Antioxidant mechanism of grape procyanidins in muscle tissues: Redox interactions with endogenous ascorbic acid and α-tocopherol

The present study investigates the antioxidant mechanism of grape procyanidins and, in particular, their aptitude to establish redox interactions with two important components of the endogenous antioxidant system of muscle tissues, α-tocopherol (α-TOH) and ascorbic acid (AA). To this end, the progress of lipid oxidation was monitored in fish muscle supplemented with grape procyanidins at the concentrations usually employed in antioxidant food applications, and then related to the redox stability of the endogenous α-TOH and AA. In addition to the lipid oxidation protective effect, the incorporation of procyanidins also provided an improvement of the redox stability of the endogenous components in a straight procyanidinic concentration-dependent manner. Results showed the capacity of procyanidins to repair oxidised α-TOH at medium-long term, and to delay the AA depletion. Therefore, such cooperative redox interaction of exogenous procyanidins adequately complements the natural α-TOH regenerative system supplied by AA that is efficient at the early post mortem stages.     

化学发光法测定原花青素的研究

本文建立了测定葡萄籽提取物中原花青素的流动注射-抑制化学发光分析方法。利用原花青素还原ClO-,抑制ClO--Luminol体系的化学发光,在碱性条件下,其抑制程度的大小与原花青素的浓度在一定范围内呈现良好的线性关系。该方法线性范围为0.08～19.0μg/ml,检出限为0.06μg/ml,11次测定的RSD为1.2%。本法对样品可直接进行测定,不需特殊处理。     

Structural diversity of nucleophilic adducts from flavanols and oak wood aldehydes

The reactions between (+)-catechin and a representative oak wood aldehyde (furfuraldehyde, 5-(hydroxymethyl)furfuraldehyde, 5-methylfurfuraldehyde, vanillin, or syringaldehyde) in a wine-like model solution were studied and the formed condensation products were characterized by LC/MS and LC/MS/MS.     

Inhibition of α-amylase activity by condensed tannins

The ability of grape seed procyanidins to inhibit α-amylase activity was studied using a colorimetric method. This ability was found to be related with the average degree of polymerisation of the tested procyanidins. These interactions were further evaluated by fluorescence quenching, dynamic light scattering (DLS) and nephelometry, in order to understand the mechanisms by which they occur. A relationship between aggregate formation and enzymatic inhibition was observed. The interaction between procyanidins and enzyme involves a specific interaction as inferred from the calculated apparent bimolecular quenching constant in the fluorescence assays. Further experiments involved the determination of the effect of carbohydrates on the enzymatic inhibition observed. It was shown that pectin and arabic gum inhibited the formation of insoluble aggregates but were unable to restore fluorescence and activity to the enzyme. This suggests that these carbohydrates resulted in a decrease in turbidity due to the formation of a ternary complex with protein/polyphenol.     

Fractionation of pine bark extracts: selecting procyanidins

Pine bark is a forest by-product that can be profitable as a source of polyphenols by its content in procyanidins. In this work, barks of two varieties of pine (Pinus pinaster and P. radiata) were extracted with ethanol, and partially purified to obtain a fraction named FOW, that contained mainly flavan-3-ol monomers and procyanidins oligomers. The mean degree of polymerization was 2.1 for pinaster (pOW) and 2.7 for radiata (rOW). FOWs were fractionated on C₁₈ Sep-Pak cartridges into three fractions for each variety by different organic solvents. The phenolic compositions of the fractions were analyzed using HPLC with UV diode array detection and electrospray-ionization mass spectrometry. The compounds identified were: catechin, dihydroquercetin, phenolic acids and their glucosides, procyanidins dimers, trimers and tetramers. FOWs and their fractions were characterized in antioxidant power by DPPH and β-carotene methods. In the former assay, pOW showed major effectiveness, with an antiradical specific activity of 46 units AR/mg procyanidins, whereas for the β-carotene bleaching test rOW (78 ± 0.71%) gave the best inhibition result. Despite this fact the derived fractions, presenting similar values, have advantages because the profile of their constituents is uniform for each one, and, hence, it is easier to investigate their action for potential applications in both medical or food fields     

Antioxidant capacities,procyanidins and pigments in avocados of different strains and cultivars

Avocado (Persea americana) is an important tropical fruit, but little is known about their antioxidant capacities and phytochemical composition. The objective of this research was to determine antioxidant capacities, total phenolic content and identify and quantify major antioxidant compounds in avocados of different strains and cultivars. Ripe Florida avocados from seven cultivars (Slimcado, Booth 7, Booth 8, Choquette, Loretta, Simmonds, and Tonnage) of West Indian or Guatemalan strains were separated into seeds, peels and pulp, and freeze dried. Hass avocado of Mexican strain was chosen for comparison. Samples were extracted with acetone/water/acetic acid solvent and analysed using the Folin–Ciocalteu assay for total phenolic content. Antioxidant capacities were determined by oxygen radical absorbance capacity (ORAC) and DPPH assays. Procyanidins were identified and quantified using HPLC-MSⁿ. Antioxidant pigments (chlorophylls and carotenoids) were estimated spectrophotometrically. For all varieties, seeds contained the highest antioxidant capacities, phenolic content, and procyanidins, whereas the pulp had the lowest. Procyanidins, including catechin, epicatechin, A- and B-type dimers, A- and B-type trimers, tetramers, pentamers and hexamers, were identified in peels and seeds using normal-phase HPLC–ESI-MSⁿ. Antioxidant capacities, phenolic contents and procyanidins in avocados were highly correlated, suggesting that procyanidins were the major phenolic compounds that contributed to antioxidant capacities. Carotenoids and chlorophylls were found to be concentrated in avocado peels but did not correlate with antioxidant capacities. This study suggested that avocado seeds and peels, industrial wastes of avocado processing, can be exploited as source of antioxidants.     

Use of commercial grape phenolic extracts to supplement solid foodstuff

Osmotic treatment (OT) has been applied to infuse phenolic compounds into a model food. Two commercial grape extracts were used as a source of phenolics, a grape seed extract (GSE) and a white grape marc extract (WGME). Three different concentrations of total phenolics were applied with and without presence of osmo-active solute (50 g/100 g and 0 g/100 g of sucrose) in the osmotic solution (OS). With a 50 g/100 g sucrose and a total phenolic content in OS ranging from 3 g/L to 15 g/L and operating time up to 8 h, the final total phenolic content in the osmo-treated model food was between 815 mg GAE/kg and 7176 mg GAE/kg. That is between the 0.5 and 1.5 times higher than that of the richest fruits. A soaking process with the same phenolic content but with no sucrose in OS led to a total phenolic content in the model food that was between 80% and 100% higher.Mass transfer of the major phenolics infused into the model food during OT and soaking process was characterized considering the diffusional approach and Peleg's model. Progress of total and individual phenolic content fitted well both models with the exception of the flavan-3-ol dimer concentration.     

Dietary procyanidins lower triglyceride levels signaling through the nuclear receptor small heterodimer partner

Hypertriglyceridemia is an independent risk factor in the development of cardiovascular diseases, and we have previously reported that oral administration of a grape seed procyanidin extract (GSPE) drastically decreases plasma levels of triglycerides (TG) and apolipoprotein B (ApoB) in normolipidemic rats, with a concomitant induction in the hepatic expression of the nuclear receptor small heterodimer partner (NR0B2/SHP). Our objective in this study was to elucidate whether SHP is the mediator of the reduction of TG-rich ApoB-containing lipoproteins triggered by GSPE. We show that GSPE inhibited TG and ApoB secretion in human hepatocarcinoma HepG2 cells and had and hypotriglyceridemic effect in wild-type mouse. The TG-lowering action of GSPE was abolished in HepG2 cells transfected with a SHP-specific siRNA and in a SHP-null mouse. Moreover, in mouse liver, GSPE downregulated several lipogenic genes, including steroid response element binding protein 1c (SREBP-1c), and upregulated carnitine palmitoyltransferase-1A (CPT-1A) and apolipoprotein A5 (ApoA5), in a SHP-dependent manner. In HepG2 cells GSPE also inhibited ApoB secretion, but in a SHP-independent manner. In conclusion, SHP is a key mediator of the hypotriglyceridemic response triggered by GSPE. This novel signaling pathway of procyanidins through SHP may be relevant to explain the health effects ascribed to the regular consumption of dietary flavonoids.     

Influence of apple purée preparation and storage on polyphenol contents and antioxidant activity

The polyphenolic components of Idared and Shampion apple purées were determined by HPLC; chlorogenic acid was the most abundant acid (20.0 mg/100 g in microwaved Idared); other polyphenols identified in high concentrations included (−)-epicatechin, procyanidin B1 and B2; quercetin and cyanidin glycosides were found in minor concentrations. The Shampion purées had higher total phenolics (142 mg/100 g) and procyanidin B2 concentrations (17.3 mg/100 g) than the Idared ones, and polymeric procyanidins represented 41% of all polyphenols. Antioxidant capacities of the samples, determined by spectrophotometric methods and EPR spectroscopy, correlated well with the concentration of polyphenols. The antioxidant properties could be better represented by EPR than by UV–vis measurements. The latter require transparent (clear) samples whereas EPR can be a method of choice in the assessment of radical-scavenging activity of dense and cloudy apple purées. Our results support the putative high antioxidant value of apple purées and define their capacity in terms of the major constituents. Apple purées are a rich source of natural antioxidants, especially of chlorogenic acid and procyanidins.