New prenylxanthones, polyketide hemiterpenoid pigments from the endophytic fungus Emericella sp. XL029 and their anti-agricultural pathogenic fungal and antibacterial activities

Abstract

Four new prenylxanthones (1–4) together with five known compounds (5–9) were isolated from the solid-substrate fermentation culture of Emericella sp. XL029 associated with the leaves of Panax notoginseng. Their structures and relative configurations were elucidated by extensive spectroscopic analysis and comparison of NMR data to those of known compounds. The anti-agricultural pathogenic fungal and antibacterial activities of all isolated compounds were evaluated against eight agricultural pathogenic fungi and nine human pathogenic bacteria. The anti-agricultural pathogenic fungal assay indicated that compounds 1, 2, 4, 8 and 9 displayed significant activity against Drechslera maydis with MIC value of 25 μg mL⁻¹. Moreover, compound 1 also exhibited significant activity against other three fungi including Rhizoctonia cerealis, Fusarium oxysporum and Physalospora piricola, and compounds 4 and 9 against Rhizoctonia cerealis with MIC value of 25 μg mL⁻¹. Compound 5 only demonstrated significant activity against Physalospora piricola with MIC value of 25 μg mL⁻¹. Further antibacterial activity tests revealed that compounds 1–9 showed significant antibacterial activity against all tested Gram-positive (except for drug resistant Staphylococcus aureus) and Gram-negative bacteria with MIC values ranging from 12.5 to 50 μg mL⁻¹. While only compounds 1, 4 and 9 displayed moderate activity against drug resistant Staphylococcus aureus with MIC value of 50 μg mL⁻¹.