Seasonal differences in antimalarial activity of hot-water extract of Dichroa febrifuga leaves against Plasmodium yoelii 17XL in ICR mice, with reference to febrifugine and isofebrifugine content

The antimalarial activity of the hot-water extract of leaves and roots of Dichroa febrifuga was evaluated against Plasmodium yoelii 17XL in ICR mice. Untreated control mice died with a gradual body weight loss and increase of parasitemia by day 9 after infection. The hot-water extract of leaves collected in June showed an antimalarial activity, and furthermore the possible adverse side effect was also observed. All mice given orally the extract of leaves (0.1 g/ml) collected in June died by day 9 without parasite multiplication. The mice given the lower concentration (0.025 g/ml) of the same leaf extract showed low parasitemia levels during administration. Following a transient increase of malaria parasites in the bloodstream, no parasites could be detected by a microscopic examination, and all mice survived during the experiment. On the other hand, the extract of leaves (0.1 g/ml) collected in December showed no activity. The extract of roots (0.1 g/ml) of D. febrifuga collected in December, however, had an antimalarial activity, and three mice out of four survived during the experiment. The leaves collected in June contained about 30 times as much febrifugine and isofebrifugine mixture as those in December.