The isolation of soyasaponins by fractional precipitation, solid phase extraction, and low pressure liquid chromatography.
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Abstract
Bioactive soyasaponins are present in soybean (Glycine max). In this study, the isolation of soyasaponins in relatively pure form (>80%) using precipitation, solid phase extraction and reverse phase low pressure liquid chromatography (RP-LPLC) is described. Soy flour soyasaponins were separated from non-saponins by methanol extraction and precipitation with ammonium sulphate. Acetylated group A soyasaponins were isolated first by solid phase extraction followed by RP-LPLC (solvent: ethanol-water). Soyasaponins, from a commercial preparation, were saponified and fractionated into deacetylated group A and group B soyasaponins by solid phase extraction (methanol-water). Partial hydrolysis of group B soyasaponins produced a mixture of soyasaponin III and soyasapogenol B monoglucuronide. RP-LPLC of deacetylated group A soyasaponins separated soyasaponin A1 and A2 (38% methanol); of group B soyasaponins isolated soyasaponin I (50% ethanol); and of the partial hydrolysate separated soyasaponin III from soyasapogenol B monoglucuronide (50% ethanol). This methodology provides soyasaponin fractions that are suitable for biological evaluation.