Comparative Studies on Microbial and Chemical Modifications of Trichothecene Mycotoxins

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RESUMO

The microbial modification of several trichothecene mycotoxins by trichothecene-producing strains of Fusarium nivale and F. solani was studied. These results were compared with the corresponding chemical modifications. The growing mycelia of Fusarium spp. did not convert 4β-acetoxy-3α,7α,15-trihydroxy-12,13-epoxytrichothec-9-en-8-one (fusarenon) into 3α,4β,7α,15-tetrahydroxy-12,13-epoxy-trichothec-9-en-8-one (nivalenol), whereas 3α,4β,7α,15-tetraacetoxy-12,13-epoxytrichothec-9-en-8-one (tetraacetylnivalenol) was deacetylated to yield 3α-hydroxy-4β,7α,15-triacetoxy-12,13-epoxytrichothec-9-en-8-one (4,7,15-triacetylnivalenol), which was resistant to further deacetylation. T-2 toxin was transformed into HT-2 toxin, and 8α-(3-methylbutyryloxy)-3α,4β,-15-triacetoxy-12,13-epoxytrichothec-9-en-8-one (T-2 acetate) was transformed into HT-2 toxin via T-2 toxin. Chemical modification with ammonium hydroxide converted tetraacetylnivalenol into fusarenon via 4,7,15-triacetylnivalenol. 3α,-7α,15-Triacetoxy-12, 13-epoxytrichothec-9-en-8-one (triacetyldeoxynivalenol) gave deacetylation products lacking the C-7 or C-15 acetyl group in addition to 7α,15 - diacetoxy - 3α - hydroxy - 12,13 - epoxytrichothec - 9 - en - 8 - one (7,15 - diacetyldeoxynivalenol). These results demonstrate the regio-selectivity in microbial modification of trichothecenes. Based on the results and available knowledge concerning the transformation of trichothecenes, mechanisms for biological modifications of these mycotoxins are postulated.

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