The production of yellow pigments from (+)-catechin and dihydroxyfumaric acid in a model wine system

The oxidation of tartaric acid by hydroxyl radicals, produced by gamma-irradiation of aqueous solutions of tartaric acid, was shown to generate dihydroxyfumaric acid. To confirm the importance of this oxidative degradation pathway in wine oxidation, dihydroxyfumaric acid was itself reacted with (+)-catechin in a wine-like solution and the yellow pigments formed were identified by liquid chromatography mass spectrometry (LC-MS) studies as xanthylium cations. The concentration of these pigments increased if the wine-like system also contained 0.6 mg/L copper(II). The results clearly demonstrate a link between the production of yellow xanthylium cation pigments from (+)-catechin and the degradation of tartaric acid by hydroxyl radicals.     

Factors influencing the production and stability of xanthylium cation pigments in a model white wine system

The influence of various wine parameters on the production and stability of xanthylium cation pigments in a wine-like medium is reported. The xanthylium pigments have an absorbance maximum in the visible region at 440 nm that is close to the measured absorbance used by the wine industry to indicate the browning of wine (i.e. 420 nm). The results of this study show that iron is more efficient than copper in both the colouration and production of xanthylium cation pigments in wine-like solutions of tartaric acid and (+)-catechin. The non-flavonoid caffeic acid can inhibit the accumulation of the xanthylium cation pigments, despite the presence of metal ions, and also influence the stability of the pigment. Sunlight leads to a decrease in the concentration of xanthylium cation pigments while a temperature difference of 20 ^oC in the absence of light was observed to have little influence on concentration. The results suggest that the xanthylium cations are more likely to be a transitory species during white wine oxidation rather than accumulating pigments based on their instability with caffeic acid.     

Influence of light exposure, ethanol and copper(II) on the formation of a precursor for xanthylium cations from tartaric acid

The production of xanthylium cation pigments was greatly increased when an aged, tartaric acid buffered, 12% (v/v) aqueous ethanol solution was used in a model white wine system. This suggested the formation of a precursor to the pigments during the ageing of the tartaric acid solution. On examining factors responsible for the generation of tartaric acid oxidation products in wine-like solutions it was observed that on exposure of samples to sunlight, glyoxylic acid, a known precursor to xanthylium cations, was produced. The production of glyoxylic acid was achieved in both the absence and presence of ethanol and copper(II). Hydrogen peroxide was also detected in these solutions. The results were consistent with the presence of glyoxylic acid in the aged tartaric acid buffered, 12% (v/v) aqueous ethanol solution that had frequent aeration and periodic exposure to sunlight throughout its storage. Studies on the role of hydrogen peroxide in the production of glyoxylic acid were also investigated. On the addition of hydrogen peroxide to tartaric acid solutions, with heating at 45°C in darkness, glyoxylic acid was only determined in solutions without ethanol.     

Xanthylium salts formation involved in wine colour changes

Summary The reaction of (+)-catechin in wine-like model solution was investigated. First appearance of colourless dimeric compounds consisting of two flavanol units linked by carboxy-methine bridge was observed. Their isolation and further incubation was found to yield two types of yellowish pigments showing visible absorption maxima at 440 and 460 nm, respectively. Mass spectroscopy (MS) spectral analysis showed that the first type were xanthylium salt pigments formed by dehydration of the colourless compounds followed by an oxidation process. The loss of a water molecule was shown to take place between two A ring hydroxyl groups of the colourless dimers. The second type were shown to be ester derivatives of the first ones. Thus ethylester of xanthylium salt was obtained and fully characterized by mass and nuclear magnetic resonance (NMR) spectroscopy. Esterification was found to involve the colourless compound before dehydration and thus a general scheme for xanthylium salt formation was postulated. The proposed scheme constitutes a new xanthylium formation pathway as up to now only anthocyanin-flavanol reactions were supposed to form xanthylium salt derivatives during wine ageing. This work also provides new support to the contribution of xanthylium salt in colour evolution observed during wine ageing which is generally expressed in an increase of absorption in the 400–500 nm, region of xanthylium salt absorption maxima.     

Alpha-anomer-selective glucosylation of (+)-catechin by the crude enzyme, showing glucosyl transfer activity, of Xanthomonas campestris WU-9701

Alpha-anomer-selective glucosylation of (+)-catechin was carried out using the crude enzyme, showing alpha-glucose transferring activity, of Xanthomonas campestris WU-9701 with maltose as a glucosyl donor. When 60 mg of (+)-catechin and 50 mg of the enzyme (5.25 units as maltose hydrolysing activity) were incubated in 10 ml of 10 mM citrate-Na2HPO4 buffer (pH 6.5) containing 1.2 M maltose at 45 degrees C, only one (+)-catechin glucoside was selectively obtained as a product. The (+)-catechin glucoside was identified as (+)-catechin 3'-O-alpha-D-glucopyranoside (alpha-C-G) by 13C-NMR, (1)H-NMR and two-dimensional HMBC analysis. The reaction at 45 degrees C for 36 h under the optimum conditions gave 12 mM alpha-C-G, 5.4 mg/ml in the reaction mixture, and the maximum molar conversion yield based on the amount of (+)-catechin supplied reached 57.1%. At 20 degrees C, the solubility in pure water of alpha-C-G, of 450 mg/ml, was approximately 100 fold higher than that of (+)-catechin, of 4.6 mg/ml. Since alpha-C-G has no bitter taste and a slight sweet taste compared with (+)-catechin which has a very bitter taste, alpha-C-G may be a desirable additive for foods, particularly sweet foods.     

Does u.v. light affect the total phenolic compound,anthocyanin, antioxidant capacity,and sensory profiles in wines?

In the study, by applying ultraviolet (u.v.) lights (254 nm) for 45 min to red wines from fermented Cabernet Franc, Cabernet Sauvignon, Merlot, and Petit Verdot (Vitis vinifera L.) grapes, we examined the total phenolic compound, total anthocyanin, and antioxidant capacity by four different methods, trans-resveratrol, (+)-catechin, gallic acid content, and the change in tasting profiles of the wines after application. According to the results of the research, the u.v.-C application has caused an increase in all parameters examined. If we talk about averages without distinguishing between varieties, after the application the total phenolic compound content of 3206 increased to 3356 mg gallic acid equivalent (GAE) per L and after u.v.-C application, the total anthocyanin content increased from 411 to 780 mg L⁻¹, the ABTS [2,2′-azinobis(3-ethyl-benzothiazoline-6-sulphonic acid)] value increased from 30 to 33 μmol trolox mL⁻¹, the DPPH ((2,2-diphenyl-1-picrylhydrazyl) level increased from 13 to 16 μmol trolox mL⁻¹, the FRAP (ferric reducing antioxidant power) level increased from 15 to 16 μmol trolox mL⁻¹, and the CUPRAC (cupric reducing antioxidant capacity) level increased from 40 to 45 μmol trolox mL⁻¹. The u.v. application affected trans-resveratrol the most among the phenolic compounds and an average increase of 12.99% was obtained. The rate of increase after u.v. application was 3.33% in (+)-catechin and 5.57% in gallic acid. The highest correlation between antioxidant activity measurement methods was measured to be 0.998 between FRAP and DPPH. In addition, u.v.-C application has had a positive effect on taste-based sensory profiles. In recent years, the search for a diet with a high antioxidant content has become even more important.     

α-Anomer-selective glucosylation of (+)-catechin by the crude enzyme, showing glucosyl transfer activity, of Xanthomonas campestris WU-9701

α-Anomer-selective glucosylation of (+)-catechin was carried out using the crude enzyme, showing α-glucose transferring activity, of Xanthomonas campestris WU-9701 with maltose as a glucosyl donor. When 60 mg of (+)-catechin and 50 mg of the enzyme (5.25 units as maltose hydrolysing activity) were incubated in 10 ml of 10 mM citrate-Na₂HPO₄ buffer (pH 6.5) containing 1.2 M maltose at 45°C, only one (+)-catechin glucoside was selectively obtained as a product. The (+)-catechin glucoside was identified as (+)-catechin 3′-O-α- -glucopyranoside (α-C-G) by ¹³C-NMR, ¹H-NMR and two-dimensional HMBC analysis. The reaction at 45°C for 36 h under the optimum conditions gave 12 mM α-C-G, 5.4 mg/ml in the reaction mixture, and the maximum molar conversion yield based on the amount of (+)-catechin supplied reached 57.1%. At 20°C, the solubility in pure water of α-C-G, of 450 mg/ml, was approximately 100 fold higher than that of (+)-catechin, of 4.6 mg/ml. Since α-C-G has no bitter taste and a slight sweet taste compared with (+)-catechin which has a very bitter taste, α-C-G may be a desirable additive for foods, particularly sweet foods.     

各食用米中活性成分及其抗氧化活性

本研究以黑米、白糯米、大米、黄米、糙米、香米、玉米、薏米、西米、高粱米10种常见食用米为研究对象,测定其总黄酮、总酚含量及其体外抗氧化活性。结果显示供试食用米品种间的总酚和总黄酮含量分别在2.61~287.61 mg/g和3.79~175.43 mg/100 g之间,黑米总酚、总黄酮含量最高(分别为287.61±18.38 mg/g和175.43±3.25 mg/100 g),西米的含量均最低(分别为2.61±0.04 mg/g和3.79±0.06 mg/100 g);黑米乙醇提取液的总抗氧化能力(354.18 U/g)和总还原力(吸光度为2.91)最强,大米提取液的总抗氧化能力(4.62 U/g)最弱,而西米的总还原力(5倍稀释时吸光度为0.11)最弱;黑米对DPPH·的清除能力最高(当加入量为2 μL时清除率为50%,IC₅₀=2 μL),西米的清除能力最弱(当加入体积大于105 μL时清除率为50%,IC₅₀>1×105 μL);黑米对·OH的清除能力最高(IC₅₀=250倍稀释),西米的最低(IC₅₀=1.71倍稀释);黑米对NO₂-的清除能力最高(IC₅₀=500倍稀释),玉米为最低(IC₅₀=2.97倍稀释);西米和糯米对O₂-·的清除能力最高(IC₅₀>105倍稀释),玉米最低(IC₅₀=2.467倍稀释)。综合比较发现黑米具有较丰富的生物活性物质,抗氧化活性相对较好,本研究为进一步开发功能性米类产品提供一定的理论基础。     

Comparison of Antimutagenic Activity of Phenolic Compounds in Newly Harvested and Stored Common Beans Phaseolus vulgaris against Aflatoxin B1

ABSTRACT: Phenolic compounds were extracted from recently harvested or stored black Jamapa beans ( Phaseolus vulgaris ) that were subjected or not to thermal treatment. The beans studied were cropped in the same area and were from the same lot. The highest amount of condensed tannins (CT) was found in the seed coat of recently harvested beans [222.41 ± 16mg of (+)-catechin equivalents per gram of seed coat]. After 2 yof storage, the amount of CT dropped significantly [35.8 ± 3.4 mg of (+) -catechin equivalents per gram of seed coat]. Thermal treatment significantly reduced the amount of CT in whole beans by approximately 70%. The raw seeds contained 13.76 ±1.2 mg of (+)-cat-echin equivalents per gram of seeds and a portion of CT appeared in the broth [9.4 ± 0.1 mg of (+) -catechin equivalents per gram of lyophilized broth]. The antimutagenic activity of these extracted phenolic compounds was tested against aflatoxin B₁ (AFB₁) in the Kado microsuspension assay. Newly harvested beans showed higher antimutagenic activity against AFB₁ mutagenicity than stored beans. The results suggest that to take the maximum advantage of components with biological activity present in beans, they must be used fresh.     

Effect of copper on oxidation of (+)-catechin in a model solution system

Summary Autoxidation of ( +)‐catechin in a model solution system, containing cupric ions, was monitored by high‐performance liquid chromatography with diode array detection. The rate of (+)‐catechin oxidation and the extent of browning increased with the copper concentration, showing an effect of copper on browning of flavanols. The progression of the reaction showed that the appearance of new compounds, which were initially absent in the mixture, was concomitant with (+)‐catechin decrease. Numerous reaction products, including both colourless compounds and pigments absorbing at 440, 460 and 550 nm, were detected. Among the colourless derivatives, four dimeric compounds, consisting of two catechin units linked by a carboxymethine bridge, were detected. Their formation involved the condensation of flavanols, mediated by glyoxylic acid, following a mechanism similar to that previously observed with iron. The yellowish compounds that were detected were identified as xanthylium salts and their corresponding esters, showing absorption maxima at 440 and 460 nm, respectively. Comparison of the results obtained with those reported with iron showed that copper ions play similar roles in enhancing the oxidation rate of (+)‐catechin and flavanols.     

邻菲啰啉活化催化褪色光度法测定食品中痕量Cu2+

研究在邻菲啰啉活化条件下,Cu2+ 催化溴酸钾氧化甲基紫的褪色反应,建立催化褪色光度法测定痕量Cu2+的新方法。讨论酸度、试剂用量、反应温度、反应时间、表面活性剂和共存离子等的影响,确定了最佳实验条件。结果表明：在25ml 溶液中,72℃恒温反应15min,根据加Cu2+ 溶液和不加Cu2+ 溶液的吸光度差值与Cu2+ 质量浓度绘制工作曲线,并由试样的吸光度差值确定痕量Cu2+ 的含量。该法的测定波长为578nm;线性范围为2.40 ×10-3～5.12 ×10-2μg/ml;检出限为2.4 × 10-6g/L,该法用于绿茶、面粉、大米、奶粉、干海带中痕量Cu2+ 的测定,最大相对标准偏差为4.22%,回收率为96.0%～104.0%。     

Interactions of Oligomeric Procyanidins in Model Wine Solutions Containing Malvidin-3-Glucoside and Acetaldehyde

Interactions of grape seed flavanols, dimeric, galloylated dimeric and trimeric procyanidins with malvidin-3-glucoside and acetaldehyde were studied in wine-like model solutions. Malvidin-3-glucoside and oligomeric procyanidins reacted very slowly, with eventual formation of yellow xanthylium salts. The concentrations of malvidin-3-glucoside and oligomeric procyanidins decreased faster in the presence of acetaldehyde and the colour augmentation with shift towards violet was attributed to the formation of new coloured compounds, detectable by HPLC and linked at different positions by CH₃CH bridges. The rate of loss of procyanidins in the presence of malvidin-3-glucoside and acetaldehyde varied according to the complexity of the components. Monomeric (+)-catechin and (-)-epicatechin reacted more slowly than dimer procyanidins B₁, B₂ and B₃ while trimer C₁ (epicatechin 4β→8 epicatechin 4β→8 epicatechin) presented the highest degradative reaction rate.     

Development and characterisation of functional cocoa (Theobroma cacao L.)-based edible films

The aim of this study was to develop functional edible films containing cocoa (Theobroma cacao L.) powder extract using alginate, pectin and chitosan in combination with proteins (whey protein isolate, soya and hemp protein). The films were examined for their physico-chemical (dry matter content, colour, thickness), mechanical (elongation at break (EAB)), bioactive (the content of total polyphenols (TPC), flavan-3-ols (F3olC), antioxidant capacity (AC)) and sensory properties. The plain alginate film exhibited the highest EAB (29.1%). The highest TPC and F3olC were determined in plain alginate (29 mg GAE/g and 2.75 mg (+)-catechin/g) and pectin (29 mg GAE/g and 2.25 mg (+)-catechin/g) films. The addition of proteins resulted in prolonged release of polyphenols and enhanced functional properties; however, the formation of protein–polyphenol complexes caused slight alterations in the bioactive composition of the films. The obtained results indicate a high potential of the developed films as functional, biodegradable form of active food packaging.     

Phenols and metals in sugar-cane spirits. Quantitative analysis and effect on radical formation and radical scavenging

A fluorescence-based analytical method for quantification of phenolic compounds in sugar cane spirits (and other distilled alcoholic beverages) was developed. Sample preparation involved reverse-phase solid phase extraction and separation by gradient reversed-phase HPLC with fluorescence detection. Twenty-one Brazilian sugar cane spirits (aged and non-aged cachaça) were analyzed and phenol, guaiacol, o-cresol, p-/m-cresol, 3, 5-xylenol, 4-ethylphenol, 4-ethylguaiacol, 2-ethylphenol, eugenol, (+)-catechin, (-)-epicatechin, and scopoletin quantified. The detection limit was between 0.01 mg l^-1 (eugenol and scopoletin) and 0.1 mg l^-1 [(+)-catechin and (-)-epicatechin]. Kaempferol and quercetin were quantified in the same spirits, together with copper and iron, using HPLC (spectrophotometric detection) and atomic absorption spectroscopy, respectively. Large variations between various spirits were noted: total phenols were between 1.5 and 70 mg l^-1, flavonoids were from below detection to 3.5 mg l^-1, Cu was between 0.04 and 7.0 mg l^-1; and Fe between 0.01 and 0.78 mg l^-1. The tendency of radical formation in the spirits was determined by electron spin resonance spectroscopy using N-t-butyl-!-phenylnitrone spin trapping, and radical scavenging capacity was determined spectrophometrically using the stable 2,2-diphenyl-1-picrylhydrazyl radical as probe. Radical formation depends mainly on the Cu content, while the radical scavenging and antioxidative capacity mainly depends on the flavonoid content. (+)-Catechin and (-)-epicatechin are most important for the antioxidative capacity as confirmed in a model experiment, where oxidation was induced by iron catalysis.     

Antioxidant Activity of Ethanol and Lipophilic Extracts of Common Fruity Vegetables in Bangladesh

The amount of phenolics, flavonoids, and anthocyanins in ethanol extracts and antioxidant activity of both ethanol and lipophilic extracts of common fruity vegetables in Bangladesh were studied. Among the ethanol extracts of 15 fruity vegetables, M. oleifera had the highest total polyphenol content (85.05 mg gallic acid equivalent/g extract) followed by L. acutangula (61.74 mg gallic acid equivalent/g extract) and A. esculentus (48.92 mg gallic acid equivalent/g extract). L. acutangula had high a content of flavonoids (14.46 mg (+)-catechin equivalent/g extract), which was almost similar to L. siceraria (13.67 mg catechin equivalent/g extract) followed by A. esculentus (11.95 mg catechin equivalent/g extract) and S. melongena (11.42 mg catechin equivalent/g extract). Highest anthocyanins content was in F. hispida (2.22 μmol/g extract) followed by S. melongena (1.04 μmol/g extract). Ethanol extracts of A. esculentus, F. hispida, L. acutangula, L. siceraria, and S. melongena exhibited high DPPH free radical scavenging activity with IC₅₀ of 70.4, 64.9, 70.4, 64.9, and 94.3 μg/mL respectively, whereas for the same lipophilic extracts of F. hispida and S. melongena showed lowest (37 μg/mL) IC₅₀ followed by M. oleifera (47.6 μg/mL), L. siceraria (57.5 μg/mL), and A. esculentus (63.3 μg/mL). These vegetables also showed high reducing powers, NO scavenging and total antioxidant capacity. Therefore, the top five potential fruity vegetables consist of both hydrophilic and lipophilic antioxidant(s), the order being F. hispida > M. oleifera > A. esculentus, L. acutangula > L. siceraria > and S. melongena.     

Kinetic Properties of (+)-Catechin Oxidation by a Basic Peroxidase Isoenzyme from Strawberries

The ability of a partially-heat stable strawberry (Fragaria × ananassa) peroxidase to oxidize (+)-catechin was studied and its oxidation followed the accepted model for peroxidase oxidations. Compound I (CoI) and compound II (CoII) were the main intermediates in the catalytic cycle. The reactivity of strawberry peroxidase with H₂O₂ [K₁= 2.63 μM^-1 s^-1] and with (+)-catechin [k₃= 0.57 μM^-1 s^-1] suggested that (+)-catechin is an excellent o-diphenol for CoII reduction. The strong cooperativity of this peroxidase isoenzyme indicates its great efficacy in oxidation of (+)-catechin at low H₂O₂ concentrations.     

(＋)-儿茶素与表没食子儿茶素没食子酸酯对乙醇诱导HepG2细胞脂代谢紊乱及氧化应激的影响

目的：体外对比(＋)-儿茶素（(＋)-catechin，(＋)-Cat）与表没食子儿茶素没食子酸酯（epigallocatechin gallate，EGCG）对乙醇诱导的HepG2细胞脂代谢紊乱及氧化应激的差异。方法：以HepG2细胞为实验对象，乙醇作用组（ETOH组）加入作用浓度300 mmol/L乙醇，(＋)-Cat＋ETOH组加入200 μmol/L (＋)-Cat和300 mmol/L乙醇，EGCG＋ETOH组加入200 μmol/L EGCG和300 mmol/L乙醇；另设相同浓度的(＋)-Cat组、EGCG组及正常组，各组均在37 ℃培养24 h。检测各组HepG2细胞甘油三酯（triglyceride，TG）含量、超氧化物歧化酶（superoxide dismutase，SOD）活力和丙二醛（malondialdehyde，MDA）浓度；油红O染色观察各组HepG2细胞的脂滴状态；荧光定量聚合酶链式反应法检测各组HepG2细胞固醇调节元件结合蛋白1（sterol regulatory element binding protein 1，SREBP-1）、二脂酰甘油转移酶2（diacylglyceryltransferase 2，DGAT2）、过氧化物酶体增殖物激活受体α（peroxisomal proliferators activate receptors α，PPARα）、肉毒碱棕榈酰基转移酶1（carnityltransferase 1，CPT1）mRNA相对表达水平。结果：ETOH组细胞发生氧化应激，同时TG含量明显高于正常组、(＋)-Cat组和EGCG组；(＋)-Cat＋ETOH组和EGCG＋ETOH组细胞氧化应激反应得到明显改善，同时TG含量显著低于ETOH组（P＜0.05，P＜0.01），并且显著下调SREBP-1和DGAT2 mRNA表达量（P＜0.05，P＜0.01），上调PPARα和CPT1 mRNA表达量（P＜0.05，P＜0.01）。结论：(＋)-Cat与EGCG均能改善乙醇诱导的HepG2细胞氧化应激反应和脂代谢紊乱，且EGCG的效果更好。     

高压液相色谱法测定食品接触材料水性模拟液中2,4-二羟基二苯甲酮

目的 探讨高压液相色谱法测定食品接触材料水性模拟液中2,4-二羟基二苯甲酮的方法。方法 食品接触材料经水、10%乙醇(v/v)、20%乙醇(v/v)、50%乙醇(v/v)以及3%乙酸(w/v)5种不同水性模拟液提取后, 以Agilent HC-CN为分析柱, 甲醇: 水(55: 45, v/v)为流动相, 经UV检测器(?=290 nm) 进行定量分析。结果 5种不同水性模拟液中2,4-二羟基二苯甲酮在0.5~10.0 mg/L浓度范围内线性关系均良好(r=0.9999), 检测限(S/N=3)均为0.02 mg/L。在低、中、高3个不同添加水平下进行加标回收实验, 2,4-二羟基二苯甲酮的平均回收率为84.0%~96.9%, RSD(n=6)为0.85%~4.60%。结论 本方法简单、快速、准确, 完全能够满足食品接触材料日常检验的需要。     

花蟹壳红色素提取工艺优化

分别以二氯甲烷、石油醚、乙醇和水为提取剂浸提花蟹壳中红色素,其中乙醇浸提花蟹壳红色素效果好,并在475 nm处有最大吸收峰。选用乙醇为提取剂,以浸提液在475 nm处的吸光值为指标,分别研究浸提温度、粉碎粒度、提取时间、料液比和乙醇浓度对花蟹壳红色素提取结果影响。在单因素研究基础上,以85.5%乙醇为提取剂,提取时间为90 min时进行浸提温度、粉碎粒度和料液比L9(33)正交实验,确定浸提温度70℃,花蟹壳粉碎粒度90目,料液比为1∶10(w/v)所得浸提液在475 nm处吸光值最高。     

Effect of winemaking practices on color indexes and selected bioactive phenolics of Aglianico wine

ABSTRACT:  Phenolic compounds are responsible for the sensory properties of wine as well as the properties beneficial to human health. The objective of this study was to establish the effect of the use of SO₂ and pectolitic enzymes in the prefermentative phase, maceration time, and oak aging on color, anthocyanins, tannins, (+)-catechin, (–)-epicatechin, rutin, trans -resveratrol, and quercetin content of Aglianico wine. Color indexes and phenolics were analyzed by HPLC and spectrophotometric methods. The addition of SO₂ and pectolitic enzymes before fermentation caused an increase in color intensity, color stability, total phenolics, anthocyanins, (+)-catechin, (–)-epicatechin rutin, trans -resveratrol, and quercetin content in Aglianico wine. Longer maceration times gave wines richer in total phenolics and with better chromatic characteristics. Storage in oak caused a decrease in anthocyanins, (+)-catechin, (–)-epicatechin, trans -resveratrol, and quercetin content but an increase in total phenolic content, and a stabilizing effect on color also occurred.