Effect of processing on the antioxidant activity of millet grains

Millets are generally dehulled and subjected to a hydrothermal treatment before consumption, thus the hulls can be used as a potential source of antioxidants. Several millet grains, namely kodo, finger (Ravi), finger (local), proso, foxtail, little and pearl millet were studied. Antioxidant activities of phenolic extracts obtained from whole grains, as well as their corresponding dehulled and cooked grains and hulls were studied for their total phenolic content (TPC), radical scavenging capacity, and antioxidant activity in a β-carotene/linoleate emulsion. The phenolics present in whole grains were identified and quantified using HPLC and HPLC/MS and results were expressed as total for each of the phenolic groups. The TPC ranged from 2 to 112 μmol ferulic acid equivalents/g defatted meal. All varieties exhibited effective inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, peroxyl and superoxide radicals. Dehulling and cooking affected the TPC and radical scavenging and antioxidant activities of the grains, depending on the variety. In general, the antioxidant activity of phenolic extracts was in the order of hull > whole grain > dehulled grain > cooked dehulled grain With the exception of the two finger millet varieties, hulls of other millet grains had high TPC, thus demonstrating their superior antioxidant activity. Hydroxybenzoic acids, hydroxycinnamic acids and flavonoids in whole grains were identified as contributors to the observed effects. Therefore, dehulling of grain and hydrothermal treatments affect the phenolic content and antioxidant potential of millet grains.     

Inhibitory effect of Chardonnay and black raspberry seed extracts on lipid oxidation in fish oil and their radical scavenging and antimicrobial properties

Ethanol extracts of Chardonnay grape and black raspberry seed flours were evaluated for their capacity to suppress lipid oxidation, preserve important fatty acids, and inhibit microbial growth. They were also tested for radical scavenging activity against DPPH and peroxyl radicals as reflected in oxygen radical absorbance capacity (ORAC), and total phenolic content (TPC). Both tested seed flour extracts suppressed lipid oxidation and rancidity development in fish oil. Black raspberry seed flour extract significantly reduced the degradation of biologically important n − 3 PUFA under accelerated oxidative conditions. Black raspberry and Chardonnay seed flour extracts at 165 and 160 μg seed flour equivalents/mL, respectively exhibited bacteriocidal activity against Escherichia coli and growth inhibition of Listeria monocytogenes under experimental conditions. Both seed flour extracts exhibited DPPH radical quenching activity and Chardonnay had the stronger ORAC of 663 μmol Trolox equivalents per gram seed flour and the higher TPC of 99 mg gallic acid equivalents/g flour. The data from this study suggest the potential for developing natural food preservatives from these seed flours for improving food stability, quality, safety, and consumer acceptance.     

Antioxidant Potential of Pea Beans (Phaseolus vulgaris L.)

ABSTRACT: Four bean varieties ( Phaseolus vulgaris L.) (white kidney, red pinto, Swedish brown, and black kidney) and their hull fractions were extracted with 80% acetone and evaluated for their phenolic contents and antiradical activities. Total phenolic content of bean hulls and whole seed extracts ranged from 6.7 to 270 and 4.9 to 93.6 mg/g extract as catechin equivalents, respectively. Trolox equivalent antioxidant capacity (TEAC) assay revealed that the antioxidant capacity of red, brown, and black whole seed extracts was in the same order of magnitude with little variation. TEAC values of red and brown whole seed extracts were superior to that of black whole seed extract. On the basis of the total phenolic content and TEAC values, it can be deduced that colored beans possess superior antioxidative activity compared with white beans. The hydrogen peroxide scavenging capacity of different bean extracts ranged from 58% to 67% at 50 ppm and 65% to 76% at 100 ppm. The corresponding superoxide radical scavenging capacity was 24% to 29% at 50 ppm and 53% to 60% at 100 ppm. The 2,2–diphenyl-1–picrylhydrazyl (DPPH) radical scavenging capacity of black bean whole seed extracts was 22% at 50 ppm, whereas the other extracts showed 100% scavenging of this radical at both 50 and 100 ppm levels. The hydroxyl radical scavenging capacities of the bean extracts at 50 and 100 ppm were 12% to 29% and 32% to 49%, respectively. All extracts used prevented human low-density lipoprotein (LDL) cholesterol oxidation by 61.4% to 99.9% at 2 to 50 ppm level as catechin equivalents.     

Antioxidative and anti-inflammatory properties of Citrus sulcata extracts

Citrus sulcata was subjected to ultrasound, high-pressure, and Soxhlet extractions. The antioxidant and anti-inflammatory activities of the extracts were evaluated qualitatively and quantitatively. The antioxidant content of the peel extract was twice that of the fruit extract. The quantitative analysis showed that the narirutin and hesperidin contents in the peel extracts were 8.8 and 7.5 mg/100 g, respectively. These extracts had a total phenolic content of 112.22 ± 2.89 gallic acid equivalent (GAE) mg/100 g, a total flavonoid content of 54.09 ± 1.01 rutin equivalent (RE) mg/100 g, DPPH radical scavenging activity of 46%, and antioxidant activity of 213.25 ± 2.82 μM of Trolox equivalents (TEAC). C. sulcata extracts could prevent hydrogen peroxide (H₂O₂)-induced oxidative stress, reduce expression of the inflammatory markers nuclear Factor kappa B (NFκB) and phosphorylated IκBα (p-IκBα) in A549 human lung carcinoma cells, and inhibit Lipopolysaccharide (LPS)-induced THP-1 monocyte differentiation to an extent of 85%.     

Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues

The extracts from kinnow peel, kinnow seeds, litchi pericarp, litchi seeds, grape seeds, and banana peel were screened for total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC), 1,1 diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, as well as reducing power. Kinnow peel extract exhibited the highest reducing power, TEAC, and DPPH free radical scavenging activity, whereas, the phenolic content of 37.4 mg GAE/g-dw was highest for grape seed extract. Banana peel extract with a low TPC showed the lowest reducing power, TEAC as well as DPPH free radical scavenging activity among the fruit residue extracts examined in the present study. Correlation analysis between the reducing power and DPPH radical scavenging ability; reducing power and ABTS radical scavenging activity; and ABTS and DPPH radical scavenging abilities showed a high degree of correlation (r² = 0.85-0.91). However, r² of 0.36, 0.66, and 0.49 between TPC and DPPH radical scavenging activity; TPC and reducing power; and TPC and ABTS radical scavenging ability, respectively, indicated that some non-phenolic compounds also contributed to the total antioxidant activity in fruit residue extracts examined in this study. To the best of our knowledge, this is the first paper presenting comprehensive data on TPC, reducing power, and antioxidant activity for the six fruit residues. This study demonstrated that kinnow peel, litchi pericarp, litchi seeds, and grape seeds, can serve as potential sources of antioxidants for use in food and pharmaceutical industry.     

Antioxidant activity of three edible seaweeds from two areas in South East Asia

Total phenolic content (TPC) and antioxidant activity (AOA) of 50% aqueous methanol extracts of the marine algae, Padina antillarum, Caulerpa racemosa and Kappaphycus alvarezzi were studied. TPC was measured using Folin-Ciocalteu method while 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), ferrous ion chelating (FIC) assay and beta carotene bleaching (BCB) assay were used to study their AOA. P. antillarum was found to have the highest TPC, 2430±208 mg gallic acid equivalents (GAE) per 100 g dried sample and ascorbic acid equivalent antioxidant capacity (AEAC), 1140±85 mg AA/100 g. C. racemosa and K. alvarezzi displayed lower TPC and AEAC. C. racemosa had 144±22 mg GAE/100 g dried sample of TPC and 14.3±2.0 mg AA/100 g of AEAC, while K. alvarezzi had 115±35 mg/100 g dried sample of TPC and 37.8±16.8 mg AA/100 g of AEAC. In addition, P. antillarum displayed the highest reducing power, 15.7±2.6 mg GAE/g and highest chelating ability. C. racemosa and K. alvarezzi exhibited lower reducing power, 0.737±0.423 mg GAE/g and 0.561±0.269 mg GAE/g, and lower chelating ability. However, the AOA of these three seaweeds as assessed by BCB assay were equally high.     

Assessment of in vitro antioxidant capacity and polyphenolic composition of selected medicinal herbs from Leguminosae family in Peninsular Malaysia

Determination of total phenolic (TPC), flavonoid and anthocyanin contents, and various antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging, ferric reducing power, ferrous ion chelating and lipid peroxidation inhibition) of leaves and flowers of Bauhinia kockiana, Caesalpinia pulcherrima and Cassia surattensis were performed in this study. The B. kockiana flower was found to possess the highest TPC (8280 ± 498 mg GAE/100 g), free radical scavenging activity (ascorbic acid equivalents 14,600 ± 2360 mg AA/100 g) and reducing ability (72.4 ± 8.7 mg GAE/g). Rutin and chlorogenic acid were detected in the plants, where the C. pulcherrima leaf contained the highest amount of rutin (669 ± 26 mg/100 g), while minute amounts of chlorogenic acid were detected in C. surattensis leaf (9.13 ± 0.44 mg/100 g). The C. pulcherrima leaf displayed the highest ferrous ion chelating and lipid peroxidation inhibition activities. Positive correlation was observed between TPC and various antioxidant activities.     

Role of carbohydrases on the release of reducing sugar, total phenolics and on antioxidant properties of oat bran

Aqueous solutions of medium oat bran flour were treated with four carbohydrases viscozyme, celluclast, alpha-amylase, and amyloglucosidase, and then extracted with equal volume of methanol. The resulting extracts were examined for their reducing sugar content, total phenolic content (TPC), oxygen radical scavenging absorbance capacity (ORAC), hydroxyl radical scavenging effect, superoxide scavenging activity, and ferrous ion chelating potential. The amount of reducing sugar increased form 2.0% in the control sample to 21.4% in the sample treated with four fungal beta-glucanase units/g of bran. The increase in reducing sugar was also associated with subsequent increase of other extractable compounds. The total phenolic content as measured by Folin-Ciocalteu’s method ranged from 0.50 to 4.80 mg of gallic acid equivalents/g of bran, whereas the ORAC values were 14.4-25.4 μM of Trolox equivalents/g of bran. All the samples treated with carbohydrases had higher TPC content and higher ORAC values than the control sample (no enzyme treatment). In the hydroxyl radical scavenging assay, except for the alpha-amylase treated sample, all other samples demonstrated a greater inhibition power than the control. These results indicated that pre-treatment of oat bran with cell wall degrading enzymes (i.e. carbohydrases) is a way to increase the amount of extracted phenols as well as the antioxidant properties of oat bran samples.     

Comparison of the antioxidant activity of two Spanish onion varieties

Phenol content and antioxidant activity of two Spanish onion varieties, namely white onion and Calçot de Valls, have been studied. White onions contained higher phenol content than Calçot onions, with values which ranged from 2.57 ± 0.51 to 6.53 ± 0.16 mg gallic acid equivalents/g dry weight (GAE/g DW) and 0.51 ± 0.22 to 2.58 ± 0.16 mg GAE/g DW, respectively, depending on the solvent used. Higher phenol content was associated with higher antioxidant capacity. White onion extracts had the highest antioxidant activity at 86.6 ± 2.97 and 29.9 ± 2.49 μmol Trolox/g DW for TEAC and FRAP assays, respectively, while the values for the Calçot variety were 17.5 ± 0.46 and 16.1 ± 0.10 μmol Trolox/g DW.     

Antioxidant and radical scavenging activities of the pyroligneous acid from a mangrove plant, Rhizophora apiculata

Total phenolics content, free radical scavenging activity, reducing power, and antioxidant activity of the pyroligenous acid from a mangrove plant, Rhizophora apiculata were evaluated. Dichloromethane extraction of the raw pyroligneous acid successfully yield 2 extracts, i.e. concentrated pyroligneous acid (CPA) and concentrated pyroligneous acid extract (CPAE). Phenolic contents in CPAE and CPA, expressed as (±)-catechin equivalents/g of the sample were 5465 ± 367 mg and 2502 ± 152 mg, and expressed as gallic acid equivalents/g of the sample were 2919 ± 209 mg and 1348 ± 90 mg, respectively. CPAE exhibited superior free radical scavenging activity with EC₅₀ value = 0.1235 mg/ml, or 80.96% of free radical scavenging capability. The ferric reducing power of CPAE was approximately 3.7, 5.1, 6.1, and 21.3 times higher than that of ascorbic acid, BHA, BHT and alpha-tocopherol. In phosphomolybdenum assay, CPAE showed the greatest antioxidant efficacy (A₆₉₅ = 1.278) compared to those of CPA and different standards. In addition, the free radical scavenging activity, ferric reducing power and total antioxidative activity of CPAE and CPA showed positive correlation with their total phenolic content with R² values ranging from 0.9624 to 0.9979.     

Antioxidant capacities of Gundelia tournefortii L. extracts and inhibition on glutathione-S-transferase activity

Gundelia tournefortii L. is an important food source and a well-known medicinal plant in Eastern Anatolia. Therapeutic effects of medicinal plants are known to be closely related to their antioxidant capacities. Antioxidant activities of G. tournefortii, both for the aerial parts and seeds, were investigated by using both 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and lipid peroxidation inhibition methods. The seeds were found to have higher antioxidant potential than the aerial, with IC₅₀ values of 0.073 mg/mL for DPPH scavenging and 0.146 mg/mL for lipid peroxidation inhibition capacities. In addition, total phenolic contents of the Gundelia tournefortii L. extracts, especially the seed extracts correlates to its high antioxidant activity with 105.1 ± 8.7 μg gallic acid equivalents (GAEs) per mg of seed extract. Plant extracts with high phenolics content are known to have important effects on various enzymes, as well as glutathione-S-transferases, which are important detoxification enzymes in phase II systems with an important role in developing multi-drug resistance to chemotherapy in tumour cells. Consequently, the effects of G. tournefortii extracts on crude cytosolic glutathione-S-transferase was also studied and the seed extracts have shown effective inhibition of cytosolic GST activity, with an IC₅₀ of 97.51 μg/mL.     

Autolysis-assisted production of fish protein hydrolysates with antioxidant properties from Pacific hake (Merluccius productus)

Fish protein hydrolysates (FPH) with antioxidative properties were prepared using Pacific hake fish with high endogenous proteolytic activity from Kudoa paniformis parasitic infection. Infection level of ∼10⁷K. paniformis spores/g fish mince or higher yielded FPH with high antioxidant potential by autolysis and/or Validase^® BNP or Flavourzyme^® 500L. Autolyzing fish mince containing 30 × 10⁶ spores/g for 1 h at 52 °C and pH 5.50 produced FPH (named E-1h) with Trolox equivalent antioxidant capacity (TEAC) in the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) radical assay of 262 ± 2 μmol/g and oxygen radical absorbing capacity (ORAC) of 225 ± 17 μmol Trolox equivalents/g freeze-dried sample. E-1h FPH also exhibited a marked concentration-dependent scavenging activity on 1,1-diphenyl-2-picrylhydrazyl radical. Antioxidant activity of E-1h FPH was higher (p < 0.05) than BHA and α-tocopherol in a linoleic acid peroxidation system over prolonged storage (∼162 h). Antioxidative FPH from Pacific hake may be useful ingredients in food and nutraceutical applications.     

Standardised Mangifera indica extract is an ideal antioxidant

The standardised ethanolic and aqueous extracts of Mangifera indica leaf were prepared and analysed for their free radicals scavenging activity. The IC₅₀ values using the DPPH assay were 0.17 ± 0.02 and 0.49 ± 0.4 mg/ml, respectively. Standardised ethanolic extracts of the M. indica leaf had a solid content of 9.1 ± 0.7%, mangiferin concentration of 73 ± 0.17 mg/g of dry weight of the extract, free radical scavenging activity (IC₅₀) of 0.17 ± 0.02 mg/ml and total phenolic content of 590 ± 48 mg/g of extract. The protection exhibited by these extracts against lipid peroxidation was superior to butylated hydroxytoluene (BHT) and commercial grape seed extract. These extracts at higher concentration did not exhibit pro-oxidant activities when compared to vitamin C. Our findings also show that the aqueous and ethanolic extracts of M. indica leaf protect NIH/3T3 cells from oxidant-induced cell death.     

Evaluation of antioxidant ability of ethanolic extract from dill (Anethum graveolens L.) flower

Antioxidant activities of ethanolic extract from dill flower and its various fractions were evaluated with 2,2-diphenyl-1-picrylhydrazyl radical scavenging, Trolox equivalent antioxidant capacity, reducing power, chelating power, and β-carotene bleaching assays. The flower extract was successively separated into n-hexane, ethyl acetate and ethanol soluble fractions by liquid–liquid partition. Dill leaf and seed extracts were used for comparison. In all assays, the flower extract showed higher antioxidant activity than the leaf and seed extracts. With regard to various fractions of the flower extract, the sequence for antioxidant activity was ethyl acetate fraction > ethanol fraction > original flower extract > n-hexane fraction. Phenols including flavonoids and proanthocyanidins should be responsible for antioxidant abilities of the flower extract. Chlorogenic acid, myricetin, and 3,3’,4′,5,7-pentahydoxyflavan (4 → 8)-3,3′,4′,5,7-pentahydoxyflavan were the major phenolic acid, flavonoid, and proanthocyanidin, respectively, in the dill flower extract.     

Study of polyphenol content in the seeds of red grape (Vitis vinifera L.) varieties cultivated in Turkey and their antiradical activity

The polyphenolic content and antioxidant capacity in the seeds of 11 red grape varieties (five international and six native) widely cultivated in Turkey were investigated. Total phenolic, total flavanol and total polymeric procyanidin content ranged from 79.2 to 154.6, 89.2 to 179.4, and 27.0 to 43.3 mg/g seed, respectively. While (+)-catechin (4.71–23.8 mg/g seed) was found as main flavanol, galloylated catechin monomer and dimeric procyanidin amounts varied between 2.89–17.2 and 0.97–2.97 mg/g seed, respectively. All seed extracts showed remarkable DPPH radical scavenging activity (EC₅₀) and oxygen radical scavenging capacity (ORAC) ranging from 2.71 to 4.62 μg/mL and 1425.9 to 3009.2 μmol Trolox equivalent/g seed, respectively. With high amount of total phenolic content and antioxidant activity, seeds of Okuzgozu, Papaz Karasi, Ada Karasi and Kalecik Karasi varieties could be evaluated as dietary supplement.     

In vitro antioxidant activity of anthocyanins of black soybean seed coat in human low density lipoprotein (LDL)

The objectives of this study were to determine the phenolic and anthocyanin contents in black soybean Mallika and Cikuray variety seed coat extract and to examine antioxidant activity of extract against DPPH radical and LDL oxidation. Black soybean seed coat of Mallika (M) and Cikuray (C) was extracted using methanol-1%HCl. The phenolic and anthocyanin contents were determined with Folin–Ciocalteu and pH differential methods, respectively. Individual anthocyanidins were identified with HPLCdiode array detector, and antioxidant activity was examined, using DPPH and TBARS assay with LDL as the oxidation substrate. BHT and rutin were used as antioxidant references. The phenolic content in M and C were 8.15 ± 0.23 and 6.46 ± 0.11 g GAE/100 g, respectively. The anthocyanin contents were 11.36 ± 0.12 and 1.45 ± 0.13 g/100 g, respectively. Cyanidin, delphinidin, and pelargonidin were found as individual anthocyanidins. The optimum DPPH radical scavenging capacity (%) of M and C were 92.78% and 91.50%, respectively, BHT and rutin were 77.0% and 91.94%, respectively. The optimum inhibition of TBARS formation from M and C were 37.10 and 30.37 nmol MDA equivalents/g LDL protein, respectively, and rutin were 30.10 nmol MDA equivalents/g LDL protein, respectively. These results suggest that black soybean seed coat has high levels of phenolic and anthocyanin, and also demonstrated considerable antioxidant activity of black soybean seed coat.     

Anti-oxidative analysis,and identification and quantification of anthocyanin pigments in different coloured rice

Anthocyanin pigments in coloured rice cultivars were isolated and identified using high-performance liquid chromatography techniques. Two black rice cultivars (Asamurasaki, Okunomurasaki) contained three major anthocyanins: cyanidin-3-glucoside, peonidin-3-glucoside and malvidin. Chinakuromai (black) rice additionally contained a fourth anthocyanin, petunidin-3-glucoside. Four red rice cultivars contained only malvidin. The total anthocyanin content varied greatly among black rice cultivars (79.5–473.7 mg/100 g), but was lower in red rice (7.9–34.4 mg/100 g). Total phenolic content was similar between red (460.32–725.69 mg/100 g) and black (417.11–687.24 mg/100 g) rice. The oxygen radical absorbing capacity was ranked as follows: red (69.91–130.32 μmol Trolox/g) > black (55.49–64.85 μmol Trolox/g) > green (35.32 μmol Trolox/g) > white (21.81 μmol Trolox/g) rice. The antioxidant capacity resulted mainly from the seed capsule, not the endosperm. The anthocyanin pigments contributed little to the total antioxidant capacity of red (0.03–0.1%) and black (0.5–2.5%) rice cultivars. Hence, the antioxidant capacity is derived mainly from other phenolic compounds.     

Antioxidant power of Iranian propolis extract

Propolis is a resinous natural hive product derived from plant exudates collected by honey bees. Due to biological and pharmacological activities, it has been extensively used in folk medicine. The present study was designed to measure the antioxidant power of ethanolic extracts of propolis samples from different parts of Iran with “ferric reducing ability of plasma” (FRAP) assay and compare the results with Trolox at concentrations of 100, 1000 and 2000 μg/ml. FRAP values of propolis ethanolic extracts were in the range of 31.5 ± 14.6 to 1650 ± 72 μM, whereas the values of Trolox ranged from 125.25 ± 9.95 to 3381.64 ± 113.83 μM. The FRAP values of Tehran propolis ethanolic extract and Trolox at concentration of 100 μg/ml did not show any significant difference (P > 0.05). Total flavonoid and polyphenol contents of ethanolic extracts of propolis samples, determined by using aluminum nitrate and Folin–Ciocalteu colorimetric methods, were in the range of 1.22 ± 0.33–7.79 ± 0.39 g/100 g and 3.08 ± 0.02–8.46 ± 0.03 g/100 g crude extract of propolis, respectively. The result of this experiment may show that propolis as a natural source of antioxidant compounds may be of use in prevention of free radical-related diseases.