Antiprotozoal Activity of Extracts and a Major Compound from the Leaves of Ranunculus multifidus Forrsk.
No Thumbnail Available
Date
2021-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Abeba University
Abstract
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
Description
Keywords
Ranunculus multifidus, Traditional medicine, Antiplasmodial, Antileishmanial and cytotoxic/antiprotozoal ratios, Antitrypanosomal activities, Anemonin.