Pharmacognosy

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Browsing Pharmacognosy by Author "Asres, Kaleab(Professor)"

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    Antiprotozoal Activity of Extracts and a Major Compound from the Leaves of Ranunculus multifidus Forrsk.
    (Addis Abeba University, 2021-06) Sirak, Betelhem; Asres, Kaleab(Professor)
    Protozoal diseases caused by the genera Leishmania, Plasmodium and Trypanosoma have devastating impact mostly on the poorest countries of the world due to their prevalence, virulence and drug resistance ability. This calls for the development and discovery of new effective and safe chemotherapeutic agents from alternative sources such as medicinal plants. This study aimed at investigating the antiprotozoal activity of Ranunculus multifidus Forrsk. (Ranunculaceae), a medicinal plant used to treat leishmaniasis, malaria and trypanosomiasis in several African countries. Fresh leaves of R. multifidus were subjected to maceration using 80% methanol and hydrodistillation to obtain hydroalcoholic extract (RM-M) and hydrodistilled extract (RM-H), respectively. Antileishmanial activities of the extracts were studied on clinical isolates of the promastigote and amastigote forms of Leishmania aethiopica and Leishmania donovani, whilst 4-day-suppressive, Rane’s and prophylactic tests were employed to investigate in vivo antimalarial activity against chloroquine sensitive Plasmodium berghei infected mice. In vitro and in vivo antitrypanosomal effects of the extracts were also investigated against Trypanosoma congolense field isolate. Results of the study revealed that both extracts were active against the studied protozoans, although RM-H demonstrated superior activity (p < 0.001) compared the RM-M. The IC 50 values of RM-H were 0.490 and 0.984 μg/ml against promastigotes and 1.49 and 1.84 μg/ml against macrophage amastigotes of L. aethiopica and L. donovani, respectively. At a dose of 35.00 mg/kg/day, RM-H demonstrated a chemosuppression value of 70% in 4-day-suppressive test. Furthermore, at a concentration of 4 mg/ml, RM-H ceased motility of T. congolense within 20 min. Further phytochemical analysis of RM-H using preparative thin layer chromatography (PTLC) led to the isolation of an α,β-unsaturated dilactone characterized as anemonin on the basis of FT-IR, APCI-MS, 1D- and 2D-NMR spectral assignments and also by comparison with the reported spectroscopic data of the same compound. Anemonin displayed significant (p < 0.001) antileishmanial activity with IC 50 of 1.33 nM and 1.58 nM against promastigotes and 1.24 nM and 1.91 nM against amastigotes of L. aethiopica and L. donovani, respectively. Anemonin was found to be relatively less toxic to macrophage cells with selectivity indices (macrophage cytotoxic/antileishmanial ratios) of 22 and 14, respectively. In a 4-day suppressive, Rane’s and prophylactic antimalarial tests, anemonin showed median effective doses (ED 50 s) of 2.17, 2.78 and 2.70 μM, respectively. At a concentration of 4 mg/ml, anemonin completely immobilized trypanosomes within 5 min of incubation, while the standard dug diminazene diaceturate immobilized the parasites within 10 min. In the in vivo antitrypanosomal assay, anemonin eliminates parasites at all the tested doses (8.75, 17.00 and 35.00 mg/kg/day) and prevented relapse. Results of the present study provided evidence that the leaves of R. multifidus possess genuine antileishmanial, antiplasmodial and antitrypanosomal activities, which may be attributed to the presence of anemonin. Thus, use of the plant in traditional medicine for the treatment of protozoal diseases seems to be well founded. values
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    In vivo Antimalarial Activity of the Hydroalcoholic Extract of Rhizomes of Kniphofia foliosa Hochst and Kniphofia insignis Rendle and their Constituents
    (Addis Abeba University, 2021-03) Alebachew, Yonatan; Asres, Kaleab(Professor); Dr.Bisrat, Daniel
    Malaria is a major public health problem that affects millions of people. The widespread emergence of antimalarial drug-resistant Plasmodium strains especially the recent emergence of artemisinin resistance poses a great challenge in future prevention and control of malaria. As a result, there is an urgent need to discover new, safe, and effective antimalarial drugs with novel mechanisms of action. In this regard, traditional medicinal plants have paramount importance as seen in the discovery of the forefront antimalarials. Kniphofia foliosa Hochst and Kniphofia insignis Rendle are endemic Ethiopian plants traditionally used to treat malaria in different parts of the country. In the present study the 80% methanol rhizome extracts of both plants and some of their constituents were investigated for their antimalarial activity. Fractionation of the hydroalcoholic extract of K. foliosa followed by preparative thin layer chromatography (PTLC) led to the isolation knipholone, dianellin, 10-knipholone gentibioside and 12-hydroxypentadec-9-en-1-yl methyl phthalate (HPMP) identified on the basis of spectroscopic (ESI-MS, 1D and 2D-NMR) data. Similarly, knipholone was isolated for the first time from crude phenolic fraction of K. insignis. The hydroalcoholic extracts of both plants, the phenolic fractions from K. foliosa and the compounds isolated thereof showed in vivo antiplasmodial activity (p<0.001) in Peters‘ 4-day suppressive test against P. berghi infected Swiss albino mice. Particularly, the hydroalcoholic extract of K. foliosa (400 mg/kg), 10- knipholone gentibioside (100 mg/kg) and knipholone (200 mg/kg) showed the highest activity with chemosuppression values of 61.52, 79.00 and 60.16%, respectively. From the dose-response plot, the median effective (ED 50 ) doses of 10-knipholone gentibioside, knipholone and dianellin were determined to be 29.04, 81.25 and 92.31 mg/kg, respectively. Molecular docking study revealed that knipholone had a strong binding affinity to Plasmodium falciparum l-lactate dehydrogenase (pfLDH) target. Results of the current study showed that the extracts and compounds of the plants possess genuine in vivo antimalarial effect against P. berghei in mice, supporting their traditional use for the treatment of malaria.