Role of Sulphur and Heavier Chalcogens on the Antioxidant Power and Bioactivity of Natural Phenolic Compounds.

The activity of natural phenols is primarily associated to their antioxidant potential, but is ultimately expressed in a variety of biological effects. Molecular scaffold manipulation of this large variety of compounds is a currently pursued approach to boost or modulate their properties. Insertion of S/Se/Te containing substituents on phenols may increase/decrease their H-donor/acceptor ability by electronic and stereo-electronic effects related to the site of substitution and geometrical constrains. Oxygen to sulphur/selenium isosteric replacement in resveratrol or ferulic acid leads to an increase in the radical scavenging activity with respect to the parent phenol. Several chalcogen-substituted phenols inspired by Vitamin E and flavonoids have been prepared, which in some cases prove to be chain-breaking antioxidants, far better than the natural counterparts. Conjugation of catechols with biological thiols (cysteine, glutathione, dihydrolipoic acid) is easily achieved by addition to the corresponding ortho-quinones. Noticeable examples of compounds with potentiated antioxidant activities are the human metabolite 5-S-cysteinyldopa, with high iron-induced lipid peroxidation inhibitory activity, due to strong iron (III) binding, 5-S-glutathionylpiceatannol a most effective inhibitor of nitrosation processes, and 5-S-lipoylhydroxytyrosol, and its polysulfides that proved valuable oxidative-stress protective agents in various cellular models. Different methodologies have been used for evaluation of the antioxidant power of these compounds against the parent compounds. These include kinetics of inhibition of lipid peroxidation alkylperoxyl radicals, common chemical assays of radical scavenging, inhibition of the OH• mediated hydroxylation/oxidation of model systems, ferric- or copper-reducing power, scavenging of nitrosating species. In addition, computational methods allowed researchers to determine the Bond Dissociation Enthalpy values of the OH groups of chalcogen modified phenolics and predict the best performing derivative. Finally, the activity of Se and Te containing compounds as mimic of glutathione peroxidase has been evaluated, together with other biological activities including anticancer action and (neuro)protective effects in various cellular models. These and other achievements are discussed and rationalized to guide future development in the field.

Pectin-Based Formulations for Controlled Release of an Ellagic Acid Salt with High Solubility Profile in Physiological Media.

Among bioactive phytochemicals, ellagic acid (EA) is one of the most controversial because its high antioxidant and cancer-preventing effects are strongly inhibited by low gastrointestinal absorption and rapid excretion. Strategies toward an increase of solubility in water and bioavailability, while preserving its structural integrity and warranting its controlled release at the physiological targets, are therefore largely pursued. In this work, EA lysine salt at 1:4 molar ratio (EALYS), exhibiting a more than 400 times increase of water solubility with respect to literature reports, was incorporated at 10% in low methoxylated (LM) and high methoxylated (HM) pectin films. The release of EA in PBS at pH 7.4 from both film preparations was comparable and reached 15% of the loaded compound over 2 h. Under simulated gastric conditions, release of EA from HM and LM pectin films was minimal at gastric pH, whereas higher concentrations-up to 300 µM, corresponding to ca. 50% of the overall content-were obtained in the case of the HM pectin film after 2 h incubation at the slightly alkaline pH of small intestine environment, with the enzyme and bile salt components enhancing the release. EALYS pectin films showed a good prebiotic activity as evaluated by determination of short chain fatty acids (SCFAs) levels following microbial fermentation, with a low but significant increase of the effects produced by the pectins themselves. Overall, these results highlight pectin films loaded with EALYS salt as a promising formulation to improve administration and controlled release of the compound.

Anti-Amyloid Aggregation Activity of Black Sesame Pigment: Toward a Novel Alzheimer's Disease Preventive Agent.

Black sesame pigment (BSP) represents a low cost, easily accessible material of plant origin exhibiting marked antioxidant and heavy metal-binding properties with potential as a food supplement. We report herein the inhibitory properties of the potentially bioaccessible fraction of BSP following simulated gastrointestinal digestion against key enzymes involved in Alzheimer's disease (AD). HPLC analysis indicated that BSP is transformed under the pH conditions mimicking the intestinal environment and the most abundant of the released compounds was identified as vanillic acid. More than 80% inhibition of acetylcholinesterase-induced aggregation of the ß-amyloid Aß1-40 was observed in the presence of the potentially bioaccessible fraction of BSP, which also efficiently inhibited self-induced Aß1-42 aggregation and ß-secretase (BACE-1) activity, even at high dilution. These properties open new perspectives toward the use of BSP as an ingredient of functional food or as a food supplement for the prevention of AD.

Fermented pomegranate wastes as sustainable source of ellagic acid: Antioxidant properties, anti-inflammatory action, and controlled release under simulated digestion conditions.

Wastes deriving from production of wines by yeast fermentation of Punica granatum (fermented pomegranate wastes, FPW) showed a marked antioxidant activity in a series of conventional chemical tests. HPLC/MS analysis of the methanol extract showed the presence of ellagic acid (EA) as the main phenolic component at levels up to 40% on a w/w basis. Experiments using murine macrophages showed that FPW extract is able to reduce the LPS-induced expression of pro-inflammatory genes IL-1ß, TNF-α and iNOS. A remarkable increase in the antioxidant properties and extractable EA content was observed following acid hydrolytic treatment of FPW. Under simulated gastrointestinal conditions, EA was slowly released from FPW up to 80% of the overall content over 2 h incubation at the slightly alkaline pHs simulating the small intestine environment, suggesting a potential of the material in nutraceuticals and other applications.

Epilutein for Early-Stage Age-Related Macular Degeneration: A Randomized and Prospective Study.

PURPOSE: The hypothesis that oral supplementation of the epilutein/lutein combination could augment the macular pigment optical density (MPOD) in patients with age-related macular degeneration (AMD) was tested. METHODS: In a prospective randomized interventional study, 40 consecutive patients with early-stage AMD were recruited. After a 2-week run-in period, patients were randomly treated with a daily oral administration of 8 mg epilutein and 2 mg lutein (group 1) or 10 mg lutein (group 2) for 2 months. At baseline (BL) and 1-month (M1) and 2-month visits (M2), all patients underwent a complete ophthalmological examination, including measurement of MPOD in a 7° area (Visucam 200; Carl Zeiss Meditec, Milan, Italy). Xanthophylls were quantified in plasma, as well as the HDL, non-HDL, and erythrocyte fractions at each study visit. RESULTS: Twenty-one patients (mean age 69.4 ± 6.7 years, 35 eyes) were included in group 1. Mean MPOD was 0.203 ± 0.02 optical density units (ODU) at BL, and increased to 0.214 ± 0.04 ODU at M1 (p = 0.008) and 0.206 ± 0.03 ODU at M2 (p = 0.04). Sixteen patients (mean age 72.0 ± 6.3 years, 29 eyes) were included in group 2. Mean MPOD was 0.215 ± 0.03 at BL, which reduced to 0.202 ± 0.03 ODU at M1 (p = 0.003) and 0.207 ± 0.02 ODU at M2 (p < 0.001). A rise in the systemic level of total xanthophylls was observed at M1 for both groups. At M2, total xanthophylls were significantly increased only in group 1 and decreased in group 2. CONCLUSION: In patients with early-stage AMD, the administration of lutein in combination with epilutein was associated with an increased MPOD compared to the administration of lutein alone.

High Antioxidant Action and Prebiotic Activity of Hydrolyzed Spent Coffee Grounds (HSCG) in a Simulated Digestion-Fermentation Model: Toward the Development of a Novel Food Supplement.

Spent coffee grounds are a byproduct with a large production all over the world. The aim of this study was to explore the effects of a simulated digestion-fermentation treatment on hydrolyzed spent coffee grounds (HSCG) and to investigate the antioxidant properties of the digestion and fermentation products in the human hepatocellular carcinoma HepG2 cell line. The potentially bioaccessible (soluble) fractions exhibited high chemoprotective activity in HepG2 cells against oxidative stress. Structural analysis of both the indigestible (insoluble) and soluble material revealed partial hydrolysis and release of the lignin components in the potentially bioaccessible fraction following simulated digestion-fermentation. A high prebiotic activity as determined from the increase in Lactobacillus spp. and Bifidobacterium spp. and the production of short-chain fatty acids (SCFAs) following microbial fermentation of HSCG was also observed. These results pave the way toward the use of HSCG as a food supplement.

Efficient Binding of Heavy Metals by Black Sesame Pigment: Toward Innovative Dietary Strategies To Prevent Bioaccumulation.

Black sesame pigment (BSP) was shown to bind lead, cadmium, and mercury at pH 7.0 and to a lower extent at pH 2.0. BSP at 0.05 mg/mL removed the metals at 15 µM to a significant extent (>65% for cadmium and >90% for mercury and lead), with no changes following simulated digestion. The maximum binding capacities at pH 7.0 were 626.0 mg/g (lead), 42.2 mg/g (cadmium), and 69.3 mg/g (mercury). In the presence of essential metals, such as iron, calcium, and zinc, BSP retained high selectivity toward heavy metals. Model pigments from caffeic acid, ferulic acid, and coniferyl alcohol showed lower or comparable binding ability, suggesting that the marked properties of BSP may result from cooperativity of different sites likely carboxy groups and o-diphenol and guaiacyl functionalities. Direct evidence for the presence of such units was obtained by structural analysis of BSP by solid-state Fourier transform infrared spectroscopy and (13)C nuclear magnetic resonance spectroscopy.

Olive oil mill wastewater for remediation of slag contaminated soil.

Two olive mill wastewaters (OMW) samples, OMWa and OMWb, containing different polyphenolic loads were used for decontaminating an unauthorized dump site in the Campania region, south Italy. In a bench-scale experiment, OMWa at pH 6.0 (OMWapH6.0) and 4.7 (OMWapH4.7), OMWb at pH 4.7 (OMWbpH4.7) and OMWa free of the polyphenolic moiety polyphenol-free OMWa (PF-OMWa) were added to the soil for a 96 h contact time. At 96 h, OMWapH4.7 was more effective than OMWapH6.0, with Cd, Cu, Pb and Zn removal percentages of 30.7-68.1. Cd and Pb levels were 6.0 and 915 mg kg(-1), respectively, decreasing below the regulatory limits for industrial and commercial areas (15.0 and 1 × 10(3) mg kg(-1), respectively). A threefold decrease in Zn levels was also observed from 13.5 × 10(3) to 4.3 × 10(3) mg kg(-1). The metal removal efficiency of PF-OMWa dropped from 30.7 % to 15.6 % for Cd and from 37.9 % to 1.3 % for Pb. OMWbpH4.7 at 96 h was more efficient than OMWapH4.7, with mean removal percentages of 32.5 versus 7.8, respectively.

A reappraisal of traditional apple cultivars from Southern Italy as a rich source of phenols with superior antioxidant activity.

Few literature data are available on the nutraceutical properties of little widespread local apple cultivars. Such lack of information prevents exploitation of these germplasms for genetic improvement of new cultivars and for the re-evaluation of local agricultural products, which may attract a large share of consumers oriented towards natural food evoking ancient flavours. In this work eight traditional apple cultivars of Southern Italy were analysed in terms of phenolic composition and free radical scavenging activity in comparison with commercial "Annurca" and "Gold Chief® Gold Pink∗" cultivars. HPLC-UV-MS analysis of methanol extracts of the cultivars under examination showed significant differences in phenol distribution within the three main classes of hydroxycinnamates, dihydrochalcones, and flavan-3-ols. Such differences were found to be associated with the antioxidant activities as determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. A good correlation was observed between the percentage of reduced DPPH and the total phenol content (R=0.79). Among all phenol classes, the flavan-3-ol content showed the highest correlation (R=0.77). Almost all of the traditional cultivars examined exhibited a much higher phenol content (2- to 7-fold) and hydrogen donor activity (1.5- to 4-fold) than widely consumed cultivars like "Annurca" and "Gold Chief® Gold Pink∗".

Black sesame pigment: DPPH assay-guided purification, antioxidant/antinitrosating properties, and identification of a degradative structural marker.

An improved purification procedure leading to black sesame ( Sesamum Indicum L.) pigment was developed involving fat removal by treatment of ground black sesame seeds with dichloromethane followed by an optimized hydrolytic protocol with 6 M HCl, at 100 °C, overnight. The black pigment thus obtained displayed good antioxidant efficiency by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay (82% reduction at 0.5 mg/mL), good ferric ion-reducing capacity (61 µM Trolox equivalent concentration at 0.5 mg/mL), and potent antinitrosating properties (74% inhibition of 2,3-diaminonaphthalene (DAN) nitrosation at gastric pH at 2.5 mg/mL). A synthetic pigment obtained by oxidative polymerization of coniferyl alcohol (polyconiferyl alcohol, PCA), the putative biosynthetic precursor to the sesame pigment, was characterized as a reference standard. FT IR spectra of the purified sesame pigment and PCA supported the structural similarity. HPLC analysis of degradation products by alkaline hydrogen peroxide of purified black sesame pigment showed the formation of vanillic acid (VA) as the main isolable fragment. Similar yields of VA were obtained by degradation of PCA. A positive correlation between VA yields and DPPH activity was determined in samples of different purities. It is suggested that VA is a structural marker of black sesame pigment, confirming the biosynthetic origin from coniferyl alcohol and pointing to the o-methoxyphenol motif as the key factor accounting for the potent antioxidant properties of the pigment.

Differential reactivity of purified bioactive coffee furans, cafestol and kahweol, with acidic nitrite: product characterization and factors controlling nitrosation versus ring-opening pathways.

Cafestol and kahweol, coffee-specific furan diterpenes, are believed to cause various physiological effects in human subjects, including an increase in cholesterol and plasma triacylglycerol levels as well as cancer chemopreventive effects. Despite the increasing interest in these compounds raised by the diverse range of biological activities, their reaction behavior and degradation pathways under physiologically relevant conditions remain uncharted. Herein, we report a detailed investigation of the structural modifications suffered by cafestol and kahweol in the presence of acidic nitrite under conditions mimicking those occurring in the stomach during digestion as well as by action of other oxidants. Prior to the chemical study, an isolation procedure for kahweol from green coffee beans was developed based on Soxhlet extraction followed by preparative HPLC. Preliminary experiments showed that kahweol is much more reactive than cafestol toward nitrite at pH 3, as evidenced by inhibition experiments with the 2,3-diaminonaphthalene assay as well as by product analysis in coffee extracts. When exposed to equimolar nitrite in phosphate buffer, pH 3, kahweol gave as a main product the ring-opened dicarbonyl derivative 1. Under more forcing conditions, cafestol reacted as well to give a main nitrogenous product identified as the 1-hydroxy-2-pyrrolinone 2. It is concluded that the conjugated double bond in kahweol is a critical structural element, increasing the susceptibility of the furan ring to protonation rather than nitrosation and favoring ring-opening routes driven by the irreversible oxidation steps. These results offer a useful background to assess the effects of coffee-specific lipids in association with abnormally high nitrite levels from the diet.

Plant catechols and their S-glutathionyl conjugates as antinitrosating agents: expedient synthesis and remarkable potency of 5-S-glutathionylpiceatannol.

With a view to elucidating the structural requisites for effective antinitrosating properties in plant polyphenolics and their metabolites, we have undertaken a comparative investigation of the nitrite scavenging effects of representative catechol derivatives of dietary relevance in the 2,3-diaminonaphthalene (DAN) nitrosation and tyrosine nitration assays. Compounds tested included caffeic acid (1), chlorogenic acid (2), piceatannol (3), hydroxytyrosol (4), and the corresponding S-glutathionyl conjugates 5-8, which were prepared using either tyrosinase (5 and 6) or a novel, o-iodoxybenzoic acid (IBX)-based oxygenation/ conjugation methodology (7b and 8). In the DAN nitrosation assay at pH 4.0, the rank order of inhibitory activities was found to be 5-S-glutathionylpiceatannol (7b) > 3 > 1 > 2 > 2-S-glutathionylcaffeic acid (5) > 2-S-glutathionylchlorogenic acid (6) > 4 approximately 5-S-glutathionylhydroxytyrosol (8). Quite unexpectedly, in the tyrosine nitration assay in 0.5 M HCl, 2 was the most efficient inhibitor followed by 1 > 4 > 3 > 7b approximately 5 > 8 > 6. Under the assay conditions, the glutathionyl conjugates were usually consumed at faster rates than the parent catechols (decomposition rates: 3 > 1 > 4 > 2). The 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) assay indicated that the most effective hydrogen donors were 4 > 7b > 1 approximately 3. Overall, these results indicated that catechol compounds and their glutathionyl conjugates may exhibit profoundly different inhibitory properties depending on the specific conditions of the assay, including especially pH, and that their antinitrosating properties do not correlate tout-court with their hydrogen donor capacity. The glutathionyl-piceatannol conjugate 7b was found to be one of the most potent inhibitors in the physiologically relevant DAN assay and may provide a new structural lead for the design of effective antinitrosating agents based on dietary polyphenolic compounds.

The catecholic antioxidant piceatannol is an effective nitrosation inhibitor via an unusual double bond nitration.

Piceatannol (1) was found to be more effective than caffeic acid, an established antinitrosating agent, in inhibiting N-nitrosation of 2,3-diaminonaphthalene. Product analysis of the reaction mixture of 1 (20 microM) with nitrite ions (80 microM) at pH 3.0 and at 37 degrees C showed conversion to a single major nitration product, (E)-3,3',4,5'-tetrahydroxy-beta-nitrostilbene (2) (68% yield). This would result from an unexpected nitration at the double bond sector via the 4-phenoxyl radical, which was analyzed at the unrestricted DFT level.

The acid-promoted reaction of the green tea polyphenol epigallocatechin gallate with nitrite ions.

Exposure of 400 microM (-)-epigallocatechin-3-O-gallate (EGCG), the main polyphenolic constituent of green tea, to equimolar concentrations of nitrite ions in 0.5 M HCl at 37 degrees C resulted in the formation of a distinct pattern of products that were trapped as phenazine derivatives by treatment with o-phenylenediamine. Repeated chromatographic fractionation eventually allowed isolation of four main species, which were identified by 2D NMR and MS analysis as 1b, derived from EGCG quinone 1a, the isomeric oximes 2b,c, arising from nitrosation of EGCG on the pyrogallol B-ring, and the dioxime 4b in which the A-ring was doubly substituted. At lower EGCG concentrations (e.g., 25 microM) and at pH 3, reaction with equimolar amounts of nitrite gave 1b as the first formed species, whereas nitrosation products 2b,c and 4b became detectable only with excess nitrite. Similar reaction of chemically prepared 1a with acidic nitrite led to the formation of 2b,c and 4b, suggesting that this quinone may be an intermediate in the nitrosation of EGCG. Exposure of green tea extracts to acidic nitrite ions resulted in the conversion of EGCG to 1a, detected as 1b. Overall these results substantiate literature reports suggesting that the protective effects of EGCG against nitrosation involve mainly an initial redox exchange process and hint at a hitherto unrecognized property of quinone 1a as a potential scavenger of nitrosating species.

Acid-induced structural modifications of unsaturated Fatty acids and phenolic olive oil constituents by nitrite ions: a chemical assessment.

The structural modifications of the unsaturated fatty acid components of triglycerides in extra virgin olive oil (EVOO) following exposure to nitrite ions in acidic media were determined by two-dimensional (2D) NMR spectroscopy, aided by (15)N labeling and GC analysis, allowing investigation of the matrix without fractionation steps. In the presence of excess nitrite ions in a 1% sulfuric acid/oil biphasic system, extensive double bond isomerization of the oleic/linoleic acid components of triglycerides was observed associated with nitration/oxidation processes. Structurally modified species were identified as E/Z-nitroalkene, 1,2-nitrohydroxy, and 3-nitro-1-alkene(1,5-diene) derivatives based on (1)H, (13)C, and (15)N 2D NMR analysis in comparison with model compounds. Minor constituents of EVOO, including phenolic compounds and tocopherols, were also substantially modified by nitrite-derived nitrating species, even under milder reaction conditions relevant to those occurring in the gastric compartments. Novel nitrated derivatives of tyrosol, hydroxytyrosol, and oleuropein (6-8) were identified by LC/MS analysis of the polar fraction of EVOO and by comparison with synthetic samples. Overall, these results provide the first systematic description at the chemical level of the consequences of exposing EVOO to nitrite ions at acidic pH and offer an improved basis for further investigations in the field of toxic nitrosation/nitration reactions and dietary antinitrosating agents.

Nitrocatechols versus nitrocatecholamines as novel competitive inhibitors of neuronal nitric oxide synthase: lack of the aminoethyl side chain determines loss of tetrahydrobiopterin-antagonizing properties.

6-Nitrocatecholamines were recently described as novel neuronal nitric oxide synthase inhibitors competing with both L-arginine and tetrahydrobiopterin (BH(4)). We report now that simple nitrocatechols are also competitive inhibitors, lacking however BH(4)-antagonizing properties. It is argued that 6-nitrocatecholamines interact with the L-arginine- and BH(4)-binding sites through the nitrocatechol and aminoethyl moieties, respectively.