Isolation, identification and toxicity of saponin from different legumes

Abstract

Saponin extracts were prepared from peas, beans and soya bean seeds by four different methods. Two biological assays were developed for measuring toxicity of crude saponin extracts based on haemolytic activity and fish mortality. The results indicated that saponin extracts were able to lyse red blood cells with different velocity. The haemolytic activity of bean extracts were significantly higher ( P < 0·05) than those of soya bean and pea extracts. Sensitivity of blood cells to crude saponin extracts was detected by sheep and rabbit blood cells. The highest haemolytic activities of sheep and rabbit blood cells were 30sd0 and 6·24 mg saponin equivalent/g legume sample, respectively. As well as being potent haemolysins, saponin extracts were lethal to guppy fish. The lethal dose (LD 50) of saponin to guppy fish was 150 μg/ml. The ethanol/water (1 : 1) extracts showed the highest toxicity as revealed by both assays. Thin-layer chromatography (TLC) of crude saponin extract from beans separated it into six fractions, whereas pea and soya bean were separated into seven and six fractions, respectively. The TLC pattern of standard saponin indicated the presence of two main spots with R f 0·75–0·85. Further purification of crude saponin extracts from legumes by silica gel column chromatography increased the haemolytic activity of the active principle 5·7, 5·1 and two-fold for bean, soya bean and pea extracts, respectively.