Defense mutualisms between social insects and microorganisms have been described in the literature. The present article describes the discovery of a Pseudallescheria boydii strain isolated from Nasutitermes sp. The microbial symbiont produces two antifungal metabolites: tyroscherin and N-methyltyroscherin, a compound not previously described in the literature. Methylation of tyroscherin has confirmed the structure of N-methyltyroscherin. Both compounds are effective antifungal agents with favorable selectivity indices for Candida albicans and Trichophyton rubrum.
Ilicicolinic acids A, C, and D (1-3) and ilicicolinal (4) were isolated from a fungus isolated from a Nasutitermes corniger nest in French Guiana. The structures of ilicicolinic acids C and D and ilicicolinal were elucidated using 1D and 2D NMR spectroscopic data as well as MS data. Ilicicolinic acids show antibacterial activity in vitro.
Chrysoporthe sp. SNB-CN74 was isolated from a Nasutitermes corniger nest, and its ethyl acetate extract was found to exhibit very strong antibacterial activity. Two antibacterial metabolites were isolated, (-)-R-skyrin (2) and (+)-rugulosin A (3). Eventually, the fungus lost its antibiotic potential when subcultured, and the use of yeast extract induced the re-expression of these two antibiotics. Yeast extract possibly activated a cryptic pathway by mimicking the presence of an ecological competitor.
This study presents flavonoids as new inhibitors of the nucleoside hydrolase from Leishmania donovani (LdNH) and the first uncompetitive inhibitor described for LdNH.
Four new sesquiterpene alkaloids (1-4) with a β-dihydroagrofuran skeleton and a new triterpenoid (5) were isolated from an ethyl acetate extract of Maytenus oblongata stems. Their structures were elucidated using 1D and 2D NMR spectroscopy as well as MS and ECD experiments. The M. oblongata stem EtOAc extract and the pure compounds isolated were tested for larvicidal activity against Aedes aegypti under laboratory conditions, and compounds 2 and 3 were found to be active.
Two new tyroscherin derivatives: N-methyl-tyroscherone (2) and tyroscherin N,O-acetonide (3), as well as two known secondary metabolites tyroscherin (1) and pseurotin A (4), were isolated from a solid culture of the termite-borne fungus Pseudallescheria boydii SNB-CN85. The structures were elucidated by spectroscopic analysis and chemical modification. Compound 3 was synthesized from tyroscherin (1) in the free amine form by heating in deuterated acetone, followed by deuterium-proton exchange in MeOH. All compounds were tested for their antimicrobial activities on C. albicans and S. aureus, and 2 and 3 exhibited minimal inhibitory concentrations between 128 and 8 g.mL-1 .
The isolation and complete structural elucidation of four complex ovalicin analogues, named pseudallicins A-D, from the fungus Pseudallescheria boydii strain SNB-CN85 are described. On the basis of structural similarities and information from the literature, a joint biosynthetic pathway for the pseudallicins is proposed.
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