Secondary Metabolites of a Deep Sea Derived Fungus Aspergillus versicolor CXCTD-06-6a and Their Bioactivity

In order to obtain novel secondary metabolites, a deep sea inhabiting fungus Aspergillus versicolor CXCTD-06-6a was investigated. One new diketopiperazine brevianamide W(1a), as well as five known diketopiperazine alkaloids, diketopiperazine V(1b), brevianamide Q(2), brevianamide R(3), brevianamide K(4), and brevianamide E(5), were isolated from the Et OAc extract of the fermentation broth. Their structures were elucidated by spectroscopy techniques(NMR, MS). The six compounds exhibited moderate radical scavenging activity against DPPH with clearance ratio of 55.0%(1a and 1b), 53.7%(2), 46.2%(3), 61.4%(4) and 19.3%(5) at a concentration of 13.9 μmol L-1, respectively; while the positive control ascorbic acid showed a ratio of 70.3% at the concentration of 28.4 μmol L-1.

Vercytochalasins A and B: Two unprecedented biosynthetically related cytochalasins from the deep-sea-sourced endozoic fungus Curvularia verruculosa

Vercytochalasins A(1) and B(2), two biosynthetically related cytochalasins featuring novel structure and substituents, were isolated from the endozoic fungus Curvularia verruculosa which was associated with the deep-sea squat lobster Shinkaia crosnieri collected from the cold seep environment in South China sea. Their structures were elucidated by detailed interpretation of NMR spectroscopic and mass spectrometric data. The absolute configurations were confirmed by NOESY experiments as well as by DP4+ and ECD calculations. Differed from common cytochalasins, compound 1 is an uncommon secocytochalasin featuring the ester group cleaved between C-9 and C-23, and incorporating an additional oxygenated C4 unit which coupled with C-20 and C-22 to form a new substituted cyclohexenone moiety, while compound 2 contains an unusual 2–hydroxy-3-oxobutan-2-yl unit at C-22. Both compounds are distinctive from the commonly described cytochalasins. Compound 1 exhibited potent activity against angiotensinI-converting enzyme(ACE) whereas compound 2 showed antibacterial activity. Molecular docking simulations were performed to explore the intermolecular interaction of compounds 1 and 2 with ACE.