Showing papers in "Journal of Agricultural and Food Chemistry in 1998"
TL;DR: In this article, the antioxidant activity and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined.
Abstract: The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. The total phenolic content, determined according to the Folin−Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the β-carotene bleaching method expressed as AOX (Δ log A470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products
3,633 citations
TL;DR: Of the tested components, carvacrol and thymol decreased the intracellular ATP pool of E. coli and also inreased extracellular ATP, indicating disruptive action on the cytoplasmic membrane.
Abstract: Carvacrol, (+)-carvone, thymol, and trans-cinnamaldehyde were tested for their inhibitory activity against Escherichia coli O157:H7 and Salmonella typhimurium. In addition, their toxicity to Photobacterium leiognathi was determined, utilizing a bioluminescence assay. Their effects on the cell surface were investigated by measuring the uptake of 1-N-phenylnaphthylamine (NPN), by measuring their sensitization of bacterial suspensions toward detergents and lysozyme, and by analyzing material released from cells upon treatment by these agents. Carvacrol, thymol, and trans-cinnamaldehyde inhibited E. coli and S. typhimurium at 1-3 mM, whereas (+)-carvone was less inhibitory. trans-Cinnamaldehyde was the most inhibitory component toward P. leiognathi. Carvacrol and thymol disintegrated the outer membrane and released outer membrane-associated material from the cells to the external medium; such release by (+)-carvone or trans-cinnamaldehyde was negligible. Of the tested components, carvacrol and thymol decreased the intracellular ATP pool of E. coli and also inreased extracellular ATP, indicating disruptive action on the cytoplasmic membrane.
1,595 citations
TL;DR: The results suggest that tannins, which are found in many plant-based foods and beverages, are potentially very important biological antioxidants.
Abstract: Representative condensed and hydrolyzable tannins and related simple phenolics were evaluated as biological antioxidants using cyclic voltammetry, the metmyoglobin assay, and the deoxyribose assay. The redox potentials of the tannins were similar to those of structurally related simple phenolics. However, the tannins were 15-30 times more effective at quenching peroxyl radicals than simple phenolics or Trolox. One of the tannins, polygalloyl glucose, reacted an order of magnitude more quickly with hydroxyl radical than mannitol. These results suggest that tannins, which are found in many plant-based foods and beverages, are potentially very important biological antioxidants.
1,345 citations
TL;DR: Different cultivars of four Vaccinium species were analyzed for total phenolics, total anthocyanins, and antioxidant capacity (oxygen radical absorbance capacity, ORAC).
Abstract: Different cultivars of four Vaccinium species [Vaccinium corymbosum L (Highbush), Vaccinium ashei Reade (Rabbiteye), Vaccinium angustifolium (Lowbush), and Vaccinium myrtillus L (Bilberry)] were analyzed for total phenolics, total anthocyanins, and antioxidant capacity (oxygen radical absorbance capacity, ORAC). The total antioxidant capacity of different berries studied ranged from a low of 13.9 to 45.9 μmol Trolox equivalents (TE)/g of fresh berry (63.2−282.3 μmol TE/g of dry matter) in different species and cultivars of Vaccinium. Brightwell and Tifblue cultivars of rabbiteye blueberries were harvested at 2 times, 49 days apart. Increased maturity at harvest increased the ORAC, the anthocyanin, and the total phenolic content. The growing location (Oregon vs Michigan vs New Jersey) did not affect ORAC, anthocyanin or total phenolic content of the cv. Jersey of highbush blueberries. A linear relationship existed between ORAC and anthocyanin (rxy = 0.77) or total phenolic (rxy = 0.92) content. In general,...
1,341 citations
TL;DR: In this article, the phenol antioxidant index, measuring both the quantity and the quality of antioxidants present, was used to evaluate 23 vegetables and found that vegetables had antioxidant quality comparable to that of pure flavonols and were superior to vitamin antioxidants.
Abstract: Fruits and vegetables in the diet have been found in epidemiology studies to be protective against several chronic diseases. Epidemiological evidence suggests that flavonoid consumption in the diet is protective against heart disease. Phenols in 23 vegetables have been measured by extraction with and without acid hydrolysis to determine the percent of conjugated and free phenols. Phenols were measured colorimetrically using the Folin−Ciocalteu reagent with catechin as the standard. The extracts' antioxidant quality was assayed by the inhibition of lower density lipoprotein oxidation mediated by cupric ions. Vegetables had antioxidant quality comparable to that of pure flavonols and were superior to vitamin antioxidants. The phenol antioxidant index, measuring both the quantity and the quality of antioxidants present, was used to evaluate 23 vegetables. Isolated lower density lipoproteins from plasma spiked with two vegetable extracts were enriched with phenol antioxidants and showed decreased oxidizabilit...
939 citations
TL;DR: In this article, several parameters mostly affecting the precision and accuracy of vanillin assay were reexamined and optimized, including acid nature and concentration, reaction time, temperature, and vanillin concentration.
Abstract: Several parameters mostly affecting the precision and accuracy of vanillin assay were reexamined and optimized. The reexamination was performed both by vanillin reaction with catechins and by vanillin reaction with purified proanthocyanidins. In addition to the acid nature and concentration, the reaction time, the temperature, and the vanillin concentration, other factors such as the water content, the presence of interfering substances, and the standard utilized, for both vanillin reaction with catechins and vanillin reaction with proanthocyanidins, were also important. However, the kinetics of the two types of reactions were markedly different. For estimating accurately catechins or proanthocyanidins that exist simultaneously in plant tissues, it is necessary to preliminarily separate them from each other. Keywords: Catechins; proanthocyanidins; vanillin assay
876 citations
TL;DR: In this article, 10 phenolic compounds were isolated from a butanol fraction of sage extracts and their structures were determined by spectral methods (NMR, MS, IR). Among them, a novel compound, 4-hydroxyacetophenone-4-O-β-d-apiofuranosyl-(1→6)-O- β-dglucopyranoside, was identified.
Abstract: Ten phenolic compounds were isolated from a butanol fraction of sage extracts. Their structures were determined by spectral methods (NMR, MS, IR). Among them, a novel compound, 4-hydroxyacetophenone-4-O-β-d-apiofuranosyl-(1→6)-O-β-d-glucopyranoside, was identified. Two test systems, DPPH free radical scavenging activity and radical cation ABTS•+ scavenging activity, were used to evaluate their antioxidant activity. The most active compounds were found to be rosmarinic acid and luteolin-7-O-β-glucopyranoside. Keywords: Sage; Salvia officinalis; phenolic compounds; antioxidant activity
643 citations
TL;DR: In this paper, the antioxidant activity of phenolic compounds present in berries was investigated by two copper-catalyzed in vitro oxidation assays: human low-density lipoproteins (LDL) and lecithin liposomes.
Abstract: The antioxidant activity of phenolic compounds present in berries was investigated by two copper-catalyzed in vitro oxidation assays: human low-density lipoproteins (LDL) and lecithin liposomes. The amount of total phenolics varied between 617 and 4350 mg/kg in fresh berries, as gallic acid equivalents (GAE). In LDL at 10 μM GAE, berry extracts inhibited hexanal formation in the order: blackberries > red raspberries > sweet cherries > blueberries > strawberries. In lecithin liposomes, the extracts inhibited hexanal formation in the order: sweet cherries > blueberries > red raspberries > blackberries > strawberries. Red raspberries were more efficient than blueberries in inhibiting hydroperoxide formation in lecithin liposomes. HPLC analyses showed high anthocyanin content in blackberries, hydroxycinnamic acid in blueberries and sweet cherries, flavonol in blueberries, and flavan-3-ol in red raspberries. The antioxidant activity for LDL was associated directly with anthocyanins and indirectly with flavo...
638 citations
TL;DR: Although the histidine-containing peptides had a quenching activity on singlet oxygen, they did not show antioxidative activity in an 2,2'-azobis(2,4-dimethylvaleronitrile)-induced oxidation system or scavenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and superoxide.
Abstract: The properties of 22 synthetic peptides containing histidine, which were designed on the basis of the antioxidative peptide (Leu-Leu-Pro-His-His) derived from proteolytic digests of a soybean protein, were examined with regard to their antioxidative activity against the peroxidation of linoleic acid and the scavenging effects on active oxygen and free radical species. The antioxidative activities of these peptides in an emulsion oxidation system using 2,2'-azobis(2-amidinopropane) dihydrochloride as a radical initiator correlated well within an aqueous system. Although the histidine-containing peptides had a quenching activity on singlet oxygen, they did not show antioxidative activity in an 2,2'-azobis(2,4-dimethylvaleronitrile)-induced oxidation system or scavenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and superoxide. The metal-ion chelating activities and the hydrophobicities of these peptides showed no direct correlation with their antioxidative activities. Leu-Leu-Pro-His-His was modified with a hydroxyl radical in an aqueous ethanol system during the peroxidation of linoleic acid.
627 citations
TL;DR: In this article, a possible way to valorize citrus peels and seeds, which are byproducts of the juice extraction industry, is to use them as natural antioxidants, and the antioxidant activity of several citrus peel and...
Abstract: A possible way to valorize citrus peels and seeds, which are byproducts of the juice extraction industry, is to use them as natural antioxidants. The antioxidant activity of several citrus peel and...
625 citations
TL;DR: In this paper, the major differences between the effects of annealing and heat-moisture treatment are pointed out and an overview is given of possible explanations for the observed effects of hydrotherma.
Abstract: Annealing and heat−moisture treatment are two hydrothermal treatments that modify the physicochemical properties of starch, without destroying granular structure They involve incubation of starch granules in excess water/intermediate water content (annealing) or at low moisture levels (heat−moisture treatment) during a certain period of time, at a temperature above the glass transition temperaturr but below the gelatinization temperature The impact of hydrothermal treatments on starch physicochemical properties is extensively discussed Such physicochemical properties include granule morphology and crystallinity, double-helix content, amount and appearance of amylose−lipid complexes, gelatinization and pasting, swelling power and solubility, gel properties, and susceptibilities to acid and enzymic hydrolysis Finally, the major differences between the effects of annealing and heat−moisture treatment are pointed out and an overview is given of possible explanations for the observed effects of hydrotherma
TL;DR: The essential oils of Origanum vulgare subsp.
Abstract: The essential oils of Origanum vulgare subsp. hirtum, Mentha spicata, Lavandula angustifolia, and Salvia fruticosa exhibited antifungal properties against the human pathogens Malassezia furfur, Trichophyton rubrum, and Trichosporon beigelii. Of the four oils, O. vulgare subsp. hirtum oil showed the highest fungicidal activity and at a dilution of 1/50000 caused a 95% reduction in the number of metabolically active cells within 6 h of exposure. Among the main components of the four oils, carvacrol and thymol exhibited the highest levels of antifungal activity. The therapeutic efficacy of the O. vulgare subsp. hirtum essential oil was tested in rats experimentally infected with T. rubrum and yielded promising results. Furthermore, the above essential oils were tested with the Ames test and did not exhibit any mutagenic activity.
TL;DR: The results suggest that anthocyanins could be the key component in red wine in light of the protection against cardiovascular diseases, although this hypothesis needs in vivo evidence.
Abstract: Using liquid/liquid extraction, three fractions were obtained from an Italian red wine containing single polyphenolic subfractions: (1) phenolic acids and quercetin-3-glucuronide, (2) catechins and quercetin-3-glucoside, and (3) anthocyanins. Beside the scavenging capacity of the different fractions against hydroxyl and peroxyl radicals, the in vitro inhibition of low density lipoprotein oxidation and platelet aggregation (two main events in the pathogenesis of atherosclerosis) were tested. The antioxidant activity of the fractions has been compared with that of the original red wine before and after dealcoholization. The anthocyanin fraction was the most effective both in scavenging reactive oxygen species and in inhibiting lipoprotein oxidation and platelet aggregation. This higher activity can be explained by both its high concentration in red wine and its antioxidant efficiency, which, at least for peroxyl radical scavenging, was three times as high as that of the other two fractions. Our results suggest that anthocyanins could be the key component in red wine in light of the protection against cardiovascular diseases, although this hypothesis needs in vivo evidence.
TL;DR: The essential oils obtained from the oregano plants Origanum vulgare subsp. hirtum, Coridothymus capitatus, and Satureja thymbra were examined by a combination of GC and GC−MS and found to be...
Abstract: The essential oils (EOs) obtained from the oregano plants Origanum vulgare subsp. hirtum, Coridothymus capitatus, and Satureja thymbra were examined by a combination of GC and GC−MS and found to be...
TL;DR: The influence of ionic interactions on quantitation of protein surface hydrophobicity was assessed by comparing the protein binding of an uncharged fluorescent probe, PRODAN, with that of an anionic probe, 1-(anilino)naphthalene-8-sulfonate (ANS-).
Abstract: The influence of ionic interactions on quantitation of protein surface hydrophobicity was assessed by comparing the protein binding of an uncharged fluorescent probe, 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN), with that of an anionic probe, 1-(anilino)naphthalene-8-sulfonate (ANS-). Binding constants for the protein−probe complexes involving bovine serum albumin (BSA) and ovalbumin (OVA) in phosphate buffer (pH 7.0, I = 0.01 M) at 30 °C were fluorometrically determined to be KP-BSA = (1.00 ± 0.01) × 106 M-1 and KP-OVA = (4.2 ± 0.1) × 103 M-1, respectively, for PRODAN, compared to KA-BSA = (6.21 ± 0.04) × 106 M-1 and KA-OVA = (1.97 ± 0.09) × 103 M-1, respectively, for ANS-. A procedure was established using PRODAN to determine protein surface hydrophobicity (S0) values from the initial slope of relative fluorescence intensity versus protein concentration plots, and the results were compared to S0 values measured using ANS-. Increasing ionic strength up to 1.0 M decreased the S0 values of BSA me...
TL;DR: The total phenolic content did not correlate with the antioxidant activity of the berry and fruit wines and liquors, therefore alleviating the importance of further characterization of the phenolic antioxidants present in berry or fruit wines.
Abstract: A total of 44 different berry and fruit wines and liquors with total phenolic contents between 91 and 1820 mg/L, expressed as gallic acid equivalents (GAE), were evaluated for antioxidant activity. Dealcoholized wine extracts were added to methyl linoleate (MeLo), and the oxidation in the dark at 40 degrees C was followed by conjugated diene measurement. Wines made of mixtures of black currants and crowberries or bilberries (240-275 µM GAE) were slightly superior to reference red grape wines (330-375 µM GAE) and equally as active as the control antioxidant, alpha-tocopherol (50 µM), in inhibiting MeLo hydroperoxide formation. Also, raw materials including apple, arctic bramble, cowberries, cranberries, red currants, or rowanberries possessed antioxidant activity. Thus, these raw materials contain phenolic compounds, some of which are capable of protecting lipids against oxidation also in a hydrophobic lipid system. Liquors, apart from arctic bramble liquor, were less active than wines. However, the total phenolic content did not correlate with the antioxidant activity of the berry and fruit wines and liquors, therefore alleviating the importance of further characterization of the phenolic antioxidants present in berry and fruit wines.
TL;DR: Findings demonstrate that olive oil phenolics inhibit oxidation of low-density lipoproteins (the most atherogenic ones) and possess other potent biological activities that if demonstrated in vivo, could partially account for the observed healthful effects of diets that include high-quality olive oil and other foods rich in flavonoids and phenols.
Abstract: Olive oil is the fat of choice in the Mediterranean area, where the diet has been associated with a lower incidence of coronary heart disease and certain cancers. Phenols in extra virgin olive oil are responsible for its peculiar pungent taste and for its high stability. Recent findings demonstrate that olive oil phenolics inhibit oxidation of low-density lipoproteins (the most atherogenic ones) and possess other potent biological activities that if demonstrated in vivo, could partially account for the observed healthful effects of diets that include high-quality olive oil and other foods rich in flavonoids and phenols. Keywords: Olive oil; phenols; atherosclerosis; Mediterranean diet; antioxidants; free radicals
TL;DR: The main characteristics of a natural product, antioxidant dietary fiber (ADF), obtained from red grape pomace is described in this article, where both nonextractable proanthocyanidins (28.6%) and extractable polyphenols (2.0%) are associated with the dietary fiber matrix.
Abstract: The main characteristics of a natural product, antioxidant dietary fiber (ADF), rich in both dietary fiber (DF) and polyphenolic compounds (PP), obtained from red grape pomace is described. Both nonextractable proanthocyanidins (28.6%) and extractable polyphenols (2.0%) are associated with the dietary fiber matrix. The antioxidant capacity of this product was in vitro determined by lipid oxidation inhibition (LOI) and free radical scavenging (FRE) procedures. One gram of the product showed similar LOI and FRE effect than 400 mg and 100 mg of dl-(α-tocopherol, respectively. Extractable PP of grape ADF showed higher antioxidant capacity than red wine PP. The physiological and nutritional significance of ADF is discussed and the requirements of vegetable materials to be considered as ADF is proposed. Keywords: Antioxidants; dietary fiber; polyphenols; grape pomace; proanthocyanidins
TL;DR: In this article, it was shown that the release of flavor-active volatile thiols during alcoholic fermentation of the must is due to the degradation, by yeast, of the corresponding S-cysteine conjugates.
Abstract: Three flavor-active volatile thiols (4-mercapto-4-methylpentan-2-one, 4-mercapto-4-methylpentan-2-ol and 3-mercaptohexan-1-ol) involved in Vitis vinifera L. var. Sauvignon blanc wine aroma can be generated in vitro from nonvolatile must extracts by the enzyme action of a cell-free extract obtained from the gastrointestinal bacterium Eubacterium limosum. The specificity of a cysteine conjugate β-lyase (EC 4.4.1.13) which is contained in the cell-free extract, strongly suggested the existence of precursor for these volatile thiols having a structure of S-cysteine conjugate. Gas-phase chromatography analysis coupled with mass spectrometry of must extract in the form of trimethylsilylated derivatives, verified this hypothesis. The release of flavor-active volatile thiols during alcoholic fermentation of the must is shown to be due to the degradation, by yeast, of the corresponding S-cysteine conjugates. This mechanism explains the amplification of the typical Sauvignon blanc grape aroma during alcoholic ferme...
TL;DR: The data support different models of precipitation for the two types of tannin: pentagalloylglucose, which is very nonpolar, precipitates by forming a hydrophobic coat around the protein, whereas the much more polar EC16-C forms hydrogen-bonded cross-links between protein molecules.
Abstract: The precipitates that form when purified pentagalloylglucose or a purified procyanidin [epicatechin16 (4→8) catechin; EC16-C] are mixed with bovine serum albumin were quantitatively analyzed. EC16-C is a more efficient protein precipitating agent than pentagalloylglucose on a molar or a mass basis. EC16-C precipitates protein independently of temperature and presence of organic solvent. Precipitation by pentagalloylglucose increases as temperature is increased and decreases when alcohols are present. When tannin is in excess, up to 40 mol of pentagalloylglucose is bound per mole of protein precipitated, but only 20 mol of EC16-C is bound per mole of protein precipitated. The data support different models of precipitation for the two types of tannin: pentagalloylglucose, which is very nonpolar, precipitates by forming a hydrophobic coat around the protein, whereas the much more polar EC16-C forms hydrogen-bonded cross-links between protein molecules. Keywords: Polyphenol−protein interaction; tannin; penta...
TL;DR: In this paper, the antiulcer activity of grape seed extracts (GSE-I and GSE-II) and procyanidin oligomers was investigated using rats.
Abstract: It is known that procyanidins, which are contained in grape seeds, are antioxidative and have certain biological effects. Antiulcer activities of grape seed extracts (GSE-I and GSE-II) and procyanidins were investigated using rats. GSE-I (with low flavanol content), GSE-II (with high flavanol content), and procyanidins at a dose of 200 mg/kg strongly inhibited the stomach mucosal injury induced by 60% ethanol containing 150 mM hydrochloride. This suppressive effect seems dependent on the content of procyanidin oligomers. Procyanidin oligomers (dimers to hexamers) were prepared and studied for their antiulcer activities at a dose of 200 mg/kg. The gastric protective activity of a series of procyanidins increased with the increasing polymerization of catechin units. Oligomers longer than tetramers showed a strong protective effect against gastric mucosal damage. The binding ability of procyanidin oligomers to bovine serum albumin in the acidified solution was strengthened with the increase of molecules. The...
TL;DR: In this article, the use of solvents containing up to 1% of 12 N hydrochloric acid for the extraction of grape anthocyanins resulted in the partial hydrolysis of malvidin 3-O-acetylglucoside.
Abstract: Several procedures for the extraction of grape anthocyanins, based on different methods described in the literature, have been assayed Results have shown that the use of solvents containing up to 1% of 12 N hydrochloric acid for the extraction of grape anthocyanins resulted in the partial hydrolysis of malvidin 3-O-acetylglucoside, leading to important changes in the relative content of anthocyanins in those extracts, despite their higher efficiency in extracting total anthocyans in some cases Nevertheless, the use of different neutral solvents resulted in a similar relative content of anthocyanins in the extracts, and some of them could be as efficient in extracting total anthocyanins as other procedures that used an acid solvent for extraction These data suggest that the use of solvents containing up to 1% of 12 N hydrochloric acid in the extraction of anthocyanins from grapes or from any other plant material containing acetylated anthocyanins should be avoided, especially if the work is related with
TL;DR: In this article, the authors investigated the antioxidant capacity of medicinal plant extracts with standardized content of polyphenols and found that green tea, oligomeric procyanidins (from grape seed and pine bark), bilberry, and ginkgo extracts exhibited TAA in the range of 5.12-2.57 mM Trolox.
Abstract: Commonly used medicinal plant extracts with standardized content of polyphenols were investigated for their total antioxidant activity (TAA). Green tea, oligomeric procyanidins (from grape seed and pine bark), bilberry, and ginkgo exhibited TAA in the range of 5.12-2.57 mM Trolox, thereby indicating a valuable antioxidant capacity. Witch hazel, propolis EPID, artichoke, and hawthorn afforded lower TAA (1.54-0.44 mM Trolox), whereas echinacea, ginseng, passionflower, sweet clover, and eleuthero were rather uneffective (TAA < 0.32 mM Trolox). Excipients normally used to prepare the extracts did not interfere with the assay, and a good correlation between the content of polyphenols and the TAA was assessed. The measured TAA was higher than those calculated from the content and antioxidant potential of specific components, as exemplified for green tea and ginkgo extracts. This may be attributed to the presence in these extracts of other substances with antioxidant capacity. On the other hand, some components (such as ginkgolides in ginkgo extract) insensitive to the TAA assay played an important antioxidant role in vivo. These results suggest that TAA determination is of interest for a comparative evaluation of in vitro antioxidant potential, but it needs to be combined with in vivo data for adequate assessment of the antioxidant capacity of medicinal plant extracts.
TL;DR: In this article, the authors used reverse-phase HPLC coupled with diode array detection following thiolysis to quantify phenolic compounds according to their classes (hydroxycinnamic acid derivatives, flavan-3-ols, flavonols, and dihydrochalcones) and provided information on the constitutive units and the average degree of polymerization of oligomeric and polymeric procyanidin structures.
Abstract: Phenolic compounds, which are present in the epidermis zone, parenchyma zone, core zone, and seeds of fruit (Malus domestica var. Kermerrien), were extracted from freeze-dried material by three successive solvent extractions. The dry methanol extract and the dry aqueous acetone extracts were analyzed using reversed-phase HPLC coupled with diode array detection following thiolysis to quantify phenolic compounds according to their classes (hydroxycinnamic acid derivatives, flavan-3-ols, flavonols, and dihydrochalcones). The method is suitable for the determination of the relative proportions of the different classes of polyphenols and provided information on the constitutive units and the average degree of polymerization of oligomeric and polymeric procyanidin structures. Results showed that procyanidins are the predominant phenolic constituents in cider apple fruits, much of them corresponding to highly polymerized structures.
TL;DR: In this paper, the authors extract volatile thiols from a dichloromethane extract of Sauvignon blanc wine by the reversible combination of the thiol extract with p-hydroxymercuribenzoate, fixation of the resulting complex in an anion exchange column, and finally release of the extract with cysteine.
Abstract: Volatile thiols were purified from a dichloromethane extract of Sauvignon blanc wine by the reversible combination of the thiols with p-hydroxymercuribenzoate, fixation of the resulting complex in an anion exchange column, and finally release of the thiols with cysteine. By analyzing the purified thiol extract from 500 mL of wine, using gas chromatography coupled with mass spectrometry, it was possible to measure the concentrations of five volatile compounds at once: 4-mercapto-4-methylpentan-2-one, 3-mercaptohexyl acetate, 3-mercaptohexan-1-ol, 4-mercapto-4-methylpentan-2-ol, and 3-mercapto-3-methylbutan-1-ol. Analysis of 10 typical Sauvignon Blanc wines (Bordeaux, Sancerre) showed that the first three compounds listed above are expected to be involved in varietal aroma, as they may be present at concentrations greatly in excess of their respective perception thresholds. Keywords: Volatile thiol; aroma; Sauvignon blanc wine; Vitis vinifera; p-hydroxymercuribenzoate
TL;DR: In this paper, commercial prune and prune juice extracts (Prunus domestica cv. French) were analyzed for phenolics by reversed phase HPLC with diode array detection and tested for the ability to inhibit the Cu2+catalyzed oxidation of human LDL.
Abstract: Phenolic compounds in foods have been associated with reduced incidences of heart disease by acting as antioxidants for low-density lipoprotein (LDL). Commercial prune and prune juice extracts (Prunus domestica cv. French) were analyzed for phenolics by reversed phase HPLC with diode array detection and tested for the ability to inhibit the Cu2+-catalyzed oxidation of human LDL. The mean concentrations of phenolics were 1840 mg/kg, 1397 mg/kg, and 441 mg/L in pitted prunes, extra large prunes with pits, and prune juice, respectively. Hydroxycinnamates, especially neochlorogenic acid, and chlorogenic acid predominated, and these compounds, as well as the prune and prune juice extracts, inhibited the oxidation of LDL. The pitted prune extract inhibited LDL oxidation by 24, 82, and 98% at 5, 10, and 20 μM gallic acid equivalents (GAE). The prune juice extract inhibited LDL oxidation by 3, 62, and 97% at 5, 10, and 20 μM GAE. These data indicate that prunes and prune juice may provide a source of dietary anti...
TL;DR: In this paper, heat-induced aggregation of β-lactoglobulin was investigated as a function of pH, heating temperature and NaCl concentration by measurements of reaction kinetics, differential scanning calorimetry, and light scattering.
Abstract: Heat-induced aggregation of β-lactoglobulin was investigated as a function of pH, heating temperature, and NaCl concentration by measurements of reaction kinetics, differential scanning calorimetry, and light scattering. The aggregation can be well interpreted using a reaction scheme consisting of two steps: a denaturation equilibrium, with a first-order unfolding reaction, followed by second-order aggregation reactions. Denaturation becomes rate limiting at high heating temperature, pH values close to the isoelectric point of the protein, and high NaCl concentration. At neutral pH a maximum is seen in the overall reaction rate as a function of NaCl concentration, which is explained by a stabilizing, salting-out effect of the salt in combination with an increase in the rate of successive aggregation reactions. At high NaCl concentrations physical bonding becomes increasingly important; large aggregates that continue to grow in time are formed, and two phases are distinguished in the aggregation step. The...
TL;DR: In this paper, a method was developed for the fractionation of grape and wine proanthocyanidins according to their degree of polymerization, and the results showed that these three fractions contained, respectively, monomeric flavan-3-ols (catechins), oligomeric, polymeric, and polymeric proantho-thiol.
Abstract: A method was developed for the fractionation of grape and wine proanthocyanidins according to their degree of polymerization. The grape and wine proanthocyanidins were fractionated on C18 Sep-Pak cartridges into three fractions by different organic solvents. The combination of TLC, analytic HPLC, and degradation with toluene-R-thiol confirmed that these three fractions contained, respectively, monomeric flavan-3-ols (catechins), oligomeric proanthocyanidins, and polymeric proanthocyanidins. The mean degrees of polymerization for oligomeric and polymeric proanthocyanidins in red wine were, respectively, 4.8 and 22.1, and those in the seed extract, 9.8 and 31.5. The method proposed is very interesting for the study of grape and wine proanthocyanidins according to their degree of polymerization, and a further quantification is also possible.
TL;DR: In this paper, an isocratic HPLC procedure was developed for simultaneous determination of six catechins, gallic acid, and three methylxanthines in tea water extract, achieving a baseline separation on a Cosmosil C18-MS packed column with a solvent mixture of methanol/doubly distilled water/formic acid (19.5:80.2:0.3, v/v/v) as mobile phase.
Abstract: An isocratic HPLC procedure was developed for simultaneous determination of six catechins, gallic acid, and three methylxanthines in tea water extract. A baseline separation was achieved on a Cosmosil C18-MS packed column with a solvent mixture of methanol/doubly distilled water/formic acid (19.5:80.2:0.3, v/v/v) as mobile phase. A gradient HPLC procedure was also provided for the separation of these tea components. The contents of catechins, gallic acid, and methylxanthines have been measured in infusions of a range of green tea, oolong tea, and pu-erh tea products sold and consumed in the China, Japan, and Taiwan. When 15 Chinese green tea and 13 Japanese green tea products were analyzed by the HPLC method, the mean levels of the total catechins, (−)-epigallocatechin 3-gallate, (+)-catechin, and caffeine were found to be very similar in these two groups, but other minor catechins such as (−)-epigallocatechin, (−)-epicatechin, and (−)-gallocatechin 3-gallate were found to be higher in Japanese green tea ...
TL;DR: In this paper, the pro-antioxidant activity of vegetables was investigated using a model system β-carotene−linoleic acid (BCLA) with a linear correlation with time, and positive slope values indicating either an increase in antioxidant activity or a decrease in prooxidant activity during the reaction.
Abstract: The pro-antioxidant activity of carrot, cauliflower, celery, eggplant, garlic, mushroom, onion, white cabbage, white potato, tomato, yellow bell pepper, and zucchini was investigated. Juices obtained by centrifugation of vegetables were treated at different temperatures (2, 25, 102 °C) and assessed for antioxidant activity (AA) using a model system β-carotene−linoleic acid. Antioxidant activity of all vegetable juices showed a linear correlation with time. The equations of all straight lines obtained showed positive slope values indicating either an increase in antioxidant activity or a decrease in prooxidant activity during the reaction. Negative intercept values were found when the juices showed prooxidant activity at least during the first phase of the reaction. Mushroom and white cabbage always showed more than 80% AA, while cauliflower, celery, and eggplant showed such high AA only after boiling. Tomato and yellow bell pepper were always prooxidant. Cluster analysis allowed the vegetables to be divid...