Synthesis of kojic acid-derived copper-chelating apoptosis inducing agents

Three classes of kojic acid derivatives were synthesized and examined for their antiproliferative activity against HeLa cells. Both 8b and 11 co-treated with copper ion exhibited synergistic effect on the HeLa cell growth inhibition with GI₅₀ values of 11.9 and 7.1 μM, respectively. Flow cytometric analysis of HeLa cells revealed that 11-Cu co-treatment induced the sub-G1 arrest in a dose-dependent manner, suggesting that the growth-inhibitory effect is attributed to DNA fragmentation. Moreover, western blot of HeLa cells cytosolic extracts displayed the cleavage of the 116-kDa protein poly(ADP-ribose) polymerase and activation of caspase-3 by the reduced level of the 32-kDa proenzyme, indicating that the caspase-dependent apoptotic pathway was involved. We further demonstrated that MAPK pathway regulators such as ERK and p38 were activated in response to 11-Cu co-treatment, suggesting that the intracellular oxidative stress was dramatically stimulated by the copper ion. Taken together, we have successfully synthesized kojic acid-derived copper-induced apoptotic agents.