Antibacterial Cyclic Tripeptides from Antarctica-Sponge-Derived Fungus Aspergillus insulicola HDN151418

Abstract

Three new aspochracin-type cyclic tripeptides, sclerotiotides M-O (<b>1</b>-<b>3</b>), together with three known analogues, sclerotiotide L (<b>4</b>), sclerotiotide F (<b>5</b>), and sclerotiotide B (<b>6</b>), were obtained from the ethyl acetate extract of the fungus <i>Aspergillus insulicola</i> HDN151418, which was isolated from an unidentified Antarctica sponge. Spectroscopic and chemical approaches were used to elucidate their structures. The absolute configuration of the side chain in compound <b>4</b> was elucidated for the first time. Compounds <b>1</b> and <b>2</b> showed broad antimicrobial activity against a panel of pathogenic strains, including <i>Bacillus cereus</i>, <i>Proteus species</i>, <i>Mycobacterium phlei</i>, <i>Bacillus subtilis</i>, <i>Vibrio parahemolyticus</i>, <i>Edwardsiella tarda</i>, MRCNS, and MRSA, with MIC values ranging from 1.56 to 25.0 µM.