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Objective: To compare the schizontocidal activity of recrystallized or crude daphnetin against malaria parasites in vivo., Methods: Schizontocidal activity of recrystallized or crude daphnetin at various dosages was assessed in mice infected with Plasmodium berghei ANKA using a "4-day suppress assay"., Results: The comparison of the reduction rate of parasitemia caused by either recrystallized or crude dephnetin showed that ED(50) of crude daphnetin was 18.36 mg/kg, with 95% confidence limit of 5.96-56.54 mg/kg while ED50 of recrystallized daphnetin was 11.46 mg/kg, with 95% confidence limit of 8.63-15.22 mg/kg., Conclusion: The results indicate that the efficacy of recrystallized daphnetin is 37.6% higher than that of crude daphnetin.

Objective: To investigate the therapeutic effect of a combination of artemether and daphnetin against Plasmodium berghei ANKA strain in mice., Methods: Groups of P. berghei infected mice were treated with various oral doses of artemether and daphnetin according to "4-day suppress assay". Thin blood smears were made on the fifth day after inoculation of parasites and the parasitemia reduction rate was calculated. The ED50 values obtained were plotted on isobolograms. A combined action of artemether and daphnetin was assessed., Results: Artemether 0.4 mg/(kg x d) x 4d exhibited no detectable antimalarial effect, while artemether 0.4 mg/(kg x d) x 4d combined with daphnetin 7.7 mg/kg. d x 4d showed potent antiparasile efficacy. The ED50s of artemether in combination with daphnetin were lower than that of single artemether or daphnetin. The R-values were higher than 0.4, but lower than 2.7., Conclusion: The combination of artemether with daphnetin showed an additive antiparasile effect.

Objective: To investigate the activity of daphnetin(DPNT) against the exo-erythrocytic stage of rodent malaria., Methods: Groups of ten male ICR mice were infected by intraperitoneal injection with sporozoites of P. yoelii. Mice were administered daphnetin 0.5 hr postinfection on d0 and once per day for three additional consecutive days(d1-d3) by the i.g. route. The effects of daphnetin at various dosages and those of the combination of daphnetin with primaquine were assessed by the number of mice with negative Giemsa-stained slides from tail blood on the seventh day after infection and by the average number of red blood cells (RBC) infected in 1,000 RBC observed on the eleventh or twelfth day after infection. We also observed the effect of daphnetin on the concentration of Hb in ICR mice., Results: Daphnetin exhibited no detectable antimalarial effect on the exo-erythrocytic stage of P. yoelii, while the antimalarial efficacy of DPNT 50 mg/(kg.d) combined with 5 mg/(kg.d) PQ, was comparable to PQ 10 mg/(kg.d) x 4 d i.g. in mice infected with sporozoites of P. yoelii. The concentration of Hb in ICR mice administered with DPNT 50 mg/(kg.d) x 4 d decreased on the eighth day after administration., Conclusion: Daphnetin alone showed no anti-exoerythrocytic activity in vivo. The combination of DPNT 50 mg/(kg.d) with PQ 5 mg/(kg.d) showed promising antimalarial efficacy comparable to that of PQ 10 mg/(kg.d). Administration of DPNT caused anemia in ICR mice.

Objective: To investigate the in vitro and in vivo schizontocidal activity of daphnetin., Methods: Schizontocidal activity of daphnetin was tested using an in vitro assay based on the routine in vitro cultivation of P. falciparum FCC1 strain. The in vivo antimalarial effects of daphnetin at various dosages were assessed in mice infected with P. b. erghei ANKA according to "4-day suppress assay"., Results: In vitro, daphnetin exhibited potent schizontocidal activity comparable to chloroquine(CQ) at the dose range of 1-10 mumol/L. In vivo, 50 or 100 mg/kg.d-1 x 4 d daphnetin i.g. and 10, 50 or 100 mg/kg.d-1 x 4 d dephnetin i.p. showed antimalarial efficacy comparable to CQ 10 mg/kg.d-1 x 4 d i.g. in mice infected with P. berghei ANKA, evaluated by both the reduction rate of parasitemia on D4 and the average surviving days in 30 days., Conclusion: Daphnetin displays certain schizontocidal activity both in vitro and in vivo.