Directional modification of chrysin for exerting apoptosis and enhancing significantly anti-cancer effects of 10-hydroxy camptothecin.

Chrysin, one of natural flavonoid compounds, has recently been found to possess anti-inflammatory, antiallergic and anticancer properties. To increase its anticancer effects, 5 chrysin derivates were synthesized on the base of DNA intercalator structure. The inhibiting effects of chrysin and its derivatives on cancer cells Hela, BGC823, MCF-7, HepG2, and normal cells HEK-293, were evaluated by MTT assays. 5-(2'-amino) phenyl-7-cyclohexanemethylchrysin (Ch-1), a unique chrysin derivate, killed all the cancer cells but kept above 60% survival rate in normal cells HEK-293 at 62.5μM. Treated with chrysin from 250μM to 500μM, those cells were still maintained above 60% survival rate. The result of circular dichroism spectra showed that Ch-1 could intercalate DNA while chrysin had no effects on DNA. Interestingly, Hela cells survival rates were 95% and 10%, after treated with 20μM and 30μM of Ch-1, respectively. Both intrinsic and extrinsic apoptotic pathway were identified in regulating the cell death caused by Ch-1 in Hela cells. p53, the upstream regulator of apoptotic pathway were extremely significantly up-regulated in Hela cells treated with 25μM Ch-1. Moreover, the inhibiting effects and apoptotic related proteins responses to Ch-1 on Hela cells were abolished after pre-treated with Pifithrin-α (Pft-α), a p53 inhibitor. So, p53-depedent apoptosis is the crucial factor governing the inhibiting effects of Ch-1 in Hela cells. Amazingly, Ch-1 at non-toxic concentration (2.5-10μM) enhanced significantly anti-cancer effect of 10-hydroxy camptothecin (HCPT) on Hela, BGC823, and MCF-7 cells.