Membrane perturbations induced by new analogs of neocryptolepine

Indoloquinoline alkaloids represent an important class of antimalarial, antibacterial and antiviral compounds. Indolo[2,3-b]quinolines are a family of DNA intercalators and inhibitors of topoisomerase II, synthetic analogs of neocryptolepine, an alkaloid traditionally used in African folk medicine. These cytotoxic substances are promising anticancer agents. Active representatives of indolo[2,3-b]quinolines affect model and natural membranes. The distinct structure and hydrophobicity of the compounds leads to marked differences in the disturbing effects on membrane organization and function. Our results also indicated a strong relationship between the presence of the chain and the Poct of the molecule as well as the capacity for incorporation into carboxyfluorescein-trapped liposomes in the 0.02-0.06 mM range. Moreover, a correlation between binding to neutral dimyristoylphosphatidylcholine (DMPC) or negative charged dimyristoylphosphatidylcholine:dimyristoylphosphatidylglycerol (DMPC:DMPG, 9:1 w/w) liposomes, as well as to erythrocyte ghosts and pKa, was also found. All the compounds cause hemolysis in isotonic conditions with concentration causing 50% hemolysis (HC50) in the 0.12-0.88 mM range. The concentration-dependent inhibitory effect of the tested agents on erythrocyte ghosts' acetylcholinesterase activity was also studied.