Antitrypanosomal Activity of Selected Medicinal Plants against Trypanosoma congolense Field Isolate
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Date
2023-11
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Addis Ababa University
Abstract
Trypanosomiasis is among the most common neglected tropical diseases (NTDs) of humans and
animals. It mainly affects countries with poor health infrastructures and the actual disease burden
is unknown. It is estimated that 10 to 14 million heads of cattle, goats and a million equines are at
risk of contracting the disease in Ethiopia. Trypanocidal drugs are currently facing a number of
problems like toxicity, resistance and availability issues. These limitations have prompted the
search for new, safe and effective drugs. In Ethiopia, the seed of Brucea antidysentrica, the leaf of
Clematis hirsuta and the root of Rumex nepalensis are used to treat animal trypanosome infection
by traditional healers. The study aimed to investigate the in vitro activity of selected medicinal
plants against Trypanosoma congolense and in vivo antitrypanosomal activity of the most active
plant. The plants were extracted by 80% methanol maceration and tested for their in vitro activity
using motility test (at concentration of 4, 2, 0.4 and 0.1 mg/ml) for cessation or reduction in
motility of trypanosomes followed by monitoring for loss of infectivity of mice. After 12 days of
T. congolense field isolate inoculation of mice and peak parasitaemia level (~108 trypanosomes/ml)
was reached, 80% methanol extract of roots of Rumex nepalensis was administered at doses of
100, 200 and 400mg/kg orally once daily for 7 days.
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The packed cell volume, body weight, parasitaemia level and rectal temperature were used as
parameters for monitoring in vivo activity by comparing with the positive control: 28 mg/kg dose
of diminazene aceturate and negative control: 1% Dimethyl Sulfoxide (DMSO) treated groups.
The statistical significance was determined by one-way ANOVA followed by Tukey post hoc test.
The motility of T. congolense was ceased by R. nepalensis, B. antidysentrica, and C. hirsuta at
concentration of 4mg/ml within 10, 25 and 35min, respectively. Mice treated with 4mg/ml of R.
nepalensis and Diminazene aceturate caused loss of infectivity of trypanosomes in mice for 21
days after the inoculation of the in vitro mixtures. The 80% methanol extract of roots of Rumex
nepalensis at dose of 2000 mg/kg did not show acute toxicity signs and symptoms. Highly
significant (p<0.001) reduction in pre-treatment parasitaemia from (7.30±0.06) to (2.70±1.21)
trypanosomes/ml on day 8 of treatment and increased PCV from (45.83±0.31) to (48.00±0.26) and
body weight increased from (22.63±0.55) to (26.60±1.14) gram at day 14 was recorded in mice
treated with 80% methanol extract of roots of R. nepalensis at the dose of 400 mg/kg. The results
revealed that the selected medicinal plants showed antitrypanosomal activity that supports their
traditional claim and prompted further studies on isolated active substances from these plants.
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Keywords
Antitrypanosomal activity, Trypanosoma congolense, Rumex nepalensis, Brucea antidysentrica, Clematis hirsuta.