In Vitro Efficacy Study of Some Selected Medicinal Plants Against Leishmania Spp
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Date
2008-07
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Addis Ababa University
Abstract
In this study, 112 gradient extracts in petroleum ether, chloroform and methanol as solvents
and three essential oils obtained from the root and aerial parts of ten Ethiopian medicinal
plants belonging to eight families were screened for their in vitro leishmanicidal activities
against clinical isolates of L. donovani and L. aethiopica. Those that showed antipromastigote
activity were further tested on promastigote and axenic amastigote forms of the
parasites. Toxicity study was done on human monocytic leukemia (THP-1) cell line and
erythrocytes in vitro. Assays were done using simple microscopic cell counting, fluorescence
or absorbance measurements as parameters. Phytochemical investigation was done on the
plant extracts using chemical test method.
Results of the preliminary screening test indicated that 78 extracts (69.6 %) had significant
growth inhibitory effect (> 90%) on at least one Leishmania spp. at the test concentrations
used. The non-polar and medium polar fractions were more active on both promastigote and
axenic amastigote forms than the polar ones. Fourty eight (61.5%) and 55 (70.5%) of the
extracts had EC50 values less than 10 μg/ml against axenic amastigotes of Leishmania
aethopica and Leishmania (L.) donovani respectively. Extracts with EC50 < 3 μg/ml were
obtained from petroleum ether extracts of Artemesia abyssinica (leaves), Croton
macrostachys (berries and leaves), Echnops kebericho (tuber), Erythrina brucei (stembark)
and chloroform extract of Echnops kebericho (tuber). Cytotoxicity and hemolysis tests
indicated that 71(91%) and 76 (97.4%) extracts respectively were safe (SI > 1) at EC50
values. The most cytotoxic extracts on THP-1 cells (SI < 1) were obtaned from Albizia
schimperiana (CC50 = 1.05 + 0.03 to 13.01 + 0.49 μg/ml) where as strongly haemolyzing
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extract (SI < 1) were obtained from polar fractions of Albizia schimperiana (stembark &
rootbark) and Aloe (stem). The anti-leishmanial effect of essential oils on promastigote (MIC
0.0097 to 0.1565 μl/ml) and axenic amastigote (EC50’s 0.018 + 0.006 to 53.36 + 7.65 nl/ml)
of L. donaovani and L. aethopica was comparable or at times higher than that of the standard
anti-leishmanial drugs. The oils also had low to moderate toxicities (SI= 0.8 to 44) on THP-1
cell line (CC50’s 0.40 + 0.01 to 350 + 5.0 μl/ml) and erythrocytes (LC50’s 0.70 + 0.27 to 2.62 +
1.0). Essential oil from Echnops kebericho had the highest activity against Leishmania and
also highest cytotoxicity on THP-1 cells. Essential oil from Artemesia abyssinica showed the
highest haemolytic effect. The phytochemical screening demostrated presence of alkaloids,
polyphenols, tannins, flavonoids, saponins, anthraquinones, coumarins, terpenes, phytosterols
and whithanoids in different fractions and most of these class of phytochemicals were
previously reported to have ant-leishmanial activity.
Findings from this study revealed that extracts from Artemesia abyssinica, Croton
macrostachys, Echnops kebericko and Erythrina brucei and all the essential oils have
potential anti-leishmanial activities and this warrants fractionation and isolation of active
constituents for further in vitro/in vivo evaluation.
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Keywords
Medicinal Plants