Tuber extracts were subjected to column chromatography technique. Eight fractions were obtained for ethyl acetate and twelve for ethanol. The brine shrimp lethality assay was used for assessment of toxicity. For the first time promising result was shown for ethanolic extract. The fractions F8, F9, F11 and F12 were represented high toxicity equal to 1.25, 7.98, 0.185, 0.041 µg/ml respectively. Also F7 and F10 showed toxic effects (89.9, 30.6 µg/ml) whereas F5 (LC50 807 µg/ml) was weakly toxic.
Ethyl acetate fractions showed moderate toxicity for F7 and F4 (299.7 and 375.4 µg/ml), while F2, F6 and F8 were weakly toxic. However F1 exhibited high toxic effect.
Ethanolic extract which is the highest bioactive extract was subjected to TLC analysis. Tests for secondary metabolites proved the presence of tannins, sterols and alkaloids. Also detection of triterpenes, sterols and flavonoid represented positive results.
The fractions F8, F9, F11 and F12 with high cytotoxic values were identified by gas chromatography/ mass spectrometry analysis. Thirty three compounds were detected; which were not recorded in any previous work in the available literature. Fraction 8 and 9 were found to be cytotoxic due to the presence of oleate and linoleate compounds; with more cytotoxicity in fraction 8 as a result of the additional presence of decenoic acid. Also, fraction 12 was more cytotoxic than fraction 11 and this was attributed to the presence of a proline derivative (Proline-N-methyl- butyl ester). This compound might be considered as the cause of the high toxicity of the fraction; since free proline was used as an inhibitor of breast cancer development. Surprisingly, M. pseudopetalosa tubers were used in the folkloric medicine of the natives of the South Blue Nile State in Sudan for the treatment of breast cancer growth without any knowledge of their chemical constituents.
Dr. Manal A. Ibrahim
Department of Botany, Faculty of Science and Technology, Omdurman Islamic University, Sudan.
El Bushra E. El Nur
Department of Botany, Faculty of Science, University of Khartoum, Sudan.
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