Quantification of polyphenols and ergothioneine in cultivated mushrooms and correlation to total antioxidant capacity

Agaricus bisporus, Lentinula edodes, Pleurotus ostreatus, Pleurotus eryngii and Grifola frondosa were analyzed for antioxidant capacity, as measured by oxygen radical absorbance capacity (lipophilic and hydrophilic) (ORAC_total), hydroxyl radical averting capacity (HORAC), peroxynitrite radical averting capacity (NORAC), superoxide radical averting capacity (SORAC) assays, Folin-Ciocalteu reagent and ergothioneine (ERG) content. ORAC_totalvalues ranged from 39 to 138 μmol of Trolox equivalents (TE)/g dry weight (dw). HORAC values ranged from 3.0 to 13.6 μmol of caffeic acid equivalents/g dw. NORAC values ranged from 2.0 to 9.0 μmol TE/g dw. SORAC values ranged from 0.37 to 2.6 kunit superoxide dismutate equivalents/g dw. Polyphenols ranged from 4.2 to 10.6 mg gallic acid equivalents/g dw. A. bisporus mushrooms, especially portabellas, had higher antioxidant capacity relative to the specialty mushrooms tested. ERG ranged from 0.21–2.6 mg/g dw with L. edodes, P. ostreatus, G. frondosa containing a statistically significant greater amount compared to A. bisporus. A good correlation was found between ORAC_total and polyphenols (R² = 0.86).     

Antioxidant activity and polyphenol content of aqueous extracts from Colombian Amazonian plants with medicinal use

The total phenol and flavonoid contents of 19 Amazonian plants and their related antioxidant activities were determined. The extracts from the plant leaf, bark, root, fruit and/or stem were prepared as infusions, as are traditionally used in popular medicine. Total phenols ranged from 0.8 to 22.2 mg gallic acid equivalents/g and flavonoids from 0.0 to 10.2 mg catechin equivalents/g, by using Folin–Ciocalteau and aluminium chloride colourimetric methods. Differences were observed in phenol and flavonoid contents at the organic level, the leaf presenting greater values than the stem. All the extracts showed different degrees of antioxidant activity with TEAC, 1.1 up to 117.4 and ORAC, 7.8 up to 359.1 μmol Trolox equivalents/g. These values correlated with total phenol content (r² = 0.90) and flavonoid content (r² = 0.70 for TEAC; r² = 0.76 for ORAC). Piper putumayoense, Piper glandulosissimum, Piper krukoffii and Senna reticulata leaves and Brownea rosademonte bark showed elevated antioxidant activities, thus representing promising plant-sources of medicine.     

Free aromatic amino acids in egg yolk show antioxidant properties

Laying hens are known to be able to “bio-convert” health-promoting components from the diet into eggs. Wheat and corn are important sources of antioxidant phenolics in the human diet. Given the fact that wheat and corn are major feed ingredients of laying hens in Canada, the objectives of this study were to characterise the presence of novel phenolic compounds in egg yolk and to determine the effect of cooking methods on their content and activity. The total phenolic content of yolk extracts was 3.83 and 3.49 μmol gallic acid equivalents/g dry yolk for wheat-based and corn-based yolks, respectively. Antioxidant properties of yolk extracts were measured by the ORAC, DPPH and ABTS assays. ORAC values were 151.1 ± 26.1 and 155.9 ± 9.5 μmol TE/g for wheat-based and corn-based yolks, respectively. All cooking methods significantly reduced (p < 0.05) the antioxidant values. Ferulic acid was detected in trace amounts and no other phenolic compounds were found. However, tryptophan and tyrosine were found to be two main contributors to the antioxidant property of egg yolk. The contents of total free amino acids were 10081.0 and 10009.5 μg/g in wheat-based and corn-based yolks, respectively; cooking methods were found to reduce significantly the amount of free amino acids.     

Inhibitory effect of raspberries on starch digestive enzyme and their antioxidant properties and phenolic composition

Seven primocane fall-bearing raspberry (Rubus idaeus L.) cultivars, Nova (red), Dinkum (red), Heritage (red), Autumn Britten (red), Josephine, Anne (yellow), Fall Gold (yellow) were analysed for potential health promoting properties including their inhibitory effect on starch and fat digestive enzymes, antioxidant activities, and phenolic composition. The tested raspberry extracts showed no detectable inhibition of pancreatic α-amylase and lipase. However, all the extracts exhibited potent inhibition of α-glucosidase with IC₅₀ from 16.8 to 34.2 μg/mL. Four phenolic compounds, ellagic acid, cyanidin-diglucoside, pelargonidin-3-rutinoside, and catechin were identified as the active α-glucosidase inhibitors. The raspberry extracts also possessed significant antioxidant activities with oxygen radical absorbance capacities (ORAC) ranging from 136.7 to 205.2 μmol Trolox equivalents (TE)/g dry weight fruit and DPPH radical scavenging activities from 305 to 351 μmol TE/g. The total phenolic content of raspberry cultivars varied significantly from 40.9 to 98.5 mg of gallic acid equivalents/g dry weight. The anthocyanin content varied widely from 0.1 to 9.5 mg cyanidin 3-glucoside equivalents/g. Nine phenolic acids were quantified in raspberries and their total amounts varied from 157.3 to 713.5 μg/g. The enzyme inhibition and antioxidant properties of raspberry cultivars were not correlated with their total phenolic, anthocyanin, and phenolic acid content. Overall, ‘Dinkum’ and ‘Josephine’ raspberry varieties possess higher total phenolic content, ORAC, DPPH radical scavenging activity, and α-glucosidase inhibitory activity than other five cultivars.     

Comparative antioxidant activity of extracts from leaves,bark and catkins of Salix aegyptiaca sp.

Leaves, bark and catkins of Salix aegyptiaca L. were extracted into solvents of increasing polarity from cyclohexane (non-polar), butanol, ethanol and water (polar) and analysed for their antioxidant capacity, total phenol and flavonoids. The highest antioxidant activity (19 μg/ml IC₅₀ for inhibition of DPPH radical activity), total phenolic content (212 mg gallic acid equivalents/g of dried extract) and total flavonoid (479 mg catechin equivalents/g of dried extract) was observed in the ethanolic extract of bark. HPLC identification of phenolic compounds from the extracts indicated the presence of gallic acid, caffeic acid, vanillin and p-coumaric acid, myricetin, catechin, epigallocatechin gallate, rutin, quercetin as well as salicin. Our data indicates the presence of high amounts of phenols and flavonoids in different parts of S. aegyptiaca species and propose that extracts from this plant may be utilised as a source of health promoting antioxidants.     

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.     

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.     

Effect of drying method on the antioxidant capacity of six Lamiaceae herbs

The present study investigated the changes in total phenols (TP), rosmarinic acid content and antioxidant capacity of six Lamiaceae herbs (rosemary, oregano, marjoram, sage, basil and thyme) after three drying treatments (air-, freeze- and vacuum oven-drying) stored for 60 days at −20 °C and compared to fresh samples. Ferric reducing antioxidant property (FRAP) and oxygen radical absorbance capacity (ORAC) were used as markers for antioxidant capacity. Air-dried samples had significantly (p < 0.05) higher TP, rosmarinic acid content and antioxidant capacity than had freeze-dried and vacuum oven-dried samples throughout the storage period. Fresh samples had the lowest values for the parameters tested. Vacuum oven-drying resulted in higher TP and FRAP values in rosemary and thyme during 60 days of storage than did freeze-drying. In ORAC assay, the difference was significantly higher only in thyme. Storage did not show any effect on the dried samples for the parameters tested.     

Mycosporine-like amino acid composition of the edible red alga, Palmaria palmata (dulse) harvested from the west and east coasts of Grand Manan Island,New Brunswick

The oxygen radical absorbance capacity (ORAC), antiproliferative activities and mycosporine-like amino acid (MAA) profiles of methanol extracts from two grades of dulse harvested from locations varying in UV-exposure (west vs east coasts of Grand Manan Island, NB) were determined in the present study. MAAs confirmed by LC/MS in both grades 1 (low-UV) and 2 (high-UV) dulse were palythine, shinorine, asterina-330, palythinol and porphyra-334; usujirene was present only in grade 2 dulse. ORAC values of grade 1 and 2 dulse extracts were 36.42 and 38.78 μmol Trolox/g extract. B16-F1 murine skin melanoma cell proliferation was inhibited (p < .05) by 68.5% and 91.9% by grade 1 and 2 dulse extracts at 6.0 mg/mL. The antiproliferative efficacy of grade 2 dulse was greater (p < .05) than grade 1 from 0.375 to 6.0 mg/mL. MAA differences between the grade 1 and 2 dulse extracts likely influenced the antiproliferative efficacies, despite the similar ORAC values.     

Microwave-assisted extraction of phenolic compounds from wine lees and spray-drying of the extract

Most research on extraction of phenol compounds from wine by-products and commercial exploitation of extracts use grape seeds and/or skins as raw materials. Looking for alternative antioxidants sources, obtaining antioxidant extracts from wine lees (also known as dregs), a sub-exploited by-product of winemaking process, is here presented. Microwave-assisted extraction (MAE) of phenolic compounds from wine lees has been optimized using the total phenols index, the ORAC values and yield of the extraction as response variables. Under the optimal working conditions, the proposed MAE method provides better extraction efficiency in a much shorter time (17 min) than the conventional extraction method for phenolic compounds (24 h). The liquid extract obtained by MAE was spray-dried. The type and amount of excipients used, as well as the spray-drying temperature, were optimized in order to minimize the oxidation of phenolic compounds and maximize the yield of the spray-drying process. The total phenols index in the dried extract thus obtained was 36.8% (expressed as gallic acid), showing an ORAC value of 3930 μmol TE/g. Additionally, Mv3G, Cm-Mv3G, myricetin, quercetin, quercetin-3-β-glucoside, caffeic acid and p-coumaric acid were quantified in the dry extract by HPLC–DAD. The results indicate that wine lees antioxidant extracts can be a suitable and cheap alternative to those obtained from grape seeds or skins.     

Effect of pulverization on the antioxidant activity of water caltrop (Trapa taiwanensis Nakai) pericarps

This study was to investigate the effect of pulverization treatment on the antioxidant properties of water caltrop pericarps. The results showed that crude fiber was the largest proportional constituent of water caltrop pericarps, comprising 72.3 g/100 g (dry basis). After 10 min milling, five fractions were obtained 1-5 different particle sizes (285, 211, 138, 62 and 41 μm, respectively). Comparing the effect of pulverization on the fiber component of each fraction, the fraction 1 exhibited higher hemi-cellulose but lower lignin than smaller particle size fraction except fraction 5. At a dosage of 250 μg/mL methanol extracts, the highest free radical-scavenging ability is obtained in the fraction 5, which is found to be 78.3 g/100 g, followed by the fractions 1-4. The same tendency was observed in the reducing power and cupric ions chelating ability. The fractions 1 and 5 contained significantly higher total phenolics and total flavonoids than fraction 2-4 (p < 0.05).     

Optimisation of the aqueous extraction conditions of phenols from meadowsweet (Filipendula ulmaria L.) for incorporation into beverages

Meadowsweet was extracted in water at a range of temperatures (60–100 °C), and the total phenols, tannins, quercetin, salicylic acid content and colour were analysed. The extraction of total phenols followed pseudo first-order kinetics, the rate constant (k) increased from 0.09 ± 0.02 min⁻¹ to 0.44 ± 0.09 min⁻¹, as the temperature increased from 60 to 100 °C. An increase in temperature from 60 to 100 °C increased the concentration of total phenols extracted from 39 ± 2 to 63 ± 3 mg g⁻¹ gallic acid equivalents, although it did not significantly affect the proportion of tannin and non-tannin fractions. The extraction of quercetin and salicyclic acid from meadowsweet also followed pseudo first-order kinetics, the rate constant of both compounds increasing with an increase in temperature up until 90 °C. Therefore, the aqueous extraction of meadowsweet at temperatures at or above 90 °C for 15 min yields extracts high in phenols, which may be added to beverages.     

Free radical-scavenging and inhibition of nitric oxide production by four grades of pine mushroom (Tricholoma matsutake Sing.)

Fractions from methanol extracts of four grades of pine mushroom (Tricholoma matsutake Sing.) were evaluated for their free radical-scavenging and inhibition of nitric oxide production, and the underlying mechanisms were elucidated. The fractions from first-grade pine mushroom exhibited the highest degree of free radical-scavenging and inhibition of nitric oxide production among the various grades of mushroom tested, and free radical-scavenging and inhibition of nitric oxide production by the second-, third-, and fourth-grade mushroom fractions were successively lower. The degree of free radical-scavenging by each fraction decreased in the order ethyl acetate > butanol > diethyl ether > water. Inhibition of nitric oxide production by each fraction decreased in the order ethyl acetate > butanol > water. The ethyl acetate and butanol fractions of methanol-extracted pine mushroom samples exhibited potential anti-oxidative and anti-inflammatory effects that might be attributable to phenolics or flavonoids.     

Evaluation of free radical-scavenging properties of commercial grape phenol extracts by a fast colorimetric method

Three commercial extracts of grape phenols (seeds, skin, whole) were used in this study. Each extract was divided by HPLC into five fractions of different polarities, and their free radical-scavenging activities were measured using the DPD (N,N-diethyl-p-phenylenediamine) colorimetric method. Total phenol contents were determined using the Folin-Ciocalteu method to assess their contribution to the antiradical activity. The results showed that there was good correlation between total phenolic compound contents and free radical-scavenging activities of the different grape extracts. Moreover, the seed extract presented the most important free radical-scavenging properties (138 USP/mg extract), whereas the whole extract presented the lowest free radical-scavenging capacity (80.5 USP/mg extract). However, the free radical-scavenging properties, reported on the basis of content of phenolic compounds in each extract, showed that the free radical-scavenging activities of seed and whole extracts were not significantly different (171 versus 162 USP/mg phenol). In addition, free radical-scavenging activities of fractions from seed and skin extracts decreased as their polarities decreased.     

The recognition of high molecular weight melanoidins as the main components responsible for radical-scavenging capacity of unheated and heat-treated Canadian honeys

As the Maillard reaction is known to occur in heat-treated foods, unheated and heated honey samples were subjected to the activity-guided fractionation and size-exclusion chromatography to compare the degree of browning, radical scavenging activity (ORAC) and molecular size of the fractions obtained. Heat-treatment increased browning in the fractions of light- and medium-coloured honeys (p < 0.002), accelerated the formation of high molecular weight melanoidins (85–232 kDa) and significantly increased ORAC values (p < 0.0001). In contrast, melanoidin content and ORAC decreased in the fractions of heat-treated dark buckwheat honey (p < 0.001). Unheated dark honey contained a significantly higher amount of melanoidins than other honeys (p < 0.007). Together, results showed that at low initial concentration of melanoidins, heat-treatment accelerated formation of new melanoidins and increased ORAC, while at high concentration it caused decrease and a reduction of radical scavenging activity. This study emphasises the importance of non-enzymatic browning in the prediction of the antioxidant pool in thermally processed honeys.     

Honey flavonoids as protection agents against oxidative damage to human red blood cells

Honey phenol extracts separated on the base of their hydrophobicity were evaluated for the antioxidant content and for the ability to inhibit oxidative damage induced by radical species generated in the water phase or in the membrane of human erythrocytes. The water and ether fractions obtained from crude methanol extract of honey exhibited a phenolic content of 5.33 and 2.62 mg caffeic acid equivalents/100 g honey, respectively. These values correlate well with those of total antioxidant power, as assessed by FRAP assay (37.67 vs. 10.65 μmol/100 g honey). Flavonoid contents were 2.57 and 1.64 mg catechin equivalents/100 g honey for ether and water fractions, respectively. Although both honey fractions protect erythrocytes against 2,2′-azobis(2-amidinopropane)dihydrochloride-induced lysis, only the ether fraction was found to be active in inhibiting hemolysis but not methemoglobin and ferrylhemoglobin formation caused by H₂O₂. In addition, the ether fraction prevents tert-butylhydroperoxide-induced lipid peroxidation in whole erythrocytes and in isolated membranes. The significant antioxidant effect against damages induced by both water-soluble and hydrophobic exogenous oxidants suggests that the ether fraction, owing to its lipophilic character, can interact with red blood cell membrane, and the protective effect can be associated with the binding of the flavonoids to the membrane. On the other hand, the water fraction is more hydrophilic than ether fraction and it acts only from the outside of the membrane by scavenging the radicals before they attack the erythrocyte membrane.     

Antioxidant potential of barley as affected by alkaline hydrolysis and release of insoluble-bound phenolics

Phenolic constituents of six barley varieties, namely Falcon, AC Metcalfe, Tyto, Tercel, Phoenix and Peregrine were separated into free, soluble conjugate and insoluble-bound fractions. Soluble conjugates and insoluble-bound phenolics were extracted into diethyl ether after consecutive alkaline hydrolysis for 4 h. Total phenolic content of each of the three fractions was determined by using Folin–Ciocalteau method. Total antioxidant capacity of the phenolic fractions was determined by trolox equivalent antioxidant capacity (TEAC) assay. The extracts were evaluated for their efficacy in scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Oxygen radical scavenging capacity (ORAC_FL) of the extracts was determined using a fluorometric assay. Effectiveness of phenolic extracts in inhibiting oxidation of human LDL cholesterol and radical-induced supercoiled DNA breakage was also evaluated. The contribution of insoluble-bound phenolics toward total phenolic content was significantly (p < 0.05) higher than the soluble phenolics for all barley extracts tested. The ratio of soluble to insoluble phenolics ranged from 1:27 to 1:35. TEAC and ORAC values and DPPH radical scavenging capacity of the insoluble phenolic fraction were significantly (p < 0.05) higher than those of their insoluble counterparts. A similar trend was observed against inhibition of LDL cholesterol oxidation and radical-induced DNA breakage.     

Antioxidant activity of microwave-assisted extract of Buddleia officinalis and its major active component

Buddleia officinalis Maxim, commonly used as rice dye for festivals, was extracted with ethanol using microwave-assisted extraction and Soxhlet extraction. The antioxidant activities of microwave-assisted extract of B. officialis (MEB) and Soxhlet extract of B. officianils (SEB) at the optimum extraction conditions were evaluated and compared with synthetic antioxidant butylated hydroxytoluene (BHT) employing DPPH free radical assay, ABTS assay, total antioxidant activity and reducing power. MEB and SEB had stronger antioxidant activities than BHT in all assays except reducing power, and the effects decreased as follows: MEB > SEB > BHT. The total phenolic contents of MEB and SEB reached 113.56 mg/g and 100.94 mg/g dry weight of extract, respectively, expressed as pyrocatechol equivalents, while the total flavonoids contents were 75.33 mg/g and 62.56 mg/g dry weight of extract, respectively, expressed as catechin equivalents (P < 0.05). Higher phenolic and flavonoids compounds may be major contributors to their higher antioxidant activities. Following activity-oriented separation, luteolin was isolated as an active principle, which exhibited excellent free radical scavenging activities with DPPH IC₅₀ 3.09 μg/ml and ABTS IC₅₀ 2.20 μg/ml.     

Antioxidant capacity of herbal infusions and tea extracts: A comparison of ORAC-fluorescein and ORAC-pyrogallol red methodologies

Oxygen radical absorbance capacity (ORAC) values have been obtained for a series of teas and herbal infusions employing 2,2′-azo-bis(2-amidinopropane) as free radical source, and fluorescein and pyrogallol red as target molecules. The amounts of phenols in the extracts were evaluated by Folin’s methodology. ORAC values are extremely dependent upon the employed target molecule. Even more, relative ORAC values measured for different infusions depend upon the employed methodology. For example, ORAC-fluorescein value of Aloysia citriodora is larger than that of green tea, while if pyrogallol red is employed as target molecule green tea appears as nearly nine times more efficient. Similarly, for extracts with comparable amounts of phenols, herbal infusions are more efficient than teas by ORAC-fluorescein, while opposite conclusions are obtained if ORAC-pyrogallol red values are considered. Extreme care must then be taken for conclusions obtained from ORAC values estimated by employing a single target molecule.