Two new compounds, a new lactone, quercilactone A (1), and (17R)-hydroxynafuredin (5), as well as five known compounds, scytalone (2), 3S,4R-hydoxy-scytalone (3), nafuredin (4), (+)-(3R,5R)-3-hydroxy-5-decanolide (6) and 3-ethyl-4-hydroxy-6-methyl-2H-pyran-2-one (7), were isolated from Raffaelea quercivora, a fungus that causes Japanese oak wilt disease. The structures of these compounds were determined by 1D and 2D NMR spectroscopic analyses. The absolute configuration at C-17 of 5 was determined to be R by the modified Mosher's method. Compounds 1, 2, and 7 exhibited weak phytotoxic activity in lettuce seedlings at a concentration of 100 μg mL-1.
Keywords: Japanese oak wilt; Quercus crispula; Raffaelea quercivora; nafuredin; phytotoxicity; quercilactone A; scytalone.