Purification and characterization of new fatty acids with antibiotic activity produced bySporothrix flocculosa

Chloroform extracts from a culture broth of the biocontrol fungusSporothrix flocculosa were separated by thin-layer chromatography (TLC). Compounds with antifungal activity were revealed with theCladosporium cucumerinum bioassay on TLC plates and were isolated by using silica gel column, preparative TLC, and reverse-phase high-performance liquid chromatography (RP-HPLC). They were identified by standard methods of nuclear magnetic resonance (NMR), gas chromatography (GC), mass spectrometry (MS), and infrared spectrum (IR). In addition to an active molecule previously described, two new fatty acids with antibiotic activity were characterized, 9-heptadecenoic acid and 6-methyl-9-heptadecenoic acid, the latter displaying the strongest activity among all three active molecules. This high number of active metabolites produced byS. flocculosa would explain its rapid and strong activity as a biocontrol agent of powdery mildews. In this context, screening ofS. flocculosa isolates for increased production of these molecules should help in selection of candidates with superior biocontrol properties.Contribution no. 150 du Centre de recherche en horticulture.