Coumarin-Based Bioactive Compounds: Facile Synthesis and Biological Evaluation of Coumarin-Fused 1,4-Thiazepines

As part of our ongoing studies on the synthesis of bioactive coumarin compounds, we synthesized a series of new coumarin-fused 1,4-thiazepines using a simple method. The biological activity of target compounds along with 3-(2-hydroxybenzylidene)chroman-2,4-dione intermediates was screened by evaluation of their antioxidant and cytotoxic activities. The antioxidant activity was assessed using two methods, namely, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method and ferric reducing antioxidant power (FRAP) assay. 4-Methoxyphenolic compound 5d in thiazepine series showed the most potent scavenging activity, while the 4-bromophenolic derivative 5b was the most efficient compound in FRAP assay. Also, the result of cytotoxic evaluation using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay demonstrated that compound 5b is at least twofold more potent than etoposide against MCF-7, SK-N-MC, and MDA-MB 231 cell lines.