Synthesis and in vitro evaluation of substituted tetrahydroquinoline-isoxazole hybrids as anticancer agents

A series of isoxazole linked to 4-(2-oxopyrrolinidyl-1)-tetrahydroquinoline derivatives was efficiently synthesized. The synthetic route started with the formation of the corresponding N -propargyl tetrahydroquinoline derivatives via cationic Povarov reaction. Tetrahydroquinoline-isoxazole hybrid systems ( 3a – p ) were obtained with good yields (42–88%) through a 1,3-dipolar cycloaddition reaction with a click chemistry approach. These compounds have been tested for their in vitro cytotoxic activity against four different human cancer cell lines, lung (A549), liver (HepG2), and melanoma murine (B16F10) using the conventional MTT assay. Among all tetrahydroquinoline-isoxazole hybrids synthesized, compounds 3a , 3e , 3j , and 3m showed promising in vitro activity against HepG2 cancer cell line with considerable selectivity. Compounds 3a (IC 50 = 6.80 µM, SI = 14.7) and 3j (IC 50 = 5.20 µM, SI > 16.1) exhibited the highest cytotoxic effect. The death pathway related to cytotoxicity of the compound 3j showed necrotic characteristics selectively on the tumor cell line, also showed an improved in vitro activity against the tested reference drug ( oxaliplatin ), without significant affectation on the viability of hepatocytes. In general, results suggested that these type of hybrid compounds might have therapeutic potential in future investigations on hepatocellular carcinoma.