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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/1909

Advisors: Prof. Asrat Hailu
Dr. Ariaya Hymete
Copyright: 2008
Date Added: 13-Jan-2009
Publisher: 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 (L.) 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 xi 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.
Description: A thesis submitted to the School of Graduate Studies of the Addis Ababa University in partial fulfillment of the requirements for the Degree of Master of Science in Medicinal Chemistry.
URI: http://hdl.handle.net/123456789/1909
Appears in:Thesis - Teaching English as a Foreign Language

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