Cytotoxicity and antiplasmodial activity of alkaloid extracts prepared from eight African medicinal plants used in Nigeria

Abstract

Objectives: To investigate the cytotoxicity and antiplasmodial activity of the ethanolic leaf extracts and alkaloid fractions of eight (8) African medicinal plants used in Nigerian traditional medicine.

Methods: In vitro antiplasmodial activity was assessed using 3D7 chloroquine-sensitive strain of Plasmodium falciparum maintained at 5% hematocrit (human type O-postive red blood cells) in complete RPMI 1640 medium, while cytotoxicity was determined by the micro assay technique using L929 animal cell fibroblasts by the lactate dehydrogenase method.
Results: Ethanolic leaf extracts of six out of the eight plants (Tridax procumbens, Ipomoea purpurea, Sida acuta, Senna alata, Phyllantus amarus, Azadirachta indica, Nauclea latifolia and Polyalthia longifolia) studied, were non-toxic (CC50 range:33.88-954.99µg/ml; Chloroquine, CQ: 79.43µg/ml), but Tridax procumbens and Sida acuta showed mild toxicity (CC50=23.99µg/ml for each plants) as judged by the standard reference (CC50: 30µg/ml= non-toxic). However all leaf extracts of the eight plants demonstrated significant (p <0.05) growth inhibition (IC50 range: 0.05-0.28µg/ml, CQ: 0.03µg/ml, standard reference: ≤5µg/ml=highly active) with very highly rated selectivity index, SI, values (range: 343-3990, CQ: 2648, reference: >10=selectable). In addition, the alkaloid fractions of the eight plants showed no toxicity (CC50:44.67-954.99µg/ml) and had very active antiplasmodial activity (IC50: 0.23-2.04µg/ml) with great selectivity index figures (22-2942).
Conclusion: This in vitro study confirms the antiplasmodial activity of these plants.