as P. eugeniicola, P. gregaria, P. scytalidii and P. stramenti, with a strong probability support (1.00), sharing 99% of ITS1–5.8S–ITS2 rDNA sequence similarity with species P. scytalidii (GenBank LC121138, Identities = 463/467)
For the TEF gene, sequences of P. eugeniicola, P. gregaria, P. scytalidii and P. stramenti were not available, so our isolates clustered with the type species of the genus Phaeophleospora (P. eugeniae) (Fig. S39)
Summary
Cataloguing microorganisms from unexplored biomes is an effective strategy to discover new species, often producers of new secondary metabolites. In our search for novel bioactive compounds, we isolated two endophytic strains from V. divergens, with characteristic of the genus Phaeophleospora. The genus Phaeophleospora Rangel[10] is an anamorph of the Mycosphaerellaceae and it is based on P. eugeniae, which was isolated in Brazil from leaf spots of Eugenia uniflora. Most species of this genus have been associated with leaf spot diseases in various plants, e.g., Myrtaceae, Polypodiaceae, Elaeocarpaceae, Plantaginaceae, Proteaceae and Apocynaceae[11,12,13,14]. Despite the fact that the genus Phaeophleospora was described as early as 1916, there were no reports of any bioactive secondary metabolites, and its metabolic potential remained unknown. Based on morphological and phylogenetic analyses we describe here Phaeophleospora vochysiae as a new species within the genus Phaeophleospora, studied its secondary metabolites, and linked these to biological activities
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