Anti-protozoan activities of Harungana madagascariensis stem bark extract on trichomonads and malaria.

AIM OF THE STUDY: The ethanolic stem bark extract of Harungana madagascariensis (Hypericaceae), (Choisy) Poir were evaluated for their activities on Trichomonas gallinae (Rivolta) Stabler isolated from the pigeon (Columba livia). It was also tested for their anti-malarial activity on N67 Plasmodium yoelii nigeriensis (in vivo) in mice and on Plasmodium falciparum isolates in vitro. MATERIALS AND METHODS: The anti-trichomonal screening was performed in vitro using Trichomonas gallinae culture. The minimum lethal concentration (MLC) is the lowest concentration of the test extract in which no motile organisms were observed. The anti-malarial effects were determined in-vivo for suppressive, curative and prophylactic activities in mice receiving a standard inoculum size of 1 x 10(7) (0.2 ml) infected erythrocytes of Plasmodium yoelii nigeriensis intraperitoneally, and the in vitro was performed against 3 isolates of Plasmodium falciparum in a candle jar procedures. RESULTS: The IC(50) of the extract and metronidazole (MDZ) (Flagyl) on Trichomonas gallinae at 48 h are 187 and 1.56 microg/ml. The IC(50) of the extract, chloroquine (CQ) and artemether (ART) on Plasmodium falciparum are between 0.052 and 0.517 microg/ml for the extract and 0.021 and 0.0412 microg/ml for ART and CQ, respectively. The actions of the extract in in vivo study on Plasmodium yoelii nigeriensis showed that in both suppressive and prophylactic tests the percentages chemo-suppressive were between 28.6-44.8% and 30.2-78.2% respectively, while only 80 mg/kg of the extract reduced the parasitaemia level when compared to the control and the standard drugs in curative test. CONCLUSIONS: Harungana madagascariensis stem bark extract therefore exhibited significant anti-protozoan effects against Trichomonas and Plasmodium both in vivo and in vitro.

In vitro antimalarial activity of methylene blue against field isolates of Plasmodium falciparum from children in Southwest Nigeria.

BACKGROUND & OBJECTIVES: Methylene blue (MB), a thiazine dye is used in the treatment of various methemoglobinaemias. However, sporadic reports have shown some antimalarial therapeutic effect when administered to patients with clinical manifestations of malaria. The inhibitory concentration of schizont maturation and antimalarial activity of MB have not been fully elucidated. The present study therefore aimed at determining the antimalarial activity of MB in Plasmodium falciparum isolates obtained from children with malaria using standard in vitro drug susceptibility test. METHODS: Twenty children (8 boys and 12 girls) within the age range 4.5-11.5 yr were enrolled into the study and 2 ml of blood withdrawn aseptically. The standard microtest technique of schizont inhibition assay was used to culture fresh isolates obtained from P. falciparum infected patients. Chloroquine (CQ) and quinine (QN) were used as reference standards for in vitro drug susceptibility tests. RESULTS: The mean 50 per cent inhibitory concentration (IC(50)) values were 9.59 +/- 3.25nM, 196 +/-21.11nM and 607 +/- 27.41nM for MB, CQ and QN respectively. Ten of the 14 isolates were sensitiveto MB, 11 were sensitive to CQ while nine were sensitive to QN. Three isolates were resistant to CQ,and of these, two were sensitive to MB and one was sensitive to QN. INTERPRETATION & CONCLUSION: This preliminary study showed that MB has high antimalarial activity comparable with CQ and QN and may be used as a potent schizonticidal drug against CQ-resistant isolates.