In vitro digestibility of the cancer-preventive soy peptides lunasin and BBI

J Agric Food Chem. 2007 Dec 26;55(26):10703-6. doi: 10.1021/jf072107c. Epub 2007 Nov 27.


Lunasin and BBI (Bowman Birk protease inhibitor) are bioactive soy peptides that have been shown to be effective suppressors of carcinogenesis in in vitro and in vivo model systems. Since they are subject to digestion in the gastrointestinal tract, we investigated here the stabilities of lunasin and BBI to digestion in vitro by simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). Samples containing lunasin and BBI of varying purities were subjected to in vitro digestion by SIF and SGF at different times and analyzed by Western blot. While the pure BBI reaction is stable after SIF and SGF digestions, the purified lunasin from soybean and synthetic lunasin are easily digested after 2 min in both in vitro digestions. In contrast, lunasin from soy protein containing BBI is comparatively stable after SIF and SGF digestions. Both lunasin and BBI are able to internalize into the cell and localize in the nucleus even after digestion, suggesting that some of the peptides are intact and bioactive. These data suggest that BBI plays a role in protecting lunasin from digestion when soy protein is consumed orally. The role of other soy protease inhibitors such as Kunitz Trypsin Inhibitor (KTI) cannot be excluded from these experiments.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Anticarcinogenic Agents / metabolism*
  • Digestion*
  • Gastric Juice / metabolism
  • In Vitro Techniques
  • Intestinal Mucosa / metabolism
  • Mice
  • NIH 3T3 Cells
  • Soybean Proteins / metabolism*
  • Trypsin Inhibitor, Bowman-Birk Soybean / metabolism*


  • Anticarcinogenic Agents
  • GM2S-1 protein, soybean
  • Soybean Proteins
  • Trypsin Inhibitor, Bowman-Birk Soybean