The macrolide brefeldin toxin A is a determinant of Alternaria leaf blight disease in safflower, which causes severe economic losses worldwide. Soilborne bacteria, classified as Bacillus subtilis spp., were isolated and shown to readily metabolize brefeldin A in laboratory culture to one major product. This product was identified by high resolution 2D 1H NMR and FAB mass spectroscopies as the acid resulting from hydrolysis of the macrolide ring in brefeldin A. In contrast to brefeldin A, the acid completely lacked phytotoxic activity in the standard leaf bioassay. Detoxification of brefeldin A by the lactonase activity from Bacillus subtilis may be exploited in the future to introduce resistance to Alternaria leaf blight in sufflower.
