Zanthoxylum zanthoxyloides – an African medicinal tree with antimalarial effects

Malaria is a serious tropical disease and an important cause of death among African children. Zanthoxylum zanthoxyloides is a West African tree that is used against malaria and other diseases by traditional healers. Usually, the bark is used, but it is not well known which constituents are responsible for the anti-malaria effect. The anti-malaria effects of substances isolated from the root bark and stem bark extracts of this tree were tested. Twenty substances were isolated and identified from the extracts. Seven of these have not been reported previously from this plant: The alkaloids buesgenine, 6-hydroxydihydrochelerythrine, bis-dihydrochelerythrinyl ether, dictamnine and (-)-p-synephrine, the coumarin 6,7,8-trimethoxycoumarin, and neochlorogenic acid. The dichloromethane extracts of the root bark and stem bark and the methanol extract of the stem bark killed the protozoa Plasmodium falciparum, the organism that gives malaria, with IC₅₀ values between 1 and 10 µg/ml. This effect was observed both towards chloroquine sensitive and chloroquine resistant protozoa. Among the isolated substances, the alkaloids skimmianine, γ-fagarine and bis-dihydrochelerythrinyl ether showed good antiplasmodial effect.