Green tea polyphenols react with 1,1-diphenyl-2-picrylhydrazyl free radicals in the bilayer of liposomes: direct evidence from electron spin resonance studies

Mechanisms of polyphenols on quality control of aquatic products in storage: A review

Aquatic products are easily spoiled during storage due to oxidation, endogenous enzymes, and bacteria. At the same time, compared with synthetic antioxidants, based on the antibacterial and antioxidant mechanism of biological agents, the development of natural, nontoxic, low-temperature, better-effect green biological preservatives is more acceptable to consumers. The type and molecular structure of polyphenols affect their antioxidant and antibacterial effectiveness. This review will describe how they achieve their antioxidant and antibacterial effects. And the recent literature on the mechanism and application of polyphenols in the preservation of aquatic products was updated and summarized. The conclusion is that in aquatic products, polyphenols alleviate lipid oxidation, protein degradation and inhibit the growth and reproduction of microorganisms, so as to achieve the effect of storage quality control. And put forward suggestions on the application of the research results in aquatic products. We hope to provide theoretical support for better exploration of the application of polyphenols and aquatic product storage.

Build-Up of a 3D Organogel Network within the Bilayer Shell of Nanoliposomes. A Novel Delivery System for Vitamin D3: Preparation, Characterization, and Physicochemical Stability

The inherent thermodynamic instability of liposomes during production and storage has limited their widespread applications. Therefore, a novel structure of food-grade nanoliposomes stabilized by a 3D organogel network within the bilayer shell was developed through the extrusion process and successfully applied to encapsulate vitamin D₃. A huge flocculation and a significant reduction of zeta potential (-17 mV) were observed in control nanoliposomes (without the organogel shell) after 2 months of storage at 4 °C, while the sample with a gelled bilayer showed excellent stability with a particle diameter of 105 nm and a high negative zeta potential (-63.4 mV), even after 3 months. The development of spherical vesicles was confirmed by TEM. Interestingly, the gelled bilayer shell led to improved stability against osmotically active divalent salt ions. Electron paramagnetic resonance confirmed the higher rigidity of the shell bilayer upon gelation. The novel liposome offered a dramatic increase in encapsulation efficiency and loading of vitamin D₃ compared to those of control.

Quantitative Metabonomic Analysis Reveals the Germination-Associated Dynamic and Systemic Biochemical Changes for Mung-Bean (Vigna radiata) Seeds

Seed germination is essential for plant survival, germplasm resource preservation, and worldwide food supplies, although the germination-associated seed biochemical variations are not fully understood. With the NMR-based metabonomics, we quantitatively analyzed the comprehensive metabolite composition (metabonome) of mung-bean (Vigna radiata) seeds at eight time points of germination covering all three phases. We found that mung-bean seed metabonomes were dominated by 63 metabolites including lipids, amino acids, oligo-/monosaccharides, cyclitols, cholines, organic acids, nucleotides/-sides, nicotinates, and the shikimate pathway-mediated secondary metabolites. During germination, metabolic changes included mainly the degradation of proteins and raffinose family oligosaccharides, glycolysis, tricarboxylic acid (TCA) cycle, anaerobic respiration, biosynthesis of osmolytes and antioxidants together with the metabolisms of nucleotides/-sides, nicotinates, and amino acids. Oligosaccharide degradation was the primary energy source for germination, which coupled with the mobilization of starch and protein storages to produce sugars and amino acids for biomaterial and energy generations. Osmotic and redox regulations were prerequisites for seed germination together with mitochondrial reparations and generations to enable TCA cycle. During the postgermination growth stage (phase-3), the use of small molecules including amino acids and saccharides was switched to meet the growth demands of radicle cells. Small metabolites passed freely through seed testa leaking into the culture media during early germination but were reabsorbed by seed cells around the postgermination growth stage. Extra after-ripening accelerated these metabolic processes of seeds in phase-1, especially the biosynthesis of cyclitols, choline, and nicotinates, increasing the germination uniformity in terms of speed and percentage. Germination-resistant seeds were incapable of activating the germination-associated metabolic processes.

An optimized method for NMR-based plant seed metabolomic analysis with maximized polar metabolite extraction efficiency, signal-to-noise ratio, and chemical shift consistency

An optimized method for NMR-based plant seed metabolomic analysis was established with extraction solvent, cell-breaking method and extract-to-buffer ratio.

Carotenoids and total phenolic contents in plant foods commonly consumed in Korea

Phytochemicals are reported to provide various biological functions leading to the promotion of health as well as the reduced risk of chronic diseases. Fat-soluble plant pigments, carotenoids, are extensively studied micronutrient phytochemicals for their potential health benefits. It is noteworthy that specific carotenoids may be responsible for different protective effects against certain diseases. In addition, each carotenoid can be obtained from different types of plant foods. Considering the fact that the phytochemical content in foods can vary according to, but not limited to, the varieties and culture conditions, it is important to establish a database of phytochemicals in locally produced plant foods. Currently, information on individual carotenoid content in plant foods commonly consumed in Korea is lacking. As the first step to support the production and consumption of sustainable local plant foods, carotenoids and total phenolic contents of plant foods commonly consumed in Korea are presented and their potential biological functions are discussed in this review.

The protective effects of Prunus armeniaca L (apricot) against methotrexate-induced oxidative damage and apoptosis in rat kidney

This study was conducted to evaluate a possible protective role of apricot in apoptotic cell death induced by methotrexate (MTX) and renal damage by different histological and biochemical parameters. Twenty-eight rats were divided into four groups, control, apricot, methotrexate, and apricot + methotrexate. Methotrexate induced renal failure, as shown by significant serum creatinine and urea elevation. Additionally, the results indicated that methotrexate significantly induced lipid peroxidation and reduced antioxidant activities in rats. In contrast, apricot significantly prevented toxic effects of methotrexate via increased catalase, superoxide dismutase, and glutathione levels but decreased formation of malondialdehyde. Also, it was determined that exposure to methotrexate leads to significant histological damage in kidney tissue such as glomerulosclerosis and apoptosis. On the other hand, these effects can be eliminated with apricot diet. These data indicate that apricot may be useful in preventing undesirable effects of MTX such as nephrotoxicity.

Identification of three novel polyphenolic compounds, origanine A-C, with unique skeleton from Origanum vulgare L. using the hyphenated LC-DAD-SPE-NMR/MS methods

Identification of new compounds especially those with new skeletons from plant kingdom has long been a vital aspect for understanding phytochemistry, plant metabolisms and discovering new bioactive compounds. In this study, we identified and isolated three novel polyphenolic compounds, origanine A-C, from a well-researched plant Origanum vulgare L. using the hyphenated LC-DAD-SPE-NMR/MS methods. Based on the combined information from UV-visible, accurate mass and 2D NMR spectra together with computational calculations, we found that these compounds all had a novel skeleton of cyclohexenetetracarboxylic acids attached with some well-known bioactive moieties including 3,4-dihydroxyphenyl, 4-(β-d-glucopyranosyloxy)benzyl alcohol (gastrodin), and 3-(3,4-dihydroxyphenyl)lactic acid (danshensu) residues. These findings provided crucial information to fill the gaps in our knowledge in terms of the plant secondary metabolism. This study also indicated the necessity for further research in plant secondary metabolism for even well-studied plants and demonstrated the powerfulness of the hyphenated LC-DAD-SPE-NMR/MS methods for comprehensive analysis of plant metabolites in particular for discovering new natural compounds.

Supplementation with lutein or lutein plus green tea extracts does not change oxidative stress in adequately nourished older adults

Epigallocatechin gallate, a major component of green tea polyphenols, protects against the oxidation of fat-soluble antioxidants including lutein. The current study determined the effect of a relatively high but a dietary achievable dose of lutein or lutein plus green tea extract on antioxidant status. Healthy subjects (50-70 years) were randomly assigned to one of two groups (n=20 in each group): (1) a lutein (12 mg/day) supplemented group or (2) a lutein (12 mg/day) plus green tea extract (200 mg/day) supplemented group. After 2 weeks of run-in period consuming less than two servings of lightly colored fruits and vegetables in their diet, each group was treated for 112 days while on their customary regular diets. Plasma carotenoids including lutein, tocopherols, flavanols and ascorbic acid were analyzed by HPLC-UVD and HPLC-electrochemical detector systems; total antioxidant capacity by fluorometry; lipid peroxidation by malondialdehyde using a HPLC system with a fluorescent detector and by total hydroxyoctadecadienoic acids using a GC/MS. Plasma lutein, total carotenoids and ascorbic acid concentrations of subjects in either the lutein group or the lutein plus green tea extract group were significantly increased (P<.05) at 4 weeks and throughout the 16-week study period. However, no significant changes from baseline in any biomarker of overall antioxidant activity or lipid peroxidation of the subjects were seen in either group. Our results indicate that an increase of antioxidant concentrations within a range that could readily be achieved in a healthful diet does not affect in vivo antioxidant status in normal healthy subjects when sufficient amounts of antioxidants already exist.

Free radicals generated during oxidation of green tea polyphenols: electron paramagnetic resonance spectroscopy combined with density functional theory calculations

Electron paramagnetic resonance spectroscopy and density functional theory calculations have been used to investigate the redox properties of the green tea polyphenols (GTPs) (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin gallate (ECG). Aqueous extracts of green tea and these individual phenols were autoxidized at alkaline pH and oxidized by superoxide anion (O(2)(-)) radicals in dimethyl sulfoxide. Several new aspects of the free radical chemistry of GTPs were revealed. EGCG can be oxidized on both the B and the D ring. The B ring was the main oxidation site during autoxidation, but the D ring was the preferred site for O(2)(-) oxidation. Oxidation of the D ring was followed by structural degradation, leading to generation of a radical identical to that of oxidized gallic acid. Alkaline autoxidation of green tea extracts produced four radicals that were related to products of the oxidation of EGCG, EGC, ECG, and gallic acid, whereas the spectra from O(2)(-) oxidation could be explained solely by radicals generated from EGCG. Assignments of hyperfine coupling constants were made by DFT calculations, allowing the identities of the radicals observed to be confirmed.

Structure-activity relationship of C6-C3 phenylpropanoids on xanthine oxidase-inhibiting and free radical-scavenging activities

We employed the techniques of DNA relaxation, DPPH (1,1-diphenyl-2-picrylhydrazyl hydrate), and DMPO (5,5-dimethyl-1-pyrroline-N-oxide)-electron spin resonance (ESR), to study the effects of reactive oxygen species (ROS) suppression by 11 selected C6-C3 phenylpropanoid derivatives under oxidative conditions. We also investigated the effects of the derivatives on the inhibition of xanthine oxidase (XO) activity, and the structure-activity relationships (SARs) of these derivatives against XO activity were further examined using computer-aided molecular modeling. Caffeic acid was the most potent radical scavenger among the 11 test compounds. Our results suggest that the chemical structure and number of hydroxyl groups on the benzene ring of phenylpropanoids are correlated with the effects of ROS suppression. All test derivatives were competitive inhibitors of XO. The results of the structure-based molecular modeling exhibited interactions between phenylpropanoid derivatives and the molybdopterin region of XO. The para-hydroxyl of phenylpropanoid derivatives was pointed toward the guanidinium group of Arg 880. The phenylpropanoid derivatives containing the meta-or ortho-hydroxyl formed hydrogen bonds with Thr 1010. In addition, meta-hydroxyl formed hydrogen bonds with the peptide bond between the residues of Thr1010 and Phe1009. CAPE, the phenylenethyl ester of phenylpropanoids, had the highest affinity toward the binding site of XO, and we speculated that this was due to hydrophobic interactions of the phenylethyl ester with several hydrophobic residues surrounding the active site. The hypoxanthine/XO reaction in the DMPO-ESR technique was used to correlate the effects of these phenylpropanoid derivatives on enzyme inhibition and ROS suppression, and the results showed that caffeic acid and CAPE were the two most potent agents among the tested compounds. We further assessed the effects of the test compounds on living cells, and CAPE was the most potent agent for protecting cells against ROS-mediated damage among the tested phenylpropanoids.

The potential pitfalls of using 1,1-diphenyl-2-picrylhydrazyl to characterize antioxidants in mixed water solvents

Approaching living systems, aqueous solutions are appropriate to characterize antioxidants, whereas the frequently used standard 1,1-diphenyl-2-picrylhydrazyl (DPPH) is insoluble in water. Therefore, mixed water-ethanol solvents were investigated using the electron paramagnetic resonance (EPR) spectroscopy. Two forms of DPPH were identified: at higher ethanol ratios a quintet spectrum characteristic of solutions, and at lower ratios, a singlet spectrum typical for solid DPPH, were found. Mixed solvents with 0-50% (v/v) water reproduced the same antioxidant equivalent points well and the reaction rate between DPPH and the antioxidant may increase considerably with increasing water ratios, as demonstrated using vitamin E as an antioxidant. But at still higher water ratios (70-90% (v/v)) the antioxidant activities dropped, since a part of the DPPH in the aggregated form does not react sufficiently with the antioxidants. Characteristics of the most common antioxidants were determined in ethanol or its 50% (v/v) aqueous solution.

In vitro free radical scavenging activities and effect of synthetic oligosaccharides on antioxidant enzymes and lipid peroxidation in aged mice

In this study we synthesized oligosaccharides using glucose as reactant via a route assisted by microwave irradiation and evaluated their antioxidant activity in vivo and in vitro. The results show that the oligosaccharides exhibited antioxidant activity in vitro as compared to standard antioxidants such as butylated hydroxytoluene (BHT), and alpha-tocopherol. This antioxidant activity depended on concentration and increased with increasing dose of sample. In addition, increased endogenous lipid peroxidation and decreased total antioxidant capacity (TAOC) were observed in aged mice. Thirty-day intraperitoneal administration of the oligosaccharides significantly decreased the lipid peroxidation in a dose-dependent manner. Oligosaccharides treatment increased TAOC and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in all organs tested in aged mice. The present study suggests that the synthetic oligosaccharides possess promising future for their strong free radical scavenging activity. Therefore they can be employed in compensating the decline in TAOC and the activities of antioxidant enzymes and in reducing the risks of lipid peroxidation.

Structure-activity relationship analysis of antioxidant ability and neuroprotective effect of gallic acid derivatives

Gallic acid and its derivatives are a group of naturally occurring polyphenol antioxidants which have recently been shown to have potential healthy effects. In order to understand the relationship between the structures of gallic acid derivatives, their antioxidant activities, and neuroprotective effects, we examined their free radical scavenging effects in liposome and anti-apoptotic activities in human SH-SY5Y cell induced by 6-hydrodopamine autooxidation. It was found that these polyphenol antioxidants exhibited different hydrophobicity and could cross through the liposome membrane to react with 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical in a time and dose-dependent manner. At the same time, the structure-antioxidant activity relationship of gallic acid derivatives on scavenging DPPH free radical in the liposome was also analyzed based on theoretical investigations. Analysis of cell apoptosis, intracellular GSH levels, production of ROS and the influx of Ca(2+) indicated that the protective effects of gallic acid derivatives in cell systems under oxidative stress depend on both their antioxidant capacities and hydrophobicity. However, the neuroprotective effects of gallic acid derivatives seem to depend more on their molecular polarities rather than antioxidant activities in the human SH-SY5Y cell line. In conclusion, these results reveal that compounds with high antioxidant activity and appropriate hydrophobicity are generally more effective in preventing the injury of oxidative stress in neurodegenerative diseases.

Structure-activity relationships in the hydrophobic interactions of polyphenols with cellulose and collagen

Polyphenol interactions with both cellulose and collagen in the solid state have been studied by using chromatography on cellulose and by evaluating the hydrothermal stability of the polyphenol treated sheepskin collagen. Twenty-four polyphenolic compounds were studied, including seven glucose-based gallotannins, five polyalcohol-based gallotannins, and twelve ellagitannins. In the cellulose-polyphenols systems, the polyphenol's affinity to cellulose is positively correlated with their molecular masses, the number of galloyl groups, and their hydrophobicity (logP). The polyphenol treatment increased the hydrothermal stability of collagen samples, and such effects are also positively correlated with the molecular masses, total number of galloyl groups and the hydrophobicity of polyphenols. Ellagitannins showed much weaker interactions with both biopolymers than gallotannins having similar molecular mass, the same number of galloyl groups, and the same number of phenolic hydroxyl groups. It is concluded that, for the polyphenol interactions with both cellulose and collagen, (1) the galloyl group of polyphenols is the functional group; (2) the strength of interactions are positively correlated with molecular size, the number of galloyl groups and the hydrophobicity of polyphenols; (3) the hydrophobic interactions are of great significance; and (4) the interactions are strongly dependent on the flexibility of galloyl groups.

Flavonoids in food and their health benefits

There has been increasing interest in the research of flavonoids from dietary sources, due to growing evidence of the versatile health benefits of flavonoids through epidemiological studies. As occurrence of flavonoids is directly associated with human daily dietary intake of antioxidants, it is important to evaluate flavonoid sources in food. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. However, there is still difficulty in accurately measuring the daily intake of flavonoids because of the complexity of existence of flavonoids from various food sources, the diversity of dietary culture, and the occurrence of a large amount of flavonoids itself in nature. Nevertheless, research on the health aspects of flavonoids for humans is expanding rapidly. Many flavonoids are shown to have antioxidative activity, free-radical scavenging capacity, coronary heart disease prevention, and anticancer activity, while some flavonoids exhibit potential for anti-human immunodeficiency virus functions. As such research progresses. further achievements will undoubtedly lead to a new era of flavonoids in either foods or pharmaceutical supplements. Accordingly, an appropriate model for a precise assessment of intake of flavonoids needs to be developed. Most recent research has focused on the health aspects of flavonoids from food sources for humans. This paper reviews the current advances in flavonoids in food, with emphasis on health aspects on the basis of the published literature, which may provide some guidance for researchers in further investigations and for industries in developing practical health agents.