Chemical Investigations Of Two Strains Of Endolichenic Fungi

Fungi are a wide range of eukaryotes and they are widely distributed in nature. They have been to be important resources for finding natural products. Especially the scientists are interesting in the fungi living in the special growth environment (such as high-acid, high-alkali, toxic garbage), and endolichenic fungi are the ones. Endolichenic fungi are parasitic inside the healthy issues of lichen, and they don’t cause any symptom to the host. Recently, the scientists had obtained lots of compounds, most of which had novel structures and a variety of activities. Therefore, the investigations on endolichenic fungi have the great potential in discovering the lead compounds.In this article, we had a research on the metabolites of the endophytic fungi isolated from lichens. On the basis of screening pre-activity on endolichenic fungi, we selected two fungi and conducted large-scale fermentations in rice medium, and extracted the secondary metabolites with ethyl acetate. By column chromatography (CC) on silica gel, reverse phase silica gel, Sephadex LH-20 and HPLC, etc.,51 compounds, including a series of heptaketides, were isolated from the crude extract. The structures of these compounds were determined by analysis of MS, NMR, CD data. Moreover, in order to determine their absolute configurations, single-crystal X-ray diffraction analysis with Cu Ka radiation were employed to some compounds. At the same time, the activities of the isolated compounds were evaluated, and the compound 4 was active to resistant strains of C. Albicans. The reversing activity of 4 to clinical-derived FLC-resistant strains, and the synergetic effect when applied by combination with FLC were further tested. The underline mechanism of this reversing effect was revealed to be through down-regulating the expression of efflux pump related genes of CDR1 and CDR1.