The influence of roasting,pasteurisation, and storage on the polyphenol content and antioxidant capacity of California almond skins

Polyphenols and antioxidant activity of skins from California almonds subjected to roasting, pasteurisation, and storage were determined by LC-MS quantification, total phenols (TP), and ferric reducing antioxidant power (FRAP). Pasteurisation did not significantly change TP, FRAP, or flavonoids and phenolic acids (FP). Roasted almonds had 26% less TP and 34% less FRAP than raw, but equivalent FP (n = 12). Storing almonds at 4 and 23 °C for 15 mo resulted in gradual increases in FP, up to 177% and 200%, respectively (n = 13). At 4 °C and 15 mo, polyphenols increased 18-fold for p-hydroxybenzoic acid, whilst others were 45–200% higher compared to baseline values. Isorhamnetin-3-O-rutinoside accounted for 48% of the increase in FP. After 15 mo, FRAP and TP increased to 200% and 190% of initial values. Accelerated ageing of whole almonds increased FP content by 10% after 3 days, but TP and FRAP values were not significantly different from baseline to day 10. Thus, in almond skins, roasting decreases TP and FRAP but not FP, whilst storage for up to 15 mo doubles FP.     

Organic acids,antioxidant capacity,phenolic content and lipid characterisation of Georgia-grown underutilized fruit crops

Four underutilized Georgia-grown fruit crops, namely loquat (Eriobotrya japonica), mayhaw (Crataegus sp.), fig (Ficus carica), and pawpaw (Asimina triloba), and their leaves were analysed for total polyphenols by Folin–Ciocalteau method, and antioxidant capacity by ferric-reducing antioxidant power (FRAP) and Trolox-equivalent antioxidant capacity (TEAC) assays. Organic acids and phenolic compounds were identified by RP-HPLC. For lipid profile, fruits were separated into two fractions – seed and fruit (i.e., without seed); lipid was extracted using the Folch method and analysed for fatty acids, phytosterols, tocopherols, and phospholipids. The major organic acid identified in all samples was malic acid (177–1918 mg/100 g FW). The predominant phenolic acids in all the fruits were gallic (1.5–6.4 mg/100 g FW) and ellagic (0.2–33.8 mg/100 g FW), and the most abundant flavonoid was catechin (12.2–37.8 mg/100 g FW). Total lipid content varied from 0.1% in mayhaw fruit to 21.5% in pawpaw seed. Linoleic acid was the predominant fatty acid in all of the samples (28.2–55.7%).     

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.     

Determination of polyphenolic content and antioxidant activity of kudingcha made from Ilex kudingcha C.J. Tseng

The total polyphenol content and the antioxidant activity of kudingcha made from Ilex kudingcha C.J. Tseng were determined by Folin–Ciocalteu reagent, and DPPH, FRAP, and TEAC methods, respectively. The crude extract (CE) of kudingcha and its four fractions of chloroform (CfF), ethyl acetate (EaF), n-butanol (nBF), and water (WtF) were prepared and subjected to antioxidant evaluation and analysis by high performance liquid chromatography. The extracts of kudingcha contained large amounts of caffeoylquinic acid (CQA) derivatives, including 3-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA, and showed potent antioxidant activity. The antioxidant activities of CE and its fractions decreased in the order of EaF > nBF > CE > WtF > CfF, according to the DPPH assay and FRAP assay, which were the same, with the exception of the rank order of CfF and WtF, as the TEAC assay. Furthermore, a satisfactory correlation between total polyphenol content and antioxidant activity was observed.     

A survey of Irish fruit and vegetable waste and by-products as a source of polyphenolic antioxidants

In this study, fruit and vegetable by-product and waste sources in Ireland were tested for their antioxidant activity and polyphenol content. The highest levels of antioxidants measured by both ferric reducing antioxidant power (FRAP) and diphenyl-picrylhydrazyl (DPPH) assays, were detected in whole kiwifruit. Of the vegetable by-products, broccoli stems showed the best antioxidant potential. The level of polyphenols as assessed by the Folin–Ciocalteu Reagent (FCR) was significantly correlated with the level of polyphenols by HPLC–DAD (r = 0.93). The level of polyphenols assessed by HPLC–DAD was not significantly correlated with the antioxidant assays. Apple pomace and vegetable by-products were found to be good sources of both polyphenols and antioxidants and due to their abundance may be exploitable resources to use as food ingredients.     

Chemical and antioxidant properties of pomegranate cultivars grown in the Mediterranean region of Turkey

Arils from six pomegranate (Punica granatum L.) cultivars obtained from various sites from the Mediterranean region of Turkey were evaluated for their chemical and antioxidant properties. These properties included total phenolics (TP), total monomeric anthocyanins (TMA), soluble solids (TSS), titratable acidity (TA), individual sugars and organic acids. Antioxidant capacities of arils were determined by both the ferric reducing antioxidant power (FRAP) and trolox equivalent antioxidant capacity (TEAC) assays. The antioxidant capacities averaged 5.60 and 7.35 mmol TE/l by the TEAC and FRAP methods. Variability among cultivars was greatest for TMA content (CV 132%); individuals ranged from 6.1 to 219 mg cy3-Gluc l⁻¹. TP means averaged 1507 mg GAE/l. Levels of FRAP, TEAC, TP, and TMA were strongly correlated (r = 0.82–0.96). The major sugars were fructose (6.4 g/100 ml) and glucose (6.8 g/100 ml), the major acids were citric (1.78 g/100 ml) and malic (0.12 g/100 ml).     

Antioxidant properties of different cultivars of Portulaca oleracea

Methanolic extracts of six cultivars of Portulaca oleracea were analyzed for their total phenol content (TPC) using the Folin–Ciocalteu method. The antioxidant activity was measured using the 1,1-diphenyl-2-picrylhydrazyl, ferric-reducing antioxidant power (FRAP) and β-carotene bleaching (BCB) assays. The iodine titration method was used to determine the ascorbic acid content (AAC). The TPC of the cultivars of P. oleracea ranged from 127 ± 13 to 478 ± 45 mg GAE/100 g of fresh weight of plant. There was good correlation between the TPC value and its AEAC, IC₅₀ and FRAP values (r² > 0.9) for all the cultivars. The AAC for the cultivars ranged from 38.5 ± 0.6 to 73.0 ± 17.5 mg/100 g. The TPC value of the common variety PO1, was the lowest compared to the ornamental cultivars (PO2–PO6). The BCB assay showed that all cultivars were capable of inhibiting lipid peroxidation and the inhibition power did not correlate with TPC value.     

Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols

The total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions was analyzed. Infusions were prepared in common way in which teas are prepared for human consumption. The total phenolics were measured by Folin–Ciocalteau assay. The total antioxidant capacity was estimated by Ferric Reducing/Antioxidant Power (FRAP) assay. To make practical comparison of relative antioxidant potential of phenolics extracted from selected medicinal plants, the phenol antioxidant coefficient (PAC) was calculated for each infusion. The total phenolic content of medicinal plant infusions ranges from 9 to 2218 mg/L. The FRAP range from 0.06 to 25 mM/L. There was significant linear correlation between total phenolic content and FRAP. According to their antioxidant capacity, 70 medicinal plant extracts can be divided in five groups: (a) very low FRAP (<1 mM/L) n = 9; (b) low FRAP (1–5 mM/L), n = 37; (c) good FRAP (5–10 mM/L), n = 15; (d) high FRAP (10–20 mM/L), n = 8; and (e) very high FRAP (>20 mM/L), n = 1 medicinal plant extract. The PAC was ranging from 1.1 to 3.9 (average 2.4). The best results were obtained for Melissae folium infusions: high phenolic concentration, very high FRAP (>20 mM/L) and PAC > 3. The effect of infusion time and infusion temperature on the phenolic content, FRAP, and free radical scavenging ability was tested. DPPH radical scavenging ability of Melissae folium phenolics was similar to (+)-catechin but not as good as for quercetin. Compared to Trolox and vitamin C, Melissae folium phenolics were more efficient free ABTS radical scavengers. The results indicate that Melissae folium infusions could be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea.     

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 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.     

Anthocyanins composition and antioxidant activity of two major wild Nitraria tangutorun Bobr. variations from Qinghai-Tibet Plateau

Nitraria tangutorun Bobr., a unique kind of fruit, widely spreads in the Qinghai-Tibet Plateau. In the present study, nine anthocyanins were identified in two variations (purple fruit and red fruit) of N. tangutorun by HPLC/DAD-ESI/MS. Cyanidin-3-O-(trans-p-coumaroyl)-diglucoside (215.76 ± 22.91 mg of Mv3G5G equivalent per 100 g of fresh weight) and pelargonidin-3-O-(p-coumaroyl)-diglucoside (5.13 ± 0.35 mg of Mv3G5G equivalent per 100 g of fresh weight) were the main anthocyanins in the purple and red fruits respectively. In addition, most of the anthocyanins were acylated by coumaric acid, and the rare anthocyanins that naturally presented a coumaric acid in both cis and trans configurations have been detected. Furthermore, the extract of the two variations showed significantly different antioxidant activity (p < 0.01) according to DPPH, ABTS and FRAP assay. Purple fruit possessed higher antioxidant activity than red fruit. There were significant correlations between antioxidant activity and both the total polyphenol content and anthocyanins content. This work is valuable for elucidation of anthocyanins composition in N. tangutorun and for further utilization as a functional food and medicine material.     

Polyphenol and glycoalkaloid contents in potato cultivars grown in Luxembourg

The polyphenol (phenolic acids, flavanols and flavonols) and glycoalkaloid (α-chaconine and α-solanine) contents of potato tubers grown in Luxembourg were analyzed by UPLC–DAD and HPLC–MS/MS separately in peel (approx. 2 mm), outer (approx. 1 cm) and inner flesh. Polyphenol contents decreased from the peel via the outer to the inner flesh and differed among the cultivars. The cultivars Vitelotte and Luminella had the highest polyphenol contents (5202 and 572 μg/g dry weight (DW) in the outer flesh), whereas Charlotte and Bintje had the lowest contents (19.5 and 48.0 μg/g DW). Chlorogenic acid and its isomers (neo- and cryptochlorogenic acid) were the major polyphenols. Glycoalkaloid contents were highest in the peel and lowest in the inner flesh, values in the flesh were below guideline limits in all cultivars. In conclusion, potatoes contribute to the daily intake of polyphenols and their consumption, thereby, may have positive effects on health.     

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.     

Raw Millefiori honey is packed full of antioxidants

Total polyphenols, flavonoids and antioxidant power of raw honey samples from two of the most common Italian varieties, i.e., Millefiori and Acacia, were evaluated. Phenolic content, expressed as caffeic acid equivalents, ranged from 12.5 to 17.5 mg/100 g and from 3 to 11 mg/100 g in Millefiori and Acacia honeys, respectively. All Millefiori samples exhibited the highest flavonoid concentration being between 1.23 and 2.93 mg catechin equivalents (CE)/100 g honey. Total flavonoids in 100 g Acacia honeys were in the range of 0.45–1.01 mg CE. Acacia honeys had lower total antioxidant power, as assessed by ferric reducing/antioxidant power assay, than Millefiori. The relationship between phenolic content and antioxidant power was discussed. Comparative experimental analysis was performed with an artificial honey and processed honeys. Raw Millefiori honey is rich in both amount and variety of antioxidant substances, and its inclusion in the diet may be recommended to complement other polyphenol sources.     

Antioxidant stability of small fruits in postharvest storage at room and refrigerator temperatures

Strawberries (Fragaria ananassa), raspberries (Rubus idaeus) and red currants (Ribes rubrum), as well as two drupes, cherries (Prunus avium), and sour cherries (Prunus cerasus), were subjected to two storage temperatures (4 °C and 25 °C) and phytochemicals concentrations (total phenols, flavonoids and anthocyanins) as well as antioxidant capacity (DPPH, ABTS and FRAP assays) were monitored until the fruit visually spoiled. Red currants and strawberries exhibited the highest initial total phenol (TP) contents (322.40 ± 5.56 and 335.47 ± 6.12 mg GAE/100 g FW, respectively) and maintained the highest TP contents throughout storage at both temperatures. Storage of at 25 °C as opposed to 4 °C, facilitated faster spoilage of analyzed fruits. In addition, most fruits stored at 4 °C, exhibited slightly higher antioxidant activity values at the end of storage according to all three antioxidant activity assays as opposed to fruits stored at 25 °C. The dynamic evolution of antioxidant capacity at both temperatures reflected the transient changes in phytochemical composition of small fruits in storage.     

Almond Polyphenols: Methods of Analysis,Contribution to Food Quality,and Health Promotion

Almond is a nutrient‐dense tree nut recognized for its favorable lipid profile, vitamin E content, and polyphenols. The objectives of this review were to determine the polyphenols reported in almond, summarize the methods of analysis, and determine the polyphenol contribution to almond quality and health‐promoting activity. Approximately 130 different polyphenols have been identified in almond, although not all of these have been quantitated. The mean and 25% to 75% percentile contents reported in literature were 162 mg (67.1 to 257) proanthocyanidins (dimers or larger), 82.1 mg (72.9 to 91.5) hydrolysable tannins, 61.2 mg (13.0 to 93.8) flavonoids (non‐isoflavone), 5.5 mg (5.2 to 12) phenolic acids and aldehydes, and 0.7 mg (0.5 to 0.9) isoflavones, stilbenes, and lignans per 100 g almond. Following solvent extraction of almond, hydrolysis of the residue liberates additional proanthocyanidins, phenolic acids and aldehydes, and total phenols. Blanching and skin removal consistently reduces almond polyphenol content, but blanch water and almond skins retain enough polyphenols to be used as antimicrobial and antioxidant ingredients. Roasting and pasteurization have inconsistent effects on almond polyphenols. Almond polyphenols contribute to shelf life by inhibiting lipid oxidation and providing pigmentation, flavor, astringency, and antimicrobial activity. The health‐promoting activity of whole almonds has been widely investigated, but few have considered the contribution of polyphenols. Preclinical studies of polyphenol‐rich almond skin or almond extracts suggest putative effects on antioxidant function, detoxification, antiviral activity, anti‐inflammatory function, and topical use for inhibiting ultraviolet A damage. Therefore, almond has a diverse polyphenol profile contributing to both its food quality and health‐promoting actions.     

Is organically produced wheat a source of tocopherols and tocotrienols for health food?

Forty organically grown spring and winter wheat genotypes were investigated for content and compositions of tocopherol and tocotrienol. The selected genotypes belonged to five different genotypic groups, i.e. landraces, old cultivars, modern cultivars, spelt wheat, and primitive wheat. The total tocochromanols content (21.9–37.3 mg/kg) wheat were in similar ranges as previously reported for conventionally grown wheat. The vitamin E activity varied among the genotypic groups and corresponded to 12–25% of the recommended daily intake. Primitive wheat was found to contain the highest percentage of tocotrienols (74%). Content of tocochromanols and vitamin E activity are known to decrease by heating. Organic wheat is more commonly consumed as whole and sprouted grain when compared to conventional wheat and might therefore be a good source of tocochromanols in health food. The large variation in tocopherols and tocotrienols in the investigated wheat genotypes indicated a great potential for the development of specific wheat genotypes with health promoting properties in future breeding programmes.     

Milk β-lactoglobulin complexes with tea polyphenols

The effect of milk on the antioxidant capacity of tea polyphenols is not fully understood. The complexation of tea polyphenols with milk proteins can alter the antioxidant activity of tea compounds and the protein secondary structure. This study was designed to examine the interaction of β-lactogolobulin (β-LG) with tea polyphenols (+)-catechin (C), (−)-epicatechin (EC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) at molecular level, using FTIR, CD and fluorescence spectroscopic methods as well as molecular modelling. The polyphenol binding mode, the binding constant and the effects of polyphenol complexation on β-LG stability and secondary structure were determined. Structural analysis showed that polyphenols bind β-LG via both hydrophilic and hydrophobic interactions with overall binding constants of K_C–β-LG = 2.2 (±0.8) × 10³ M⁻¹, K_EC–β-LG = 3.2 (±1) × 10³ M⁻¹, K_ECG–β-LG = 1.1 (±0.6) × 10⁴ M⁻¹ and K_EGCG–β-LG = 1.3 (±0.8) × 10⁴ M⁻¹. The number of polyphenols bound per protein molecule (n) was 1.1 (C), 0.9 (EC), 0.9 (ECG) and 1.3 (EGCG). Molecular modelling showed the participation of several amino acid residues in polyphenol–protein complexation with extended H-bonding network. The β-LG conformation was altered in the presence of polyphenols with an increase in β-sheet and α-helix suggesting protein structural stabilisation. These data can be used to explain the mechanism by which the antioxidant activity of tea compounds is affected by the addition of milk.     

Rosmarinic acid,scutellarein 4′-methyl ether 7-O-glucuronide and (16S)-coleon E are the main compounds responsible for the antiacetylcholinesterase and antioxidant activity in herbal tea of Plectranthus barbatus (“falso boldo”)

Plectranthus barbatus, known as “falso boldo” in Brazil, is used in herbal tea or cooked as a vegetable. Infusions and decoctions of leaves from P. barbatus were analysed for their inhibition of acetylcholinesterase and their antioxidant activity. The decoction showed high inhibition activity (31% inhibition with 0.5 mg of extract/ml) and also high antioxidant activity (IC₅₀ = 45.8 ± 0.5 μg of dry extract/ml in the DPPH test; IC₅₀ = 69.8 ± 3.1 μg of dry extract/ml in the β-carotene–linoleic acid test). Rosmarinic acid, scutellarein 4′-methyl ether 7-O-glucuronide and (16S)-coleon E were the main constituents identified. These compounds have antiacetylcholinesterase activity. Rosmarinic acid and the scutellarein derivative have IC₅₀ = 440 μg/ml and 1 mg/ml, respectively. One milligram per millilitre of (16S)-coleon E showed 61% inhibition of the enzyme. Other Plectranthus species, P. ecklonii, P. fructicosus, P. lanuginosus and P. verticillatus, were also analysed and the results obtained correlated with the content in rosmarinic acid.     

The effects of solvents on the phenolic contents and antioxidant activity of Stypocaulon scoparium algae extracts

Water, water/methanol (1/1), methanol and ethanol crude extracts from a brown alga Stypocaulon scoparium were examined for total phenolic contents (TPC) using Folin–Ciocalteu method. DPPH scavenging assay was performed to measure the radical scavenging activities (RSA) of the extracts. Results showed a significant association between the antioxidant potency and the TPC. The aqueous extract showed both, the highest antioxidant activity and highest phenolic contents. The identification and quantification of phenolic antioxidants were carried out with a rapid and simple method of reverse phase high performance liquid chromatography (RP-HPLC). This method was developed for the simultaneous analysis of 14 polyphenols, namely gallic acid, catechin, epicatechin, rutin, p-coumaric acid, myricetin, quercetin and protocatechuic, vanillic, caffeic, ferulic, chlorogenic, syringic and gentisic acids. The chromatographic separation of 14 polyphenols was achieved in less than 40 min by RP-HPLC (Varian, Pursuit XRs C18 column, 5 μm, 250 mm × 4.6 mm) using linear gradient elution of methanol and water (0.1% formic acid) with a flow rate of 1 ml/min. Gallic acid was by far the predominant polyphenol.