Effective measures for controlling trypanosomiasis

Evaluation of the antiplasmodial properties of selected plants in southern Ethiopia

BACKGROUND

The majority of the Ethiopian population is at risk of malaria largely caused by Plasmodium falciparum. The resistance of the parasite to existing drugs is the main challenge in the control of the disease and thus new therapeutic drugs are required. In Ethiopia, people use different plant species to treat malaria. However, very few of them have so far been evaluated for their safety level and antimalarial activity. Thus, the aim of this study was to evaluate the safety and antimalarial activity of extracts of Ajuga integrifolia, Clerodendrum myricoides, Melia azedarach, Peponium vogelii and Premna schimperi, locally used by the Sidama people of Ethiopia to treat malaria.

METHODS

The safety level of 80 % methanol extracts of the plants were evaluated using standard acute toxicity test procedure. The antiplasmodial activity of 80 % methanol extracts of the plants were assessed in vivo using Swiss albino mice against chloroquine sensitive rodent malaria parasite, Plasmodium berghei, using the standard 4-day suppressive test procedure at doses of 200,400 and 800 mg/kg/day. The 80 % methanol extract of Ajuga integrifolia that exhibited better antimalarial activity was fractionated using different solvents and screened for its phytochemical constituents and evaluated in vivo for its antimalarial activity at doses of 100, 200 and 400 mg/kg/day.

RESULTS

All extracts given at the three different doses caused no lethal effect on mice in 24 h and within 10 days of observation. All extracts and fractions exhibited antimalarial activity in a dose dependant manner. The highest inhibition was exhibited by the crude extracts of A. integrifolia (35.17 %) at 800 mg/kg/day (P < 0.05). Among fractions of A. integrifolia, n-butanol fraction demonstrated the highest inhibition (29.80 %) at 400 mg/kg/day (P < 0.05). The extracts and fractions prolonged the survival time and prevented weight loss of the mice, but did not prevent PCV reduction. Phytochemical test on Ajuga integrifolia indicated the presence of alkaloids, flavonoids, saponins, terpenoids, anthraquinone, steroids, tannins, phenols and fatty acids.

CONCLUSIONS

Findings show that the plants are non-toxic and demonstrate antimalarial activity in a dose dependant manner suporting claims of their traditional therapeutic value for malaria treatment. However, further in-depth investigation is required to assess the potential of the plants towards the development of new antimalarial agent.

Antimalaria Effect of the Ethanolic Stem Bark Extracts of Ficus platyphylla Del

The antimalarial effect of the ethanolic stem bark extract of Ficus platyphylla Del was evaluated against Plasmodium berghei infection in mice. Nontreated, experimental control mice died of fulminant parasitemia from day 7 to 9 post-infection but mice treated with the extract at 300 mg/kg showed markedly reduced parasitaemia bouts of 43.50% and a mean survival time of 28 days postinfection. The plant extract prevented a drastic reduction in PCV showing its efficacy in ameliorating anaemic conditions in Plasmodium berghei-infected mice. Histological examination of liver tissues of treated and untreated mice further supports the antimalaria potential of this plant. This observation validates the traditional use of this plant for the treatment of malaria.

Complementary medicinal chemistry-driven strategies toward new antitrypanosomal and antileishmanial lead drug candidates

Trypanosomiases and Leishmaniases are neglected tropical diseases that affect the less developed countries. For this reason, they did not and still do not have high visibility in Western societies. The name neglected diseases also refers to the fact that they often received little interest at the level of public investment, research and development. The drug discovery scenario, however, is changing dramatically. After a period in which different socioeconomic factors have prevented massive research efforts in this field, such efforts have increased considerably in the very recent years, with significant scientific advancements. In this context, we have embarked on a new drug discovery project devoted to identification of new small molecules for the treatment of trypanosomal and leishmanial diseases. Two complementary approaches have been pursued and are reported here. The first deals with a structure-based drug design, and a privileged structure-guided synthesis of quinazoline compounds able to modulate trypanothione reductase activity was accomplished. In the second, a combinatorial library, built on a natural product-based strategy, was synthesized. Using whole parasite assays, different quinones have been identified as promising lead compounds. A combination of both approaches to hopefully overcome some of the challenges of anti-trypanosomatid drug discovery has eventually been proposed.