Acokanthera oppositifolia Lam (family: Apocynaceae) is a shrub or small tree with white latex, thick leathery leaves, attractive white flowers and red berries which turn dark purple when ripen. The latex, fruit and decoctions of the wood of this plant were widely used as arrow poisoning in southern Africa. These plant parts can sometimes be combined with Euphorbia latex, the sap of Acacia mellifera and the venom from the poison glands of snake and used as arrow poisoning. In the Northern Cape of South Africa, arrows poisoned with Acokanthera and snake venom were used to kill antelope and buffalo, and against enemies [1–4]. Poisoning of animals by this plant is surprisingly rare but cattle are sometimes at risk during droughts .
The leaves of this plant are used in the form of a snuff to treat headaches and in infusions for abdominal pains and convulsions and septicaemia. Powdered roots are administered orally or as snuff to treat pain and snake-bite and root decoctions are used against anthrax and tapeworm [4, 6, 7]. The leaves of this plant when boiled in water for ten minutes, strained and left to stand overnight are given to goats and sheep (200 ml) to treat heart water disease . Members of the genus Acokanthera contain several toxic cardiac glycosides such as ouabain [4, 8, 9]. Acovenoside, a cardiac glycoside, is the major toxic component of both A. oppositifolia and A. oblongifolia .
Adenia gummifera Harv of the family Passifloraceae is a distinctive woody climber with bright green stems and lobed leaves. Infusions are used as emetics and are said to help with some forms of depression. Though the thick, green stem is said to be very poisonous but is popular for treating of leprosy and malaria [4, 6]. Species of Adenia have been used as fish poisons  and have also been implicated in stock losses, homicide and suicide [1, 2, 4, 5]. The toxicity of Adenia species is due to the combination of a highly toxic protein, modeccin, and cyanogenic glycosides [4, 10–12]. Gummiferol, a cytotoxic polyacetylenic diepoxide was isolated from the leaves of Adenia gummifera by KB cytotoxicity-guided fractionation and this compound exhibited significant activity against the KB human cell line and a broad cytotoxic spectrum against other human cancer cell lines . KB or NFKB is nuclear activated kappa B, and is a transcription factor that has a key role in the induction of inflammatory and immune response .
Lipid peroxidation has gained more importance today because of its involvement in pathogenesis of many diseases like atherosclerosis, cancer, diabetes mellitus, myocardial infarction, and also ageing. Free radicals or reactive oxygen species (ROS) are produced in vivo from various biochemical reactions and also from the respiratory chain as a result of occasional leakage. These free radicals are the main agents in lipid peroxidation . Antioxidants thus play an important role of protecting the human body against damage by reactive oxygen species [16, 17]. Plants containing phenolic compounds, in particular flavonoids have been reported to possess strong antioxidant properties [18, 19].
In the present study, the methanol extracts of the stem of Acokanthera oppositifolia and Adenia gummifera were screened for antioxidant properties using in vitro standard procedures so as to assess the medicinal potential of these 2 plants and thus justify their folklore use.