Soybeans soaking in warm water could become a new "green" source for production of a cancer-fighting substance now manufactured in a complicated and time-consuming industrial process, scientists are reporting in ACS' Journal of Agricultural and Food Chemistry.
Hari B. Krishnan and colleagues explain that the substance, Bowman-Birk Protease Inhibitor (BBI), has shown promise for preventing certain forms of cancer in clinical trials. Those human tests resulted from evidence of BBI's beneficial effects, including indications that BBI derived from the large amounts of soybeans in traditional Japanese diets might underpin low cancer mortality rates in Japan. However, the current method of extracting BBI from soybeans is time-consuming and involves harsh chemicals. The scientists set out to see if there might be a greener and more environmentally friendly way of obtaining BBI.
They found that soybean seeds incubated in water at 122 degrees Fahrenheit naturally release large amounts of BBI that can easily be harvested from the water. The protein appeared to be active, with tests showing that it stopped breast cancer cells from dividing in a laboratory dish. "The abundance of BBI in soybean seed exudates by incubating the seeds in warm water provides a simple and alternative method to isolate this low molecular weight protein," the researchers said.
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More information: Imbibition of Soybean Seeds in Warm Water Results in the Release of Copious Amounts of BowmanBirk Protease Inhibitor, a Putative Anticarcinogenic Agent, J. Agric. Food Chem., 2012, 60 (12), pp 31353143, DOI: 10.1021/jf205308w
Protease inhibitors play a protective role against pathogenic microorganisms and herbivorous insects. The two predominant protease inhibitors of soybean seeds are the Kunitz trypsin inhibitor (KTI) and BowmanBirk protease inhibitor (BBI). In this study, we report that soybean seeds incubated in warm water release large amounts of proteins into the surrounding media. Two-dimensional gel electrophoresis analysis of the seed exudates resulted in the separation of 93 distinct protein spots out of which 90 spots were identified by LC-MS/MS. The basic 7S globulin and the BBI are the two predominant proteins found in the soybean seed exudates. In addition to 7S and 11S seed storage proteins, others known to protect the seeds against pathogens and pests including KTI, peroxidase, α-galactosidase, and endo-1.3-β-glucanase were also identified in the seed exudates. Soybean seed exudate obtained by incubating the seeds in warm water was also able to inhibit the growth of human breast cancer cell line MCF-7. Since soybean seeds release large amounts of enzymatically active BBI when immersed in warm water, our procedure could be exploited as a simplified alternative method for the preparation of BBI concentrate which is being used as a cancer chemoprotective agent.