Predicting Buckwheat Flavonoids Bioavailability in Different Food Matrices Under In Vitro Simulated Human Digestion

The digestibility and bioaccessibility of major flavonoids (rutin, quercetin, and isoquercitrin) in various buckwheat food matrices were evaluated as a function of the rutin levels using an in vitro simulated digestion model. Food matrices were unprocessed samples (buckwheat flour [BF], flavonoid extract [FE], rutin‐enhanced flavonoid extract [REFE], and pure rutin) and processed samples (cakes with BF, FE, and REFE and a rutin‐spiked cake). FE showed the highest digestibility out of all the unprocessed samples (FE > REFE > BF > rutin), whereas BF exhibited the highest bioaccessibility (BF > FE > REFE = rutin). Moreover, the processed samples improved their flavonoid bioaccessibility upon baking. Thus, unprocessed FE is a good source for highly bioavailable flavonoids; moreover, baking exerts a positive effect on flavonoid digestibility and bioaccessibility. Because flavonoids can be further fermented by microorganisms in the large intestine into various metabolites, determining the digestibility and bioaccessibility of various flavonoids is useful for predicting flavonoid bioavailability in buckwheat and buckwheat‐based food products.     

Bioguided Fraction of Antioxidant Activity of Ethanol Extract from Tartary Buckwheat Bran

This study describes the activity‐guided isolation of antioxidant agents from tartary buckwheat bran (TBB). The ethanol crude extract of oil‐free TBB was partitioned sequentially into ethyl acetate, n‐butanol, and residual aqueous fractions. The ethyl acetate fraction (EAF) had the highest phenolic and flavonoid contents and showed the strongest antioxidant activity. EAF was superior to rutin and inferior to vitamin C (Vc) in DPPH radical scavenging ability, had an advantage over rutin and Vc in ABTS radical scavenging ability, and again surpassed rutin and quercetin in reducing power. Then EAF was subjected to column chromatography, and isolated compounds were identified using nuclear magnetic resonance data by comparing with those reported in the literature. Finally, the bioassay‐guided fractionation of the crude ethanol extract of TBB afforded three known compounds (quercetin, p‐hydroxybenzoic acid, and daucosterol) responsible for antioxidant activity. p‐Hydroxybenzoic acid and daucosterol were isolated from buckwheat grain for the first time. Taken together, establishing of the three pure compounds is of paramount importance to the understanding of antioxidant activity of TBB, and there is an immense potential to process TBB or its EAF into value‐added functional foods and beverages.     

Antioxidant activity of tartary (Fagopyrum tataricum (L.) Gaertn.) and common (Fagopyrum esculentum moench) buckwheat sprouts

This study compared the differences of two types of buckwheat sprouts, namely, common buckwheat ( Fagopyrum esculentum Moench) and tartary buckwheat ( Fagopyrum tataricum (L.) Gaertn.), in general composition, functional components, and antioxidant capacity. The ethanol extracts of tartary buckwheat sprouts (TBS) had higher reducing power, free radical scavenging activity, and superoxide anion scavenging activity than those of common buckwheat sprouts (CBS). As for chelating effects on ferrous ions, CBS had higher values than TBS. Rutin was the major flavonoid found in these two types of buckwheat sprouts, and TBS was 5 fold higher in rutin than CBS. The antioxidant effects of buckwheat sprouts on human hepatoma HepG2 cells revealed that both of TBS and CBS could decrease the production of intracellular peroxide and remove the intracellular superoxide anions in HepG2 cells, but TBS reduced the cellular oxidative stress more effectively than CBS, possibly because of its higher rutin (and quercetin) content.     

Trace element water improves the antioxidant activity of buckwheat (Fagopyrum esculentum Moench) sprouts

Buckwheat (Fagopyrum esculentum Moench) was grown in trace element water (TEW) (100, 200, 300, 400, and 500 ppm) and deionized water (DIW) to evaluate whether the beneficial effects of trace elements on the antioxidant activity could be accomplished with the supplement of TEW. At 300 ppm, TEW significantly increased the Cu, Zn, Mn, and Fe contents in buckwheat sprout but not the Se content. However, the levels of rutin, isoorientin, vitexin, and isovitexin did not differ between buckwheat sprouts grown in TEW and DIW. The ethanolic extract from buckwheat sprout grown in 300 ppm of TEW showed higher ferrous ion chelating activity and inhibitory activity toward lipid peroxidation than that grown in DIW. The extract in the TEW group also enhanced intracellular superoxide dismutase activity and lowered reactive oxygen species and superoxide anion in the human Hep G2 cell. It was concluded that TEW could increase the antioxidant activities of buckwheat sprouts.     

苦荞麸皮黄酮类化合物的微波辅助提取和HPLC-ESI-MS~n测定

以苦荞(F.tataricum(L.)Gaertn)麸皮为试材,采用HPLC-UV和HPLC-ESI-MSn测定技术研究了麸皮中黄酮类化合物用微波辅助提取工艺的最佳条件及其提取过程中黄酮类化合物各化学组分的动态变化。结果表明,苦荞麸皮黄酮类化合物的最佳提取工艺条件为微波加热时间15min,乙醇体积分数40%,压力400kPa。在此条件下总黄酮提取产率达20.6μmol/g,其组分芦丁、槲皮素、表儿茶素分别达11.2、5.6和3.8μmol/g。在提取压力超过400kPa时,芦丁开始失去一个芸香糖转化为槲皮素;随着微波照射时间的延长,芦丁、表儿茶素和槲皮素提取产率先增加,而后下降。提取压力越大,提取速率越快,分解速度也越快,达到最高提取产率的时间越短。     

Pharmacokinetic profile of total quercetin after single oral dose of tartary buckwheat extracts in rats

As an important edible and medicinal material, tartary buckwheat ( Fagopyrum tataricum Gaertn.) is commonly used as a kind of food or drug in eastern Asian countries. To investigate the pharmacokinetic profile of total quercetin after a single oral dose of tartary buckwheat extract in rats, a sensitive, simple, and accurate HPLC-UV method was developed to determine total quercertin following plasma enzyme hydrolysis with glucuronidase/sulfatase. Eighteen male Wistar rats were randomly assigned into three groups, which were given three different doses of tartary buckwheat extract. The pharmacokinetic results showed that the area under the plasma concentration-time curve (AUC) of total quercetin after single oral doses of tartary buckwheat extract presented a linear relationship. The peak plasma concentrations (C(max)) of total quercetin afte plasma enzyme hydrolysis with glucuronidase/sulfatase were 0.55 ± 0.26, 1.10 ± 0.53, and 2.05 ± 0.26 μg/mL; the peak times (T(max)) were 2.33 ± 1.94, 2.75 ± 3.67, and 2.50 ± 1.82 h; the areas under the curves (AUC(0-36h)) were 5.29 ± 1.35, 10.02 ± 4.43, and 22.51 ± 3.05 μg·mL(-1)·h(-1) for three doses of tartary buckwheat extract (60, 120, and 240 mg/kg). The present study has provided a basic pharmacokinetic profile of total quercetin after a single oral dose of tartary buckwheat extract in rats.     

Tartary buckwheat (Fagopyrum tataricum Gaertn.) as a source of dietary rutin and quercitrin

Two samples of tartary buckwheat (Fagopyrum tataricum Gaertn.) from China and one from Luxembourg were studied by high-performance liquid chromatography (HPLC) to reveal the possibilities of growing tartary buckwheat herb as a possible source of rutin, quercetin, and quercitrin. The content of rutin was determined as up to 3% dry weight (DW) in tartary buckwheat herb. Quercitrin values were in the range of 0.01-0.05% DW. Only traces of quercetin were detected in just some of the samples. Tartary buckwheat seeds contained more rutin (about 0.8-1.7% DW) than common buckwheat seeds (0.01% DW). Rutin and quercetin content in seeds depends on variety and growing conditions. Tartary buckwheat seeds contained traces of quercitrin and quercetin, which were not found in common buckwheat seeds.     

Synthesis of antioxidants in wheat sprouts

Aqueous and ethanolic extracts from wheat (Triticum aestivum) sprout powder were analyzed to determine its reduction and antioxidant activities. Mean and standard deviation of five independent samples were reported. The results showed that the micromoles of potassium ferricyanide reduced by aqueous and ethanolic extracts corresponding to 1 g of sprout powder (80.6 +/- 11.2 and 9.7 +/- 1.8, respectively) were higher than that reduced by 1 mg of other reducing compounds: ascorbic acid, rutin, quercetin, and reduced gluthatione (4.8 +/- 0.7, 3.8 +/- 1.2, 4.8 +/- 1.7, and 1.6 +/- 0.4, respectively). In addition, the oxygen superoxide scavenging activity performed by sprout extracts (from 1 g of powder) is comparable to that shown by 10 mg of antioxidant pure compounds (rutin and quercetin). Biochemical analysis of the sprout extracts shows that the antioxidant activity is mainly due to reducing glycoside and polyphenolic compounds.     

Impact of Buckwheat Flavonoids on In Vitro Starch Digestibility and Noodle‐Making Properties

The effects of various buckwheat materials (buckwheat flour [BF], dietary fiber extract [DE], flavonoids extract [FE], and rutin‐enhanced flavonoids extract [REFE]) on starch digestibility and noodle‐making properties were evaluated. When FE and REFE were incorporated into noodles, the amount of rapidly digestible starch and the predicted glycemic index (pGI) were reduced. However, BF and DE did not significantly decrease the pGI value of noodles. When assessing noodle properties, hardness was increased with increasing content of buckwheat materials, whereas other texture parameters were not significantly affected by buckwheat addition. All noodles were similar in regard to water absorption and swelling index, but cooking loss was slightly increased in FE and REFE noodles. FE and REFE demonstrated higher flavonoid stability during noodle making and, additionally, were more effective at reducing starch digestibility than BF and DE. REFE, specifically, does not generate quercetin (the cause of a bitter taste), and, therefore, REFE was effective in suppressing the hydrolysis of starch in the noodles, lowering the pGI.     

Chemical composition and hepatoprotective effects of polyphenol-rich extract from Houttuynia cordata tea

This study was designed to investigate the antioxidant activity, hepatoprotective effect, and phenolic composition of the ethyl acetate fraction (EAF) extracted from Houttuynia cordata tea. EAF was shown to exhibit strong ferric-reducing antioxidant power (FRAP) and scavenging activity against DPPH radical in vitro, and the antioxidant effects were further verified by suppressing CCl?-induced oxidative stress in mouse liver at three tested doses of EAF (250, 500, and 1000 mg/kg bw). Pretreatment with EAF (1000 mg/kg bw) prior to CCl? administration significantly (p < 0.001) decreased the CCl?-elevated levels of serum AST, ALT, alkaline phosphatase, total bilirubin, and hepatic MDA in mice and prevented the increases in GSH, SOD, and CAT caused by CCl?. HPLC analysis revealed that three predominantly polyphenolic compounds present in EAF were quercitrin (111.7 μg/mg), quercetin (43.8 μg/mg), and hyperoside (29.1 μg/mg). These results combined with liver histopathology indicate that EAF possesses a significant protective effect against acute hepatotoxicity induced by CCl?, which may be due to the strong antioxidant activity of phenolic components.     

Influence of extraction parameters on the phytochemical characteristics of extracts from buckwheat (Fagopyrum esculentum) herb

In recent years, the interest in herbal medicinal products, especially in the field of dermatology and cosmetics, has risen enormously. Many plant-derived substances show photoprotective properties in terms of absorption of UV radiation and preventing photodamage to molecular structures of human skin. Modern phytopharmaceutics as well as phytocosmetics require standardized, defined extracts from the herbal matrix. Buckwheat herb is rich in flavonoids, which have been identified as potent antioxidants. Up to now, there have been no systematic investigations available concerning the extraction conditions for phenolic substances from buckwheat herb. In this paper, we report the influence of three extraction parameters, ethanol concentration, temperature, and extraction time, on the response variables extractable matter, antioxidant activity, and content of fagopyrin, rutin, and chlorogenic acid. Our results suggest that an extract with good antioxidant activity, a high content of phenolics, and a low content of the phototoxic fagopyrin can be yielded by agitated maceration with 30% ethanol at 60 degrees C for 2 h. Furthermore, there is good correlation between the antioxidant activity and the rutin content, whereas the extractable matter is not an appropriate parameter for extract quality. Huge differences in the content of rutin and chlorogenic acid when using herbal drugs from different suppliers confirm the demand of standardized procedures for the production of herbal drugs.     

Dietary iron-initiated lipid oxidation and its inhibition by polyphenols in gastric conditions

The gastric tract may be the first site where food is exposed to postprandial oxidative stress and antioxidant activity by plant micronutrients. After food intake, dietary iron, dioxygen, and emulsified lipids come into close contact and lipid oxidation may take place. This study investigated lipid oxidation and its inhibition by dietary polyphenols in gastric-like conditions. Lipid oxidation induced by heme and nonheme iron was studied in acidic sunflower oil-in-water emulsions. The emulsifier type (bovine serum albumin, phospholipids), pH, and iron form were found to be factors governing the oxidation rates. Quercetin, rutin, and chlorogenic acid highly inhibited the metmyoglobin-initiated lipid oxidation in both emulsified systems at pH 5.8. Additionally, quercetin inhibited nonheme iron-initiated processes, while it was inefficient with hematin as an initiator. The presence of human gastric juice did not influence lipid oxidation, although it diminished the antioxidant activity of phenolics. Model emulsions may thus be valuable tools to study the gastric stability of polyunsaturated lipids.     

Determination of rutin, catechin, epicatechin, and epicatechin gallate in buckwheat Fagopyrum esculentum Moench by micro-high-performance liquid chromatography with electrochemical detection

A simple and sensitive method has been developed for determining rutin, catechin, epicatechin, and epicatechin gallate in buckwheat (Fagopyrum esculentum Moench) flour and seeds by micro-high-performance liquid chromatography with electrochemical detection. Chromatography was performed using an octadecylsilica column, acetonitrile-water-formic acid (13:87:1, v/v/v) as a mobile phase, and an applied potential at +0.5 V vs Ag/AgCl. We found that Japanese buckwheat flour contains rutin (12.7 mg/100 g), catechin (3.30 mg/100 g), epicatechin (20.5 mg/100 g), and epicatechin gallate (1.27 mg/100 g). The relative standard deviations for rutin, catechin, epicatechin, and epicatechin gallate peak heights were less than 0.86% (n = 5). The detection limit of rutin was 0.86 ng/mL. Moreover, the present method was applied to the distribution analysis of these compounds in buckwheat seed. The embryo proper and cotyledons of a mature buckwheat seed contained rutin with the highest concentration as compared to other parts. This method is useful in determining rutin, catechin, epicatechin, and epicatechin gallate in buckwheat with a small amount of sample for quality control in the food industry.     

Exudation of allelopathic substances in buckwheat (Fagopyrum esculentum Moench)

Root exudates of the common buckwheat, especially phenolic compounds, were studied. Their contents, both in the soil during the growing season and in agar medium during germination, were determined by HPLC and GC-MS. The allelopathic activity of the soil from a buckwheat stand was evaluated, as well. Palmitic acid, squalene, epicatechin, vitexin, a gallic acid derivative, and a quercetin derivative were the main compounds of the agar medium. In the soil, palmitic acid methyl ester, vanillic acid, rutin, a gallic acid derivative, and a 4-hydroxyacetophenone derivative were identified. The effects of vitexin, squalene, epicatechin, 4-hydroxyacetophenone, and vanillic and gallic acids were tested on eight plant species. Inhibitive effects were observed in the cases of 4-hydroxyacetophenone and vanillic and gallic acids. Comparisons of the identified compounds and inhibitive effects of soil extracts indicated that palmitic acid and the gallic acid derivative probably have an important function in the allelopathic root response of buckwheat.     

不同种类及加工方式对杂粮酸奶体外抗氧化活性的比较

为探究杂粮品种及加工方式对杂粮酸奶体外抗氧化活性的影响,选择小米、黄米、燕麦、藜麦、糙米、荞麦、高粱米7种杂粮为原料,经过蒸制、煮制、打浆3种常见加工方式,比较其多酚含量及抗氧化活性,对特性较好的杂粮经恰当处理后与牛奶共发酵制备酸奶,研究该杂粮酸奶的多酚含量及抗氧化活性,开发具备抗氧化活性的杂粮酸奶。结果表明,7种杂粮的之间的抗氧化能力存在显著（P<0.05）差异,采用抗氧化综合（antioxidant potency composite,APC）指数法评定杂粮的抗氧化活性,发现抗氧化活性最高的杂粮为荞麦。进一步对荞麦进行加工处理,发现蒸制处理后其抗氧化活性优于煮制和打浆。将蒸制的荞麦与牛奶混合制备酸奶,制成的荞麦酸奶总酚含量为52.85 mg/100g,是普通酸奶的5.16倍;且其抗氧化能力显著高于普通酸奶（P<0.05）。该研究为功能性杂粮酸奶的开发提供借鉴。     

Bioactive components of caper (Capparis spinosa L.) from Sicily and antioxidant effects in a red meat simulated gastric digestion

An increasing body of evidence on the association between adherence to the Mediterranean diet and healthy status is being accumulated. Floral buds of Capparis spinosa L. are commonly used in the Mediterranean cuisine as flavoring for meat and other foods. The present study evaluated bioactive components and antioxidant activity of Sicilian capers stabilized in salt. Whereas alpha-tocopherol was absent, low levels of gamma-tocopherol and vitamin C were measured. With reference to one serving size (8.6 g of capers), rutin was 13.76 mg, isothiocyanates, recently acknowledged as anticarcinogen phytochemicals, were 42.14 micromol, total phenols were 4.19 mg of gallic acid equivalents (GAE), and the total antioxidant potential measured using the [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] diammonium salt (ABTS) cation radical decolorization assay was 25.8 micromol of Trolox equivalents. The antioxidative activity of a caper hydrophilic extract was assessed in a number of assays. The extract at 3.5 and 7.0 microM GAE exhibited a dose-dependent peroxyl radical scavenging activity in a methyl linoleate methanol solution oxidized by azo initiator, and reduced hypervalent iron myoglobin species formed from met-Mb an H 2O 2, at 180 microM GAE. The hydrophilic extract, at 70-280 microM GAE, caused a dose-dependent inhibition of lipid autoxidation in heated red meat, incubated with simulated gastric fluid for 180 min. In the same model rutin tested at a concentration corresponding to its content in the extract was ineffective, and alpha-tocopherol at 25 microM was poorly effective. The hydrophilic extract (70 microM GAE) prevented the consumption of the co-incubated alpha-tocopherol, whereas lipid oxidation was inhibited for the experimental time, suggesting cooperative interactions between extract components and the vitamin. The findings encourage the use of caper with foods that contribute oxidizable lipids in view of the association between dietary oxidized lipids and risk of oxidative stress-based diseases.     

Isolation and identification of sea buckthorn (Hippophae rhamnoides) phenolics with antioxidant activity and α-glucosidase inhibitory effect

This study was performed to evaluate the antioxidant and α-glucosidase inhibitory effects from the extract, fractions, and isolated compounds of sea buckthorn leaves. Six compounds, kaempferol-3-O-β-D-(6'-O-coumaryl) glycoside, 1-feruloyl-β-D-glucopyranoside, isorhamnetin-3-O-glucoside, quercetin 3-O-β-D-glucopyranoside, quercetin 3-O-β-D-glucopyranosyl-7-O-α-L-rhamnopyranoside, and isorhamnetin-3-O-rutinoside, were isolated from sea buckthorn leaf extracts. The butanol fraction (EC(50) = 1.81 μg/mL) along with quercetin 3-O-β-D-glucopyranoside (EC(50) = 1.86 μg/mL) had a higher DPPH radical-scavenging activity and showed stronger reducing power (OD(700) = 1.83 and 1.78, respectively). The butanol fraction (477 mg GAE/g) contained the highest amount of phenolic compounds and also the most powerful α-glucosidase inhibitory effect (86%) at 5 μg/mL. The results indicate that sea buckthorn leaf extracts could potentially be used for food additives and the development of useful natural compounds.     

Effect of pectolytic enzyme preparations on the phenolic composition and antioxidant activity of asparagus juice

Commercial pectolytic enzymes were investigated for their influence on phenolics and antioxidant activities of asparagus juice. The antioxidant activity of asparagus juice was analyzed according to 2,2'-diphenyl-l-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) methods. The enzymes, with the exception of pectinase from Rhizopus sp., contained rutinase, which hydrolyzed rutin to quercetin. Asparagus juice treated with Viscozyme had the highest quercetin content without exhibiting a significant increase in the antioxidant activity. For a pectinase from Aspergillus niger, the antioxidant activity of asparagus juice was markedly reduced. Caution should be paid in the selection of pectolytic enzyme preparations for production of antioxidant activity-rich juice.     

欧李种质叶片类黄酮含量及不同组分特征研究

为筛选出欧李叶片类黄酮和9种类黄酮物质中单一物质含量较高的品种,并分析确定具有抗氧化和抑制酪氨酸酶活性的物质,本研究以38份欧李种质基生枝成熟期叶片为试材,利用超高效液相色谱法(UHPLC)测定儿茶素、表儿茶素、甘草素、芦丁、槲皮素、槲皮素-7-O-葡萄糖苷、杨梅素、光甘草定、根皮素活性物质含量,对其抗氧化及抑制酪氨酸酶能力进行分析。结果表明,38份欧李种质叶片中,Y09-14品种类黄酮含量最高,为64.84 mg·g^-1,且类黄酮及其9种组分的变异系数均超过20%,表明其遗传多样性丰富。根据叶片类黄酮含量进行聚类分析,发现70%以上的种质为中类黄酮类型。通过对不同种质欧李叶片类黄酮及不同组分物质含量的测定发现,儿茶素、表儿茶素、芦丁、槲皮素-7-O-葡萄糖苷在38份种质中均能被检测到,且儿茶素含量为6.271~935.295 mg·100 g^-1,极显著高于另外8种物质。4种不同活性物质(儿茶素、表儿茶素、芦丁、槲皮素-7-O-葡萄糖苷)与DPPH清除率呈极显著正相关(P<0.01),表明这种活性物质的抗氧化能力较强;芦丁、槲皮素-7-O-葡萄糖苷、光甘草定与酪氨酸酶抑制率呈正相关。本研究为欧李后期相关物质的检测及提取提供了依据。