Antimalarial activity of the root extract of Lobelia giberroa Hemsl. and its major constituent against Plasmodium berghei infection in mice.
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Date
2021-10
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Addis Abeba University
Abstract
Lobelia giberroa Hemsl. is an indigenous plant in Ethiopia. Ethiopian traditional healers use its
different parts to treat malaria, bacterial and fungal infections, and cancer. For treatment of
malaria, in particular, the traditional healers utilize the plant’s root parts. This study was carried
out to investigate the antimalarial activity of L. giberroa.
The roots of L. giberroa were extracted using 80% methanol and the hydroalcoholic extract was
successively fractionated with hexane, ethyl acetate, methanol and water. Chromatographic and
spectroscopic methods were used to isolate and identify the active compound from the methanol
fraction. Acute oral toxicity study was conducted on the hydroalcoholic extract, solvent
fractions, sub-fractions and the isolated compound. The hydroalcoholic extract and the isolated
compound were evaluated for antimalarial activity using the standard four-day suppressive
method, Rane’s and prophylactic tests in Plasmodium berghei infected albino mice. The solvent
fractions and sub-fractions from column chromatography were evaluated for antimalarial activity
using four-day suppressive method.
The hydroalcoholic extract, solvent fractions, subfractions and the isolated compound were
found to be safe at a dose of 2000 mg/kg. The hydroalcoholic extract of L. giberroa root and its
methanol fraction exhibited the highest antimalarial activity and significantly increased the mean
survival time of the treated mice. In fact, the hydroalcoholic extract exhibited 73.05%, 49.35%
and 43.16% parasitemia suppression for four-day suppressive test, Rane's test and prophylactic test, respectively. The methanol fraction demonstrated 64.37% parasitemia suppression for four-
day suppressive test.
The isolated compound, characterized as lobetyolin, suppressed the level of parasitaemia by
39.96, 53.46 and 68.21% at a dose of 25, 50 and 100 mg/kg, in standard four-day suppressive
test, respectively. Mice treated with 100 mg/kg/day lobetyolin survived longer (18.6 days) when
compared with negative control group (6.8 days).
In conclusion, the current study supports the traditional use of the plant for the treatment of
malaria and identified the main active compound lobetyolin, the potential to be an antimalarial
lead for further development. The active ingredient, lobetyolin, was also isolated for the first
time from the root of Lobelia giberroa. To the best of our knowledge, this is the first report on
the biological activity of L. giberroa.
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Keywords
Lobelia giberroa, antimalarial activity, in vivo, solvent fraction, Plasmodium berghei, lobetyolin