Contents and Bioactivities of Lunasin, Bowman−Birk Inhibitor, and Isoflavones in Soybean Seed

Abstract

It has been previously demonstrated that lunasin is a novel and promising cancer preventive peptide from soybean. The Bowman-Birk protease inhibitor (BBI) and isoflavones are well-studied substances from soy. This study evaluated the levels and bioactivities of these three compounds as affected by stages of seed development and sprouting under light and dark conditions. BBI and lunasin appear at 7 and 6 weeks, respectively, after flowering and increase as the seed matures. Daidzein and genistein both decrease during seed maturation. During sprouting under light, BBI increases up to the 6th day and decreases thereafter, disappearing at the 9th day after soaking. Under dark conditions, BBI increases up to the 7th day after soaking and decreases thereafter, disappearing at the 10th day. Lunasin starts to decrease at 2 days after soaking and disappears completely at 7 days under light and dark conditions. Daidzein and genistein increase continuously during the 10 days of soaking, and both increase more in the dark than under light conditions. Protein extracts from early seed development (2-5 weeks after flowering) suppress cell viability to a greater degree than those from later stages (6-9 weeks). Inhibition of foci formation by protein extracts from later stages is greater than those from earlier stages. Lunasin and BBI suppress foci formation more than the isoflavones. Sprouting decreases lunasin and BBI contents but increases isoflavones. Protein extracts from early soaking times inhibit foci formation more and suppress cell viability less than those from later soaking times. Light and dark conditions have no influence on the bioactivities of protein extracts. These data are useful in the preparation of soy fractions enriched in lunasin, BBI, and isoflavones and in making dietary recommendations.

Legume-Derived Bioactive Compounds for the Prevention and Treatment of Breast Cancer

“…A notable increase of lunasin content is observed during seed maturation while the opposite occurs during sprouting. Breeding conditions (light and dark cycles) do not seem to affect the content of this peptide (Park et al, 2005). Large-scale processing of soy also influences lunasin concentration which was observed to vary from 12 to 44 mg lunasin/g of flour among different U.S. commercially available soy proteins (Gonzalez de Mejia et al, 2004).…”

“…It was observed that during the process of seed maturation the contents of isoflavones decrease, whereas sprouting led to a continuing increase of isoflavone content. Interestingly, the protein extracts from the developing seeds showed clearly opposite effects on cell viability and inhibition of foci formation compared with those from sprouting seeds (Park et al, 2005). Individual differences in the absorption and metabolism of ingested isoflavones are another variable not usually addressed on breast cancer studies.…”

“…The concentration of PIs is affected by the stage of seed development and sprouting. For example, soy-derived BBI content increases during the process of seed maturation while it decreases with soaking time during sprouting (Park et al, 2005). PIs are classified in more than 20 families according to their inhibitory activity and structural features (Laskowski et al, 2000;Joanitti et al, 2006).…”

1997-2012: Fifteen Years of Research on Peptide Lunasin

“…This variation has been found to mainly depend on the soybean genotype, suggesting the possibility of selecting and breeding varieties of soybean with higher lunasin contents [16]. The stages of seed development have also been found to affect lunasin's concentration, and a notable increase occurs during seed maturation [18]. However, sprouting leads to a continuing decrease of lunasin with soaking time.…”

Lunasin, a Cancer Preventive Seed Peptide

“…Soybean seeds devoid of BBI also showed varying concentrations of lunasin ranging from 3.3 to 16.7 ng lunasin/mg seed indicating that lunasin is still produced on soybean seed even in the absence of BBI (de Mejia and Dia, 2010b). Analysis of lunasin in Korean soybean cultivar Taekwongkong showed that lunasin appears at 6 weeks after flowering (0.01 µg/g seed) with its highest level found at maturity with concentration of 0.12 µg/g seed (Park et al, 2005). Processing also affects lunasin concentration in soybean and soybean products.…”