Isolation and Identification of Antifungal Fatty Acids from the Basidiomycete Gomphus floccosus

Bioautography of extracts of the fruiting bodies of the basidiomycete Gomphus floccosus (Schw.) Singer indicated the presence of fungitoxic compounds in the ethyl acetate fraction against the plant pathogens Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum acutatum. Bioassay-guided fractionation of this fraction resulted in the isolation of the bioactive fatty acids (9S,10E,12Z)-9-hydroxy-10,12-octadecadienoic acid (1), (9E,11Z)-13-oxo-9,11-octadecadienoic acid (2), and (10E,12E)-9-oxo-10,12-octadecadienoic acid (3). These three oxylipins were further evaluated for activity against a greater range of fungal plant pathogens (C. fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, Phomopsis obscurans, and Phomopsis viticola) in in vitro dose−response studies. Phomopis species were the most sensitive fungi to these compounds. At 120 h of treatment, the IC₅₀ values for compounds 1, 2, and 3 for P. obscurans were 1.0, 4.5, and 23 μM, respectively, as compared to 1.1 μM for the captan positive control.