Uronic acid-containing glycopeptides from Fusarium oxysporum: Possible significance as chemotypes

Hot aqueous extraction of mycelia of Fusarium oxysporum, followed by fractionation on an anionic resin column gave glycopeptides FL-2 and FL-3. Methylation analysis and 1D and 2D NMR data demonstrated β-d-Manp units and partial hydrolysis gave α-d-GlcpA(1→2)-d-Gal, arising from β-d-Galf-containing groups. Both are chemotaxonomic markers of Fusarium spp. FL-3 contained 2,6-di-O-substituted Manp, as well as 2,6-di-O-substituted Galf units, raising the possibility that the former are main-chain constituents, as well as the expected latter structure. The carbohydrate structures of FL-2 and FL-3 differ from those of previously examined polysaccharides of Fusarium spp., which are in turn all different from each other, so that they can serve as fingerprints. Possible variations in their main-chain structures can occur as well as those of their side-chains.