np5b00436_si_001.pdf (2.69 MB)
Antibacterial Azaphilones from an Endophytic Fungus, Colletotrichum sp. BS4
journal contribution
posted on 2016-02-23, 21:09 authored by Wen-Xuan Wang, Souvik Kusari, Hartmut Laatsch, Christopher Golz, Parijat Kusari, Carsten Strohmann, Oliver Kayser, Michael SpitellerThree new compounds, colletotrichones
A–C (1–3), and one known compound,
chermesinone B (4a), were isolated from an endophytic
fungus, Colletotrichum sp. BS4, harbored in the leaves
of Buxus sinica, a well-known boxwood plant used
in traditional Chinese medicine
(TCM). Their structures were determined by extensive spectroscopic
analyses including 1D and 2D NMR, HRMS, ECD spectra, UV, and IR, as
well as single-crystal X-ray diffraction, and shown to be azaphilones
sharing a 3,6a-dimethyl-9-(2-methylbutanoyl)-9H-furo[2,3-h]isochromene-6,8-dione scaffold. Owing to the remarkable
antibacterial potency of known azaphilones coupled to the usage of
the host plant in TCM, we evaluated the antibacterial efficacy of
the isolated compounds against two commonly dispersed environmental
strains of Escherichia coli and Bacillus
subtilis, as well as against two human pathogenic clinical
strains of Staphylococcus aureus and Pseudomonas
aeruginosa. Compound 1 exhibited marked antibacterial
potencies against the environmental strains that were comparable to
the standard antibiotics. Compound 3 was also active
against E. coli. Finally, compound 2a exhibited the same efficacy as streptomycin against the clinically
relevant bacterium S. aureus. The in vitro cytotoxicity of these compounds on a human acute monocytic leukemia
cell line (THP-1) was also assessed. Our results provide a scientific
rationale for further investigations into endophyte-mediated host
chemical defense against specialist and generalist pathogens.