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

Current research status on the structure, physicochemical properties, bioactivities, and mechanism of soybean-derived bioactive peptide lunasin

Since the 21st century, chronic diseases have become a worldwide health problem due to their high morbidity and mortality. Soybean bioactive substances, especially soybean peptides, are considered to have health benefits beyond nutritional effects. As the most studied peptide in soybean, lunasin has been proven to exert beneficial effects on various chronic disorders. This review summarizes the content of lunasin in soybeans, soy derived foods, and other crops, as well as its structural characteristics and bioavailability. Moreover, we focused on the relationship between the physicochemical characteristics and structural composition of lunasin, and its significance for the bioactivities of lunasin. Ultimately, the therapeutic effects of lunasin on cancer, oxidative stress, inflammation, immune response, and hyperlipidemia were described, as well as the molecular mechanisms involved in these impacts. In conclusion, lunasin is a promising multifunctional bioactive peptide, yet further research is required to optimize and expedite its application in the food industry.

Design of Experiments Approach for the Development of a Validated UPLC-Q-ToF/MS Method to Quantitate Soy-Derived Bioactive Peptide Lunasin in Rabbit Plasma: Application to a Pharmacokinetic Study

A novel ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometric (UPLC-Q-ToF/MS) method for quantifying soy-derived bioactive peptide lunasin in rabbit plasma was developed using design of experiments (DoE) methodology. Lunasin and Neuropeptide Y as an internal standard (IS) were separated on a BEH-C18 column (50 mm × 2.1 mm, 1.7 μm particle size) using 0.1% formic acid solution and acetonitrile as mobile phase delivered for 9 min at a constant flow rate of 0.4 mL/min in gradient mode. The Q-ToF mass spectrometer, equipped with electrospray combined ionization (ESCi) interface, was operated in positive ion mode, and the quantifier ions of lunasin and IS were at m/z 838 and m/z 602, respectively. The lower limit of quantification (LLOQ) was 34.6 ng/mL, and the assay was linear over the concentration range 35-10,000 ng/mL. The accuracy was within a range from 86.7% to 88.9% in terms of mean recovery (R), and the intraday and interday precisions in terms of relative standard deviation (RSD) were < 2.65% and < 6.22%, respectively. The method was successfully applied to a pharmacokinetic study involving oral administration of lunasin-rich processed soybeans (6.56 and 19.1 g/kg) to rabbits.

"Top-down" overexpression optimization of butelase-1 in Escherichia coli and its application in anti-tumor peptides

Butelase-1, the fastest known Asn/Asp-specific peptide ligase capable of catalyzing peptide ligation and cyclization, holds promising application prospects in the fields of food and biology. However, limited research exists on its recombinant expression and potential applications in peptide drugs. In this study, the activity of recombinantly-produced butelase-1 was enhanced by co-expressing it with a molecular chaperone in the SHuffle T7 strain. By introducing single or multiple synonymous rare codons at the beginning of the coding regions of beta-strand or alpha-helix, in combination with ribosomal binding site engineering, the activity of butelase-1 could be further improved. Consequently, the butelase-1 with a specific activity of 386.93 U/mg and a catalytic efficiency of 11,048 M-1 s-1 was successfully prepared in E. coli, resulting in a total activity of 8183.54 U/L and a yield of about 100 mg/L. This optimized butelase-1 was then used to efficiently cyclize the redesigned anti-cancer peptide lunasin, leading to enhanced bioavailability and anti-cancer effects. Overall, this study not only provided valuable biotechnology strategies for improving the recombinant expression of butelase-1 but also demonstrated a successful application for enhancing the biological efficacy of anti-cancer peptides.

Lunasin as a Promising Plant-Derived Peptide for Cancer Therapy

Cancer has become one of the main public health problems worldwide, demanding the development of new therapeutic agents that can help reduce mortality. Lunasin is a soybean peptide that has emerged as an attractive option because its preventive and therapeutic actions against cancer. In this review, we evaluated available research on lunasin’s structure and mechanism of action, which should be useful for the development of lunasin-based therapeutic products. We described data on its primary, secondary, tertiary, and possible quaternary structure, susceptibility to post-translational modifications, and structural stability. These characteristics are important for understanding drug activity and characterizing lunasin products. We also provided an overview of research on lunasin pharmacokinetics and safety. Studies examining lunasin’s mechanisms of action against cancer were reviewed, highlighting reported activities, and known molecular partners. Finally, we briefly discussed commercially available lunasin products and potential combination therapeutics.

Soybean proteins/peptides: A review on their importance, biosynthesis, vacuolar sorting, and accumulation in seeds

Soybean is one of the most important sources of plant protein and is known for its wide range of agricultural, food, and industrial applications as well as health benefits. Interest in soybean proteins has been steadily growing as progressively more applications and benefits are discovered. This review article is focused on the major seed storage proteins of soybean, their three-dimensional structures, their nutritional importance and bioactive peptides, cellular synthesis, and accumulation in seeds. This will also summarize past efforts in the recombinant production of foreign proteins or bioactive peptides in soybean seed.

Potential Health Benefits Associated with Lunasin Concentration in Dietary Supplements and Lunasin-Enriched Soy Extract

Lunasin has demonstrated antioxidative, anti-inflammatory, and chemopreventive properties. The objectives were to evaluate the concentration of lunasin in different lunasin-based commercial dietary supplements, to produce a lunasin-enriched soy extract (LESE) using a two-step pilot-plant-based ultrafiltration process, and to evaluate their biological potential in vitro. LESE was produced using 30 and 1 kDa membranes in a custom-made ultrafiltration skid. Lunasin was quantified in eight products and LESE. Lunasin concentrations of the lunasin-based products ranged from 9.2 ± 0.6 to 25.7 ± 1.1 mg lunasin/g protein. The LESE extract contained 58.2 mg lunasin/g protein, up to 6.3-fold higher lunasin enrichment than lunasin-based dietary supplements. Antioxidant capacity ranged from 121.5 mmol Trolox equivalents (TE)/g in Now® Kids to 354.4 mmol TE/g in LESE. Histone acetyltransferase (HAT) inhibition ranged from 5.3% on Soy Sentials® to 38.3% on synthetic lunasin. ORAC and lunasin concentrations were positively correlated, and HAT and lunasin concentrations were negatively correlated (p < 0.05). Melanoma B16-F10 and A375 cells treated with lunasin showed dose-dependent inhibitory potential (IC50 equivalent to 330 and 370 μM lunasin, respectively). Lunasin showed protein kinase B expression (57 ± 14%) compared to the control (100%) in B16-F10. Lunasin concentration found in commercial products and lunasin-enriched soy extract could exert benefits to consumers.

Lipopolysaccharide neutralizing protein in Miso, Japanese fermented soybean paste

Miso, a fermented paste made from soybeans, is used traditionally for seasoning of food. It has been a protein and nitrogen source since ancient times in Japan because of its high nutritional value. Furthermore, it has important health functions such as the estrogen-like activity of isoflavones, anti-oxidation, and angiotensin-converting-enzyme inhibition activity. Moreover, it has activity for neutralization of lipopolysaccharide (LPS) from Escherichia coli. Nevertheless, the mechanisms of that activity remain unclear. For this study, we purified and identified the proteins responsible for LPS-neutralization. After proteins were isolated from a miso extract using Blue native polyacrylamide gel electrophoresis, a protein found at 10 to 30 kDa on the polyacrylamide gel was identified using nano LC-MS/MS as 2S albumin in soybean (Glycine max). The protein had two LPS binding motifs: SKWQHQ (22 amino acid residues) and EKQKKKMEKE (131 amino acid residues). The protein in miso was found to have LPS neutralization activity, as assayed by prostaglandin D2 (PGD2 ) production from macrophage cells. The PGD2 production by macrophage cells was inhibited by LPS-neutralizing protein (LNP) from miso. Particularly, 50 mg/mL of LNP solution and LPS (10 µg/mL) inhibited production of PGD2 from the cells. The data were inferred as significantly different (P < 0.05) from statistical analyses by analysis of variance testing and Tukey tests. The 2S albumin in soybean is LNP, an LPS-neutralizing protein, produced in miso. PRACTICAL APPLICATION: A protein from miso fermented soy paste neutralizes an Escherichia coli intestinal bacterial product, lipopolysaccharide (LPS), which causes intestinal inflammation. Miso and its protein are anticipated for use as a probiotic agent to prevent intestinal inflammation in humans and domestic animals. Miso is useful not only as a seasoning for food, but also as a health-functional food because it is an LPS-neutralizing agent.

Physicochemical and structural properties of lunasin revealed by spectroscopic, chromatographic and molecular dynamics approaches

Lunasin is a 43-amino acid peptide from seeds and grains with bioavailability in humans and potent chemotherapeutic action against several cancer cell lines. Here, we investigate new information about the physicochemical and structural properties of lunasin using circular dichroism (CD), fluorescence spectroscopy, electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS), size exclusion chromatography (SEC), molecular dynamics (MD), and bioinformatics. CD analysis and disorder prediction obtained by PONDR indicate that lunasin has a mostly unordered structure. Double wavelength [θ]222nm x [θ]200nm plot data suggests that lunasin is an intrinsically disordered peptide (IDP) in a pre-molten globule-like (PMG-like) state, while CD spectrum deconvolution and MD simulation indicate small β-strand content. The presence of residual structure was supported by loss of CD signal at 222 nm after treatment with urea and by increasing fluorescence emission upon bis-ANS binding. Lunasin also demonstrated stability to heating up to the temperature of 100 °C, as verified by CD. MD and CD analyses in the presence of TFE and MoRFpred prediction indicated the helix propensity of lunasin. ESI-IMS-MS data revealed that lunasin shows a propensity to form disulfide bonds at the conditions used. MD data also indicated that disulfide bond formation affects the adopted structure, showing a possible role of aspartyl-end in structure stabilization and compaction. In conclusion, our data support a characterization of lunasin as a peptide with an intrinsic disorder in a PMG-like state and reveal new aspects about its structural stability and plasticity, as well as the effects of disulfide bond formation and electrostatic attractions.

The Effect of Soybean Lunasin on Cardiometabolic Risk Factors: A Randomized Clinical Trial

Lunasin, a peptide isolated from soybeans, has been shown to exert antioxidant, anticarcinogenic, and hypocholesterolemic effects in animal and in vitro models. In a triple-blind, placebo-controlled crossover study, 31 participants (female: 19, male: 12, mean age 61 ± 9.9 years) were randomized to an 8-week treatment of lunasin-enriched soy extract (335mg/d) or placebo. A 3-week washout period was utilized between treatments. Serum lipids, glucose, and insulin, as well as blood pressure and anthropometrics, were measured at baseline, week 7, and week 8 of each treatment period. There were nonsignificant reductions in cardiometabolic risk factors with treatment: total cholesterol -0.1mmol/L, 95% CI [-0.28, 0.03]; LDL cholesterol -0.07mmol/L, 95% CI [-0.2, 0.06]; triglyceride 0% mmol/L, 95% CI (-10%, 11%]; fasting serum glucose -2% mmol/L, 95% CI [-4%, 1%]; BMI -0.05 kg/m2, 95% CI [-0.17, 0.07] and waist circumference -0.63cm, 95% CI [-1.8, 0.53]. Supplementation with lunasin-enriched soy extract for 8 weeks did not result in significant changes in serum lipids, glucose, insulin resistance, blood pressure, BMI, or waist circumference. Future studies should focus on a higher dosage, larger sample size, and/or longer treatment to determine the independent role of lunasin, if any, in the effect of soy on cardiometabolic risk factors.

Soybean Bioactive Peptides and Their Functional Properties

Soy consumption has been associated with many potential health benefits in reducing chronic diseases such as obesity, cardiovascular disease, insulin-resistance/type II diabetes, certain type of cancers, and immune disorders. These physiological functions have been attributed to soy proteins either as intact soy protein or more commonly as functional or bioactive peptides derived from soybean processing. These findings have led to the approval of a health claim in the USA regarding the ability of soy proteins in reducing the risk for coronary heart disease and the acceptance of a health claim in Canada that soy protein can help lower cholesterol levels. Using different approaches, many soy bioactive peptides that have a variety of physiological functions such as hypolipidemic, anti-hypertensive, and anti-cancer properties, and anti-inflammatory, antioxidant, and immunomodulatory effects have been identified. Some soy peptides like lunasin and soymorphins possess more than one of these properties and play a role in the prevention of multiple chronic diseases. Overall, progress has been made in understanding the functional and bioactive components of soy. However, more studies are required to further identify their target organs, and elucidate their biological mechanisms of action in order to be potentially used as functional foods or even therapeutics for the prevention or treatment of chronic diseases.

Updating the research on the chemopreventive and therapeutic role of the peptide lunasin

Chronic diseases have become the medical challenge of the 21st century because of their high incidence and mortality rates. Modulation of diet and lifestyle habits is considered as the best strategy for the prevention of these disorders. Health promoting benefits beyond their nutritional effects have been described for multiple dietary compounds. Among these compounds, the peptide lunasin is considered as one of the most promising. Naturally present in soybean, lunasin has been extensively studied in the last two decades because of its potential against chronic diseases such as cancer, cardiovascular and immunological disorders. The purpose of this article is to summarise the evidence on the presence of lunasin in soybean and derived foods, and its bioavailability once it is orally ingested. The protective and therapeutic effects of this peptide against cancer, oxidative stress, inflammation, and high cholesterol levels as well as the molecular mechanisms of action involved in these effects are also described in this review. © 2017 Society of Chemical Industry.

Lunasin: A promising polypeptide for the prevention and treatment of cancer

Strategies for the treatment of cancer remain unsatisfactory due to the poor understanding of the complicated underlying molecular mechanisms of carcinogenesis. A number of types of cancer exhibit a marked association with dietary habits and lifestyles. Therefore, the modulation of dietary habits or lifestyles may be an effective strategy for preventing the formation and progression of cancer. Proteins and polypeptides from soybean have been developed as healthcare products due to their marked activity in inhibiting the progression of cancer at various stages. Lunasin, containing 43 amino acid residues, is one such example of a soybean-derived polypeptide that has been demonstrated to exhibit marked anti-cancer activity. In the present review, studies of the underlying molecular mechanisms and potential advantages of lunasin in the prevention and treatment of cancer have been examined, to provide a theoretical reference for the development of natural product-based agents or healthcare products for the prevention and treatment of cancer.

Effects of Disulfide Bond Reduction on the Conformation and Trypsin/Chymotrypsin Inhibitor Activity of Soybean Bowman-Birk Inhibitor

Soybean seeds contain three groups (A, C, and D) of Bowman-Birk inhibitors (BBIs). In this study, highly purified BBI-A (approximately 96%) was obtained from soybean whey at the 0.1 g level by the complex coacervation method. BBI-A has seven disulfide bonds (SS) and no sulfhydryl group and exhibits trypsin inhibitor activity (TIA) and chymotrypsin inhibitor activity (CIA). The X-ray structure has shown that BBI-A has five exposed SS and two buried SS. Because of steric hindrance, it was reasonable to consider that dithiothreitol first attacks the five exposed SS and then the two buried SS, which was supported by the results that SS reduction with dithiothreitol could be divided into quick and slow stages, and the critical point was close to 5/7. The effects of SS reduction on TIA and CIA could be divided into three stages: when one exposed SS was reduced, both TIA and CIA decreased to approximately 60%; with further reduction of exposed SS, CIA gradually decreased to 8% and TIA gradually decreased to 26%; with further reduction of buried SS, CIA gradually decreased to 2% and TIA slightly decreased to 24%. Far-ultraviolet (far-UV) circular dichroism (CD) spectra showed that the secondary structure of BBI-A was slightly changed, whereas near-ultraviolet (near-UV) CD spectra showed that the conformation of BBI-A was substantially changed after the five exposed SS were reduced; further reduction of buried SS affected the conformation to some extent. The results of Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and from a C8 column showed the same trend as near-UV CD spectra. BBI-A has a structural peculiarity in that two hydrophobic patches are exposed to the exterior (in contrast to typical soluble proteins), which was attributed to the seven SS by some researchers. These results support the hypothesis that hydrophobic collapse of the exposed hydrophobic patches into a regular hydrophobic core occurred after the reduction of SS in BBI-A.

Proteins in Soy Might Have a Higher Role in Cancer Prevention than Previously Expected: Soybean Protein Fractions Are More Effective MMP-9 Inhibitors Than Non-Protein Fractions, Even in Cooked Seeds

The search for anticancer MMP-9 inhibitors (MMPIs) in food products has become a major goal for research. MMPIs in soy have been related only to saponins and isoflavones, but recently, low specific protein fractions in soybeans were shown to reduce MMP-9 activity as well. The present work aimed at comparing the MMPI potential of protein fractions (P) and non-protein fractions (NP) isolated from soybean seeds, before and after soaking and cooking, mimicking dietary exposures. Reverse and substrate zymography, as well as a fluoregenic DQ gelatin assay were used to evaluate MMP-9 activities. Colon cancer cell migration and proliferation was also tested in HT29 cells. Regarding MMP-9 inhibition, proteins in soy presented IC₅₀ values 100 times lower than non-protein extracts, and remained active after cooking, suggesting that proteins may be more effective MMP-9 inhibitors than non-protein compounds. Using the determined IC₅₀ concentrations, NP fractions were able to induce higher inhibitions of HT29 cell migration and proliferation, but not through MMP-9 inhibition, whilst protein fractions were shown to specifically inhibit MMP-9 activity. Overall, our results show that protein fractions in soybeans might have a higher role in soy-related cancer prevention as MMPIs than previously expected. Being nontoxic and active at lower concentrations, the discovery of these heat-resistant specific MMPI proteins in soy can be of significant importance for cancer preventive diets, particularly considering the increasing use of soy proteins in food products and the controversy around isoflavones amongst consumers.

A Bowman-Birk protease inhibitor purified, cloned, sequenced and characterized from the seeds of Maclura pomifera (Raf.) Schneid

A new BBI-type protease inhibitor with remarkable structural characteristics was purified, cloned, and sequenced from seeds of Maclura pomifera , a dicotyledonous plant belonging to the Moraceae family. In this work, we report a Bowman-Birk inhibitor (BBI) isolated, purified, cloned, and characterized from Maclura pomifera seeds (MpBBI), the first of this type from a species belonging to Moraceae family. MpBBI was purified to homogeneity by RP-HPLC, total RNA was extracted from seeds of M. pomifera, and the 3'RACE-PCR method was applied to obtain the cDNA, which was cloned and sequenced. Peptide mass fingerprinting (PMF) analysis showed correspondence between the in silico-translated protein and MpBBI, confirming that it corresponds to a new plant protease inhibitor. The obtained cDNA encoded a polypeptide of 65 residues and possesses 10 cysteine residues, with molecular mass of 7379.27, pI 6.10, and extinction molar coefficient of 9105 M^-1 cm^-1. MpBBI inhibits strongly trypsin with K _i in the 10^-10 M range and was stable in a wide array of pH and extreme temperatures. MpBBI comparative modeling was applied to gain insight into its 3D structure and highlighted some distinguishing features: (1) two non-identical loops, (2) loop 1 (CEEESRC) is completely different from any known BBI, and (3) the amount of disulphide bonds is also different from any reported BBI from dicot plants.

Protease inhibitors in various flours and breads: Effect of fermentation, baking and in vitro digestion on trypsin and chymotrypsin inhibitory activities

In this study trypsin (TIA) and chymotrypsin inhibitory (CIA) activities were determined in the extracts of wheat, rye mix, mixed cereals and, whole wheat flours and, breads made with these flours. In addition, effects of fermentation, baking and in vitro digestion on TIA and CIA were studied. Whole wheat flour, dough, and bread did not show any TIA. Other flours displayed TIA. Contrary to, all flours, doughs, and breads exhibited CIA. Although TIA was not detected in the protein extracts obtained from wheat and rye mix breads, protein extract of rye mix flour exhibited TIA. Following in vitro digestion process, TIA of wheat bread was found as 5.91units/mL gastric dialysate and 9.17units/mL intestine dialysate. CIA was determined in dialysates obtained from wheat (2.12CI/mL and 3.78CI/mL for gastric and intestinal dialysate respectively) and rye breads (4.16CI/mL and 2.46CI/mL for gastric and intestinal dialysate respectively).

Pharmacological research on natural substances in Latvia: Focus on lunasin, betulin, polyprenol and phlorizin

In this concise review the current research in plant bioactive compound studies in Latvia is described. The paper summarizes recent studies on substances from edible plants (e.g., cereals and apples) or their synthetic analogues, such as peptide lunasin, as well as substances isolated from inedible plants (e.g., birch and conifer), such as pentacyclic triterpenes (e.g., betulin, betulinic acid, and lupeol) and polyprenols. Latvian researchers have been first to demonstrate the presence of lunasin in triticale and oats. Additionally, the impact of genotype on the levels of lunasin in cereals was shown. Pharmacological studies have revealed effects of lunasin and synthetic triterpenes on the central nervous system in rodents. We were first to show that synthetic lunasin causes a marked neuroleptic/cataleptic effect and that betulin antagonizes bicuculline-induced seizures (a GABA A receptor antagonist). Studies on the mechanisms of action showed that lunasin binds to dopamine D1 receptors and betulin binds to melanocortin and gamma-aminobutyric acid A receptors therefore we suggest that these receptors play an essential role in lunasin's and betulin's central effects. Recent studies on conifer polyprenols demonstrated the ability of polyprenols to prevent statin-induced muscle weakness in a rat model. Another study on plant compounds has demonstrated the anti-hyperglycemic activity of phlorizin-containing unripe apple pomace in healthy volunteers. In summary, research into plant-derived compounds in Latvia has been focused on fractionating, isolating and characterizing of lunasin, triterpenes, polyprenols and phlorizin using in vitro, and in vivo assays, and human observational studies.

The protective role of the Bowman-Birk protease inhibitor in soybean lunasin digestion: the effect of released peptides on colon cancer growth

Lunasin is a naturally-occurring peptide demonstrating chemopreventive, antioxidant and anti-inflammatory properties. To exhibit these activities, orally ingested lunasin needs to survive proteolytic attack of digestive enzymes to reach target tissues in active form/s. Preliminary studies suggested the protective role of protease inhibitors, such as the Bowman-Birk inhibitor and Kunitz-trypsin inhibitor, against lunasin's digestion by both pepsin and pancreatin. This work describes in depth the behaviour of lunasin under conditions simulating the transit through the gastrointestinal tract in the absence or presence of soybean Bowman-Birk isoinhibitor 1 (IBB1) in both active and inactive states. By liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), the remaining lunasin at the end of gastric and gastro-duodenal phases was quantified. Protection against the action of pepsin was independent of the amount of IBB1 present in the analyzed samples, whereas an IBB1 dose-dependent protective effect against trypsin and chymotrypsin was observed. Peptides released from lunasin and inactive IBB1 were identified by MS/MS. The remaining lunasin and IBB1 as well as their derived peptides could be responsible for the anti-proliferative activity against colon cancer cells observed for the digests obtained at the end of simulated gastrointestinal digestion.

"Potential health benefits of lunasin: a multifaceted soy-derived bioactive peptide"

Bioactive peptides are small protein fragments derived from enzymatic hydrolysis of food proteins, fermentation with proteolytic starter cultures, and gastrointestinal digestion. These peptides have positive impacts on a number of physiological functions in living beings. Lunasin, a soy-derived bioactive peptide, is one of the most promising among them. Lunasin encoded within 2S albumin (GM2S-1) gene, identified as a novel peptide extracted from soybean seed. It is composed of 43 amino acid residues with a molecular weight of 5.5 kDa. Extensive scientific studies have shown that lunasin possesses inherent antioxidative, anti-inflammatory, anticancerous properties and could also play a vital role in regulating of cholesterol biosynthesis in the body. Its high bioavailability and heat stable nature allow its potential use as dietary supplement. The present review summarizes some of the potential health and therapeutic benefits of lunasin reported hitherto.

Preventive and therapeutic potential of peptides from cereals against cancer

Epidemiological studies have shown that regular consumption of food based on whole-grain cereals and their products is associated with reduced risks of various types of degenerative chronic diseases. Food proteins are considered an important source of nutraceutical peptides and amino acids that can exert biological functions to promote health and prevent disease, including cancer. There have been several reports on peptides with anti-tumour activity in recent years. Plant-derived peptides, such as rapeseed, amaranth and soybean lunasin have received main attention. In this review, we extend this vision to analyse the evidence of current advances in peptides in cereals such as wheat, maize, rice, barley, rye and pseudocereals compared with soybean. We also show evidence of several mechanisms through which bioactive peptide exerts anti-tumour activity. Finally, we report the current status of major strategies for the fractionation, isolation and characterisation of bioactive peptides in cereals.

BIOLOGICAL SIGNIFICANCE

In recent reports, it has been shown that peptides are an interesting alternative in the search for new treatments for cancer. One of the most studied sources of these peptides is food proteins; however, a review that includes more recent findings for cereals as a potential source of bioactive peptides in the treatment of cancer, the techniques for their isolation and characterisation and the assays used to prove their bioactivity is not available. This review can be used as a tool in the search for new sources of anti-cancer peptides. The authors have no conflicts of interest, financial or otherwise.

Bowman-Birk inhibitors from legumes as colorectal chemopreventive agents

Aberrant functioning of serine proteases in inflammatory and carcinogenic processes within the gastrointestinal tract (GIT) has prompted scientists to investigate the potential of serine protease inhibitors, both natural and synthetic, as modulators of their proteolytic activities. Protease inhibitors of the Bowman-Birk type, a major protease inhibitor family in legume seeds, which inhibit potently and specifically trypsin- and chymotrypsin-like proteases, are currently being investigated as colorectal chemopreventive agents. Physiologically relevant amounts of Bowman-Birk inhibitors (BBI) can reach the large intestine in active form due to their extraordinary resistance to extreme conditions within the GIT. Studies in animal models have proven that dietary BBI from several legume sources, including soybean, pea, lentil and chickpea, can prevent or suppress carcinogenic and inflammatory processes within the GIT. Although the therapeutic targets and the action mechanism of BBI have not yet been elucidated, the emerging evidence suggests that BBI exert their preventive properties via protease inhibition; in this sense, serine proteases should be considered as primary targets in early stages of carcinogenesis. The validation of candidate serine proteases as therapeutic targets together with the identification, within the wide array of natural BBI variants, of the most potent and specific protease inhibitors, are necessary to better understand the potential of this protein family as colorectal chemopreventive agents.

Effect of germinated soy protein on the growth of HeLa cervical cancer cells in female athymic mice

Previous studies showed that germination could improve the antiproliferative effect of soy protein on cervical cancer cells and that a peptide fraction (MAPF) from germinated soybeans decreases the expression of PTTG1 and TOP2A (2 genes considered as therapeutic targets) causing apoptosis of cancer cells. The aim of this work was to study the effect of feeding germinated soybean protein diets on the tumor growth in nude mice inoculated with cervical cancer cells and identify the bioactive component. Mice were randomly assigned to 1 of the 6 dietary groups based in AIN-93G formulation with 6 protein sources: casein, ungerminated soy protein (SP), and SP from 2 and 6 days of germination, with and without ethanol-soluble phytochemicals (ESPC). Compared with casein-fed controls, the tumor volumes after 5 wk were reduced by 44.6% by ungerminated SP, 98.9% by 2-day-germinated SP, 97.7% by 2-day-germinated SP without ESPC, 94.7% by 6-day-germinated SP, and 92.7% by 6-day-germinated SP without ESPC (P < 0.05). Liquid chromatography coupled with tandem mass spectrometry analysis of MAPF showed that the bioactive peptide might be the leginsulin, a peptide involved in signal transduction of soybean cells. Germination is a simple procedure that could help to increase the anticancer activity of soy protein probably through generation of biologically active peptides.

Bowman-Birk and Kunitz protease inhibitors among antinutrients and bioactives modified by germination and hydrolysis in Brazilian soybean cultivar BRS 133

Soybean contains constituents that have antinutritional and bioactive properties. Enzymatic hydrolysis and germination can enhance the biological activity of these compounds in soybean. The objective of this study was to investigate the effect of germination, Alcalase (protease) hydrolysis, and their combination on the concentrations of antinutritional and bioactive compounds in Brazilian soybean cultivar BRS 133. A combination of germination and Alcalase hydrolysis resulted in the degradation of Bowman-Birk inhibitor (BBI), Kunitz trypsin inhibitor (KTI), and lunasin by 96.9, 97.8, and 38.4%. Lectin was not affected by any of the processing treatments when compared to nongerminated and nonhydrolyzed soy protein extract. Total isoflavones (ISF) and total saponins (SAP) increased by 16.2 and 28.7%, respectively, after 18 h of germination, while Alcalase hydrolysis led to the reduction of these compounds. A significant correlation was found between concentrations of BBI and KTI, BBI and lunasin, BBI and ISF, KTI and lunasin, KTI and ISF, KTI and SAP, lunasin and ISF, and ISF and SAP. Germination and Alcalase hydrolysis interacted in reducing BBI, ISF, and SAP. This study presents a process of preparing soy flour ingredients with lower concentrations of antinutritional factors and with biologically active constituents, important for the promotion of health associated with soybean consumption. In conclusion, 18 h of germination and 3 h of Alcalase hydrolysis is recommended for elimination of protease inhibitors, while bioactives are maintained by at least 50% of their original concentrations.

Bowman-Birk Inhibitor attenuates experimental autoimmune encephalomyelitis by delaying infiltration of inflammatory cells into the CNS

Bowman-Birk Inhibitor (BBI), a serine protease inhibitor derived from soybeans, has anti-inflammatory properties and is able to suppress the development of central nervous system (CNS) autoimmunity in animal models. Experimental autoimmune encephalomyelitis (EAE), a widely used animal model of multiple sclerosis (MS), is characterized by breakdown of the blood-brain barrier and infiltration of inflammatory cells into the CNS, resulting in pathology. In this study, we observed that BBI-treated mice showed delayed onset of EAE and reduced disease severity compared to control mice. BBI-treated mice had fewer inflammatory cells in the CNS including significantly reduced numbers of Th1 and Th17 cells. In the periphery, BBI treatment suppressed the development of encephalitogenic Th1 and Th17 responses early on [day 7 post-immunization (p.i.)], while after disease onset (day 14 p.i.) BBI-treated mice had stronger Th responses, as determined by antigen-specific proliferation and cytokine production. These results demonstrate that BBI treatment temporarily suppressed the development of encephalitogenic responses, but these responses eventually attained normal magnitude. Given that BBI-treated mice exhibited stronger encephalitogenic responses in the periphery during clinically manifesting EAE, delayed disease onset, and reduced numbers of CNS-infiltrating cells, it appears likely that BBI impedes the exit of pathogenic Th1 and Th17 cells from lymphoid organs, thereby delaying their migration into the CNS.

Interleukin-10 plays a crucial role in suppression of experimental autoimmune encephalomyelitis by Bowman-Birk inhibitor

The Bowman-Birk inhibitor (BBI) is a soybean-derived serine protease inhibitor with anti-inflammatory properties. Experimental autoimmune encephalomyelitis (EAE) serves as an animal model of the central nervous system (CNS) inflammatory disorder multiple sclerosis (MS). EAE is mediated by Th1 and Th17 cells which migrate into the CNS and initiate inflammation directed against myelin components, resulting in CNS pathology and neurological clinical deficit. We have shown previously that oral treatment with BBI delays onset of EAE and reduces its severity. These beneficial effects were associated with an increase in IL-10 secretion by immune cells of BBI-treated mice. It is not known, however, whether this was a causal relationship or simply an epiphenomenon. In the present study we provide evidence that BBI regulates CD4+ T cell immune responses in EAE. BBI administration delayed the onset of EAE and reduced its severity in an IL-10-dependent manner, as BBI-mediated suppression of EAE was abrogated in IL-10 knockout mice. The beneficial effects were accompanied by reduced IFN-γ, IL-17 and increased IL-10 production, as well as increased Foxp3 expression. CD4+ T cells were the major source of IL-10 in the periphery and in the CNS during BBI treatment. Furthermore, BBI-treated mice had reduced numbers of infiltrated cells in the CNS, including Th17 cells, as compared with PBS-treated control animals. In conclusion, our data provide clear evidence for the essential role of IL-10 in BBI-mediated suppression in EAE, and indicate that BBI may be a promising candidate for the development of a novel MS therapy.

Synthesis of the cancer preventive peptide lunasin by lactic acid bacteria during sourdough fermentation

This study aimed to exploit the potential of sourdough lactic acid bacteria to release lunasin during fermentation of cereal and nonconventional flours. The peptidase activities of a large number of sourdough lactic acid bacteria were screened using synthetic substrates. Selected lactic acid bacteria were used as sourdough starters to ferment wholemeal wheat, soybean, barley, amaranth, and rye flours. Proteinase activity during fermentation was characterized by SDS-PAGE analysis of the water-soluble extracts. Albumins having molecular masses of 18 to 22 kDa, which included the size of lunasin precursors, were markedly affected by proteolysis of lactic acid bacteria. After fermentation, lunasin from the water-soluble extracts was quantified, purified, and identified through RP-HPLC and nano-LC-ESI-MS analyses. Compared to control doughs, the concentration of lunasin increased up to 2-4 times during fermentation. Lactobacillus curvatus SAL33 and Lactobacillus brevis AM7 synthesized the highest concentrations of lunasin in all the flours. Besides the presence of the entire lunasin sequence, fragments containing the immunoreactive epitope RGDDDDDDDDD were also found. This study shows that fermentation by lactic acid bacteria increased the concentration of lunasin to levels that would suggest new possibilities for the biological synthesis and for the formulation of functional foods.

Simultaneous and rapid determination of the anticarcinogenic proteins Bowman-Birk inhibitor and lectin in soybean crops by perfusion RP-HPLC

There are numerous studies demonstrating a direct association between the ingestion of soybean and low cancer incidence. This fact has been related to the presence of Bowman-Birk inhibitor (BBI) and lectin in soybean. The simultaneous and fast determination of BBI and lectin in soybean is proposed, for the first time, in this work. Two different strategies were designed for the extraction of BBI and lectin: extraction of soybean proteins using a Tris-HCl buffer followed by isolation of BBI and lectin by the isoelectric precipitation of other soybean proteins (method I) or by the direct extraction of BBI and lectin using an acetate buffer (method II). The effect of the previous soybean defating on the extraction of BBI and lectin was also studied. Moreover, the possibility of using a high-intensity focalized ultrasonic probe for accelerating the extraction was explored and an optimization of the extraction time and ultrasound amplitude was performed. The extracts obtained were analysed by RP-HPLC-ESI-MS for the correct identification of BBI and lectin in soybean. Moreover, a fast chromatographic methodology using a perfusion column and UV detection was optimized for the rapid determination of BBI and lectin in soybean. After evaluating its analytical characteristics (linearity, precision, and recovery), the method was applied to the quantitation of BBI and lectin in different soybean varieties.

Soybean peptide lunasin suppresses in vitro and in vivo 7,12-dimethylbenz[a]anthracene-induced tumorigenesis

Lunasin is a novel peptide identified in soybean and other seeds. This study evaluated the anti-tumorigenic effects of lunasin on 7,12-dimethylbenz(a)anthracene (DMBA) and 3-methylcholanthrene-treated (MCA) fibroblast NIH/3T3 cells. Lunasin significantly inhibited cell proliferation and cancerous foci formation in these 2 chemical carcinogens-treated cells. An in vivo SENCAR mouse model induced with DMBA was used to study the mammary cancer preventive properties of dietary lunasin contained in soy protein. Tumor incidence was 67% and 50%, and the tumor generation was 1.88 ± 0.48 and 1.17 ± 0.17, respectively, for the mice fed control diet and experimental diet obtained after AIN-93G supplementation with lunasin-enriched soy protein concentrate (containing 0.23% lunasin). However, no effects were observed in mice fed AIN-93G supplemented with soy protein concentrate (containing 0.15% lunasin). The data provided illustrate the anticancer potential of lunasin both in vitro and in vivo and supports the recommendation of soy protein as a dietary component that may aid in the prevention of mammary cancer.

Recombinant expression of bioactive peptide lunasin in Escherichia coli

Lunasin, a cancer-preventive peptide, was isolated from soybean, barley, and wheat. Previous studies showed that this 43-amino acid peptide has the ability to suppress chemical carcinogen-induced transformation in mammalian cells and skin carcinogenesis in mice. In this study, we attempted to use the Escherichia coli T7 expression system for expression of lunasin. The lunasin gene was synthesized by overlapping extension polymerase chain reaction and expressed in E. coli BL21(DE3) with the use of vector pET29a. The recombinant lunasin containing his-tag at the C-terminus was expressed in soluble form which could be purified by immobilized metal affinity chromatography. After 4 h, the expression level is above 4.73 mg of recombinant his-tagged lunasin/L of Luria-Bertani broth. It does not affect the bacterial growth and expression levels. This is the first study that successfully uses E. coli as a host to produce valuable bioactive lunasin. The result of in vitro bioassay showed that the purified recombinant lunasin can inhibit histone acetylation. Recombinant lunasin also inhibits the release of pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, and nitric oxide production). Compared with other research methods on extraction or chemical synthesis to produce lunasin, our method is very efficient in saving time and cost. In the future, it could be applied in medicine and structure-function determination.

Complementary roles in cancer prevention: protease inhibitor makes the cancer preventive peptide lunasin bioavailable

BACKGROUND

The lower incidence of breast cancer among Asian women compared with Western countries has been partly attributed to soy in the Asian diet, leading to efforts to identify the bioactive components that are responsible. Soy Bowman Birk Inhibitor Concentrate (BBIC) is a known cancer preventive agent now in human clinical trials.

METHODOLOGY/PRINCIPAL FINDINGS

The objectives of this work are to establish the presence and delineate the in vitro activity of lunasin and BBI found in BBIC, and study their bioavailability after oral administration to mice and rats. We report that lunasin and BBI are the two main bioactive ingredients of BBIC based on inhibition of foci formation, lunasin being more efficacious than BBI on an equimolar basis. BBI and soy Kunitz Trypsin Inhibitor protect lunasin from in vitro digestion with pancreatin. Oral administration of (3)H-labeled lunasin with lunasin-enriched soy results in 30% of the peptide reaching target tissues in an intact and bioactive form. In a xenograft model of nude mice transplanted with human breast cancer MDA-MB-231 cells, intraperitoneal injections of lunasin, at 20 mg/kg and 4 mg/kg body weight, decrease tumor incidence by 49% and 33%, respectively, compared with the vehicle-treated group. In contrast, injection with BBI at 20 mg/kg body weight shows no effect on tumor incidence. Tumor generation is significantly reduced with the two doses of lunasin, while BBI is ineffective. Lunasin inhibits cell proliferation and induces cell death in the breast tumor sections.

CONCLUSIONS/SIGNIFICANCE

We conclude that lunasin is actually the bioactive cancer preventive agent in BBIC, and BBI simply protects lunasin from digestion when soybean and other seed foods are eaten by humans.

Antidiabetic effects of fermented soybean products on type 2 diabetes

Historically, the incidence of type 2 diabetes has been lower in Asian populations compared with those in Western countries. One possible reason for the lower incidence among Asians is that they consume fermented soybean products, which are unique to the traditional Asian diet. Some have hypothesized that dietary phytoestrogens and soy peptides in fermented soybean foods consumed in traditional Asian diets may help prevent and slow the progression of type 2 diabetes. This review evaluates the existing evidence from animal studies and clinical and epidemiologic investigations on fermented soybeans in the prevention and treatment of type 2 diabetes. Nutritional studies performed in animals and intervention studies with humans suggest that the ingestion of soy protein with isoflavones improves glucose control and reduces insulin resistance. Korean fermented soybean products such as doenjang, kochujang, and chungkookjang contain alterations in the structures and content of isoflavonoids and small bioactive peptides, which are produced during fermentation. Several studies revealed improvements in insulin resistance and insulin secretion with the consumption of these fermented products. Therefore, fermented soybean products may help prevent or attenuate the progression of type 2 diabetes. Although the lack of human intervention trials does not permit definitive conclusions, the evidence does suggest that fermented soy products may be better for preventing or delaying the progression of type 2 diabetes compared with nonfermented soybeans.

Nutritional Value of Cassava for Use as a Staple Food and Recent Advances for Improvement

  Cassava is a drought-tolerant, staple food crop grown in tropical and subtropical areas where many people are afflicted with undernutrition, making it a potentially valuable food source for developing countries. Cassava roots are a good source of energy while the leaves provide protein, vitamins, and minerals. However, cassava roots and leaves are deficient in sulfur-containing amino acids (methionine and cysteine) and some nutrients are not optimally distributed within the plant. Cassava also contains antinutrients that can have either positive or adverse effects on health depending upon the amount ingested. Although some of these compounds act as antioxidants and anticarcinogens, they can interfere with nutrient absorption and utilization and may have toxic side effects. Efforts to add nutritional value to cassava (biofortification) by increasing the contents of protein, minerals, starch, and β-carotene are underway. The transfer of a 284 bp synthetic gene coding for a storage protein rich in essential amino acids and the crossbreeding of wild-type cassava varieties with Manihot dichotoma or Manihot oligantha have shown promising results regarding cassava protein content. Enhancing ADP glucose pyrophosphorylase activity in cassava roots or adding amylase to cassava gruels increases cassava energy density. Moreover, carotenoid-rich yellow and orange cassava may be a foodstuff for delivering provitamin A to vitamin A-depleted populations. Researchers are currently investigating the effects of cassava processing techniques on carotenoid stability and isomerization, as well as the vitamin A value of different varieties of cassava. Biofortified cassava could alleviate some aspects of food insecurity in developing countries if widely adopted.

Lunasin, a novel seed peptide for cancer prevention

Carcinogenesis is a multistage process derived from a combination of multiple heritable and environmental factors. It has been reported that populations consuming high levels of soybean products have both lower cancer incidence and mortality rates in the western countries. Lunasin is a novel and promising peptide initially discovered in soy and now found in wheat, barley and other seeds. Its cancer-preventive efficacy has been shown in mammalian cells which were induced by chemical carcinogens and viral oncogenes. Moreover, this peptide has been found to prevent skin cancer in a mouse cancer model induced by chemical carcinogens. Its bioavailability after oral administration makes it a perfect candidate as a chemopreventive agent. The purpose of this article is to review the discovery of this seed peptide and the most recent evidence on its possible benefits as an anticancer agent.