MATERIALS AND METHOD: In this experiment, the potential of embelin, isolated from Embelia ribes, to inhibit the growth and sensitize CQ action was screened using SYBRE-green-I based drug sensitivity and isobologram assays, respectively. Its effect on red blood cells stability was screened to assess its safety. To explore its molecular mechanism, its effect on plasmodial Hemozoin and the in vitro β-hematin formation was screened as well. Furthermore, its anti-oxidant activity was measured using the conventional in vitro tests and its molecular characters were obtained using Molispiration program.

RESULTS: The results showed that its anti-plasmodial effect was weaker than CQ but synergism was obtained when they were combined at ratios lower than 5:5 CQ/embelin. Furthermore, β-hematin formation was inhibited by embelin without showing any synergism after mixing with CQ.

Method: The stem powder of T. crispa was soaked in absolute ethanol for 72 hours. The resulting ethanolic extract was screened for the presence of phytochemicals. Vero cells monolayer in 96-well plate was infected with RH strain of T. gondii and treated with concentrations of the EETC, Veratrine alkaloid, and clindamycin ranging from 1.56 to 200 μg/mL. MTT assay was conducted after 24 hours to evaluate the cytotoxicity and antiparasitic activities of the EETC. Four and 24 hours treatment models were adapted to assess the infection index and intracellular proliferation of T.

Results: The study revealed that the EETC had no cytotoxic effects on Vero cells with IC50 = 179 μg/mL, as compared to clindamycin (IC50 = 116.5 μg/mL) and Veratrine alkaloid (IC50 = 60.4 μg/mL). The EETC had good anti-toxoplasma activities with IC50 = 6.31 μg/mL in comparison with clindamycin (IC50 = 8.33 μg/mL) and Veratrine alkaloid (IC50 = 14.25 μg/mL). The EETC caused more than 70% and 80% reduction in infection index and intracellular proliferation in both treatment models, respectively.