Complete Quantification of Group A and Group B Soyasaponins in Soybeans

Mark A. Berhow,*† Suk Bin Kong,‡ Karl E. Vermillion,† and Sandra M. Duval†
National Center of Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, Illinois 61604, and Chemistry Department, University of the Incarnate Word, 4301 Broadway, San Antonio, Texas 78209
J. Agric. Food Chem., 2006, 54 (6), pp 2035–2044
DOI: 10.1021/jf053072o
Publication Date (Web): February 28, 2006
Copyright © 2006 American Chemical Society
*

 To whom correspondence should be addressed. Tel:  +011-309-681-6347. Fax:  +011-309-681-6524. E-mail:  berhowma@ncaur.usda.gov.

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†

 U.S. Department of Agriculture.

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‡

 University of the Incarnate Word.

Abstract

A combination of high-pressure extraction and preparative chromatography was used to purify the group A and group B soyasaponins from soy germ for use as analytical standards and for use in biological assays. A standardized sample preparation and extraction method was developed for the analysis of phytochemicals found in soy and processed soy products, which is reproducible in other laboratories. The extracts can be analyzed with standard liquid chromatography−mass spectrometry and high-performance liquid chromatography methods to identify and quantitate the group A and group B forms of the soy saponins, as well as the soy isoflavones. Complete saponin analysis of the extracts prepared from soy germ (hypocots), hulls, and cotyledons shows that a significant portion of the saponins is concentrated in the germ. The germ contains nearly all of the group A soyasaponins, while the group B soyasaponins are nearly equally distributed between the germ and the cotyledons. The hulls contain little of either isoflavones or saponins. Whole (full fat) soybeans grown on a tract in central Illinois in 2003 contain approximately 4−6% saponins on a weight basis, of which about one-fifth or less of the total saponin content are group A soyasaponins; the balance is group B soyasaponins.

Keywords: Soy; Glycine max; germ; hull; cotyledons; purification; analysis; saponins; isoflavones; phytochemicals

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History

  • Published In Issue March 22, 2006
  • Received for review December 8, 2005. Revised manuscript received February 3, 2006. Accepted February 3, 2006. Funding for S.B.K.'s summer fellowship was provided by the U.S. Department of Agriculture's Hispanic-Serving Institutions (HSIs) Fellows Program.

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