Effect of pH,heat, and light treatments on the antioxidant activity of sweet potato leaf polyphenols

In the present study, the antioxidant activity of sweet potato leaf polyphenols was measured, and the effect of different pH values (3.0, 5.0, 7.0, and 8.0), temperatures (55, 65, 80, and 100°C), and light treatments on sweet potato leaf-polyphenols was investigated. Results showed that the O₂^? scavenging activity of sweet potato leaf polyphenols from cultivar Jishu No. 04150 was 5.84 and 6.20 times of that of tea polyphenols and grape seed polyphenols, respectively, at the concentration of 20 μg/mL. The oxygen radical absorbance capacity was 1.28 and 1.27 times of that of tea polyphenols and grape seed polyphenols, respectively. Sweet potato leaf polyphenols dissolved in pH 5–7 solutions showed higher retention rates of antioxidant activity. Heat treatment at 50 and 65°C and light treatment had little effects on sweet potato leaf polyphenols. In conclusion, sweet potato leaf polyphenols possessed high antioxidant activity and processing stability, having the potential to be a new type of natural antioxidant.     

板栗仁中多酚氧化酶活性的研究

采用分光光度法对板栗仁中多酚氧化酶的活性进行了研究.结果表明,酶液加入量与吸光度值成正比关系,多酚氧化酶的最适反应温度为30～40 ℃,最适反应pH值为5.4,板栗仁表层多酚氧化酶的活性显著高于心部的活性.同时,对酶的热稳定性以及抑制剂亚硫酸钠、抗坏血酸对酶活力的影响进行了探讨.     

Effect of cooking on the antioxidant properties of coloured peppers

Pepper (Capsicum annum L.) has long been recognized as an excellent source of antioxidants, being rich in ascorbic acid and other phytochemicals. This study was conducted to investigate the effect of different cooking methods on the antioxidant properties of coloured peppers. Six varieties of peppers were subjected to different cooking methods, such as microwave heating, stir-frying and boiling in water, for 5 min individually. The cooked and raw peppers were analyzed for radical-scavenging activity (RSA) and total polyphenol content (TP) using 1,1-diphenyl-2-picrylhydrazyl–high-pressure liquid chromatography (DPPH)–HPLC and Folin-Ciocalteu methods, respectively. The samples were also evaluated for ascorbic acid content (AsA) by HPLC. Total carotenoid content was determined spectrophotometrically. Results suggest that there is no significant (P > 0.05) difference in RSA, TP, AsA and total carotenoid contents between the cooked and raw peppers when processed for 5 min. However, the cooked peppers show marked differences (P < 0.05) in the RSA, TP and AsA when cooked for 5 min in boiling water with further reduction observed after boiling for 30 min. This may be due to the leaching of antioxidant compounds from the pepper into the cooking water during the prolonged exposure to water and heat. Therefore, it is vital to use less water and cooking time and also to consume the water used for boiling so as to obtain the optimum benefits of bioactive compounds present in peppers. It is concluded that microwave heating and stir-frying without using water are more suitable cooking methods for pepper, to ensure the maximum retention of antioxidant molecules.     

Sugars,organic acids,phenolic composition and antioxidant activity of sweet cherry (Prunus avium L.)

Sugars, organic acids, phenolics and anthocyanins in fruits of 13 sweet cherry cultivars: Badascony, Burlat, Early Van Compact, Fercer, Fernier, Ferprime, Lala Star, Lapins, Noire de Meched, Sylvia, Vesseaux, Vigred (red-coloured) and Ferrador (bi-coloured) were quantified by HPLC. Sweet cherry cultivars of different pomological characteristics and different time of ripening were evaluated sensorily. Cultivars were evaluated for their total phenolic content and antioxidant activity. The sum of sugars (glucose, fructose, sucrose and sorbitol) ranged from 125 to 265 g/kg fresh weight (FW) and the sum of organic acids (malic, citric, shikimic and fumaric) ranged from 3.67 to 8.66 g/kg FW. Total phenolic content ranged from 44.3 to 87.9 mg gallic acid equivalents/100 g FW and antioxidant activity ranged from 8.0 to 17.2 mg ascorbic acid equivalent antioxidant capacity mg/100 g FW. The correlation of antioxidant activity with total phenolics content and content of anthocyanins was cultivar dependent.     

Effects of short-term anoxia treatment on browning of fresh-cut Chinese water chestnut in relation to antioxidant activity

The effects of short-term anoxia pre-treatment on browning of fresh-cut Chinese water chestnut (CWC), stored at 4 °C, in relation to antioxidant activity were investigated. CWC slices were exposed to pure N₂ for 4 h and then stored at 4 °C for 18 d. Anoxia significantly inhibited browning of CWC slices during storage, accompanied by lower contents of malondialdehyde, H₂O₂, and lipoxygenase activity. Furthermore, anoxia induced the activities of superoxide dismutase and ascorbate peroxidase, which could benefit scavenging reactive oxygen species and alleviating lipid peroxidation. In addition, better maintenance of reducing power and free-radical-scavenging activities against α,α-diphenyl-β-picrylhydrazy (DPPH), superoxide anions and hydroxyl was observed in N₂-treated CWC slices, with higher phenolic compounds and ascorbic acid contents. Collectively, these finds suggest that N₂ pre-treatment enhanced enzymatic and non-enzymatic antioxidant activity in CWC slices, and thereby contributed to alleviating lipid peroxidation and maintenance of storage quality.     

Evaluation of antioxidant activity and total phenolics of selected Czech honeys

Honey serves as a good source of natural antioxidants, which are effective in reducing the risk occurrence of heart disease, cancer, cataracts, different inflammatory processes and immune-system decline. In the fresh selected Czech honey samples originated mainly from the region North Moravia antioxidant activity and total polyphenol content were determined. A total of 40 honey samples (multifloral, lime, rape, raspberry, mixture and honeydew honeys) native to different stations gained in the period from May by August year 2006 were analysed. Total phenolics (TP) content was determined by the modified Folin-Ciocalteau method [TP was expressed as mg of gallic acid equivalent (GA eq.) per kg of honey]. For evaluation of the antioxidant activity (AOA) three different methods were used, the ferric reducing antioxidant power (FRAP) assay, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and the 2,2′-azinobis(3-ethylbenzothiazolin)-6-sulfphonate (ABTS) assay. AOA was expressed in mg ascorbic acid equivalent (AA eq.) per kg of honey. The results indicated that TP and AOA in Czech honey varied greatly between the honey kinds, location and time of the harvest. Average TP ranged from 89.9 mg GA eq. kg^-1 in lime honey to 215.2 mg GA eq. kg⁻¹ in honeydew honey. Antioxidant activity determined by the DPPH, ABTS and FRAP methods was lowest in floral honeys. The highest values were obtained for honeydew and mixture honeys. ABTS and FRAP assays have been shown to be the optimal methods for AOA determination in honey. A positive linear correlation between AOA and TP was observed (in FRAP assay R² = 0.852). It indicates that phenolics are one of the main components responsible for antioxidant behaviour of honey. The obtained results support and extend complete knowledge about the content of bioactive phenolics and antioxidant activity in the Czech honeys.     

Antioxidant compound contents and antioxidant activity before and after cooking in sweet and bitter Chenopodium quinoa seeds

The antioxidant activity and the relationship between total antioxidant activity and the main classes of antioxidants in the seeds of bitter and sweet Chenopodium quinoa seeds were measured before and after boiling, in order to establish which one showed the best antioxidant property and how a traditional cooking method could affect it. Our results, obtained by using DPPH (1,1-diphenyl-2-picrilhydrazyl) and FRAP (Ferric Reducing/Antioxidant Power) methods, showed that antioxidant activity of bitter seeds was higher than that of sweet seeds. This activity principally depended on phenols and flavonoids in bitter seeds, while it was mainly due to phenol, flavonoid and carotenoid compounds in sweet seeds. Moreover, boiling caused a significant loss of antioxidant capacity in water.     

Phenolics and antioxidant activity of lentil and pea hulls

Hulls obtained by pilot-scale dehulling process from green and red lentils and yellow peas were fractionated into hulls (> 500 ??m) and residues (< 500 ??m). These fractions together with the corresponding whole seeds were extracted with four solvents, aqueous (70%) acetone, (80%) ethanol, hot water (70-80 °C) and water (22 ± 1 °C) and evaluated for antioxidant activity in relation to phenolic contents. Aqueous acetone (70%, v/v) extracted the highest level of total phenolics at about 87 mg of catechin equivalent per gram of sample from lentil hulls followed by hot water, water and aqueous ethanol (80%, v/v). Red lentil hull with maximum concentration of phenolic compounds exhibited the strongest antioxidant activity of 260 mg (1040 ??M) trolox equivalent/g hull. Hot water and water extracted significantly higher total phenolics from whole pulse and their residue than other solvents, but with weaker antioxidant activity. Aqueous ethanol was always the best extractant of phenolic antioxidant from yellow pea irrespective of its millstream. The most potent phenolic antioxidant was obtained from water extract of green and red lentil hulls, followed by those extracted with ethanol, acetone, and hot water. Total phenolic content was highly correlated with antioxidant activity of pulses and its millstreams.     

Evaluation of the antioxidant activity of asparagus,broccoli and their juices

Antioxidant activity of asparagus, broccoli and their juices was evaluated using 2,2′-diphenyl-l-picrylhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and β-carotene bleaching assays. Asparagus showed greater antioxidant activity than broccoli. Asparagus juice also had greater antioxidant activity than broccoli juice. Methanol and acetone extracts of asparagus and broccoli had significantly greater antioxidant activity than their water extracts. Asparagus and broccoli extracts, as well as their juices, showed no significant difference in total phenolics content. However, asparagus contained more flavonoids than broccoli. The antioxidant activity of asparagus and broccoli extracts demonstrated a linear relationship with their flavonoid content.     

Effects of drying and extrusion on colour,chemical composition,antioxidant activities and mitogenic response of spleen lymphocytes of sweet potatoes

Antioxidative and physiological property changes of freeze-dried, hot air-dried and extruded products made from two different colours of sweet potatoes (yellow and orange) were investigated. The results showed that there were no significant differences of dietary fibre content amongst all the treatments, except that the extruded products of orange sweet potatoes had higher dietary fibre contents. However, the water solubility index (WSI) values and antioxidant content were significantly different between yellow and orange sweet potatoes, and significantly different amongst freeze-dried, hot air-dried and extruded samples. The WSI values of the extruded samples were significantly higher than those of the hot air- and freeze-dried samples. The freeze-dried samples of orange sweet potatoes had more total phenolic compounds, β-carotene, and anthocyanin and had better scavenging effect on DPPH radicals than had freeze-dried yellow sweet potatoes. However, the scavenging effect on DPPH radicals was appreciably greater for hot air-dried than freeze-dried yellow sweet potatoes, but this trend was opposite for orange sweet potatoes. The extrusion process significantly increased the WSI values, scavenging effect on DPPH radicals and total phenolic compounds but decreased the β-carotene and anthocyanin for both yellow and orange sweet potatoes. At lower concentration (25–50 μg/ml), the methanolic extract of freeze-dried yellow sweet potatoes possessed a greater capacity of increasing the mitogenic response than did freeze-dried orange sweet potatoes; at higher concentration (100–200 μg/ml), the proliferation of the lymphocytes increased when stimulated with mitogen Con A for all the samples. This suggests that mitogen Con A selectively promotes T-cell-dependent proliferative activity.     

Phenolic content and antioxidant activity of cantaloupe (cucumis melo) methanolic extracts

The objectives of this study were to determine phenolic content and antioxidant activity of methanolic extracts from different parts of cantaloupe (leaf, stem, skin, seed and flesh). The flesh extract afforded the highest yield (89.6 ± 0.3%) whilst the lowest yield was obtained from the seed (13.7 ± 0.5%) (p < 0.05). The leaf extract showed the highest total phenolic content (26.4 ± 0.3 mg GAE/g extract) and total flavonoid content (69.7 ± 3.37 μg RE/g extract) accompanied with best antioxidant activity through all antioxidant assays (p < 0.05). In addition, the stem extract also exhibited good antioxidant activity. Thus, these results suggest that methanolic extracts of cantaloupe leaf and stem may serve as a potential source of natural antioxidant for food and nutraceutical application.     

In vivo antioxidant potential of Sweet chestnut (Castanea sativa Mill.) wood extract in young growing pigs exposed to n-3 PUFA-induced oxidative stress

BACKGROUND: Farm animals in intensive farming systems are frequently exposed to oxidative stress, which demands adequate antioxidant protection. The aim of this study was to evaluate the antioxidant potential of different concentrations of Sweet chestnut wood extract (SCW; 0.75, 1.5 and 3 g kg^?1) in case of n‐3 PUFA‐induced oxidative stress in young pigs. RESULTS: The highest concentration (3 g kg^?1) of SCW decreased malondialdehyde excretion in urine by 31.7%, but had no effect on plasma malondialdehyde. A linear trend towards decrease of urine isoprostanes iPF_2α‐VI was observed with the addition of SCW. All three concentrations of SCW efficiently protected blood lymphocytes from DNA damage and lowered plasma alanine aminotransferase levels. The antioxidative and antigenotoxic effect of 3 g SCW kg^?1 feed was comparable to the effect of 90.4 mg kg^?1 of added vitamin E. CONCLUSION: The results from this study show that, besides being known as antihelmintic, antimicrobial and antiviral agent, Sweet chestnut wood extract could also be considered as a promising natural antioxidant in animal nutrition. Copyright © 2011 Society of Chemical Industry     

超声波辅助提取菱角壳总黄酮及抗氧化性研究

目的:采用超声波辅助提取菱角壳总黄酮的优化工艺确定,并测定其抗氧化性。方法:采用正交实验法考察提取液浓度、液料比、提取时间及超声波功率等,对总黄酮提取率的影响,用标准曲线法测定总黄酮含量。在此基础上用分光光度法测定菱角壳中黄酮类组分体外清除羟基自由基、超氧阴离子自由基和DPPH自由基的能力,并将其与常用的L-抗坏血酸和BHT抗氧剂的抗氧化性能进行比较。结果:最佳工艺参数为70%(v/v)的甲醇、液料比30:1(mL/g),超声功率120W、提取时间20min,在此条件下总黄酮提取得率可达1.722%。同时显示菱角壳中黄酮类组分对自由基有消除作用,具有良好的抗氧化性。     

Study on chemical composition,antioxidant and anti-inflammatory activities of hot water extract from Piceamariana bark and its proanthocyanidin-rich fractions

Hot water extract (HWE) from Picea mariana (black spruce) bark was evaluated for its antioxidant and anti-inflammatory activities. HWE was fractionated into an oligomeric proanthocyanidin-rich fraction (OPF) and a polymeric proanthocyanidin-rich (PPF) fraction, and their bioactivities were also evaluated. OPF exhibited the highest antioxidant and anti-inflammatory activities. The compositions of HWE, OPF and PPF were also evaluated. OPF was richest in total polyphenol but the lowest in total proanthocyanidin (PA) content. Thiolysis coupled with HPLC-DAD has shown that the PAs of the black spruce bark were procyanidin type. The mean degrees of polymerisation (DPm) of HWE, OPF and PPF were, respectively, 6.0, 3.3 and 7.6.     

Effect of fermentation on antioxidant properties of some cereals and pseudo cereals

The influence of fermentation by two types of microorganisms (lactic acid bacteria Lactobacillus rhamnosus, and yeast Saccharomyces cerevisiae) on antioxidant activities and total phenolics of 4 cereals, namely buckwheat, wheat germ, barley and rye, was determined and compared with those of their unfermented counterparts. The total phenolic content (TPC), determined by the Folin–Ciocalteu method, increased upon fermentation. Antioxidant activities (AOA) were assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging capacity, ferric ion-reducing antioxidant power (FRAP) and thiobarbituric acid (TBA) methods. The presence of those microorganisms was more or less important for enhanced levels of antioxidant activity. Thus fermentation offers a tool to further increase the bioactive potential of cereal products.     

Indian Grape Wines: A Potential Source of Phenols,Polyphenols, and Antioxidants

Indian grape wines are analyzed for total phenolic content and antioxidant activity along with other parameters, such as pH, alcohol content, and reducing sugars. Concentration of polyphenols, like tannic acid, catechol, vanillin, caeffic acid, ferullic acid, and resveratrol, was quantified using reverse phase-high performance liquid chromatography and ultra high performance liquid chromatography. The red wines showed the highest concentration of phenolic content (6.5 ± 0.1 mg/ml) and antioxidant activity (84.60 ± 1%) as compared to white and port wines, while red wine R2 showed the highest radical scavenging activity among red wines and R4 showed the lowest total phenolic content. The white wine W3 showed less total phenolic content and antioxidant activity. Further, a positive correlation between phenolic content and antioxidant activity was observed.     

Effects of origins and fermentation time on the antioxidant activities of kombucha

Effects of kombucha origins and fermentation time on their antioxidant properties were investigated using in vitro free radical scavenging assays. Kombucha from various sources demonstrated different antioxidant activities, and most showed the time-dependent characteristics. The average antioxidant potentials of kombucha after fermenting for 15 days were raised to about 70%, 40%, 49% determined, respectively, by the assays of DPPH, ABTS radical scavenging, and inhibition of linoleic acid peroxidation, while the ferrous ion binding ability was inversely diminished by 81%. The total phenol content increased up to 98% which implied that thearubigin might be subjected to biodegradation during fermentation, resulting in the release of smaller molecules with higher antioxidant activities.     

Effects of genotype and treatment on the antioxidant activity of sweet potato in Taiwan

Six genotypes of sweet potato commercially available in Taiwan, including TNG57, TNG66, TNG68, TYY1, RP and WP, were used as samples in this study of the effects of steaming and kneading with pre-steaming treatments on the antioxidant components and antioxidant properties of methanolic extracts. Steam treatment increased the total phenols contents of all genotypes (2–13 times), flavonoids content of RP (1.3 times) and anthocyanins contents of RP and WP (5–6 times). Steam treatment also increased the reducing power and scavenging DPPH radical effect of sweet potato flours. For the methanolic extracts of steamed and kneaded flours, reducing powers were 0.02–1.70 at 5.0 mg ml⁻¹ and the scavenging effects on DPPH radicals were 19–92% at 2.5 mg ml⁻¹. Both showed the order of RP > WP > TYY1 and TNG66 > TNG57 and TNG68. However, the chelating effect of the six genotypes at 1.0 mg ml⁻¹ ranged from 50% to 73%. Contents of total phenols, flavonoids, and anthocyanins of sweet potato flours were significantly positively correlated with the reducing power and scavenging DPPH radical effects. After steaming and kneading treatments, RP showed the highest increase in the contents of total phenols, flavonoids and anthocyanins among the six genotypes studied.     

Physical, biochemical and antioxidant properties of some Indian honeys

The study was intended to characterise the physicochemical and antioxidant properties of some commercial brands of Indian honeys. All the samples showed considerable variations with reference to their level of total phenolics, protein, radical scavenging activity, ascorbic acid equivalent antioxidant content (AEAC) and ferric reducing antioxidant potential (FRAP). Comparative studies of Indian honeys indicated the strong correlation between proline content and AEAC as well as 2,2-diphenyl-1-picryl-hydrazyl (DPPH) scavenging activity whereas phenol content was strongly correlated with FRAP values. Thus, overall antioxidant activity seems to be contributed by proline and phenol contents. Besides these major factors, colour pigments (ABS₄₆₀) were also found to contribute significantly to the overall observed antioxidant activity.