Induced secondary metabolites from the endophytic fungus Aspergillus versicolor through bacterial co-culture and OSMAC approaches

Miada F. Abdelwahab, T. Kurtán, Attila Mándi, Werner E.G. Müller, Mostafa A. Fouad, Mohamed S. Kamel, Zhen Liu, Weaam Ebrahim, Georgios Daletos, Peter Proksch

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16 Citations (Scopus)

Abstract

Two new cryptic 3,4-dihydronaphthalen-(2H)-1-one (1-tetralone) derivatives, aspvanicin A (1) and its epimer aspvanicin B (2), as well as several known cryptic metabolites (3–8), were obtained from the ethyl acetate extract of the co-culture of the endophytic fungus Aspergillus versicolor KU258497 with the bacterium Bacillus subtilis 168 trpC2 on solid rice medium. When A. versicolor was cultured axenically in liquid Wickerham medium supplemented with 3.5% DMSO, an additional three known secondary metabolites (9–11) were isolated that were lacking when the fungus was fermented on rice medium. The structures of the new compounds were elucidated using one- and two-dimensional NMR spectroscopy as well as HRESIMS. The relative and absolute configurations of 1 and 2 were determined by the combination of NMR and electronic circular dichroism (ECD) analysis aided by DFT conformational analysis and TDDFT-ECD calculations. The ECD calculations revealed that although the sign of the blue-shifted overlapping n-π ECD transition follows the helicity rule of cyclic aryl ketones, the calculation of low-energy conformers and ECD spectra was necessary to determine the stereochemistry. All metabolites were assessed for their antibacterial and cytotoxic activities; one of the new diastereomers, compound 2, showed moderate cytotoxic activity against the mouse lymphoma cell line L5178Y.

Original languageEnglish
Pages (from-to)2647-2652
Number of pages6
JournalTetrahedron Letters
Volume59
Issue number27
DOIs
Publication statusPublished - Jul 4 2018

Keywords

  • Absolute configuration
  • Aspergillus versicolor
  • ECD calculations
  • Tetralone derivatives

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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    Abdelwahab, M. F., Kurtán, T., Mándi, A., Müller, W. E. G., Fouad, M. A., Kamel, M. S., Liu, Z., Ebrahim, W., Daletos, G., & Proksch, P. (2018). Induced secondary metabolites from the endophytic fungus Aspergillus versicolor through bacterial co-culture and OSMAC approaches. Tetrahedron Letters, 59(27), 2647-2652. https://doi.org/10.1016/j.tetlet.2018.05.067