Bioactive bianthraquinones and meroterpenoids from a marine-derived Stemphylium sp. fungus

Three new bianthraquinones, alterporriol Z1–Z3 (1–3), along with three known compounds of the same structural class, were isolated from the culture broth of a marine-derived Stemphylium sp. fungus. Based upon the results of spectroscopic analyses and ECD measurements, the structures of new compounds were determined to be the 6-6⁰- (1 and 2) and 1-5⁰- (3) C–C connected pseudo-dimeric anthraquinones, respectively. Three new meroterpenoids, tricycloalterfurenes E–G (7–9), isolated together with the bianthraquinones from the same fungal culture broth, were structurally elucidated by combined spectroscopic methods. The relative and absolute configurations of these meroterpenoids were determined by modified Mosher’s, phenylglycine methyl ester (PGME), and computational methods. The bianthraquinones significantly inhibited nitric oxide (NO) production and suppressed inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-stimulated RAW 264.7 cells.