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 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.     

Antioxidant activity and phenolic content of 16 raisin grape (Vitis vinifera L.) cultivars and selections

Six raisin grape cultivars and 10 new raisin grape selections were analyzed for antioxidant activity (ABTS assay) and for total and individual phenolic compounds. Samples were freeze–dried and values are reported on a dry weight basis. Antioxidant activity across the 16 samples ranged from 7.7 to 60.9 μmol Trolox/g DW, with A95-27 exhibiting the greatest activity. Total phenolic content, determined in gallic acid equivalents using the Folin–Ciocalteau assay, ranged from 316.3 to 1141.3 mg gallic acid/100 g DW and was strongly correlated (r = 0.990) with antioxidant results. Concentrations of individual phenolics were determined by HPLC. trans-Caftaric acid was the predominant compound in all samples. A95-15 contained the lowest concentration (153.5 μg/g DW) of caftaric acid, while Fiesta contained the highest concentration (598.7 μg/g DW). Selections A56-66, A95-15, and A95-27 had much higher levels of catechin (86.5–209.1 μg/g DW) and epicatechin (126.5–365.7 μg/g DW) than the other samples.     

Relative antioxidant and cytoprotective activities of common herbs

Many studies have been carried out on bioactivities of individual herbs, however, no collective study on their comparative antioxidant and cytoprotective activities against oxidative damage has been reported. We selected 17 common commercial herbs and studied their relative phenolic contents, antioxidant activities, and cytoprotective activities on gap–junction intercellular communication and antioxidative enzymes in vitro under the same conditions. Total polyphenol content ranged from 464 to 870 gallic acid equivalents (GAE) mg/100 g and total flavonoid content from 212 to 494 catechin equivalents (CE) mg/100 g. Among the samples, chamomile, rosehip, hawthorn, lemon verbena, and green tea contained relatively high total phenolics (769–844 mg GAE/100 g) and flavonoids (400–4 mg CE/100 g). Chamomile also showed the highest antioxidant activity with 960 mg/100 g of vitamin C equivalent (VCE), followed by hawthorn (929 mg VCE/100 g) and black tea (916 mg VCE/100 g). Total phenolic and total flavonoids showed a higher correlation with antioxidant activity. Most of herbs enhanced cell viability and showed protective effects against oxidative stress induced by hydrogen peroxide in Chinese hamster lung fibroblast (V79-4) cells. Furthermore, herbs used in this study showed higher protective effect on gap–junction intercellular communication (GJIC) as compared to gallic acid and catechin, and also enhanced activity of the antioxidative enzymes such as superoxide dismutase (SOD) and catalase (CAT) in a dose-dependent manner.     

Phenolic composition,antioxidant and acetylcholinesterase inhibitory activities of Sclerocarya birrea and Harpephyllum caffrum (Anacardiaceae) extracts

Total phenolic content, proanthocyanidins, gallotannins, flavonoids, and antioxidant activities of Sclerocarya birrea and Harpephyllum caffrum methanolic extracts were evaluated using in vitro assays. S. birrea young stem extract contained the highest levels of total phenolic content (14.15 ± 0.03 mg GAE/g), flavonoids (1.21 ± 0.01 mg CE/g) and gallotannins (0.24 ± 0.00 mg GAE/g). H. caffrum stem bark extract had the highest content of proanthocyanidins (1.47%). The EC₅₀ values of the extracts in the DPPH free radical scavenging assay ranged from 4.26 to 6.92 μg/ml, compared to 6.86 μg/ml for ascorbic acid. A dose-dependent linear curve was obtained for all extracts in the ferric-reducing power assay. Dichloromethane and methanol extracts exhibited dose-dependent acetylcholinesterase inhibitory activity. Similarly, all extracts exhibited high antioxidant activity comparable to butylated hydroxytoluene based on the rate of β-carotene bleaching (84.1–93.9%). The two Anacardiaceae species provide a source of natural antioxidants and acetylcholinesterase inhibitors, and may be beneficial to the health of consumers.     

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%.     

Chemical characterization and antioxidant evaluation of muscadine grape pomace extract

Concentrated muscadine pomace extract was chromatographically analyzed for its individual phenolic, flavonoid, and anthocyanidin compounds. This extract was also characterized regarding its total phenolic content (TPC), total flavonoid content (TFC), antioxidative activities in terms of scavenging DPPH free radicals, reducing ferric, and chelating Fe²⁺. The TPC of this product was 34.1 ± 1.8 mg of gallic acid equivalents(GAE)/g of extract, and TFC was 3.0 ± 0.3 mg of quercetin equivalents/g of extract. Some phenolic compounds including ellagic acid, gallic acid, (−)-epicatechin, (−)-epigallocatechin, catechin, myricetin, quercetin, and kaempferol were identified. Some anthocyanidins including delphinidin, cyanidin, petunidin, peonidin, and malvidin were also identified in the extract by using a combination of retention and spectral properties on a reverse-phase HPLC–PDA. In addition, 3,3′,4,4′5,5′-hexahydroxystilbene-a resveratrol analogue present in the extract was identified for the first time by LC–MS. The results from this study demonstrate that the muscadine pomace extract is rich of natural antioxidants such as phenolics, flavonoids and anthocyanins, and possesses strong antioxidant properties. Besides, the developed methods can be used for routine quality control of the muscadine products for manufacturing efficiency and consistency.     

Effects of various solvents on the extraction of antioxidant phenolics from the leaves, seeds, veins and skins of Tamarindus indica L.

The effects of solvents, of varying polarities, on the extraction of antioxidant phenolics from the leaves, seeds, veins and skins of Tamarindus indica (T. indica) were studied. The efficiencies of the solvents for extraction of the antioxidant phenolics were in the order: methanol > ethyl acetate > hexane. Phenolic content ranged from 3.17 to 309 mg of gallic acid equivalents/g. Methanol leaf extract (MEL) had the highest phenolic content and was the most potent scavenger of DPPH and superoxide radicals. Methanol vein extract had the highest ferric reducing activity whereas methanol seed extract was the most potent ABTS radical-scavenger. A positive correlation existed between phenolic content and antioxidant activities of the plant parts. HPLC analyses of MEL revealed the presence of catechin, epicatechin, quercetin and isorhamnetin. Overall, methanol was the most effective solvent for extraction of antioxidant phenolics from T. indica. T. indica, particularly the leaf, can be a useful source of natural antioxidants.     

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.     

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.     

Bioprospecting traditional Pakistani medicinal plants for potent antioxidants

Antioxidant potential of four methanol extracts from three selected plant species, namely Salvia nubicola (Lamiaceae), Acer oblongifolium (Aceraceae) and Hedera nepalensis (Araliaceae) was measured using assays in aqueous and lipid systems. Antioxidant activities were investigated in aqueous systems by using DPPH radical-scavenging assay, ABTS radical-scavenging assay and DNA protection assay, while antioxidant activity in a lipid system was determined by using the thiobarbituric acid-reactive substances (TBARS) assay. Additionally, the Folin-Ciocalteu method was used to measure total phenolic content. Methanol extracts of leaves and flowers of S. nubicola showed the highest Trolox equivalent (TE) values in the case of the DPPH assay, 2484 ± 4.9 mmol TE/g extract, as well as total phenolic content, 139 ± 0.2 mg gallic acid equivalents/g extract. Three fractions (A-C) of the methanol extract of S. nubicola leaves and flowers were produced by semi-preparative HPLC. Fraction B was found to be the most active in the DPPH radical-scavenging assay and had the highest total phenol content. HPLC-DAD and LC-MS revealed rosmarinic acid in S. nubicola extracts and chlorogenic acid and rutin in H. nepalensis extracts as the main phenolic antioxidants.     

Antioxidant activity of the phenolic compounds released by hydrothermal treatments of olive tree pruning

The liquors from liquid hot water treatment (LHW) and from steam explosion (SE) of Olea europea pruning were characterised for phenolic content and in vitro antioxidant activity. Rising the temperature treatment enhanced the release of phenolic compounds to the aqueous phase and the fraction of them which are soluble in ethyl acetate was increased. Up to 2.29 and 1.88 g gallic acid equivalents (GAE)/100 g pruning were solubilised in LHW and SE, respectively, 80% of these compounds were recovered in the ethyl acetate extract. Syringol and syringaldehyde were the most abundant lignin derived volatile products identified. Hydroxytyrosol, oleuropein, syringaldehyde and tyrosol were the major phenolic compounds identified by HPLC. The antioxidant activity of the extracts, comparable to that of synthetic antioxidants, depended on the extract concentration but was scarcely affected by treatment temperature.     

Phenolics, betacyanins and antioxidant activity in Opuntia joconostle fruits

Sour prickly pears (xoconostles) are fruits from Opuntia joconostle cactus, which are cultivated in the central Mexico area. Phenolic and pigment content in various parts of O. joconostle fruits were analyzed. The antioxidant activity of a methanolic extraction and different semi-purified fractions were also evaluated by the DPPH⁺ method. Xoconostle fruits were obtained from a commercial orchard in Mexico State. Fruits were analyzed as whole fruit and each fruit part including pericarp, mesocarp and endocarp. Samples were homogenized and kept at 4 °C until sample preparation. Total phenolic content and total flavonoid content varied among the different parts of the fruit. The highest amount of phenolic compounds and total flavonoids content were found in pericarp 2.07 mg gallic acid equivalents (GAE)/g fresh weight (FW) and 0.46 mg(+)-catechin equivalents (CE)/g FW respectively. Seven phenolics were identified as protocatechuic, 4-hydroxybenzoic, caffeic, vanillic and syringic acids, rutin, and quercetin. The color of the fruit parts was mainly due to the presence of betacyanins. The betacyanin concentration was higher in the endocarp (23.03 mg betanin equivalents/100 g fresh weight) than in the pericarp and mesocarp. Betacyanins were identified by HPLC-PDA-MS as betanin, isobetanin, betanidin, isobetanidin, and phyllocactin. Methanolic extracts and semi-purified fractions A (phenolics and flavonols) and B (betacyanins) of xoconostle showed high antioxidant activity mainly in the pericarp. These results suggest that xoconostle is a rich source of antioxidant compounds such as phenolic compounds and betacyanins.     

Antioxidant tannins from Rosaceae plant roots

Polyphenols were analyzed by HPLC after thioacidolysis of proanthocyanidins polymers and acid hydrolysis of phenolic acid esters. The predominant constitutive units of the procyanidins of Aruncus Silvester and Potentilla alba roots were (−)epicatechin, and Geum rivale and Waldsteinia geoides roots (+)catechin. The highest proanthocyanidin concentrations were found in Potentilla alba roots (close to 80 g/kg) and W. geoides (64 g/kg). Ellagic acid was present at high concentration in G. rivale (2.68 g/kg) and W. geoides (2.75 g/kg) in dried roots. The antioxidant activity, measured by the DPPH method, ranged from 0.72 (Filipendula vulgaris) to 4.40 (W. geoides) mM trolox equivalents/kg dried roots and, measured by the ABTS method, from 1.50 to 6.60 mM trolox equivalents per kg of dried roots.     

Phytochemical constituents and antioxidant capacity of different pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars

Six pecan cultivars were analyzed for their antioxidant capacity (AC), total phenolics (TP), condensed tannin (CT), HPLC phenolic profile, tocopherol and fatty acid composition. Kernels which included the outer brown testa or pellicle, and shells which is the hard cover that surrounds the kernel, were evaluated for each cultivar. Strong correlations were found in kernels between AC and TP for both DPPH (r² = 0.98) and AC_ORAC (r² = 0.75) antioxidant assays. AC_ORAC values ranged from 372 to 817 μmol trolox equivalents/g defatted kernel, corresponding to Desirable and Kanza cultivars, respectively. CT ranged from 23 to 47 mg catechin equivalents/g defatted kernel and TP from 62 to 106 mg of chlorogenic acid equivalents/g defatted kernel. After a consecutive basic-acid hydrolysis, gallic acid, ellagic acid, catechin and epicatechin were identified by HPLC. The TP, AC and CT were 6, 4.5 and 18 times higher, respectively, for shells compared to kernels. The presence of phenolic compounds with high antioxidant capacity in kernels and shells indicates pecans can be considered an important dietary source of antioxidants.     

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.     

Composition and antioxidant activity of raisin extracts obtained from various solvents

Experiments were conducted to determine if the contents of phenolics and browning reaction products and antioxidant activity of raisin extracts were closely dependent on the extraction solvent. Enhanced extraction yields were obtained from solvent containing higher water concentrations. However, total phenolic content (TPC) was highest for extracts obtained from solvent to water ratios of 60:40 (v/v), whereby the extract obtained from ethanol:water (60:40, v/v) had the highest TPC of 375 mg gallic acid equivalents (GAE)/100 g extract. HMF content was highest in extracts obtained from 60% solvent, regardless of solvent type. The extract obtained from 60% methanol had the highest HMF content at 199 μg/g extract. Although the 60% solvents provided extract with high antioxidant components, the antioxidant activity of raisin extracts obtained from 80:20 (v/v) solvent/water was significantly higher than other raisin extracts obtained from different solvent concentrations. Phenolic acids, HMF, and low-molecular-weight flavonoids were responsible for the antioxidant activity, but not the high-molecular-weight flavonoids.     

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.     

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

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

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.