Chemical investigation of fungal endophytes from Echinacea purpurea

Botanical extracts of Echinacea purpurea have been traditionally used for treatment of respiratory infections. Recently, efforts to chemically examine the fungal endophytes inhabiting these plants were undertaken to investigate the role of endophyte colonization on the bioactivity of such medicinal herbs. In this study, twenty-four fungal isolates belonging to fourteen different OTUs were obtained in axenic culture from surface sterilized seeds and root segments of Echinacea. Most of the fungal endophytes belonged to the Ascomycota, whereas one isolate showed phylogenetic affinities to mushroom forming Basidiomycota. Solid-substrate fermentation extracts of the fungal cultures were subjected to various separation techniques after dereplication. Approximately twenty-five secondary metabolites belonging to different structural classes were encountered. The known compounds were identified by comparison of their NMR and mass spectrometry data. Sixteen compounds were tested for their ability to regulate production of the inflammatory cytokine TNF-α. Four compounds were found to inhibit production of TNF-α from RAW 264.7 macrophages stimulated with LPS in the absence of any detectable cytotoxicity, while none were found to induce TNF production.