Abstract
The marine-derived fungus Aspergillus falconensis, isolated from sediment collected from the Canyon at Dahab, Red Sea, yielded two new chlorinated azaphilones, falconensins O and P (1 and 2) in addition to four known azaphilone derivatives (3−6) following fermentation of the fungus on solid rice medium containing 3.5% NaCl. Replacing NaCl with 3.5% NaBr induced accumulation of three additional new azaphilones, falconensins Q−S (7−9) including two brominated derivatives (7 and 8) together with three known analogues (10−12). The structures of the new compounds were elucidated by 1D and 2D NMR spectroscopy and HRESIMS data as well as by comparison with the literature. The absolute configuration of the azaphilone derivatives was established based on single-crystal X-ray diffraction analysis of 5, comparison of NMR data and optical rotations as well as on biogenetic considerations. Compounds 1, 3−9, and 11 showed NF-κB inhibitory activity against the triple negative breast cancer cell line MDA-MB-231 with IC50 values ranging from 11.9 to 72.0 µM.
Highlights
In the last two decades, marine-derived fungi have gained considerable attention for drug discovery due to their ability to produce a vast diversity of bioactive secondary metabolites [1]
The H and 13 C NMR spectra of 7 (Tables 1 and 2) were comparable to those of the co-isolated azaphilones obtained from A. falconensis following fermentation of the fungus on solid rice medium that known compound, falconensin K (10) [23]
The fungus was isolated from marine sediment which was collected at a depth of 25 m from the Canyon at Dahab, Red Sea, Egypt in November 2016
Summary
In the last two decades, marine-derived fungi have gained considerable attention for drug discovery due to their ability to produce a vast diversity of bioactive secondary metabolites [1]. Changing the cultivation conditions of fungi may activate silent biosynthetic gene clusters and eventually lead to either upregulation of constitutively present compounds or accumulation of new natural products [9]. As a part of our ongoing research on marine-derived fungi [14,15,16], we have investigated the fungus Aspergillus falconensis (formerly known as Emericella falconensis [17]). All tested compounds revealed inhibition of NF-κB signaling with IC50 values at two-digit micromolar concentrations
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