Antiplasmodial activity of steroidal chalcones: evaluation of their effect on hemozoin synthesis and the new permeation pathway of Plasmodium falciparum-infected erythrocyte membrane.

Chalcone derivatives on an estradiol framework were evaluated for their ability to inhibit the growth and development of the malaria parasite Plasmodium falciparum. Out of twelve steroidal chalcones and one indanone derivative studied, three were found to have 50% growth inhibitory concentration less than 5μm and minimum inhibitory concentration for parasite development from ring to schizont stage as ≤20μm with best activity for gallic acid-based chalcone derivative 1 as 2.07 and 10μm, respectively. Two of the active derivatives 1 and 10 did not exhibit cytotoxicity against vero cells as evident by the good selectivity ratio. Study of structure-activity relationship indicated that increasing substitution in the benzoyl ring-enhanced antiplasmodial activity. Hemozoin synthesis of the parasite remained unaffected by these derivatives. These derivatives were also investigated for their effect on parasite-induced new permeation pathway in the erythrocyte membrane by sorbitol-induced hemolysis, and four derivatives 1, 2, 9, and 10 exhibited significant inhibition (>70%) at 20μm concentration. A positive correlation was also observed among the antiplasmodial activity and inhibition of new permeation pathway. These observations suggest that steroidal chalcones with selective activity for the parasite may be considered as antimalarial leads for further optimization and preclinical study.