Biotransformation of Stypotriol triacetate by Aspergillus niger

Biological transformation of the meroditerpenoid, stypotriol triacetate (1) by the fungi Aspergillus niger, Cunninghamella elegans, Gibberella fujikuroi and Mucor plumbeus was studied. The incubation of 1 with A. niger yielded the new compound 6′,14-diacetoxy-stypol-4,5-dione (2) whose structure was established by 1H, 13C and 2D NMR and supported by DFT/GIAO.

► Stypotriol triacetate isolated from the brown alga Stypopodium flabelliforme.
► Four filamentous fungus were used to the biotransformation of stypotriol triacetate.
► Only Aspergillus niger yielded the new compound 6′,14-diacetoxy-stypol-4,5-dione.
► This structure was established by 1H, 13C and 2D NMR and supported by DFT/GIAO.