Isolation, characterization and biological activity of inositol sphingophospholipids fromPhytophthora capsici

Several inositol sphingophospholipids (ISPL) were isolated from mycelia of Phytophthora capsici , a phytopathogenic fungus of pepper ( Capsicum annuum c.v. Yolo Wonder). The sphingophospholipids induce a protective response by cotyledons of young peppers against necrotic lesions caused by the pathogen P. capsici . The ISPL structures were determined by chemical methods, fast atom bombardment mass spectrometry and by fast atom bombardment collision‐induced tandem mass spectrometry. All ISPL consisted of ceramides linked to inositol phosphate. The amidelinked fatty acids were found to have 16, 20 and 22 carbon chains. The long chain bases were identified as trimethylsilyl derivatives and shown to be C 16 ‐sphingosine and C 16 ‐dihydrosphingosine. The protective effect of the ISPL on cotyledons of young peppers against necrotic lesions caused by the pathogen P. capsici was shown not to be dependent on the unsaturation of the C 16 ‐sphingosine base and the nature of the acyl chain. We also investigated the effect of growth conditions on the ISPL produced in three different, chemically defined media that are commonly used for fungi cultures. We showed that P. capsici synthesized one major class of compounds with molecular weights of M r =833 and 835 containing the 16∶1 base and the 22∶1 or the 22∶0 N ‐acyl group, independent of the growth medium used. The presence of phosphite or fosetyl‐A1 did not affect the result.