Pigmentosins from <i>Gibellula</i> sp. as antibiofilm agents and a new glycosylated asperfuran from <i>Cordyceps javanica</i>

Abstract

In the course of our exploration of the Thai invertebrate-pathogenic fungi for biologically active metabolites, pigmentosin A (<b>1</b>) and a new bis(naphtho-α-pyrone) derivative, pigmentosin B (<b>2</b>), were isolated from the spider-associated fungus <i>Gibellula</i> sp. Furthermore, a new glycosylated asperfuran <b>3</b>, together with one new (<b>6</b>) and two known (<b>4</b> and <b>5</b>) cyclodepsipeptides, was isolated from <i>Cordyceps javanica</i>. The pigmentosins <b>1</b> and <b>2</b> showed to be active against biofilm formation of <i>Staphylococcus aureus</i> DSM1104. The lack of toxicity toward the studied microorganism and cell lines of pigmentosin B (<b>2</b>), as well as the antimicrobial effect of pigmentosin A (<b>1</b>), made them good candidates for further development for use in combination therapy of infections involving biofilm-forming <i>S. aureus</i>. The structure elucidation and determination of the absolute configuration were accomplished using a combination of spectroscopy, including 1D and 2D NMR, HRMS, Mosher ester analysis, and comparison of calculated/experimental ECD spectra. A chemotaxonomic investigation of the secondary metabolite profiles using analytical HPLC coupled with diode array detection and mass spectrometry (HPLC-DAD-MS) revealed that the production of pigmentosin B (<b>2</b>) was apparently specific for <i>Gibellula</i> sp., while the glycoasperfuran <b>3</b> was specific for <i>C. javanica</i>.