Full Length Research Paper

The importance of including toxicity assays when screening plant extracts for antimalarial activity

Sandra van Dyk¹*, Sharon Griffiths¹, Robyn L. van Zyl² and Sarel F. Malan¹

¹Pharmaceutical Chemistry, School of Pharmacy, North-West University, Potchefstroom, South Africa.

²Pharmacology Division, Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Parktown, South Africa.

*Corresponding author. E-mail: Sandra.VanDyk@nwu.ac.za.

Tel.:+27-018-299-2267. Fax: +27-18-299-4243.

Accepted 31 August, 2009

   Abstract

Identifying plant extracts as sources of antimalarial compounds needs to be addressed as numerous studies screen extracts without the means of eliminating extracts that are merely cytotoxic. Fifty-nine organic solvent extracts from South African plants were screened for antiplasmodial activity using the [3H]-hypoxanthine incorporation assay against the chloroquine-resistant Plasmodium falciparum.  Variable antiplasmodial activity and toxicity was observed. Extracts form Combretum erythrophyllum and Crinum bulbispermum, had IC50 values ≤ 1 mg/ml with the ethyl acetate extracts of C. bulbispermum roots and bulbs having values comparable to chloroquine (0.04 mg/ml). Nine extracts had toxicity indexes ≥ 100. Lycorine, isolated from C. bulbispermum was as active as chloroquine (IC50 of 0.03 mg/ml) and had a favourable security index.

Key words: Antiplasmodial, Combretum erythrophyllum, Crinum bulbispermum, Maytenus heterophylla, Pavetta gardeniifolia, lycorine.