Preparative isolation of isoflavones from soy and red clover

Abstract

Numerous studies have demonstrated the potential of isoflavones occurring in soy (Glycine max L.) and red clover (Trifolium pratense L.) to alleviate climacteric complaints. They have also shown beneficial effects on the cardiovascular system and in the prevention of osteoporosis. As a result, several companies offer nutraceuticals based on soy or red clover extracts. The aim of the present study was the isolation of pure isoflavones on a preparative scale, in order to obtain standards for biological tests and for the quantification of isoflavones in nutraceuticals and foods. High‐speed countercurrent chromatography, a special type of liquid–liquid partition chromatography, was applied to the preparative isolation of isoflavones. By using this technique the major monoglucosylated and acetylated isoflavones from soy extracts were obtained after a cleaning‐up step on Amberlite XAD‐7 material. Furthermore, it was possible to isolate isoflavone aglycones as well as glycosides from a red clover extract. Purity and identity of the isolated isoflavones were confirmed by HPLC with DAD, HPLC‐ESI multiple‐MS, and NMR spectroscopy.