In vivo antimalarial activity, toxicity and phytochemical screening of selected antimalarial plants.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria continues to kill over a million people each year and in many populations affected by malaria, conventional drugs are often unaffordable or inaccessible. Historically, plants have been a prominent source of antimalarial drugs. Those plants currently used by indigenous people to treat malaria should be documented and investigated as potential sources of new antimalarial drugs. AIM OF THE STUDY: To investigate in vivo antimalarial activity, toxicity and carry out phytochemical screening of selected plants which have been used in traditional medicine for the treatment of malaria. MATERIALS AND METHODS: Organic and water extracts of four medicinal plants used for the treatment of malaria in traditional health systems of Msambweni people in Kenya were tested for antimalarial activity against Plasmodium berghei and brine shrimp lethality. They were also screened for their major phytochemical constituents. RESULTS: Aqueous extract of the stem bark of Adansonia digitata exhibited highest chemosuppression of parasitaemia, >60% in a murine model of Plasmodium berghei infected mice. Aqueous and organic extracts of Launaea cornuta and Zanthoxylum chalybeum were toxic to the brine shrimp (LD50<1000µg/ml) while aqueous and organic extracts of Adansonia digitata and aqueous extracts of Canthium glaucum were not toxic to brine shrimp (LD50>1000µg/ml). Phytochemical screening revealed the presence of alkaloids and flavonoids in all the crude extracts of the selected plant species studied. Sesquiterpene lactones and saponis were present in organic extracts but absent in the aqueous extracts of Adansonia digitata, Canthium glaucum, Launaea cornuta and Zanthoxylum chalybeum. CONCLUSION: The results showed that the crude extracts of Adansonia digitata and Canthium glaucum demonstrated promising antimalarial activity and there is potential for isolation of lead compounds from their extracts.

Evaluation of herbs as potential drugs/medicines.

Herbal drugs have been used since ancient times as medicines for the treatment of a wide range of diseases, for both human and livestock. A study conducted in the Lake Victoria Basin Kenya revealed vast knowledge and reliance on traditional medicine as a source of healthcare. The study documented 34 medicinal plant species distributed among 21 botanical families and 34 genera, used in the management of human ailments. The highest numbers of species were from the families Asteraceae and Leguminosae. The most commonly harvested plant parts were leaves (46.51%) and roots (34.88%). The most common growth forms utilised were herbs (40.54%) followed by shrubs (27.03%). The major methods of herbal drug preparation were concoction (31.03%) and decoction (24.14%) administered mainly through oral and dermal routes, (64.29%) and (32.14%) respectively. The use of herbal drugs as mixtures was reported to be a common practice by the herbal practitioners; 57.14% of the preparations were dispensed as mixtures while 42.86% of the preparations composed of single plants. A rich knowledge of medicinal plants was recognized and phytochemical and bioactivity analyses of these herbal plants are recommended to determine their safety and efficacy.