A new sesquiterpenoid and three other unusual compounds from Xylaria hypoxylon

A new sesquiterpenoid and three other unusual compounds (1-4) along with four known compounds (5-8) were isolated and identified from the fungus Xylaria hypoxylon. Structures of compounds 1-4 with absolute configurations were elucidated by extensive NMR spectral analyses, X-ray crystallography, experimental ECD spectra comparison, and acid hydrolysis combined with GC analysis. Among them, the sesquiterpenoid (1) possesses a presilphiperfolane structure which is characterized by a 5/5/6 tricyclic system. An unusual polyketide (2), a polyacetylene forming a glycoside with a L rhamnose (3), and a highly degraded sterol glucoside (4) were obtained together. These previously unreported compounds have enriched the secondary metabolite family from Xylaria hypoxylon with their diversity of chemical structures. Compounds 1-4 were evaluated for their anti-inflammatory activities, cytotoxicity, enzymes inhibitory activities, and antibacterial activities. In the antibacterial activity evaluation against test strains including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, compound 2 showed mild inhibitory effects against E. coli and P. aeruginosa, with an inhibition zone diameter of 16 mm respectively.