PURPOSE:To easily obtain the subject compound exhibiting lipid oxidation suppressing action and antiinflammatory action, etc., and having high saponin/ isoflavone ratio by washing a raw material containing soya saponin with a specific solution and extracting with a (hydrated) alcohol. CONSTITUTION:A raw material containing soya saponin is washed with a solution having a pH maintained near the isoelectric point of the reserve protein. The pH is 3.5-6.5, especially 4-5 and the amount of the washing solution used in one washing operation is 5-20 pts.wt. per 1 pt.wt. of the saponin-containing raw material. The washing is repeated 2-3 times or more at 15-85 deg.C. The washed raw material is extracted with an alcohol or a hydrated alcohol. Especially preferably, the material is washed with an alcohol before the extraction treatment, i.e., before or after washing with a solution having a pH maintained near the isoelectric point of the reserve protein. The extraction temperature is -20 deg.C to +50 deg.C and the amount of the extraction liquid used in one extraction process is 5-10 pts. per 1 pt. of the raw material. The extraction is carried out once or more to obtain the objective compound.
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