New Bioactive Rosigenin Analogues and Aromatic Polyketide Metabolites from the Freshwater Aquatic Fungus Massarina tunicata

Abstract
Four new rosigenin analogues (massarigenins A−D; 1−4) and two new aromatic polyketide-derived secondary metabolites (massarinins A and B; 6, 7) and have been isolated from the freshwater aquatic fungus Massarina tunicata. The structures of these compounds were determined primarily by analysis of NMR data, and that of compound 1 was verified by X-ray crystallography. The known compound 4-(2-hydroxybutynoxy)benzoic acid (11) was also obtained, and its absolute stereochemistry was assigned. Several of these metabolites showed antibiotic activity against Gram-positive bacteria.