Low antiplasmodial activity of alkaloids and amides from the stem bark of Zanthoxylum rubescens (rutaceae)

Abstract

The stem bark of Zonthoxylum rubescens (syn. Fagara rubescens) is used for treating fevers associated with malaria in the Ivory Coast. Three alkaloids: N-nornitidine, 7,9-dimethoxy-2,3-methylenedioxybenzophenanthridine, and bis[6(5,6-dihydrochelerythrinyl)] ether; and two amides: zanthomamide and lemairamide, were isolated from the stem bark of this plant. These compounds were screened in vitro against the chloroquine-sensitive 3D7 strain and the chloroquine-resistant FCM29 strain of P. falciparum. N-nomitidine was found to be inactive. 7,9-dimethoxy-2,3-methylenedioxybenzophenanthridine, lemairamide and zanthomamide showed weak activity with average IC50 values ranging from 45.6 μM to 149.9 μM. Bis[6-(5,6-dihydrochelerythrinyl)] ether was the most active of the tested compounds with mean IC50s of 14.9 ± 1.4 μM in FCM29 strain and 15.3 ± 3.4 μM in 3D7 strain (∼ 58 to - 1130 times less active than chloroquine respectively). The anti-Plasmodium activities of the tested alkaloids of Z. rubescens were low; and do not encourage the use of this plant as antimalarial.