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Indian Journal of Pharmacology, Vol. 36, No. 4, August, 2004, pp. 245-246 Research Letter Antiplasmodial activity of seven plants used in African folk medicine Bidla G, Titanji VPK, Joko B, Ghazali GEl, Bolad A, Berzins K Biotechnology Unit, Department of Life sciences, University of Buea, Cameroon Code Number: ph04080 Sir, Currently, there is a considerable increase in mortality caused by malaria due to the rapid spread of drug-resistant strains of P. falciparum. It is important, therefore, that new antimalarial drugs are developed to cope with the spread of resistance. In areas that are endemic for malaria in Africa a feverish patient may consume aqueous or alcoholic decoctions of barks, roots and leaves of different plants for relief form the clinical manifestation of malaria. China, on its part, added the artimisinin derivative of quinghoasu, (a chinese medicinal herbal plant product) to the antimalaria armamentarium. However, depressing reports show that more than 5% of 65 isolates from South East Asia are resistant to artemisinin and artesunate.[1] This further underscores the need to search for new antimalarials. Herein, we tested the in vitro inhibition assay on the chloroquine-sensitive (F32) laboratory strain of P. falciparum with extracts from seven plants used in Cameroon by some traditional healers. The plants, Achromanes difformis, Cleome rutidosperma, Cymbopogon citratus, Piper umbellatum, Mellotus appositofolius, Mangifera indicus and Annona muricata were collected from various parts of Cameroon and identified in the Limbe Botanic Garden. The voucher specimens were deposited at the University of Buea Herbarium. The leaves of each plant were dried, ground and soaked in 1:1 chloroform/methanol mixture. The soluble extracts were sieved and concentrated in a speed vacuum concentrator. The plant extracts were then weighed and dissolved in a malaria culture medium (10.49 g RPMI, 2 g NaHCO3, 6 g HEPES, 10% AB sera and 0.025 mg gentamycin per liter). M. indicus, A. difformis and M. appositofolius could not dissolve directly and were first dissolved in dimethyl sulphoxide (DMSO) and were finally diluted in the malaria culture medium to a final DMSO concentration of 0.16% w/v. Serial dilutions of each extract were tested on an asynchronous F32 strain of P. falciparum in 96 flat-bottom well plates in duplicate using chloroquine as a positive control. Serial dilutions of DMSO were used to check the effect of DMSO. A control containing everything but the extract was included and used in calculating the percentage inhibition of parasite growth. In addition to the extract, each test well contained 1% parasitized blood Group O of 2% hematocrit in malaria culture medium. Growth inhibition was assessed after 24 h of culture under conditions as previously described.[2] Assessment of inhibition was done by fluorescent microscopic examination of acridine orange-stained thin smears from each well on an eight-well multi-test slide. The number of parasitized erythrocytes was estimated by counting at least 6000 erythrocytes (25 microscopic fields) per well. Percentage inhibition was calculated as the number of parasites in the control well minus number of parasites in the test well divided by the number of parasites in the control well. Final percentage inhibition for each concentration of extract was obtained as mean of percentage inhibition for that concentration. The results are summarized in [Table - 1]. While Piper umbellatum and Mellotus appositofolius extracts had moderate activity against the parasite with 40 µg/ml of each giving 70% and 57% inhibition, respectively, extracts from Cymbopogon citratus, Mangifera indicus and Annona muricata were found to possess greater effects on the growth with 20 µg/ml of each giving 57.9%, 50.4% and 67% inhibition, respectively. Achromanes difformis and Cleome rutidosperma extracts showed the least antiplasmodial activity even with 40 µg/ml of each resulting in 32.4% and 31.6% inhibition, respectively [Table - 1]. It is not known whether the in vitro effect of these extracts against F32 P. falciparum is due to the concerted activity of their components. This issue could be addressed after chemical fractionation and isolation of the principles. Toxicology studies in animals may provide additional information on the feasibility of their use in humans. ACKNOWLEDGEMENT We acknowledge the advice of the late Prof. Johnson Ayafor on the plant extraction procedure, and of Mr. Nahou Ndam in identifying the plant extracts. This investigation received financial support from the University of Buea, Cameroon and the International Program in Chemical Sciences (IPICS) Uppsala University, Sweden. REFERENCES
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