Abstract

Gardenia thunbergia, Siphonochilus aethiopicus, Schotia brachypetala, Acorus calamus, Withania somnifera, Elaeodendron transvalense, Hypoxis hemerocallidea, Vernonia adoensis and Acanthosperum australe are medicinal plants commonly used by traditional healers in South Africa to treat malaria. Aqueous, dichloromethane and methanol extracts of these plants were screened for larvicidal, antioxidant, in vivo antipyretic and in vitroantiplasmodial activities. The plant extracts either killed or reduced spontaneous movement inCulex quinquefascitus larvae after 24 h following treatment. Methanol extracts exhibited antioxidant (2,2-diphenyl-1-picrylhydrazyl free radical  (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging, Fe²⁺ chelating) activity, albeit to varying degree of efficiency. The dichloromethane and methanol extracts significantly (p≤0.05) reduced pyrexia with activity increasing in a concentration dependent manner. The antiplasmodial activity against chloroquine sensitive strain of Plasmodium falciparum (D10) showed that the methanol extracts of G. thunbergia, V. adoensis and the dichloromethane extracts of E. transvalense, A. australe and W. somnifera were active (IC₅₀ of 1.04 to 5.07 µg/ml). The results support the use of these plants in folk medicine and suggest that these plants contained constituents that could be developed as potent antimalarial drugs (mosquito larvicide, anti-fever and anti-plasmodial).

Key words: Antiplasmodial, larvicidal, antipyretic activity, medicinal plants.