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

A new steroid ganodermanic acid (1) and seventeen known compounds 2–18 were isolated from the marine fungus Aspergillus sp. ZJUT223. Extensive spectroscopic data (1D/2D NMR and HR-ESI-MS) established the planar structure of 1. 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 (17) dose-dependently inhibited violacein production in Chromobacterium violaceum CV026, suggesting that it interfered with quorum sensing signalling in this reporter strain. This is the first report of aspergilol I (17) as a potential quorum sensing inhibitor.