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Violaceimides A–E, sulfur-containing metabolites from a sponge-associated fungus Aspergillus violaceus

Yin, Jiaoding, Zhang, Chanjuan, Huang, Jiguo, Zhang, Jianping, Liu, Dong, Huang, Jian, Proksch, Peter, Lin, Wenhan
Tetrahedron letters 2018 v.59 no.33 pp. 3157-3160
Aspergillus, chemical reactions, colorectal neoplasms, cysteine, cytotoxicity, fungi, humans, leukemia, metabolites, neoplasm cells, nuclear magnetic resonance spectroscopy, structure-activity relationships, sulfur
Five new methylsuccinimide-based sulfur-bearing compounds, namely violaceimides A–E (1–5), were isolated from the sponge-associated fungal strain Aspergillus violaceus WZXY-m64-17. Their structures were determined by analyses of the HRESIMS, 1D and 2D NMR data, along with the Mosher’s and Snatzke’s methods, experimental and calculated ECD data, as well as chemical conversion for the configurational assignment. The structures of 1–5 featured the fusion of methylsuccinimide with a modified cysteine to incorporate sulfur element, which was found from nature for the first time. The biogenetic relationship of the sulfur-containing compounds was postulated. Violaceimides A and B exerted selective inhibition against the growth of human leukemia U937 and human colorectal cancer cell HCT-8 with low cytotoxicity toward Vero cells, whereas violaceimide E showed moderate activity to inhibit U937 cells. The preliminary structure-activity relationship was discussed.