3-acetyldeoxynivalenol and sambucinol

The first two oxygenation steps post-trichodiene in the biosyntheses of the trichothecenes 3-acetyldeoxynivalenol and sambucinol were investigated. The plausible intermediates 2-hydroxytrichodiene (2alpha- and 2beta-) and 12,13-epoxytrichodiene and the dioxygenated compounds 12,13-epoxy-9,10-trichoene-2-ol (2alpha- and 2beta-) were prepared specifically labeled with stable isotopes. They were then fed separately and/or together to Fusarium culmorum cultures, and the derived trichothecenes were isolated, purified, and analyzed. The stable isotopes enable easy localization of the labels in the products by 2H NMR, 13C NMR, and mass spectrometry. We found that 2alpha-hydroxytrichodiene is the first oxygenated step in the biosynthesis of both 3-acetyldeoxynivalenol and sambucinol. The stereoisomer 2beta-hydroxytrichodiene and 12,13-epoxytrichodiene are not biosynthetic intermediates and have not been isolated as metabolites. We also demonstrated that the dioxygenated 12, 13-epoxy-9,10-trichoene-2alpha-ol is a biosynthetic precursor to trichothecenes as had been suggested in a preliminary work. Its stereoisomer was not found in the pathway. A further confirmation of our results was the isolation of both oxygenated trichodiene derivatives 2alpha-hydroxytrichodiene and 12,13-epoxy-9, 10-trichoene-2alpha-ol as natural metabolites in F. culmorum cultures.

Topics: Cyclohexenes; Fusarium; Magnetic Resonance Spectroscopy; Mass Spectrometry; Oxidation-Reduction; Oxygen; Sesquiterpenes; Trichothecenes

Fusarium culmorum produces two major trichothecenes, 3-acetyldeoxynivalenol and sambucinol, and some minor apotrichothecenes. It was desired to investigate if during their biosynthesis a C-11-keto intermediate was involved. To verify this postulate, trichodiene, a known precursor to trichothecenes, was synthesized with two deuteriums at C-11 and one at C-15. It was then fed to F. culmorum cultures, and the derived metabolites were purified and analyzed. The results ruled out the involvement of an 11-keto intermediate but revealed two novel apotrichothecenes. The characterization of their structures suggested that one of the 2-hydroxy-11alpha-apotrichothecene stereoisomers (2alpha or 2beta) could be converted to sambucinol. These apotrichothecenes were therefore synthesized labeled specifically with two deuteriums at C-4 and C-15 and fed to F. culmorum cultures. Indeed, the result established for the first time that 2alpha-hydroxy-11alpha-apotrichothecene was a precursor to sambucinol. A biosynthetic scheme for the production of trichothecenes and apotrichothecenes is described.

Topics: Deuterium; Fusarium; Models, Chemical; Mycotoxins; Solanum tuberosum; Trichothecenes

A kinetic pulse-labeling method was utilized in Fusarium culmorum to detect plausible biosynthetic intermediates and differentiate them from dead-end metabolites. The ultimate test to demonstrate a precursor relies on feeding experiments. We now report the detection of four new metabolites, one of them (compound 1) behaves as a dead-end metabolite, whereas compounds 2, 3, and 4 seem to be putative intermediates: they metabolize with time just when 3-acetyldeoxynivalenol (3-ADN) and/or sambucinol (SOL) start to be produced. Feeding experiments confirmed these results: compound 1 is not converted to 3-ADN or SOL, and compounds 2-4 are precursors to 3-ADN. In addition 3 is a precursor to SOL.

Topics: Fusarium; Kinetics; Mevalonic Acid; Models, Biological; Trichothecenes

A novel dead-end metabolite of Fusarium culmorum was isolated and characterized (Zamir, L. O., and Devor, K. A. (1987) J. Biol. Chem. 15348-15353). This 3 alpha, 13-dihydroxy-apotrichothec-9-ene is herein given the trivial name of apotrichodiol to indicate its basic structure. The characterization of apotrichodiol was established through the application of spectroscopic techniques (ultraviolet, 1H-NMR, 13C-NMR, COSY, and DEPT experiments) on the natural product as well as on its diacetate derivative. The mode of folding of its precursor farnesyl pyrophosphate was derived from feeding experiments with 3,4-[13C2]mevalonolactone. 13C-NMR assignments were also made of 3-acetyldeoxynivalenol and sambucinol which were derived from these feedings with enriched mevalonolactone.

Topics: Chromatography, High Pressure Liquid; Fusarium; Magnetic Resonance Spectroscopy; Mevalonic Acid; Sesquiterpenes; Trichothecenes