New Tool for Mining Phytochemicals From Soy

Saponins—natural compounds found in soybeans and a wide variety of plants—are typically used as foaming agents in shampoos and cleaning products. Now, a new method for extracting saponins could shed new light on their health-promoting potential in both whole soybeans and processed soy foods.

Agricultural Research Service (ARS) chemist Mark Berhow spearheaded the method's development as part of his collaboration with other research labs to ascertain the anticancer potential of group-A and -B saponins, isoflavones and other phytochemicals in soy. Berhow works in the ARS National Center for Agricultural Utilization Research (NCAUR) at Peoria, Ill.

For example, in a 2005 in-vitro study, Berhow and University of Illinois professor Keith Singletary showed that exposing cancerous human colon cells to group-B saponins reduced the cells' growth by 27 to 68 percent. Through mode-of-action studies, the scientists determined that the saponins acted as "chemoprotectants" that prompted cancerous cells to self destruct.

Berhow also recently teamed with ARS colleagues and University of the Incarnate Word (UIW) scientists to improve the extraction of saponins and isoflavones from whole soybeans and processed foods like soy flour. One problem that has plagued saponin studies in the past has been the difficulty of purifying sufficient amounts of saponins for analysis, notes Berhow.

To address the problem, Berhow, UIW scientist Suk Bin Kong, and NCAUR scientists Sandra Duval and Karl Vermillion chose a combination of steps that other laboratories could easily follow and adapt to their studies. The method involves grinding dried beans, defatting them and using solvents to extract the saponins. The final step uses high-pressure liquid chromatography to identify individual saponins based on their molecular weights. Soy isoflavones can be similarly obtained with the process, according to Berhow.

In another project, Berhow and Iowa State University professor Ruth MacDonald are assessing the effects of isolated soy protein, isoflavones and saponins on the development of cancerous cells in the colons of mice used as animal models.

ARS is the U.S. Department of Agriculture's chief scientific research agency.