Objective: In the present study, in vitro cytotoxic activities and in vivo antimalarial efficacies of caffeic acid, oleic acid, and oleuropein, which have shown strong antimicrobial activities, were aimed to be investigated in a malaria model, along with various biological activities.

Methods: We established five groups, each with five mice: first, second, third and the fourth groups were given caffeic acid, oleic acid, oleuropein, and chloroquine, respectively, while the fifth served as an untreated control. All mice were intraperitoneally infected with the suspension having 2.5x10⁷ parasites/mL of Plasmodium berghei-infected erythrocytes, followed by oral administration of active substances at specified doses for four days. Parasitemia was monitored for 27 days through blood smears obtained from the tail-tip.

Results: The average rates of parasitemia in the group of mice that did not receive any treatment was 33% on day 9, 30.8% for the caffeic acid group on day 25, 28.6% for the oleic acid group on day 11, and 31.2% for the oleuropein group on day 11. It was observed that the life span of the mice in the caffeic acid group extended for 16 days compared to the untreated control group. No parasites were found in the blood smears stained with Giemsa during the experiment in the control group of mice.

Conclusion: It was found that all three active ingredients, especially the caffeic acid, suppressed parasite development and extended the lifespan of mice in vivo. The data obtained from this study will make significant contributions to the literature for more comprehensive research on these active substances as next-generation antimalarial agents.