Abstract: 〔Abstract〕Objective: To explore the antimalarial activity and the possible mechanism of Embelia ribes and its main constituent
embelin. Methods: The antimalarial activity of the testing samples were evaluated by in vitro and in vivo assays. And β-hematin
formation inhibitory experiment was selected as in vitro assay while 4-day suppression assay of Plasmodium yoelii（BY265RFP）in
mice was used as in vivo assay. Results: Both of the crude extract and ethyl acetate fraction of E. ribes showed good activities with the
suppression rates of 25.25% and 32.17% against P. yoelii in mice, respectively, while the suppression rate of embelin was 41.59% at
the dose of 100 mg/（kg·d）. The results from the β-hematin formation inhibitory experiment indicated that the crude extract of E. ribes
had a certain activity with IC50 = 500.61 μg/mL, but embelin was almost inactive with the IC50 value much bigger than 1 388.89 μg/mL.
Conclusion: Both extract of E. ribes and its main constituent embelin do reveal certain antimalarial activity. The antimalarial activity
of E. ribes should be mainly attributed to embelin, but the antimalarial mechanism of embelin should not come from the pathway of
β-hematin formation inhibition.

Key words: 〔Key words〕antimalarial activity, Embelia ribes, embelin, rodent malaria, β-hematin formation inhibitory experiment