Bioactivity-Guided Isolation of Antimicrobial and Antioxidant Metabolites from the Mushroom Tapinella atrotomentosa

Bioassay-guided fractionation of the chloroform extract of led to the isolation of four secondary metabolites ⁻ . Two of the compounds are lactones—osmundalactone ( ) and 5-hydroxy-hex-2-en-4-olide ( )—while and were identified as terphenyl quinones, spiromentins C and B, respectively. The structures of the compounds were established on the basis of NMR and MS spectroscopic analysis. The isolated fungal metabolites were evaluated for their antibacterial activities against several Gram-positive and negative bacteria. In addition, their synergistic effect with cefuroxime against methicillin-resistant (MRSA) was also evaluated. Compounds ⁻ proved to possess significant antibacterial activity against multiresistant and extended-spectrum β-lactamase (ESBL)-producing . The investigation of the antioxidant effect of the isolated compounds in DPPH and ORAC assays revealed that spiromentins C ( ) and B ( ) have remarkable antioxidant activity.