Silphiperfolene-Type Terpenoids and Other Metabolites from Cultures of the Tropical Ascomycete Hypoxylon rickii(Xylariaceae)

A culture isolated from ascospores of Hypoxylon rickii,a xylariaceous ascomycete collected in Martinique,had yielded botryane,noreremophilane and abietane-type terpenoids in a preceding study,but additional metabolites were detected by extensive HPLC–MS analysis in other fractions.Herein we report the further isolation of four new sesquiterpenoids with a silphiperfol-6-ene skeleton from extracts of H.rickii.The planar structures were elucidated by NMR and HRMS data as 13-hydroxysilphiperfol-6-ene(1),9-hydroxysilphiperfol-6-en-13-oic acid(2),2-hydroxysilphiperfol-6-en-13-oic acid(3)and 15-hydroxysilphiperfol-6-en-13-oic acid(4).For compounds 2–4 we propose the trivial names rickinic acids A–C.Their stereochemistry was assigned by ROESY correlations as well as by the specific optical rotation.Additionally,the known compounds,botryenanol,dehydrobotrydienol,cyclo(Phe-Pro),cyclo(Pro-Leu),(?)-ramulosin and aeleostearic acid were isolated.The antimicrobial and cytotoxic activities of the new compounds are also reported.