Stability of the total antioxidant capacity and total polyphenol content of 23 commercially available vegetable juices before and after in vitro digestion measured by FRAP, DPPH, ABTS and Folin-Ciocalteu methods

Vegetables are known to contain a wide variety of antioxidants which may provide protection against the development of a number of disease states. Recently there has been a large increase in the number of vegetable juices which have become commercially available. The objective of the present study was to analyse the total antioxidant capacity of 23 commercially available vegetable juices [via Ferric Reducing Antioxidant Power (FRAP), 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) and Folin-Ciocalteu Reagent (FCR) for total polyphenols] and to determine the stability of the antioxidant capacity following an in vitro digestion procedure using the same methods. All 23 juices were significant sources of antioxidants both in terms of total antioxidant capacity and total polyphenols, although results varied considerably between the juices [1369-9500 ??mol/L (FRAP), 57.8-100% inhibition of DPPH, 10.9-90.7% inhibition of ABTS⁺ and 449-3025 ??g ferulic acid equivalents/mL for FCR]. Beetroot juice displayed the highest level of total antioxidants and total polyphenols compared to the other juices which were analysed (tomato, carrot, mixed vegetable, mixed fruit and vegetable). The antioxidant capacity of the juices remained high throughout the in vitro digestion.     

Elucidation of the flavonoid and furocoumarin composition and radical-scavenging activity of green and ripe chinotto (Citrus myrtifolia Raf.) fruit tissues,leaves and seeds

Citrus myrtifolia Raf. (chinotto) flavedo, albedo and carpel membranes from green and ripe fruits, as well as seeds and leaves, were investigated for the first time for their flavonoid and furocoumarin composition. Twenty-three unique compounds distributed in the different fruit/plant parts were identified and quantified. All samples analysed contained flavanone O-glycosides, flavone C- and O-glycosides and furocoumarins; flavedos and albedos also contained significant amounts of polymethoxyflavones. Flavedo and albedo extracts were found to be richest in flavonoids and furocoumarins, containing up to 1.95 g/kg fresh weight. Flavedo, albedo and carpel membranes from ripe fruits were found to be richer than the corresponding tissues from unripe fruits. The remarkable radical-scavenging activity of all the extracts was tested by DPPH^•, ABTS^•+ and FRAP methods, revealing that (i) they were particularly efficient in quenching ABTS^•+ radical cations (up to 9.8 mM Trolox equivalents), and (ii) flavedo and albedo extracts, on average, showed the highest antioxidant capacity.     

Changes in the catechin and epicatechin content of grape seeds on storage under different water activity (aw) conditions

Storage effect on antioxidant content and capacity of grape seeds under different a_w conditions (a_w 0.33; 0.53; 0.75/50 days, 25 °C) was examined. Total phenol content (determined by the Folin–Ciocalteu method) decreased during storage though changes were trivial for samples stored at 33% or 53% RH. High level of humidity (75%) accelerated degradation and resulted in a ∼50% reduction of total phenol content. Minor loss of the DPPH radical scavenging activity (%RSA) of the extracts was observed. Catechin and epicatechin content monitored by RP-HPLC was reduced during storage, particularly at 75% RH. Epicatechin content proved to be less sensitive to water activity conditions than catechin content. Results of various in vitro assays (Folin–Ciocalteu, FRAP, DPPH, ABTS, CBA, ORAC and copper induced liposome oxidation) did not support difference in terms of resistance to oxidation. Based on the continuous release of gallic acid, our finding was related to hydrolytic reactions. Control of a_w of grape seeds can be of practical importance for the wine industry.     

Antioxidant activity of various extracts and fractions of Chenopodium quinoa and Amaranthus spp. seeds

The antioxidant potency of various extracts and fractions from Chenopodium quinoa and Amaranthus sp. was evaluated using three established methods, specifically the DPPH scavenging activity, FRAP, and β-carotene bleaching assays. Satisfying results were obtained, which lead to expect the use of these seeds as health-promoting ingredients. The antioxidant activity was less correlated to the phenolics content suggesting that non-phenolic compounds might play major free radicals scavenging activity in studied plant materials.     

Antioxidant activity and constituents of propolis collected in various areas of China

Propolis is a resinous substance collected by honeybees from various plant sources. The composition of propolis depends on time, vegetation, and the area of collection. This study examined the antioxidant activity of propolis from various areas of China: Heilongjiang, Neimongol, Hebei, Shandong, Shanxi, Gansu, Henan, Hubei, Sichuan, Hunan, Yunnan and Hainan. Ethanol extracts of propolis (EEP) were prepared and evaluated for their antioxidant activities by β-carotene bleaching, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging, and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation decolorization assays. Furthermore, the major constituents in EEP were identified by high-performance liquid chromatography (HPLC) analysis with a photodiode array (PDA) and mass spectrometric (MS) detection, and each component was quantitatively analyzed. All propolis samples except that from Yunnan had relatively strong antioxidant activity accompanied by high total polyphenol contents. Propolis with strong antioxidant activity contained large amounts of antioxidative compounds, such as caffeic acid, ferulic acid and caffeic acid phenethyl ester. On the other hand, propolis from Yunnan and Hainan had compounds not present in propolis from other areas.     

Antioxidant activity and phenolics of an endophytic Xylaria sp. from Ginkgo biloba

The objective of this study was to evaluate the antioxidant activity of cultivated fruiting bodies of an endophytic Xylaria sp. (strain number YX-28), from Ginkgo biloba. The results indicated that the methanol extract exhibited strong antioxidant capacity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) analysis and β-carotene–linoleic acid model system. Total phenolic and flavonoid contents extracted by different solvents were determined using Folin–Ciocalteu procedure and the flavonoid–aluminium method. The results showed that total phenolic and flavonoid contents were the highest in methanol extract (54.51 ± 1.05 mg gallic acid equivalent/g dry weight and 86.76 ± 0.58 mg rutin equivalent/g dry weight), while the hexane extract was the lowest (9.71 ± 0.57 mg GAE/g dw and 10.14 ± 0.76 mg RE/g dw, respectively). The correlation coefficients from regression analysis showed a positive relationship between total phenolic content in the extracts and DPPH activity (R² = 0.7336), as well as between total flavonoid content and DPPH activity (R² = 0.9392). Furthermore, GC/MS method was used to confirm the presence of phenolics with antioxidant activity in the methanol extract and resulted in the identification of 41 compounds, esters, phenolics, alkanes, carboxylates and alcohols being the main components. In conclusion, cultivated fruiting bodies of Xylaria sp.YX-28 may have potential as natural antioxidant.     

The effect of sorghum type and processing on the antioxidant properties of African sorghum-based foods

This work determined the effect of sorghum type and different processing technologies of traditional African sorghum foods on total phenols, tannin content and antioxidant activity. The products were prepared by fermentation, conventional and extrusion cooking of whole and decorticated ground grain. The tannin sorghum types, had higher ABTS and DPPH antioxidant activities, compared to the types without tannins. Antioxidant activity was significantly correlated with total phenols and tannins (r > 0.95). Decortication, reduced antioxidant activity of both tannin and non-tannin sorghum by 82–83% due to the removal of the pericarp and the testa, which decreased phenols. Processing, generally decreased antioxidant activity, however, conventionally cooked porridges had higher antioxidant activity than the extrusion cooked products. The retention of antioxidant activity, particularly in fermented and unfermented porridges, means that whole tannin sorghum can be processed into foods with potential health benefits.     

Impact of limited drying on Momordica cochinchinensis Spreng. aril carotenoids content and antioxidant activity

Food product based on gac fruit (Momordica cochinchinensis Spreng.) arils have a high potential due to the high carotenoids content of this fruit. Drying is a key preparation step for carotenoids extraction from gac fruit in a economically viable process. The impact of different drying technics, temperature, final product moisture content on the carotenoid content, hydrophilic and lipophilic antioxidant activity (evaluated with three methods) and color of the gac arils is discussed based on laboratory scale experimental tests. The results highlight an optimal temperature between 50 °C and 60 °C to conserve the color, the carotenoid content and the antioxidant activity. Also, these properties are better preserved by limiting the drying to dry based moisture content between 15% and 18% while the advantages of drying for further processing and for refrigerated conservation for a few months are achieved.     

Flavonoid content and antioxidant activity of vegetables from Indonesia

Extracts from 11 vegetables of Indonesian origin were screened for flavonoid content, total phenolics, and antioxidant activity. The flavonols myricetin, quercetin, and kaempferol and flavones luteolin and apigenin were quantified by HPLC. Flavonoid content in mg/100 g fresh weight (fw) was apparently initially reported for Cosmos caudatus H.B.K. (52.19), Polyscias pinnata (52.19), Pluchea indica Less. (6.39), Nothopanax scutellarius (Burm.f.) Merr (5.43), Talinum triangulare (Jacq.) Willd. (3.93), Pilea melastomoides (Poir.) Bl. (2.27), and Etlingera elatior (Jack) R.M.Sm (1.18). The flavonoid content of the vegetables studied were mainly quercetin and kaempferol and ranged from 0.3 to 143 mg/100 g fw, with the highest level found in Sauropus androgynus (L) Merr. C. caudatus H.B.K. had the greatest total phenols among the vegetables analysed, with 1.52 mg GAE/100 g fw. P. indica Less. and C. caudatus H.B.K. had the highest antioxidant activity as measured by ferric cyanide reducing power, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) scavenging, and inhibition of linoleic acid oxidation. Therefore, S. androgynus (L) Merr, C. caudatus H.B.K., and P. pinnata were identified as potentially rich sources of dietary flavonoids and antioxidants.     

Cytoprotective and antioxidant activity studies of jaggery sugar

Jaggery and other sugars namely white, refined and brown sugars were evaluated for cytoprotectivity on NIH 3T3 fibroblasts and erythrocytes, DPPH radical scavenging activity, reducing power and DNA protection. In addition, total phenol content and phenolic acid composition were also determined. Results indicated a total phenolic content of 26.5, 31.5, 372 and 3837 μg GAE/g for refined, white, brown and jaggery, respectively. The HPLC analysis revealed the presence of different phenolic acids in brown sugar and jaggery. On NIH 3T3 cells oxidation, at 4 mg/ml concentration, jaggery showed 97% protection compared to brown sugar, and both sugars effectively reduced erythrocyte oxidation. A dose dependent reducing power and DPPH radical scavenging activity was also observed for jaggery and brown sugar. An EC₅₀ of 7.81 and 59.38 μg/ml were observed for jaggery and brown sugar in the DPPH scavenging assay. In DNA oxidation studies, higher protection was observed in jaggery followed by brown, white and refined sugar treated samples.     

Effects of binary solvent extraction system,extraction time and extraction temperature on phenolic antioxidants and antioxidant capacity from mengkudu (Morinda citrifolia)

An investigation into the effects of ethanol concentration (0–100%, v/v), extraction time (20–120 min) and extraction temperature (25–65 °C) on the extraction of phenolic antioxidants from mengkudu (Morinda citrifolia) was performed using a single-factor experiment. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used for determination of phenolic compounds. Antioxidant capacity was evaluated by measuring the scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radicals. Experimental results showed that extraction conditions had significant effect on extraction of phenolic compounds and antioxidant capacities. The optimised conditions were 40% ethanol for 80 min at 65 °C, with values of 919.95 mg GAE/100 g DW for TPC, 472.73 mg CE/100 g DW for TFC, 791.71 μmol TEAC/100 g DW for ABTS and 1928.5 μmol TEAC/100 g DW for DPPH. TPC was significantly correlated with DPPH under the effects of ethanol concentration (r = 0.932) and extraction time (r = −0.938).     

Phenolic acids composition and antioxidant activity of canola extracts in cooked beef,chicken and pork

Crude polyphenol extracts (15 or 100 mg gallic acid equivalents (GAE)/kg meat) from canola meal reduced the formation of 2-thiobarbituric acid-reactive substances (TBARS) in pre-cooked beef (66–92%), pork (43–75%) and chicken (36–70%). The canola extract contained sinapic (99.7%), ferulic (0.28%) and p-hydroxybenzoic acids (0.07%).     

Purification and characterization of an antioxidant protein (∼16 kDa) from Terminalia chebula fruit

Terminalia chebula fruit is used as folk medicine in India and Southeast Asia. An antioxidant protein was isolated by bioassay guided fractionation of T.chebula fruit by homogenizing in the citrate phosphate buffer. The isolated protein (TCP-III) obtained from fruit was purified by gel chromatography and preparative HPLC, showed apparent molecular weight of 16 kDa by SDS-PAGE and MALDI-TOF/MS analyses. Amino acid sequence obtained by LC-MS^E analysis showed homology with the predicted protein fragments of Populus trichocarpa, putative uncharacterized protein fragments from Oryza sativa and with fragments of 17 kDa thylakoid lumenal protein from Spinacia oleracea. TCP-III exhibited significant radical scavenging in DPPH, NO, H₂O₂ and ABTS assays. In addition, TCP-III inhibited oxidation of linoleic acid in β-carotene bleaching assay, reduced ferric ions and chelated ferrous ions. The present finding demonstrates uniquely, for the first time, characterization of an antioxidant protein from T. chebula fruit.     

Cytoprotective and antioxidant activity of free,conjugated and insoluble-bound phenolic acids from swallow root (Decalepis hamiltonii)

Swallow root (Decalepis hamiltonii) was extracted for free (SRFP), conjugated (SRCP) and insoluble-bound phenolic acids (SRIBP), and evaluated for cytoprotectivity, 1,1,diphenyl-2-picrylhydrazyl (DPPH) scavenging ability, reducing power and protection to DNA damage. In addition, the constituent phenolic acids in the extracts were also analysed. Results indicated a total phenol content of 20.72, 7.97 and 11.52 mg gallic acid equivalents (GAE)/g for SRFP, SRCP and SRIBP extracts, respectively. At 0.12 μg/mL concentration SRCP showed 87% cytoprotection (on NIH 3T3 cells) compared to SRFP (47%) and SRIBP (65%). DPPH radical scavenging activity indicated an IC₅₀ of 0.046, 0.06 and 0.128 μg/mL for SRCP, SRIBP and SRFP, respectively. Also, SRCP showed higher reducing power and DNA protectivity (80%). HPLC analysis of phenolic acid extracts showed the presence of hydroxybenzoate and cinnamate derivatives. Among the phenolics identified gallic, gentisic, protocatechuic and p-coumaric acids were the major contributors to antioxidant activity.     

In vitro and in vivo studies on the antioxidant activities of the aqueous extracts of Douchi (a traditional Chinese salt-fermented soybean food)

The aqueous extracts of Douchi were obtained and evaluated for their antioxidant properties. The isoflavones and peptides contents of extracts were determined. Antioxidant activities in vitro of extracts were conducted by determining the α,α-diphenyl-β-pricrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activities, and the chelating ability of ferrous ions, of which IC₅₀ values were found to be 0.658, 0.204 and 206 mg/mL, respectively. Antioxidant enzymatic activities of extracts in cholesterol-fed rats and an index of lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) were determined, and hepatic tissue ultramicrostructure was also observed under transmission electron microscope (TEM). These results showed that, in Douchi extracts groups, superoxide dismutase (SOD) activities in liver and kidney, catalase (CAT) activity in liver, and glutathione peroxidase (GSH-Px) activity in kidney increased significantly compared with the negative control group (p < 0.05). TBARS in liver and kidney of extracts groups decreased significantly (p < 0.05). Less fatty degeneration in hepatocytes of extracts groups was found on TEM photos. The percentage of total isoflavones and peptides contents in aqueous extracts were 0.087% and 40.7%, respectively. These results showed that Douchi extracts had excellent antioxidant activities, might affect the activities of antioxidant enzymes and lipid peroxidation, and mitigate the lipidosis of hepatocytes.     

Antioxidant capacity and the relationship with polyphenol and Vitamin C in Actinidia fruits

Fruit of eight Actinidia genotypes were evaluated for antioxidant potential by several assays (DPPH, ABTS, ORAC, FRAP, SASR and MCC) and tested for their polyphenol composition and vitamin C contents. The significance analysis demonstrated that the antioxidant capacity of Actinidia eriantha and Actinidia latifolia fruits were significantly higher than that of other genotypes, which was about 3.3–8.7-fold higher than the Actinidia deliciosa cv. Hayward assayed in ABTS, DPPH, ORAC and FRAP methods. The total polyphenols and vitamin C contents showed a great variety amongst Actinidia genotypes and highly correlation with the total antioxidant capacity. It is concluded that significant genotypic difference exists in the total antioxidant capacity of Actinidia fruits. The wild A. eriantha and A. latifolia species have significantly higher antioxidant capacity than the cultivars of A. chinensis and A. deliciosa. Both total polyphenols and vitamin C are major contributors to the total antioxidant capacity in Actinidia fruit.     

Antioxidant and antimicrobial activities of consecutive extracts from Galla chinensis:The polarity affects the bioactivities

The gallotannins of Galla chinensis (GAC) were extracted consecutively by five solvents of different polarity, and the antioxidant and antimicrobial activities of the extracts were evaluated. All of the ether-, ethyl acetate-, ethanol-, and water-extracts presented remarkable antioxidant abilities in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), β-carotene linoleic acid system, and hydroxyl radical scavenging assays. The minimum inhibitory concentrations (MICs) of these extracts against 3 species of gram-positive bacteria, 3 species of gram-negative bacteria, and 3 species of fungi were also determined using the agar dilution method. All of the extracts showed excellent antibacterial activities, but no antifungal activities. The gallotannins in different extracts were analyzed by the HPLC and HPLC-ESI-MS. The results indicated that the extracts with weaker polarity contained gallotannins with higher molecular weight, and had stronger antioxidant and antibacterial activities.     

Polyphenol content and antioxidant activity of California almonds depend on cultivar and harvest year

The polyphenol content and antioxidant activity of Nonpareil, Carmel, Butte, Sonora, Fritz, Mission, and Monterey almond cultivars harvested over three seasons in California were examined. LC–MS was employed to quantify 16 flavonoids and two phenolic acids in acidified methanol extracts of almond skins. The 3-year mean polyphenol content of cultivars ranged from 4.0 to 10.7 mg/100 g almonds. Isorhamnetin-3-O-rutinoside was the most abundant flavonoid, present at 28–49% of total polyphenols among cultivars. Almonds from 2006 and 2007 had 13% fewer polyphenols than 2005, but FRAP and total phenols were comparable. Cultivar, but not season, had a differential impact on individual polyphenol synthesis. Using the results of polyphenol, total phenol, and FRAP, multivariate analysis distinguished harvest years and most cultivars with 80% confidence. Flavonoid content and antioxidant activity of almonds may be more dependent on cultivar than on seasonal differences.     

Antioxidant and antimicrobial activity of Cynara cardunculus extracts

The whole, fresh involucral bracts of cardoon, Cynara cardunculus L. (Compositae), were extracted with EtOH and an aqueous suspension of the obtained EtOH extract was partitioned successively with CHCl₃, EtOAc and n-BuOH, leaving a residual water extract. All obtained extracts were evaluated for their antioxidant and antimicrobial properties. The antioxidant potential was evaluated using following in vitro methods: FRAP (ferric reducing antioxidant power) assay, and scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. Antimicrobial activity was estimated using a microdilution technique against food-borne, mycotoxin producers and human pathogenic bacteria and micromycetes. The following bacteria were tested: Salmonella typhimurium, Escherichia coli, Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, as well as micromycetes: Aspergillus niger, Aspergillus ochraceus, Aspergillus flavus, Penicillium ochrochloron, Penicillium funiculosum, Trichoderma viride, Fusarium tricinctum and Alternaria alternata. Results showed that all extracts possessed concentration-dependent antioxidant activity. In biological assays, C. cardunculus extracts showed antimicrobial activity comparable with standard antibiotics.