Toxicity studies of Tithonia diversifolia A. Gray (Asteraceae) in rats.

OBJECTIVE: To investigate the toxicity of an ethanolic extract of the aerial parts of Tithonia diversifolia, used in Nigeria to treat malaria, in rats. MATERIALS AND METHODS: A 70% ethanol extract was administered orally to adult Wistar rats at various dosages (400-1600 mg/kg) and the animals sacrificed and various organs examined at a range of times from 30 min up to 24 h after administration. RESULTS: The studies showed a dose- and time-dependent toxic effect, which was reversible on the kidney and liver while there was no noticeable adverse effect on the morphology of the heart, spleen and brain. CONCLUSION: A 70% ethanol extract of the aerial parts of Tithonia diversifolia, which had previously been shown to reduce parasitemia in mice infected with Plasmodium, displayed kidney and liver toxicity at the lowest dose tested. The use of this plant extract against malaria therefore raises concerns over its safety.

Toxicity and mutagenic activity of some selected Nigerian plants.

The toxicity and mutagenic potential of most African plants implicated in the management of cancer have not been investigated. The ethanolic extracts of selected Nigerian plants were subsequently studied using the brine shrimp lethality tests, inhibition of telomerase activity and induction of chromosomal aberrations in vivo in rat lymphocytes. Morinda lucida root bark, Nymphaea lotus whole plant and Garcinia kola root were active in the three test systems. Bryophyllum calycinum whole plant, Annona senegalensis root, Hymenocardia acida stem bark, Erythrophleum suaveolens leaves and Spondiathus preussii stem bark were toxic to brine shrimps and caused chromosomal damage in rat lymphocytes. Ficus exasperata leaves, Chrysophyllum albidum root bark and Hibiscus sabdariffa leaves were non-toxic to all the three test systems. Chenopodium ambrosioides whole plant was non-toxic to brine shrimps and rat lymphocyte chromosomes but showed inhibition in the conventional telomerase assay indicating a possible selectivity for human chromosomes. The result justified the use of the first eight plants and Chenopodium ambrosioides in the management of cancer in south west Nigeria although they appear to be non-selective and their mode of action may be different from plant to plant. All these plants except Chenopodium ambrosioides are also mutagenic and cytotoxic.

Studies on the anti-inflammatory and toxic effects of the stem bark of Khaya ivorensis (Meliaceae) on rats.

Khaya ivorensis A. Chev. (Meliaceae) is a common feature in anti-malarial recipe prescribed by African traditional medical practitioners. Investigations have proved that Khaya species possesses some level of anti-plasmodial activity. Anti-inflammatory and toxicity studies were carried out on this plant using the Ugo Basile model 7140 and routine toxicity study methods, respectively, on adult wistar rats. The brain, spleen, heart, liver and kidneys were examined for dismorphological features, following oral administration of the ethanolic extract of K. ivorensis at the daily dose levels of 1000, 500 or 125 mg/kg for 7, 14 and 7 days after cessation of drug administration. The study showed that tissue toxicity, especially neurotoxicity was dose dependent, similarly the anti-inflammatory effect. The toxicity appeared to be reversible at lower doses. The wide margin between the therapeutic and toxic dosages makes the extract a possible safe drug in the management of malaria.

An investigation into the wound-healing properties of essential oil of Ocimum gratissimum linn.

OBJECTIVE: To investigate the effects of Ocimum oil and two antibacterial preparations, Cicatrin (GlaxoWellcome) and Cetavlex (AstraZeneca), on the healing of full-thickness excisional and incisional wounds, created under anaesthesia, on the back of test and control groups of adult albino rabbits. METHOD: Treatment was by topical application of the test substances onto the wound surface for 15 days. Observation continued for a further six days. Quantitative parameters of wound healing were determined daily. Swabs were taken from wound sites that appeared not to be healing for identification of wound contaminants and sensitivity tests. RESULTS: There was a marked enhancement in the inflammatory and proliferative phases of wound healing in the rabbits treated with Ocimum oil, suggesting that the oil facilitated the healing process to a greater extent than the control and reference products. Wounds treated with Cetavlex showed no sign of healing for eight days but responded to Ocimum oil after a three-day wash-out period. CONCLUSION: The essential oil Ocimum gratissimum can promote wound healing. However, large studies will need to be carried out using domestic pigs, followed by clinical trials on human wounds. DECLARATION OF INTEREST: None.