In vivo antimalarial activities of glycoalkaloids isolated from Solanaceae plants

Malaria is one of the most common and serious protozoan tropical diseases. Multi-drug resistance remains pervasive, necessitating the continuous development of new antimalarial agents.

Many glycosides, such as triterpenoid saponins, were shown to have antimalarial activity against Plasmodium falciparum in vitro. This study was to elucidate the ability of five glycoalkaloids against Plasmodium yoelii and develop new antimalarial lead compounds.

Glycoalkaloids were isolated from three kinds of Solanaceae plants: chaconine and solanine were isolated from Solanum tuberosum L. sprouts, solamargine and solasonine from Solanum nigrum L. fruit, tomatine from Lycopersicon esculentum Mill. fruit. The five isolated glycoalkaloids were evaluated against Plasmodium yoelii 17XL in mice with 4-day parasitemia suppression test in different concentrations.

Chaconine showed a dose-dependent suppression of malaria infection, ED50, 4.49 mg/kg; therapeutic index (TI), approximately 9. At a dose of 7.50 mg/kg, the parasitemia suppressions of chaconine, tomatine, solamargine, solasonine and solanine were 71.38, 65.25, 64.89, 57.47 and 41.30%, respectively. At 3.75 mg/kg, the parasitemia suppression of chaconine was 42.66%, but the derivative, chaconine-6-O-sulfate, appeared to show no antimalarial activity. Simultaneous administration of chaconine and solanine in 1:1 did not show any synergistic effects.

The results showed that the glycoalkaloids with chacotriose (chaconine and solamargine) were more active than those with solatriose (solanine and solasonine). Chaconine was the most active among the five glycoalkaloids. We propose that the activity is dependent upon non-specific carbohydrate interactions. The 6-OH of chaconine is important for antimalarial activity.