Patrick McCue

Health benefits of soy isoflavonoids and strategies for enhancement: a review.

Soybean consumption has been linked to a reduced risk for certain cancers and diseases of old age. The health benefits associated with soybean consumption have been linked to the action of isoflavonoids, the major phenolic phytochemicals found in soybean. Isoflavonoids possess numerous biological activities that may support chemoprevention through the promotion of apoptosis in diseased cells. In this study, we discuss the current state of knowledge concerning soybean isoflavonoids, their chemopreventive actions against postmenopausal health problems, cancer, and cardiovascular disease, and also biotechnology approaches toward the enrichment of soybean for isoflavonoid content.

Role of carbohydrate-cleaving enzymes in phenolic antioxidant mobilization from whole soybean fermented with Rhizopus oligosporus

Previous research has suggested a relationship between free phenolic content and β-glucosidase activity in solid-state fermented food substrates and to amylase activity in germinating soybeans. This study was undertaken to examine the role of a number of carbohydrate-cleaving enzymes in phenolic antioxidant mobilization from whole soybean during solid-state fermentation. In addition to total soluble phenolic content, α- and β-glucosidase, α-amylase, and β-glucuronidase activities were measured in extracts of soybean fermented with a food-grade fungus, Rhizopus oligosporus. Antioxidant activity of the extracts was determined as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability. Our results demonstrate that while total soluble phenolic content increased 120–135% in the extracts, increased antioxidant activity (+61%) was limited to the early fermentation period, with activity decreasing with increased culture time. Higher antioxidant activity was linked to increased glucosidase and glucuronidase activities, while high total phenolic content partly linked to increased amylase activity. The overall results (enzymatic activities and phenolic antioxidant contents) suggest the possible involvement of lignin remobilization and/or degradation activities, as well as phenolic detoxification activities, by Rhizopus oligosporus in phenolic antioxidant mobilization from fermented whole soybean.

A model for enhanced pea seedling vigour following low pH and salicylic acid treatments

Abstract In the simplest of terms, seed vigour is a visual measure of a seed’s ability to germinate and survive its early growth and development period. Improvement of seed vigour is important for optimal emergence, stress resistance and uniform growth of emerging seedlings. We have hypothesized that acid-induced cell growth and elongation is regulated through the pentose-phosphate pathway; therefore, the effect of acidification linked to salicylic acid (SA) on growth, cell elongation, and phenolic synthesis was investigated. The experiments consisted of low pH and SA treatments followed by the measurement of phenolic levels and assay of the key regulatory enzyme of the pentose-phosphate pathway, glucose-6-phosphate dehydrogenase (G6PDH), and guaiacol peroxidase (GPX), during post-germination growth and elongation of peas. Phenolic and enzyme levels were determined by UV spectrophotometric assays. A low pH environment stimulated phenolic synthesis and increased tissue rigidity. Stimulating phenolic synthesis through low pH treatment supports the hypothesis that acid-induced cell growth and elongation may be regulated through the pentose-phosphate pathway. Based on concomitant stimulation of G6PDH and increase in proline content, the pentose-phosphate pathway may be linked to stimulation of proline metabolism in response to the above treatments. It has been hypothesized that this pathway produces the critical precursors for the synthesis of phenolic secondary metabolites that are important for plant growth and lignification.

Phenolic Antioxidant Biosynthesis in Plants for Functional Food Application: Integration of Systems Biology and Biotechnological Approaches

We are applying a dynamic systems biology approach to the development of several phenolic phytochemicals in food-grade plants as ingredients for functional food applications. Phenolic antioxidant phytochemicals from food-grade plants will be an important part of a healthy diet in a global population that is projected to reach 9 billion in the next 50 years. Such phytochemicals are being targeted for designing conventional foods with added health benefits (functional foods). Such value-added foods are needed for dietary support to manage major oxidation-linked diseases, such as diabetes, cardiovascular disease, arthritis, cognition diseases and cancer. Plants produce phenolic metabolites as a part of growth, developmental and stress-adaptation response. These stress and developmental-modulated phenolic phytochemicals can be targeted for the design of functional foods. In order to design consistent food-grade phytochemical profiles for safety and clinical relevancy, novel tissue culture and bioprocessing technologies have been developed. The strategy for designing these phenolic phytochemicals is based on the model that phenolic metabolites in plants are efficiently produced through an alternative mode of metabolism that links proline synthesis to activity of the pentose–phosphate pathway. Using the proline-linked pentose–phosphate pathway model, techniques have been developed to isolate high phenolic clonal lines of food-grade plants from single heterozygous seeds. Further, using the same model, elicitation concepts and techniques have been applied to over-produce phenolic metabolites in seeds and sprouts. In both clonal and seed sprout systems, exogenous treatment of phenolic phytochemicals from a non-target species elicited endogenous stimulation of phenolic synthesis and, potentially, an antioxidant response. From these investigations, a hypothetical model has been proposed in which the proline-linked pentose–phosphate pathway is critical for modulating protective antioxidant response pathways in diverse biological systems, including humans. This model, when confirmed precisely, may provide a mechanism for understanding the mode of action of phenolic phytochemicals in modulating antioxidant pathways in relation to human health. An understanding of the interconnection of the proline-linked pentose–phosphate pathway and antioxidant response pathway can provide dietary and nutritional mechanisms as well as new strategies to manage oxidation-linked diseases through improvement of host physiological response. In this review we have focused on clonal herbs, fava bean sprouts and cranberry bioprocessing as 3 model systems for understanding biosynthesis of phenolic metabolites for functional food application.

A BIOCHEMICAL ANALYSIS OF MUNGBEAN (VIGNA RADIATA) RESPONSE TO MICROBIAL POLYSACCHARIDES AND POTENTIAL PHENOLIC-ENHANCING EFFECTS FOR NUTRACEUTICAL APPLICATIONS

ABSTRACT Foods that contain plant phenolic secondary metabolites that are antioxidants are getting more attention due to an increase in experimental data suggesting health-promoting effects when such foods are ingested as part of a low-fat diet. As the synthesis of phenolic compounds in plants is known to increase during the defense response to microorganisms, we investigated specific food-grade microbial polysaccharides as potential elicitors of mungbean phenolic content. Mungbean (Vigna radiata) was pretreated with solutions of both xanthan and gellan gums, as well as commercial yeast extract and purified yeast glucan (as potential fungal elicitors), and dark-germinated for 1–5 days. Tissue samples were assayed for enzymatic (glucose-6-phosphate dehydrogenase and guaiacol peroxidase) and antioxidant activity, and for proline and phenolic content. Microbial polysaccharide treatments were found to stimulate phenolic content and enzyme activity, as well as occasional cotyledon pigmentation. In addition, xanthan gum, yeast extract, and purified yeast glucan treatments stimulated antioxidant activity. Possible mechanisms linking acid-induced plant growth to growth induced by food-grade microorganisms (and related polysaccharides), such as yeasts and acid-producing bacteria, are hypothesized and discussed.

Sprouting and Solid-State Bioprocessing by Rhizopus oligosporus Increase the In Vitro Antibacterial Activity of Aqueous Soybean Extracts Against Helicobacter pylori

Abstract Helicobacter pylori infection has been implicated as a major cause of gastric inflammation, peptic ulcer disease, and gastric cancer. While antibiotics have been the mainstay of current therapies for gastrointestinal disease linked to H. pylori infection, negative side-effects and antibiotic resistance issues have strengthened the need for alternative therapeutic strategies. In the search for new antimicrobial agents, much recent research has focused on the potential of dietary phenolic compounds. In this study, soybean extracts enriched for phenolic content via sprouting or solid-state bioprocessing by the dietary fungus Rhizopus oligosporus were investigated for in vitro antibacterial activity against H. pylori. Helicobacter pylori growth inhibition by soybean extracts was increased most effectively by 2 d sprouting or 2 d R. oligosporus bioprocessing. Anti-H. pylori activity was not associated with antioxidant activity, but was linked to extracts when activity of the phenolic-polymerizing enzymes guaiacol peroxidase (in sprouted soybean extracts) and laccase (in R. oligosporus-bioprocessed soybean extracts) were the highest. This suggests the potential involvement of polymeric phenolics in the anti-H. pylori activity of soybean extracts and possible mechanisms for such action are discussed.

Characterization of the Effect of Sprouting or Solid-State Bioprocessing by Dietary Fungus on the Antibacterial Activity of Soybean Extracts Against Listeria monocytogenes

Listeria monocytogenes is one of the most severe food-borne bacterial infections causing Listeriosis. As L. monocytogenes can survive harsh adverse conditions – such as low pH, high NaCl, and refrigeration temperatures – as well as resist current antimicrobial measures such as the use of disinfectants and antibiotics, there is a need for alternative anti-Listeria strategies. In the search for new antimicrobial agents, much recent research has focused on the potential of dietary phenolic compounds. In this study, soybean extracts enriched for phenolic content via dark-germination sprouting or solid-state bioprocessing by the dietary fungus Rhizopus oligosporus or Lentinus edodes were investigated for in vitro antibacterial activity against L. monocytogenes. L. monocytogenes growth was inhibited most effectively by R. oligosporus bioprocessed soybean extracts, which showed anti-Listeria activity at total phenolic concentrations as low as 10 µg 100 µL−1. In both sprouted soybean extract and L. edodes-bioprocessed soybean extract the anti-Listeria activity was not observed until at least 200 µg total phenolic content 100 µL−1 was used. Anti-Listeria activity by soybean extract was associated with phenolic mobilization but not with antioxidant activity. Further, R. oligosporus bioprocessed soybean extracts were shown to inhibit the growth of L. monocytogenes in fish and meat systems at refrigeration temperatures. The potential involvement of mobilization of antimicrobial versus non-antimicrobial phenolics during sprouting and solid-state bioprocessing was hypothesized and discussed.

Low Microbial Load Sprouts with Enhanced Antioxidants for Astronaut Diet

• Novel methods to stimulate phenolic antioxidants from legume, mung bean (Vigna radiata) sprouts with low microbial count were developed to support a healthy diet for astronauts on the International Space Station (ISS) as well as lunar and Mars programs. INTRODUCTION • ANTIOXIDANTS AND NUTRITION • Plants are excellent sources of phenolic antioxidants • Phenolic phytochemicals – antioxidative action • scavengers of singlet oxygen and free radicals. • Donate hydrogen from hydroxyl groups positioned along the aromatic ring to terminate free radical oxidation of lipids and other biomolecules short-circuit a destructive chain reaction that ultimately degrades cellular membranes. • Implications for human health and in particular cancer. • Understanding Biosynthesis is essential for the development of functional foods, which refers to the improvement of conventional foods with added health benefits. Antioxidants for Protection from Radiation damage • Radiation exposure-linked oxidative stress and biological damage likely to be encountered by astronauts. • In addition to cell membrane damage can cause oxidative damage at the DNA level, having consequences for mutagenesis and cancer. • Preventive nutrient support through use of food-grade antioxidants, such as vitamin C, E and A, have the potential to reduce damage. • Phenolic antioxidants also have the potential to be used as diet-based support for managing radiation-linked antioxidant protection . • Sprout-based phenolic antioxidants can be designed as functional foods for diet-based protection. Phenolic Antioxidants from Plants • Secondary metabolites, which have diverse medicinal applications. – Curcumin from Curcuma longa – Rosmarinic acid from Rosmarinus officinalis . – Isoflavonoids from Glycine max and galanigin from Origanum vulgare – Ellagic acid via solid-state bioprocessing from fruits . – L-tyrosine and L-DOPA from fava bean and related legumes for stress adaptogenic and Parkinson’s diet therapy • Implications for stress-management in advanced life support systems beyond Earth. PHENOLIC ANTIOXIDANTS FROM LEGUME SPROUTS AND BIOCHEMICAL CONCEPTS • PEAS – a link between proline biosynthesis, oxidation, stimulation of glucose-6-phosphate dehydrogenase (G6PDH), and phenolic synthesis. • MUNG BEAN – microbial polysaccharide treatments stimulated phenolic content, proline, G6PDH and GPX. – In addition specific elicitors, xanthan gum, yeast extract and yeast glucan stimulated antioxidant activity. – oregano phenolic extracts as elicitors to stimulate phenolic content during dark germination of mung bean.

A Hypothetical Model for Action of Soybean Isoflavonoids Against Cancer Involving a Shift to Proline-Linked Energy Metabolism Through Activation of the Pentose-Phosphate Pathway

Abstract Soybean isoflavonoids and related phenolic antioxidants from other dietary plant species have long been associated with numerous biological activities linked to the chemoprevention of cancers and oxidation-linked diseases. But until now, no mechanisms or models have been put forth to explain how all of these activities of dietary phenolics could work together to promote health and protect from disease. Here, we present a hypothetical model based on the soybean isoflavonoid genistein for the beneficial action of dietary phenolic antioxidants that incorporates not only the known molecular activities, but also the known metabolic effects that dietary phenolics have on cellular systems such as energy metabolism and the antioxidant enzyme response to reactive oxygen species. Our model presents in a clear manner how a cancerous cell, although mutated and dysfunctional on both biochemical and genetic levels, cannot escape its beginnings as a normal cell and the underlying response mechanisms that are retained from that heritage. By our model, we present how dietary phenolics such as genistein may trigger a switch in energy metabolism from an NADH-supported system to one supported by proline (via the proline-linked pentose-phosphate pathway) through the activation of a stress-response mechanism known to occur in normal cells during stress conditions and which may still remain in cancerous cells. Further, we postulate how an inability of cancer cells to disengage this stress response-induced change in energy metabolism due to biochemical and/or genetic mutations could result in the death of the diseased cell. This metabolic model has implications for the further understanding of how dietary phenolics may confer their beneficial effects and also for the design of chemopreventive agents and functional foods.

PARTIAL PURIFICATION OF A BASIC GUAIACIOL PEROXIDASE FROM FAVA BEAN (VICIA FABA L.): CHARACTERIZATION OF ENZYME STABILITY FOLLOWING ELICITOR TREATMENT

Previous research in our lab investigated the stimulatory effects of phenolic elicitors on plant seed development and the production of phenolics for lignification and nutraceutically relevant antioxidants. Metabolic flux of metabolites through the pentose-phosphate pathway towards eventual lignin formation might be driven by regulated activity of the rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PDH) in response to phenolic-scavenging peroxidase activity. Through regulated activity of such enzymes, the metabolism for plant recovery and defense may be optimized under stressful conditions. As of yet, no direct correlation between stress-inducing treatments in plant cultures and possible stimulatory effects on purified enzymes involved inlignification and phenolic antioxidant pathways (specifically, peroxidases) has been reported. In order to investigate our hypothesis of an elicitor-induced stimulatory effect on peroxidase activity, we studied partially-purified guaiacol peroxidase (GPX) enzyme extracts from fava bean (Vicia faba L.) following treatment with proline and a proline analogue, azetidine-2-carboxylic acid (A2C), and six days of dark-germination. Using preparative isoelectric focusing, GPX enzyme was purified from crude extract to a purification factor of 11.1 and a specific activity of 1.25 U/mg protein at pH 10.39. The purified basic peroxidase (pI<9.6) showedsignificant changes in an acidic shift of the enzymes pH optimum (pH 6.1, broad, to pH 4,6, and 8), as well as a decrease in temperature stability by 25% activity following elicitor treatment in comparison to untreated extracts. These results may support the hypothesis that an ability of the peroxidase enzyme, and other enzymes perhaps, to tolerate a stress-inducedintracellular acidification may help the plant to survive periods of metabolic instability and generate phenolic compounds during stress responses.