New sesquiterpenoids from an endophytic fungus Paraconiothyrium brasiliense ECN258

Paraconiothyrium brasiliense was a plant endophyte distributing worldwide and has been ever isolated from a wide range of host plants such as Coffea arabica in Brazil, Ginko biloba in Canada, and Prunus spp. in South Africa. Paraconiothyrium brasiliense ECN258 that we used in this study was isolated from a stem of Cinnamomum camphora in Japan. To discover new natural resources for beneficial compounds, we have obtainined endophyte strains more than 400 from various plants in Japan and continue to investigate the metabolites produced by them [1], [2]. In this study, eleven new sesquiterpenoids (1–11) were isolated from cultures of Paraconiothyrium brasiliense ECN258 as well as five known sesquiterpenoids (12–16). The structures of new compounds were elucidated by analyzing IR, MS, NMR, and ECD spectroscopic data. Compounds 1–7 are eremophilane sesquiterpenoids, whereas compounds 8–10 have new or rare carbon frameworks that are probably biosynthesized by rearrangement of eremophilanes. Furthermore, paraconiothyrins K (11) is a C18 compound containing an eremophilane within the backbone. Compounds 1–5 and 8–16 were evaluated for their effects on some nuclear receptors including RXRα, PPARγ, PPARδ, RARα, and LXRα by means of luciferase reporter gene assay for each receptor. Among test compounds, compound 9 exhibited an inhibitory effect on LXRα at the concentration of 50 μM.