Antioxidant properties of water and ethanol extracts from hot air-dried and freeze-dried daylily flowers

Daylily (Hemerocallis fulva Linn.) flowers were hot air-dried and freeze-dried after harvest. Water and ethanol extracts were prepared from these dried flowers and their antioxidant properties were evaluated using total antioxidant activity, reducing capacity, metal chelating activity, and DPPH and superoxide anion radical scavenging activities, comparing with standards. Extracts from daylily flowers exhibited strong antioxidant activity. Ethanol was more efficienct to extract antioxidants than water and that freeze-drying preserved higher activities than air-drying. Ethanol extract from freeze-dried daylily flowers showed the highest antioxidant activity and phenol content.     

Antioxidant properties of phenolic compounds occurring in edible mushrooms

Total phenolic and flavonoid contents occurring in eight types of edible mushrooms (Agaricus bisporus, Boletus edulis, Calocybe gambosa, Cantharellus cibarius, Craterellus cornucopioides, Hygrophorus marzuolus, Lactarius deliciosus and Pleurotus ostreatus) have been respectively evaluated by the Folin–Ciocalteau assay and by the colorimetric reaction with NaNO₂ and AlCl₃ in a basic media. Generally, the assayed mushrooms contained between 1 and 6 mg of phenolics per gram of dried mushroom, depending on the species, while the flavonoid concentrations ranged between 0.9 and 3.0 mg per gram of dried matter. The profile and concentration of individual phenolics was determined by means of high performance liquid chromatography. Homogentisic acid was the free phenolic acid significantly present in all mushrooms although the content varied considerably among the analysed species. Flavonoids, such as myricetin and catechin were also detected in the mushrooms studied. The antioxidant properties of the methanolic extracts from mushrooms were evaluated by monitoring the linoleic acid autoxidation, and all the mushrooms species showed inhibition, with C. cibarius being the most effective against lipid oxidation (74% of inhibition) and A. bisporus the species with lowest antioxidant activity (10% of inhibition).     

Antioxidant compounds and antioxidant capacity of Peruvian camu camu (Myrciaria dubia (H.B.K.) McVaugh) fruit at different maturity stages

The antioxidant capacities of ascorbic acid and phenolic compounds present in camu camu fruit were screened during ripening. Ascorbic acid decreased, and anthocyanin, flavonol and flavanol contents, and DPPH antioxidant capacity increased during ripening. Antioxidant compounds from camu camu were fractionated in two fractions: an ascorbic acid-rich fraction (F-I) and a phenolics-rich fraction (F-II). F-I was the major contributor to the DPPH antioxidant capacity (67.5–79.3%) and F-II played a minor role (20.7–32.5%). A total of 30 different phenolic compounds were detected by HPLC-PAD. The presence of catechin, delphinidin 3-glucoside, cyanidin 3-glucoside, ellagic acid and rutin was elucidated. Other phenolic compounds, such as flavan-3-ol, flavonol, flavanone and ellagic acid derivatives, were also present. For the three ripening stages the flavan-3-ols and ellagic acid group were the most representative phenolic compounds in this fruit. Acid hydrolysis of F-II revealed the presence mainly of gallic and ellagic acids, suggesting that camu camu fruit possesses important quantities of hydrolysed tannins (gallo- and/or ellagitannins). These results confirm that camu camu fruit is a promising source of antioxidant phenolics.     

Antioxidant capacity and major phenolic compounds of spices commonly consumed in China

The antioxidant capacity, total phenolic content, and major phenolic compounds of a total of 19 commonly consumed spices in China were systematically investigated. Ultra performance liquid chromatography (UPLC) coupled with photodiode array detector (PDA) was used to identify and quantify the phenolic compounds in the spice extracts. Galangal exhibited the highest antioxidant capacity, associated with the highest total phenolic content. Furthermore, galangin was identified as the principal phenolic component and the main contributor to the highest antioxidant capacity of galangal. Spices in the family Rutaceae and Lauraceae possessed very high antioxidant capacity and high levels of phenolics. Generally, chlorogenic acid and rutin were identified as the dominant phenolic compounds in the spice extracts. This study might provide useful information not only for human health, but also for screening new economic natural antioxidants that could be used in foods.     

Antioxidant phenolic compounds from Smilax sebeana Miq.

Methanol extract and sub-fractions of Smilax sebeana rhizomes and roots were analyzed to evaluate the compounds involved in antioxidant activity. In all separated fractions of the different polarity solvents, ethyl acetate fraction showed the highest antioxidant activity and total phenolic content. This fraction was subjected to the sephadex LH-20 column and preparative HPLC for purification. Six phenolic compounds, chlorogenic acid (1), 4-formylphenol (2), epicatechin (3), cinchonain IIa (4), Ia (5) and Ib (6) were isolated and identified by spectroscopic analyses and further evaluated their potential antioxidant activities by DPPH and superoxide radical scavenging assays. Compared with synthetic antioxidant Trolox, except 4-formylphenol, the other isolated five compounds exhibited excellent antioxidant activities. This is the first report on the chemical constituents of S. sebeana which potentially involved in antioxidant activity. The results suggest that the ethyl acetate extract of S. sebeana might be used as a readily accessible source of natural antioxidant.     

Polyphenolic compounds and antioxidant properties of selected China wines

Thirty-seven China wines, produced from different geographical origins, were examined in this study. The antioxidant activity of wines was measured by different analytical methods: oxygen radical absorbance capacity (ORAC), reducing power, 2,2-azino-di-(3-ethylbenzothialozine-sulphonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH·), hydroxyl radical-scavenger activity, superoxide radical-scavenger activity, lipid peroxidation and chelating capacity. Furthermore,total phenols, total flavonoids, total flavanols and total anthocyanins of wines were determined. As expected, the red wines had much higher phenolic content and antioxidant capacity than rosé wines or white wines. Among the red wines, Cabernet Sauvignon and Muscat Hamburg, respectively, represented the wines with the highest and lowest phenolic contents and antioxidant capacity. Among the white wines, Italian Riesling had the lowest phenolic content and antioxidant capacity. Taken together, a close relationship between phenolic contents and antioxidant capacity, for all wines, was observed.     

Phenolic content and antioxidant capacity of tropical highland blackberry (Rubus adenotrichus Schltdl.) during three edible maturity stages

Tropical highland blackberry (Rubus adenotrichus Schltdl.) is a good source of antioxidants and contains appreciable levels of phenolic compounds, mainly ellagitannins and anthocyanins. This study examined the influence of three ripening stages on phenolic contents. Major anthocyanin pigments increased from 0.20 (red fruit) to 1.34 mg g⁻¹ fresh weight (FW) (fully ripe fruit), whereas ellagitannins and ellagic acid derivatives dropped from 3.8 to 2.2 mg ellagic acid equivalents g⁻¹ (FW). Flavonols also dropped from 5.1 to 2.0 mg quercetin equivalents 100 g⁻¹ (FW). Consequently, values for total phenolic compounds ranged from 5.8 to 5.2 mg gallic acid equivalents g⁻¹ (FW), showing no specific trend. Antioxidant activity (H-ORAC) increased from 38.29 to 64.00 μmol of Trolox equivalents g⁻¹ (FW) during ripening. When compared with other commercial cultivars, R. adenotrichus stands out for high H-ORAC value, although comparatively it possesses low anthocyanin content and average total phenolic content.     

Antioxidant activity and total phenolic content of Agaricus brasiliensis (Agaricus blazei Murril) in two stages of maturity

The antioxidant capability and total phenolic contents of methanolic extracts of Agaricusbrasiliensis in two stages of maturity, young (YB) and mature (MB), were evaluated in this work. Four complementary assays, reducing power, radical scavenging capacity, inhibition of lipid peroxidation and chelating ability for ferrous ions were used to screen the antioxidant properties of extracts. Minor differences in the composition of phenolic compounds were detected, but the extracts showed similar antioxidant activities, except for the chelating ability for ferrous ions, higher in MB than in YB. Our results support the use of both young and mature fruiting bodies of Agaricus blazei as sources of antioxidant compounds.     

Assessment of in vitro antioxidant capacity of the seed coat and the cotyledon of legumes in relation to their phenolic contents

Methanolic extracts of the seed coat and the cotyledon of two varieties of lentils (Lens culinaris L.) and two varieties of dark peas (Pisum sativum L.), were analysed for their antioxidant capacities (EC₅₀), in the form of free radical-scavenging activities. Huge differences have been observed in the antioxidant capacity in the seed coat and the cotyledon in both legumes. The seed coat, in which are located, principally, phenolic compounds with flavonoid structures, presents higher antioxidant activity than the cotyledon in lentils and peas, showing differences in both species but not very large differences between varieties. An analysis of principal components was applied to the results in order to relate the antioxidant capacity of these legumes with their phenolic composition previously established by the authors.     

Antioxidant,antiradical and antimutagenic activities of phenolic compounds present in maple products

The phenolic compounds in maple sap and syrup were extracted at different periods of the season and were separated to collect the glycosylated compounds and the aglycone compounds. The antioxidant and antiradical activities of each phenolic compound were studied using the thiobarbituric acid reactive substances (TBARS) assay and the N,N-diethyl-p-phenylenediamine (DPD) decoloration test to measure the free radical scavenging. The results showed that in general the phenolic compounds had a good antioxidant and antiradical properties. The glycosylated compounds from maple sap and maple syrup showed a better activity than the aglycones. The antimutagenic effects of each phenolic compounds from maple sap and syrup were also investigated as the inhibition of SOS induction by chemical agents in Salmonella typhimurium TA1535/pSK1002 containing the fusion gene umuC-lacZ. Induction of the SOS gene (umuC) expression was assayed by measuring accumulated β-galactosidase activity using a modified Umu test. The antimutagenic properties were studied per se and after metabolisation by S9 fraction. The results showed that an optimum of antimutagenic properties of the glycosylated metabolites phenolic compounds from sap and syrup was observed at 75% of the season for the sap and at 25% of the season for the syrup. A higher antimutagenic activity was observed at 25% and 100% of the season for aglycones present in syrup and at 75% of the season for aglycones present in sap.     

Antioxidant activity and phenolic compounds of fractions from Portulaca oleracea L.

Portulaca oleracea fractions obtained from the crude extract of the plant by reversed-phase separation were investigated for their antioxidant activities and phenolic compounds content. Five fractions were classified based on optical absorption between the wavelength range of 200–400 nm. Fraction 3 displayed higher absorption than the other fractions. The total amount of quantified phenolics in this fraction was found to be quite high compared to that of crude extract. Chlorogenic, caffeic, p-coumaric, ferulic and rosmarinic acids were the free phenolic acids, and quercetin and kaempferol were the free flavonoids detected in Fraction 3. IC₅₀ value of crude extract was found to be 511.8 μg/ml whereas Fraction 3 exhibited an IC₅₀ value of 154.1 μg/ml. TEAC of Fraction 3 was found to be almost four times higher than that of the crude extract. Fraction 3 was also found to show the highest lipid peroxidation inhibiting capacity, determined by TBARS assay.     

Antioxidant activity and phenolic compounds of Holotrichia parallela Motschulsky extracts

Insects have been relatively unexplored as potential sources of natural antioxidants. We report the antioxidant activity of extracts of the adult large black chafer beetle Holotrichia parallela Motschulsky, a common crop pest in China. The antioxidant activity of the ethanolic extract (EE) and the water extract (WE) of adult H. parallela were evaluated by four different in vitro assays. EE showed potent metal-chelating activity and inhibition of lipid peroxidation. WE proved to be an excellent antioxidant in the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and metal-chelating activity. Catechin was identified in the ethanolic extract and proteins were the main components in the water extracts. Both compounds could contribute to the antioxidant activity of the species. These results suggest that adult H. parallela might be used as a nutraceutical to alleviate oxidate-induced diseases and as a natural antioxidant additive in the food industry.     

Antioxidant phenolic compounds loss during the fermentation of Chétoui olives

Evolution of phenolic compounds was studied during spontaneous and controlled fermentations of “Chétoui” cultivar olives at three degree of ripeness. Both spontaneous and controlled fermentations led to an important loss of total phenolic compounds with a reduction rate of 32–58%. Consequently, the antioxidant activity decreased by 50–72%. After fermentations, hydroxytyrosol and caffeic acid concentrations increased, whilst protocatechuic acid, ferulic acid and oleuropein concentrations decreased. The hydroxytyrosol concentration in black olives increased from 165 mg/100 g dry weight to 312 and 380 mg/100 g dry weight, respectively, after spontaneous and controlled fermentation. The oleuropein concentration in green olives decreased from 266 mg/100 g dry weight to 30.7 and 16.1 mg/100 g dry weight, respectively, after spontaneous and controlled fermentation. During olive fermentation, phenolic loss is essentially due to the diffusion of these compounds into the brine; the main phenolic compound identified and quantified in the different brines was hydroxytyrosol. To preserve antioxidant quality of table olives it is necessary to use a controlled process to minimise phenolic compound loss.     

Phenolic Profiles and Total Antioxidant Capacity of Marketed Beers in Serbia

The aim of this research was to determine the total phenolic and flavonoid contents as well as to measure antioxidant activity of 24 different commercial beers consumed in Serbia. The major phenolic acids (gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, 2,5-dihydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, sinapic acid, salicylic), (+)-catechin, and (-)-epicatechin were also determined by high pressure liquid chromatography method using a photodiode array detector. Gallic acid, ferulic acid, and protocatechuic acid are the most abundant phenolic acids in all samples, followed by (+)-catechin. The total phenolic content was determined using the Folin-Ciocalteu assay. The total flavonoids were measured using spectrophotometrics as the aluminum chloride assay. The results showed that the highest total phenolic and flavonoid contents were established in dark and light beer samples. 2,2-Diphenyl-1-picrylhidrazyl radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical cation scavenging activity, and ferric reducing/antioxidant power were used to assess the antioxidant potential of beers. These assays, based on different chemical mechanisms, were selected to take into account the wide variety and range of action of antioxidant compounds present in selected beer samples. All beers showed antioxidant power, but a wide range of antioxidant capacities was observed. Statistical differences between ferric reducing-antioxidant power and the other two antioxidant capacity assays were confirmed. This study will be useful for the appraisal of phenolic profile and antioxidant activities of various beers, and it will also be of interest for people who like drinking this beverage.     

Antioxidant capacity and phenolic composition of different woods used in cooperage

This study has investigated the antioxidant capacity of different woods used in cooperage and the effect of the botanical species of wood on this capacity. Quercus robur and Castanea sativa were the species with the highest antioxidant capacity, due to their relatively high content of phenolic compounds. However, the phenolic content of Prunus avium samples was very low, also reflected in its antioxidant capacity. All measurements of antioxidant capacity were consistent with the content and composition of the phenolic compounds detected in the wood samples. The major contributors to the antioxidant capacity were identified as phenolic acids, including gallic, protocatechuic, p-coumaric and ellagic acid and all the ellagitannins, due to their characteristic structure.     

Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity,occurrence, and potential uses

Phenolic compounds, ubiquitous in plants are an essential part of the human diet, and are of considerable interest due to their antioxidant properties. These compounds posses an aromatic ring bearing one or more hydroxyl groups and their structures may range from that of a simple phenolic molecule to that of a complex high-molecular weight polymer. Flavonoids, which bear the C₆–C₃–C₆ structure, account for more than half of the over eight thousand different phenolic compounds. The antioxidant activity of phenolic compounds depends on the structure, in particular the number and positions of the hydroxyl groups and the nature of substitutions on the aromatic rings. Fruits, vegetables and beverages are the major sources of phenolic compounds in the human diet. The food and agricultural products processing industries generate substantial quantities of phenolics-rich by-products, which could be valuable natural sources of antioxidants. Some of these by-products have been the subject of investigations and have proven to be effective sources of phenolic antioxidants. When tested in edible oils, and in fish, meat and poultry products, phenolic-rich extracts have shown antioxidant activities comparable to that of synthetic antioxidants. Practical aspects of extraction and production of sufficient amounts of natural antioxidants from most of these sources remain to be elucidated.     

Antioxidant activity, browning and volatile Maillard compounds in Pedro Ximénez sweet wines under accelerated oxidative aging

Pedro Ximénez wine, aged by thermal treatment during 10, 20 and 30 days in the presence or absence of oak chips, was studied in terms of antioxidant activity, browning and volatile Maillard compounds. The phenolic fractions obtained by the SepPack tC-18 column revealed that the antioxidant activity after 10 days of thermal treatment was due to the presence of phenols and polar compounds possibly formed by the Maillard reaction. After 30 days, however, the antioxidant activity was also due to high-molecular weight procyanidins. Volatile Maillard compounds increased throughout the thermal treatment. It should be noted that there was an increase in the 5-ethoxymethylfurfural content and the presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-2-one, which was recently shown to inhibit growth of colon tumor cells. The presence of oak chips had a substantial effect on the contents in volatile Maillard compounds after the thermal treatment with the exception of corylon. The wine obtained after 10 days of thermal treatment was judged to be the best in terms of sensory properties. In fact, it exhibited the optimum balance between varietal and aging aromas due to Maillard compounds.     

Antioxidant capacity,total phenolics,glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326 μmol Trolox/100 g) and DPPH (3194–6346 μmol Trolox/100 g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324 mg sinapic acid/100 g), glucosinolates (4.2–87.5 μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r = 0.9332, 0.9339, p < 0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L^∗) or red colour intensity (a^∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.