Evaluation of the Antiplasmodial and Antimicrobial Properties of the Medicinal Plants Rumex nepalensis Spreng and Centella asiatica L
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Date
2017-06
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Addis Ababa Universty
Abstract
Infectious diseases are the major health problems in the world particularly in developing
countries. To combat this problem various drugs, antibiotics and vaccines have been developed
through time, but these successes have been challenged by the emergence of drug resistant
pathogens. In Ethiopia, most people use traditional medicinal plants which are the natural source
of medicine to treat different diseases. However, traditional healers in this country apply
medicinal plants to heal different infections without scientific prescription and optimization of
the right doses. This study was conducted to investigate antiplasmodial, antibacterial, antifungal
properties, evaluate acute toxicity and possibly isolate the active compounds of two widely used
medicinal plants: Rumex nepalensis Spreng and Centella asiatica L. The two plants were
collected from Dejen District, Northen part of Ethiopia, and air dried in shade. The specific plant
parts (leaves, roots. aerial parts) were separately ground into powder. Each plant powder was
soaked in water, methanol and hexane in separate Erlenmeyer flasks and placed on shaker of 120
rpm for 72 hours. The extracts were concentrated in rotary evaporator and by lyophilizer
(aqueous extract). The crude extracts of water, methanol and hexane of the two plants were
tested for antiplasmodial, antimicrobial activities, acute toxicity and screened for
phytochemicals. The higher antimicrobial performing extract, methanol extracts of the roots of
R. nepalensis and further fractionnated by solvent-solvent extraction (hexane, chloroform,
ethanol, water and methanol) and these fractions were evaluated on pathogenic microorganisms
(Plasmodium berghei, Esherchia coli, Pseudomonas aeruginosa, Shigella flexneri and
Salmonella typhimurium, Klebsiella pneumonia, Candida albicans). Similarly the best fraction,
ethanol fraction, was further fractionnated by column chromatography (CC) and tested for
antiplasmodial and antimicrobial activities. Furthermore, column Chromatographic profiles of the roots of R. nepalensis were analyzed by thin layer chromatography (TLC). The crude
methanol and hexane extracts of the root, the leaf extracts of R. nepalensis and the aerial parts of
C. asiatica at the highest concentration of 5000 mg/kg BW was not toxic to the albino mice.
Furthermore the phytochemical screening of the R. nepalensis revealed the presence of
flavonoids, alkaloids, glycosides, triterpenoids, sterols, saponin and tannin. On the other hand,
phytochemical screening of C. asiatica showed the presence of flavonoids, alkaloids, glycosides
and saponin, triterpenoids and sterols but tannins were not clearly observed. CC and TLC
profiles of ethanol fraction of the roots of R. nepalensis showed the presence of chrysophanol,
emodin and 5 undefined compounds. The crude extracts of water, methanol and hexane of the
two plants had shown suppression to Plasmodium berghei in vivo in mice. Particularly, the crude
extracts of water, methanol and hexane of the roots of R. nepalensis had significantly higher day-
4 suppressive effect 52.00 %, 59.90 % and 39.30 % respectively than the negative control (2%
DMSO). But all extracts had significantly lower day-4 suppressive level than the positive
control, chloroquine in P. berghei infected albino mice. The ethanol fraction of the roots of R.
nepalensis showed higher plasmodium percent suppression in vivo in albino mice (70.08 %)
compared to water (54.31 %), chloroform (19.61 %) and methanol (10.27 %) suppression at 500
mg/kg body weight (BW). Similarly the mean survival time value of the mice administered with
ethanol fraction was significantly higher than all extracts (water, chloroform and methanol) at
500 mg/kg BW and negative control, 2% DMSO treated mice. More specificaly the ethanol
fraction of the roots of R. nepalensis fractionnated by column chromatography in ethyl acetate:
methanol (1:1) v/v showed 73.66% plasmodium suppression in vivo in albino mice at 300 mg/kg
BW. The re-fractionnated ethyl acetate: methanol fraction by column chromatography in
methanol increased its suppression to 79.66% at 150 mg/kg BW. In the antimicrobial test, the ethanol fraction of the roots of R. nepalensis showed zone of inhibition for P. aeruginosa
(19.33±0.33 mm), S. aureus (18.03±0.14 mm) and S. flexneri (12.77±0.15 mm) and S.
typhimurium (8.33±0.33 mm) at 6 mg/well by using agar well diffusion method compared to the
negative control (2% DMSO) which have no inhibition zone on the tested bacteria. However, the
positive control (teteracyclin and chloramphenicol) significantly higher bacterial inhibition than
ethanol fraction of the roots of R. nepalensis. From the result obtained it can be concluded that
the five undefined compounds played a role in synergizing the atiplasmodial, antibacterial and
antifungal activities of the roots of R. nepalensis. In conclusion this work has demonstrated the
high potential of R. nepalensis and C. asiatica as sources for further exploitation of
antiplasmodial, antibacterial and for use in herbal medicine.
Key words: antibacterial, antifungal, Plasmodium suppression, phytochemical screening,
toxicity
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Keywords
Antibacterial, Antifungal, Plasmodium suppression, Phytochemical screening, Toxicity