Yuan-Tong Lin

Stimulation of phenolics, antioxidant and antimicrobial activities in dark germinated mung bean sprouts in response to peptide and phytochemical elicitors

The phenyl propanoid pathway (PPP) was stimulated in mung bean sprouts through the pentose phosphate and shikimate pathways, by natural elicitors such as fish protein hydrolysates (FPH), lactoferrin (LF) and oregano extract (OE). Elicitation significantly improved the phenolic, antioxidant and antimicrobial properties of mung bean sprouts. The optimal elicitor concentrations were 1 ml/l FPH, 250 ppm LF and 1 ml/l OE for the highest phenolic content that was approximately 20, 35 and 18% higher than control, respectively, on day 1 of dark germination. The antioxidant activity estimated by β-carotene assay in mung bean sprouts was highest on day 1 of germination for all treatments and control. In general, higher antioxidant activity was observed in the elicited sprouts compared with control. In the case of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay the antioxidant activity for all treatments and control was highest on day 2. Among the different elicitor treatments, OE elicited mung bean sprouts showed the highest antioxidant activity of 49% DPPH inhibition on day 2. This increased activity correlates with high guaiacol peroxidase (GPX) activity indicating that the polymerizing phenolics required during lignification with growth have antioxidant function. For all elicitor treatments a higher glucose-6-phosphate dehydrogenase (G6PDH) activity was observed during early germination following the high phenolic content. This is due to the general mobilization of carbohydrates to the growing sprouts in response to elicitation. In general the GPX activity steadily increased with germination for treatments and control. The higher phenolics produced on day 1 was utilized for GPX-mediated polymerization to form polymeric phenolics and lignin required during germination. The late stage polymerization linked to GPX activity preceded stimulation of G6PDH. This indicated that as phenolics were polymerized by GPX in late stages, G6PDH linked precursors such as NADPH2 and sugar phosphates were being made available. Antimicrobial activity against Helicobacter pylori was observed in the mung bean sprout extract from control, LF and OE treatments from the day 1 stage. Both the LF and OE elicited extracts showed high antimicrobial activity, which correlated to high antioxidant activity on day 1. The higher antimicrobial activity was also observed with the higher stimulation of G6PDH and GPX activity during early stages of germination. This leads to the hypothesis that enhanced mobilization of carbohydrates (as indicated by G6PDH activity on days 2 and 4), enhanced polymerization of simple phenols (as indicated by GPX activity on day 3) contributed to high antioxidant activity producing intermediary metabolites (day 2).

Inhibition of Helicobacter pylori and associated urease by oregano and cranberry phytochemical synergies.

ABSTRACT Ulcer-associated dyspepsia is caused by infection with Helicobacter pylori. H. pylori is linked to a majority of peptic ulcers. Antibiotic treatment does not always inhibit or kill H. pylori with potential for antibiotic resistance. The objective of this study was to determine the potential for using phenolic phytochemical extracts to inhibit H. pylori in a laboratory medium. Our approach involved the development of a specific phenolic profile with optimization of different ratios of extract mixtures from oregano and cranberry. Subsequently, antimicrobial activity and antimicrobial-linked urease inhibition ability were evaluated. The results indicated that the antimicrobial activity was greater in extract mixtures than in individual extracts of each species. The results also indicate that the synergistic contribution of oregano and cranberry phenolics may be more important for inhibition than any species-specific phenolic concentration. Further, based on plate assay, the likely mode of action may be through urease inhibition and disruption of energy production by inhibition of proline dehydrogenase at the plasma membrane.

Inhibition of Listeria monocytogenes in Fish and Meat Systems by Use of Oregano and Cranberry Phytochemical Synergies

ABSTRACT Optimized phenolics from oregano and cranberry extracts were evaluated for antimicrobial activity against Listeria monocytogenes in laboratory media and in beef and fish. The antimicrobial activity increased when oregano and cranberry extracts were mixed at a ratio of 75% oregano and 25% cranberry (wt/wt) with 0.1 mg of phenolic per disk or ml, and the efficacy was further enhanced by lactic acid. The inhibition by phytochemical and lactic acid synergies was most effective when beef and fish slices were stored at 4°C.

Enterotoxigenicity and Genetic Relatedness of Clostridium perfringens Isolates from Retail Foods in the United States

ABSTRACT Clostridium perfringens is a leading cause of bacterial food-borne illness in countries where consumption of meat and poultry is high. For example, each year in the United States, this organism is the second or third most common cause of confirmed cases of food-borne illness. Surveys of the incidence of this organism in retail foods were done in the 1960s without regard to whether isolates were enterotoxigenic. It is now known that not all strains of this organism possess the enterotoxin gene responsible for illness. We examined the incidence of this organism in 131 food samples from retail food stores in an area of the northeastern United States. Forty isolates were obtained by using the iron milk method at 45°C, with confirmation by use of motility nitrate and lactose gelatin media. The presence of the C. perfringens enterotoxin (cpe) and alpha toxin (cpa) genes was determined by PCR using previously published primer sequences. All isolates possessed cpa. None of the isolates were identified as carrying the cpe gene by this method or by another method using a digoxigenin-labeled gene probe. Consistent with these results, none of the sporulating-cell extracts contained enterotoxin as determined by reverse passive latex hemagglutination. Pulsed-field gel electrophoresis was used to determine the genetic relatedness of the isolates. About 5% of the isolates were considered to be closely related (2- to 3-band difference). The others were considered to be unrelated to one another. The results demonstrate the rarity of cpe+ strains in retail foods and the genetic diversity among nonoutbreak strains.

Enrichment of Phenolic Antioxidants and Anti-Helicobacter pylori Properties of Cranberry Pomace by Solid-State Bioprocessing

Cranberry pomace modified by solid-state bioprocessing with the food-grade fungi Rhizopus oligosporus and Lentinus edodes was investigated for antimicrobial effects against Helicobacter pylori. The results indicated that solid-state bioprocessing enriched the cranberry pomace with phenolic antioxidants and important phenolic phytochemicals such as ellagic acid. The antimicrobial activity of the extracts against H. pyloriwas also enriched by solid-state bioprocessing. Further, the results also indicated that the antimicrobial activity correlated strongly with total soluble phenolic content and ellagic acid, suggesting different modes of antimicrobial function. A dose-dependent analysis of antimicrobial activity suggested that there could be a possible synergistic mode of interaction between the phenolic phytochemicals. Solid-state bioprocessing of cranberry pomace using the food-grade fungi R. oligosporus and L. edodes could therefore be an innovative approach to develop antimicrobial ingredients for dietary management of H. pylori infections.

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.