Synthesis and cytotoxic evaluation of usnic acid benzylidene derivatives as potential anticancer agents.

A series of usnic acid benzylidene derivatives (groups I-V ) were designed, synthesized and evaluated for their anticancer activity in the search for potentially new anticancer agents. Compounds 1a , 5b , 2b , 2e and 2f exhibited the most potent cytotoxcity against K562 cell line with IC ₅₀ values of 10.0 ± 3.6, 5.6 ± 0.4, 8.8 ± 1.0, 4.5 ± 0.1 and 8.4 ± 0.4 μM, respectively. It is noteworthy that compound 2e displayed potent cytotoxicity against K562 cells without any cytotoxic effect on HEK293 normal cell line.