Methodology optimization for quantification of total phenolics and individual phenolic acids in sweetpotato (Ipomoea batatas L.) roots

ABSTRACT:  Phenolic acids are one of the several classes of naturally occurring antioxidant compounds found in sweetpotatoes. Simplified, robust, and rapid methodologies were optimized to quantify total and individual phenolic acids in sweetpotato roots. Total phenolic acid content was quantified spectrophotometrically using both Folin–Denis and Folin–Ciocalteu reagents. The Folin–Ciocalteu reagent gave an overestimation of total phenolic acids due to the absorbance of interfering compounds (that is, reducing sugars and ascorbic acid). Individual phenolic acids were quantified by high-performance liquid chromatography (HPLC) using the latest in column technology. Four reversed-phase C18 analytical columns with different properties (dimensions, particle size, particle shape, pore size, and carbon load) were compared. Three different mobile phases using isocratic conditions were also evaluated. A column (4.6 × 150 mm) packed with 5-μm spherical silica particles of pore size 110 Å combined with 14% carbon load provided the best and fast separation of individual phenolic acids (that is, chlorogenic acid, caffeic acid, and 3 isomers of dicaffeoylquinic acid) with a total analysis time of less than 7 min. Among the 3 mobile phases tested, a mobile phase consisting of 1% (v/v) formic acid aqueous solution: acetonitrile: 2-propanol, pH 2.5 (70:22:8, v/v/v) gave adequate separation. Among the solvents tested, aqueous mixtures (80:20, solvent:water) of methanol and ethanol provided higher phenolic acid extraction efficiency than the aqueous mixture of acetone.     

沙田柚不同组织部位酚类物质组成及其抗氧化活性研究

摘 要：目的 揭示沙田柚不同部位酚类物质组成和抗氧化活性的差异。方法 提取沙田柚油胞层、白皮层、囊衣和籽中游离酚和结合酚,测定其总酚、总黄酮含量,单体酚组成和抗氧化活性,并采用皮尔森相关性分析确定酚类物质含量与抗氧化活性之间的相关性。结果 沙田柚各部位酚类物质主要以游离酚为主,其总酚、总黄酮含量变幅分别为2.01~13.28 mg GAE/g DW和3.79~15.2 mg RE/g DW,油胞层和白皮层总酚、总黄酮含量均高于囊衣和籽。从沙田柚各部位鉴定出柚皮苷、橙皮素、甜橙黄酮、对羟基苯甲酸、对香豆酸和阿魏酸共6个单体酚,柚皮苷是各部位中最主要的黄酮类化合物且以白皮层中含量最高。沙田柚各部位铁离子还原能力(ferric reducing antioxidant power,FRAP)和氧自由基吸收能力(oxygen radical absorbance capacity, ORAC)变幅分别为7.6336~69.26 mmol TE/g DW和116.9~625.111.69~62.51 μmol TE/g DW,甜橙黄酮是各部位发挥FRAP活性的重要成分,而柚皮苷是各部位发挥ORAC活性的重要成分。结论 沙田柚副产物,尤其是果皮(油胞层和白皮层),是天然酚类物质的来源。     

Phenolic composition,antioxidant and antimicrobial activities of free and bound phenolic extracts of Moringa oleifera seed flour

Phenolic compounds, antioxidant and antibacterial activities of defatted Moringa oleifera seed flour (DMF) were investigated. The total phenolic and flavonoid contents were measured using colorimetric methods. Free phenolic acid and flavonoid profiles were analyzed by high performance liquid chromatography, while antioxidant capacities were evaluated using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), ferric reducing antioxidant power and total antioxidant capacity. The results showed that extractability of phenolic compounds was significantly higher (p < 0.05) in bound phenolic extract (4173.00 ± 32.22 mg gallic acid equivalents (GAE)/100 g) than in free phenolic extract (780.00 ± 14.2 mg GAE/100 g) and it showed higher antioxidant and antimicrobial activities. The IC₅₀ value for DPPH radical scavenging activity was 0.9 ± 0.05 and 14.9 ± 0.07 mg/mL for bound phenolic and free phenolic extracts, respectively. Bound phenolic extract was more effective (minimum inhibitory concentration (MIC), 0.06–0.157%) than free phenolic extract (MIC, 0.117–0.191%) against tested bacteria. Ten phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, caffeic acid, protocatechuic acid, cinnamic acid, catechin, epicatechin, vanillin and quercetin) were identified and quantified in both extracts. These natural plant phenolics from Moringa seeds could be a good source of antioxidants and antibacterials for food and pharmaceutical industries.     

Changes in physio-biochemical metabolism,phenolics and antioxidant capacity of different Chinese pea varieties during germination

In this study, changes in physiological and biochemical metabolism, phenolics and antioxidant capacity of six different Chinese pea varieties during germination were investigated. Results showed that germination had a positive effect on the physiological indexes and bioactive substances of pea. The bud length, root length, fresh weight and respiration rate of pea sprouts increased with germination time. The content of free and bound phenolics in germinated peas increased significantly. Meanwhile, activated phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H) and 4-coumaric acid coenzyme A ligase (4CL) led to the accumulation of phenolics. Antioxidant capacity of pea sprouts increased with the extension of germination time. From the perspective of principal component analysis, compared with the other five varieties, Longwan 7 can be distinguished by free phenolic content in the later stage of germination. The result provides a new perspective for further development of pea as a functional food for human consumption.     

Phenolic acid content and composition in leaves and roots of common commercial sweetpotato (Ipomea batatas L.) cultivars in the United States

ABSTRACT:  Phenolic acids in commercially important sweet potato cultivars grown in the United States were analyzed using reversed-phase high-performance liquid chromatography (HPLC). Caffeic acid, chlorogenic acid, 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, and 3,4-di-O-caffeoylquinic acid were well separated with an isocratic elution in less than 25 min compared to about 120 min for analyzing and re-equilibrating the column with a gradient method. The isocratic elution order of these caffeoylquinic acid derivatives was confirmed by LC-MS/MS. Chlorogenic acid was the highest in root tissues, while 3,5-di-O-caffeoylquinic acid and/or 4,5-di-O-caffeoylquinic acid were predominant in the leaves. Steam cooking resulted in statistically nonsignificant increases in the concentration of total phenolics and all the individual phenolic acids identified. Sweetpotato leaves had the highest phenolic acid content followed by the peel, whole root, and flesh tissues. However, there was no significant difference in the total phenolic content and antioxidant activity between purees made from the whole and peeled sweet potatoes.     

Phenolic acid profiles and antioxidant activities of wheat bran extracts and the effect of hydrolysis conditions

Four different types of wheat bran were extracted and analyzed for phenolic acids using the Folin–Ciocalteu method and HPLC. The extracts and their hydrolysis products were also evaluated for their antioxidant activities. The total phenolic content of the red wheat bran was higher than that of the white wheat. We found that the majority of the phenolic acids existed in a bound form in wheat bran. These phenolic acids can be released by hydrolyzing the bran under alkaline or acidic conditions; however, the former was more efficient in the release of free phenolic acids than the latter. Ferulic, vanillic, and syringic acids were the major individual phenolic acids in the studied wheat bran. The main portion of the total ferulic acid was from alkaline hydrolysis. The alkaline hydrolysable fractions had greater antioxidant activities, while the acid hydrolysable fractions showed lower activities in both the red and white bran. The antioxidant activity of bran extract was stronger than that of free phenolic acids.     

The phenolic profiles and antioxidant activity in different types of tea

Phenolics are suggested to be the major bioactive compounds responsible for the health benefits of tea. Seven types of tea were extracted using boiling water. The extraction kinetics was investigated. To more fully characterise the antioxidant profiles and possible associated health benefits of these tea types, the total water‐soluble solid content, phenolics, flavonoids, and antioxidant and antiproliferative activities were quantified. Green tea leaves (GTL) were found to have the highest phenolic content (128.7 ± 1.7 mg g^?1, P < 0.05), followed by teas of decaffeinated green tea bag (dGTB), green tea bag (GTB), black tea bag (BTB), decaffeinated BTB, black tea leaves and oolong tea leaves (OTL). Among the three leaf teas, GT displayed the greatest antioxidant activity (4850.2 ± 60.7 μmol g^?1, P < 0.05), followed by black tea (BT) and oolong tea (OT). As for the four bag teas, decaffeinated GT possessed the strongest antioxidant activity (4431.1 ± 335.0 μmol g^?1, P < 0.05), followed by GT, BT and decaffeinated BT. The results display that phenolic/flavonoid content well correlated with antioxidant activity. Proliferation of three human cancer cells was significantly inhibited in a dose‐dependent manner after exposure to some tea extracts. This may influence consumers in selecting the type of tea and tea brewing times, exhibiting greater health benefits.     

The influence of brewing method on bioactive compounds residues in spent coffee grounds of different roasting degree and geographical origin

The content of bioactive compounds in spent coffee grounds (SGC) was studied. SGC were obtained from Coffea arabica beans of different roasting degrees (light and dark) and different geographical origins (Nicaragua, Columbia and Mexico) processed using four brewing methods (mocha, filtered, drip and infusion). The highest caffeine and chlorogenic acid contents were determined in filtered spent coffee extracts. All extracts of light roasted spent coffee grounds showed lower browning index levels in comparison to that from dark roasted spent coffee grounds. Generally, the highest content of total polyphenolic compounds and highest antioxidant capacity were determined in extracts prepared in drip. In conclusion, the results obtained in this study indicate that the spent coffee grounds produced of domestic levels, especially those obtained from filter coffeemaker, could be considered as a good source of natural antioxidants.     

Fermentation alters antioxidant capacity and polyphenol distribution in selected edible legumes

This study was designed to investigate the influences of fermentation by naturally occurring bacteria on legumes and lactic acid bacteria on antioxidant capacity and polyphenols in both soluble and bound extracts of eight common edible legumes, including black cow gram, mottled cowpea, speckled kidney bean, lentil, small rice bean, small runner bean and two soya beans. Fermentation had varying effects on the antioxidant capacity of soluble and bound extracts in different edible legumes, with fermented mottled cowpea, speckled kidney bean and small rice bean showing increased total antioxidant capacity. In addition, fermentation in general enhanced total phenolic content in all the selected legumes, which could be associated with the biotransformation between soluble phenolics and the release of bound phenolics induced by micro‐organisms involved in the fermentation process. Phenolic compounds, such as catechin, were increased in fermented mottled cowpea. Overall, fermentation could increase the bioavailability of legume polyphenols and fermented legume powders rich in antioxidant polyphenols can be used to develop novel functional foods.     

红薯叶中绿原酸的提取纯化工艺研究

通过单因素实验对红薯中绿原酸进行基础研究,选择出了红薯的最佳干燥方式,绿原酸含量最高的部位和提取绿原酸的最佳试剂：烘干的红薯材料中绿原酸的含量大于晒干的;红薯叶中绿原酸的含量为最高;70％的乙醇对于绿原酸的提取效果为最佳。     

Tocopherols composition of Portuguese wild mushrooms with antioxidant capacity

The antioxidant composition and properties of 18 Portuguese wild mushrooms (Clitocybe alexandri, Cortinarius glaucopus, Fistulina hepatica, Hydnum repandum, Hygrophoropsis aurantiaca, Hypholoma capnoides, Laccaria amethystina, Laccaria laccata, Lactarius aurantiacus, Lactarius salmonicolor, Lepista inversa, Lepista sordida, Mycena rosea, Russula delica, Russula vesca, Suillus collinitus, Suillus mediterraneensis, Tricholoma sulphureum) were evaluated, in order to contribute to the overall characterisation of these products. Their radical-scavenging capacity, reducing power and inhibition of lipid peroxidation measured in liposome solutions was fully studied. Furthermore, the tocopherols composition was determined by HPLC-fluorescence. The analysed mushrooms contain powerful antioxidants such as phenols (0.51–7.90 mg/g) and tocopherols (0.02–8.04 μg/g). β-Tocopherol was the vitamer detected in higher amounts, while δ-tocopherol was not detected in the majority of the samples. All the species proved to have antioxidant activity being more significant for H. aurantiaca (EC₅₀ values lower than 1.35 mg/ml) due to the contribution of antioxidants such as phenols (7.90 mg/g) and tocopherols (0.02–1.94 μg/g). The ongoing research states the nutraceutical potential of all these unique species, making the information available for a better management and conservation of mushrooms and related habitats.     

藏茜草不同溶剂提取物的抗氧化活性研究

采用DPPH自由基清除法、ABTS自由基清除法、羟自由基清除法、超氧阴离子清除法、还原力测定法和螯合力测定法六种抗氧化模型对藏茜草95%乙醇提取物以及石油醚相,乙酸乙酯相,正丁醇相和水相等4个不同极性部位的抗氧化活性进行评价,同时分析抗氧化活性与总酚和总黄酮含量的关系。研究结果表明,除水提部位外,藏茜草其它4个极性部位提取物均表现出一定的抗氧化活性,其抗氧化活性与多酚和总黄酮含量呈显著相关。其中,乙酸乙酯部位总黄酮和总多酚含量最高,抗氧化活性也最强,其总黄酮和总多酚含量分别为(232.03±1.74)mg芦丁当量/g提取物和(173.53±1.75)mg没食子酸当量/g提取物,其清除DPPH自由基、超氧阴离子、羟自由基和ABTS自由基的EC50分别为0.06±0.01、0.17±0.01、(0.24±0.02)mg/m L和(1.75±0.23)μg/m L,对金属离子螯合力的EC50为(0.11±0.01)mg/m L。藏茜草的乙酸乙酯极性部位具有显著的抗氧化活性,是天然抗氧化活性化合物的良好来源。      

Dynamic changes in phytochemical composition and antioxidant capacity in green and black mung bean (Vigna radiata) sprouts

The mung bean (Vigna radiata) sprout is a popular fresh vegetable in many parts of the world. In this study, the dynamic change of ascorbic acid, phenolic composition and antioxidant capacity were evaluated in green and black mung bean sprouts. Germination increased ascorbic acid, total phenolic content and antioxidant capacity in both mung beans. The green mung bean sprout generally had higher ascorbic acid, total phenolic content and antioxidant capacity than the black mung bean sprout. Most phenolic compounds, such as caffeic acid, catechin, ferulic acid, gallic acid and rutin, were found to gradually increase after germination. Therefore, mung bean sprouts, especially green mung bean sprout possessing high level of antioxidant phytochemicals, can be valuable functional vegetables and good sources of natural antioxidants.     

Phenolic composition and antioxidant activity of culms and sugarcane (Saccharum officinarum L.) products

The present work reports amounts of flavonoids and phenylpropanoids of culms of three sugarcane varieties and of raw juice, syrup, molasse and VHP sugar. The antioxidant activity of those materials was evaluated by the DPPH and β-carotene/linoleic acid methods. The predominant phenolics in culms were phenylpropanoids (caffeic, chlorogenic and coumaric acids), while flavones (apigenin, tricin and luteolin derivatives) appeared in lower amounts. Differences were noted either among phenolic profiles of sugarcane culms or between culms and sugarcane products. The antioxidant activities of solutions from most samples were similar or higher than a 80 μM Trolox solution.     

The phenolic composition and antioxidant capacity of soluble and bound extracts in selected dietary spices and medicinal herbs

Phenolic compounds, commonly found in plant‐based foods, exist in free or bound form. Despite much research on the soluble phenolics in spices and herbs, their bound phenolics have not been intensively investigated. In this study, six common dietary spices and medicinal herbs (Padang cassia, oregano, clove, Chinese cassia, Japanese knotweed and peel of pomegranate) were selected to evaluate and compare their phenolic composition and antioxidant capacity in soluble extracts (SEs) and bound extracts (BEs). Generally, the samples had high total phenolic content and antioxidant capacity, with lower levels in the BEs. From the HPLC results, (+)‐catechin, (?)‐epicatechin, eugenol, cinnamaldehyde and carvacrol were the major phenolic compounds in the SEs, and gallic acid, p‐coumaric acid and ellagic acid in the BEs. Phenolic compounds are likely the major contributors to the antioxidant capacity of these plant samples. Overall, these dietary spices and medicinal herbs can be excellent sources of natural antioxidant phenolics.     

黄褐毛忍冬中酚酸类化合物含量及其抗氧化活性相关性

为探究黄褐毛忍冬总绿原酸含量、总黄酮含量与抗氧化活性相关性;利用50％甲醇恒温震荡提取黄褐毛忍冬花蕾中总绿原酸、总黄酮,紫外分光光度法测定其含量,DPPH比色法测定其抗氧化活性,采用SPSS软件对化合物含量与抗氧化活性进行相关性分析;结果表明：在0．01水平上总绿原酸含量、总黄酮含量与黄褐毛忍冬抗氧化活性呈正相关,相关数为分别为0．734和0．683,即绿原酸对黄褐毛忍冬的抗氧化活性贡献最大,其次是黄酮。     

Comparison of the antioxidant activities of roasted and explosive puffed coffees

We investigated the explosive process effect on antioxidant activities of coffee bean. The total polyphenol contents of powdered extract of explosive puffing coffee bean at 0.75 MPa (PEP 7.5) and powdered extract of explosive puffing coffee bean at 0.9 MPa (PEP 9.0) were at a significantly higher than that of the powdered extract of roasting coffee bean (PER) (P < 0.05). PEP 7.5 showed the highest levels of 3‐CQA (86.23 μg mg^?1), 4‐CQA (43.71 μg mg^?1), and 5‐CQA (31.66 μg mg^?1), and PEP 9.0 had also similar levels of chlorogenic acids, with 3‐CQA (77.99 μg mg^?1), 4‐CQA (43.71 μg mg^?1), and 5‐CQA (30.32 μg mg^?1). PEP 7.5 and PEP 9.0 showed relatively higher antioxidant capacities in DPPH, ABTS, taurine, FRAP, and β‐carotene/linoleic acid assays. PEPs partly recovered the HepG2 cell damage induced by t‐BOOH. These results suggest that puffed coffee has beneficial health effects, and could be used for the development of novel processed coffee products.     

Involvement of Anthocyanins and other Phenolic Compounds in Radical-Scavenging Activity of Purple-Fleshed Sweet Potato Cultivars

ABSTRACT: The 80% ethanol extracts of 5 purple-fleshed sweet potato cultivars were separated into 2 fractions, anthocyanins- and phenolic compounds-rich fractions, to clarify the contribution of these constituents to the radical-scavenging activity. The separation was accomplished with an ethyl acetate liquid/liquid extraction. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity in each fraction and the contributors varied according to the cultivars. The dominant DPPH radical-scavengers in "Ayamurasaki" and "Kyushu-132" were anthocyanins rather than phenolic compounds, while those in "Miyanou-36" and "Bise" were phenolic compounds, such as chlorogenic acid. Furthermore, the high-performance liquid chromatography analysis of anthocyanins showed that "Ayamurasaki" and "Kyushu-132" were rich in anthocyanins with peonidin aglycon, whereas "Miyanou-36,""Bise," and "Tanegashimamurasaki" contained cyanidin aglycon.