Discovery of 2,5-diketopiperazine alkaloids with quorum sensing inhibitory activity from the marine fungus Penicillium sp. ZJUT-34.

One new 2,5-DKP derivative -dihydroxycyclopenol () and seven known congeners - were isolated from the marine fungus sp. ZJUT-34 cultured on rice medium. The planar structure of was established by extensive spectroscopic analysis, including 1D, 2D NMR and HR-ESI-MS, while the relative configuration of was determined by quantum chemical calculation. In the QS inhibitory assay, significantly inhibited the production of violacein in ATCC12472 (20.65%) at a concentration of 6.25 μg/mL without affecting the growth of the strain, as compared with norharmane (22.14%), a quorum sensing inhibitor (QSI) identified in our previous study. It represented the first report on the QS inhibitory activity of the seven-membered 2,5-DKPs. In addition, compounds - were subjected to antibacterial assay against six pathogenic bacteria Compound exhibited comparable antibacterial activity against FA2-2 (MIC = 96 μg/mL) with the positive control gentamicin (MIC = 80 μg/mL).