Indolyl-α-keto-1,3,4-oxadiazoles: Synthesis, anti-cell proliferation activity, and inhibition of tubulin polymerization.

A series of novel indolyl-α-keto-1,3,4-oxadiazole derivatives have been synthesized by employing molecular iodine-mediated oxidative cyclization of acylhydrazones. In vitro anti cell proliferation activity of these derivatives against various cancer cells lines such as human lymphoblast (U937), leukemia (Jurkat & SB) and human breast (BT474) was investigated. Among the synthesized indolyl-α-keto-1,3,4-oxadiazoles 19a-p, only one compound (19e) exhibited significant antiproliferative activity against a panel of cell lines. The compound 19e with 3,4,5-trimethoxyphenyl motif, endowed strong cytotoxicity against U937, Jurkat, BT474 and SB cancer cells with IC50 values of 7.1, 3.1, 4.1, and 0.8 µM, respectively. Molecular docking studies suggested a potential binding mode for 19e in the colchicine binding site of tubulin. When tested for in vitro tubulin polymerizaton, 19e inhibited tubulin polymezations (IC50 = 10.66 µM) and induced apoptosis through caspase 3/7 activation. Further, the derivative 19e did not cause necrosis when measured using lactate dehydrogenase assay.

Design and synthesis of bis(indolyl)ketohydrazide-hydrazones: Identification of potent and selective novel tubulin inhibitors.

A novel series of ketohydrazide-hydrazones as analogues of naturally occurring coscinamides has been synthesized and evaluated for their anticancer activity against five cancer cell lines. Of the twenty-synthesized ketohydrazide-hydrazones, compounds, 21c, 21f, 21g, 21k and 21o showed cytotoxic effects (less than 50% cell survival) against multiple cancer cell lines when tested at a final concentration of 10 µM. IC50 of three compounds 21f, 21k and 21o was determined to be less than 5 µM for all tested cancer cell lines. Compound 21k exhibited significant anticancer activity against MCF-7, MDA-MB-231, HCT-116 and JURKAT cancer cell lines with IC50 values of 0.8 µM, 0.50 µM, 0.15 µM, and 0.22 µM, respectively. Also, 21k was found to be more selectively cytotoxic against tumor cells when compared to normal cells. Preliminary mechanism of action studies indicated that the most active compound 21k induced caspase-dependent apoptosis in cells. 21k arrests cell cycle in G2/M phase by inhibiting of tubulin polymerization (IC50 = 0.6 µM).