Ganodermanic acid, a new steroidal compound derived from the marine fungus <i>Aspergillu</i> s sp. ZJUT223

A new steroid ganodermanic acid (<b>1</b>) and seventeen known compounds <b>2</b>-<b>18</b> were isolated from the marine fungus <i>Aspergillus</i> sp. ZJUT223. Extensive spectroscopic data (1D/2D NMR and HR-ESI-MS) established the planar structure of <b>1</b>. Its stereochemistry was assigned using NOESY, density functional theory (DFT)-calculated NMR with DP4+ analysis, and calculated electrical circular dichroism (ECD). In the quorum sensing (QS) inhibition assay, aspergilol I (<b>17</b>) dose-dependently inhibited violacein production in <i>Chromobacterium violaceum</i> CV026, suggesting that it interfered with quorum sensing signalling in this reporter strain. This is the first report of aspergilol I (<b>17</b>) as a potential quorum sensing inhibitor.