Discovery of Novel Antioomycete Metabolites from the Marine-Derived Fungus Paraconiothyrium sporulosum

In our screening program for natural products that are effective in controlling plant diseases, we found that the culture filtrate of Paraconiothyrium sporulosum SFC20160907-M11 effectively suppressed the development of tomato late blight disease caused by Phytophthora infestans . Using a bioassay-guided fractionation of antioomycete activity, 12 active compounds ( 1 – 12 ) were obtained from an ethyl acetate extract of the culture filtrate. Chemical structures of five new compounds 1 – 5 were determined by the extensive analyses of nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS), and circular dichroism (CD) data. Interestingly, mycosporulonol ( 1 ) and botrallin ( 8 ) completely inhibited the growth of P. infestans at concentrations of 8 and 16 μg/mL, respectively. Furthermore, the spray treatment of 1 and 8 (500 μg/mL) successfully protected tomato seedlings against P. infestans with disease control values of 92%. Taken together, these results suggest that the culture filtrates of P. sporulosum SFC20160907-M11 and their bioactive metabolites can be used as new antioomycete agents for Phytophthora late blight control.