Several new chalcone analogues were synthesized and evaluated as inhibitors of malaria parasite. Inhibitory activity was determined in vitro against a chloroquine-sensitive Plasmodium falciparum strain of parasites. The compound 3-(4-methoxyphenyl)-1-(4-pyrrol-1-yl-phenyl)prop-2-en-1-one was found to be the most active with 50% inhibition concentration (IC 50 ) of 1.61 lg/ml. This inhibitory concentration is comparable to a prototype phytochemical chalcone, licochalcone A, with an IC 50 of 1.43 lg/ml. The present study suggests that small, lipophilic nitrogen heterocyclic ring A together with small hydrophobic functionality at ring B can enhance antimalarial activity. These results suggest that chalcones are a class of compounds that provides an option of developing inexpensive, synthetic therapeutic antimalarial agents in the future.

Twenty‐seven novel chalcone derivatives were synthesized using Claisen‐Schmidt condensation and their antimalarial activity against asexual blood stages of Plasmodium falciparum was determined. Antiplasmodial IC50 (half‐maximal inhibitory concentration) activity of a compound against malaria parasites in vitro provides a good first screen for identifying the antimalarial potential of the compound. The most active compound was 1‐(4‐benzimidazol‐1‐yl‐phenyl)‐3‐(2, 4‐dimethoxy‐phenyl)‐propen‐1‐one with IC50 of 1.1 μg/mL, while that of the natural phytochemical, licochalcone A is 1.43 μg/mL. The presence of methoxy groups at position 2 and 4 in chalcone derivatives appeared to be favorable for antimalarial activity as compared to other methoxy‐substituted chalcones. Furthermore, 3, 4, 5‐trimethoxy groups on chalcone derivative probably cause steric hindrance in binding to the active site of cysteine protease enzyme, explaining the relative lower inhibitory activity.

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