Stilbene Derivatives from Photorhabdus temperata SN259 and Their Antifungal Activities against Phytopathogenic Fungi

Chemical investigation of an insect pathogenic enterobacterium, Photorhabdus temperata SN259, led to the isolation and identification of seven metabolites, which include three new compounds, 3-hydroxy-2-isopropyl-5-phenethylphenyl carbamate, 1, 2-(1-hydroxypropan-2-yl)-5-[2-phenylethyl]benzene-1,3-diol, 2, 2-(1-hydroxypropan-2-yl)-5-[( E )-2-phenylethenyl]benzene-1,3-diol, 3, and four known metabolites ( 4 – 7 ). Their structures were elucidated on the basis of MS and NMR data and by comparison with those reported previously. The activities of compounds 1 – 7 were evaluated against four phytopathogenic fungi ( Pythium aphanidermatum, Rhizoctonia solani Kuhn, Exserohilum turcicum, and Fusarium oxysporum ). In an agar medium assay, compounds 1 and 7 showed strong inhibition against P. aphanidermatum with EC 50 values of 2.8 and 2.7 μg/mL, respectively. By comparing the structure of compounds 1 – 7, we deduced that the acylamino group in compound 1 and the isopropyl group in compound 7 contribute to the inhibitory activity.