Synthesis and biological activity of new indole based derivatives as potent anticancer, antioxidant and antimicrobial agents

Indoles have very critical roles to design new biologically active molecules in medicinal chemistry. They display higher biological activities or create new biological properties when compared to the other heteroaromatic compounds. In the present study, 1-ethyl-2-phenyl-3-(thiophen-2-yl)-1 H -indole (3), 8-ethyl-8 H -benzo[a]thieno[3,2-c]carbazole (4), 1-ethyl-2-phenyl-3-(5-(phenylethynyl)thiophen-2-yl)-1H-indole (6) and 1-ethyl-3-(furan-2-yl)-2-phenyl-1H-indole (7) are prepared via Pd-catalyzed cross-coupling reactions and iodocyclization reactions. It was determined that compound 3 and 7 were also seemed to be better drug candidates at the end of in silico evaluation. Furthermore, compound 7 provided the best antibacterial and antifungal activity against the test indicator strains. It showed a potent antifungal effect on Aspergillus niger ATCC 16404 (MIC: 1.17 µg mL − 1; MFC: 2.7 µg mL −1 ). In addition, while compounds 3, 6 and 7 showed significantly high molybdenum reducing activity compared to trolox, 7 exhibited almost the same antioxidant activity (EC 50 = 7.1 µM) compared to the trolox standard (EC 50 = 5.07 µM). After characterization, the cytotoxic activities of novel indoles were tested against different cancer cell lines and non-cancerous human cell line. Compound 3 and 7 had selective cytotoxic activity towards cancer cells. EC 50 values of compound 3 were found to be 248.15 µM for LnCap, 139.81 µM for HepG2, and 164.72 µM for the Caco-2 cell line. Similarly, The EC 50 value of 7 was found as 38.725 µM for LnCap, 70.02 µM for HepG2, and 86.98 µM for Caco-2, and 90.97 µM for Hek293 cell line. Moreover, it was revealed that these two compounds showed strong apoptotic properties towards these cancer cell lines as described by image cytometry and real time PCR. Consequently, these results improved that our molecules 3 and 7 could be new candidates as anticancer agents and apoptosis inducers.