Neuronal cell protective and antioxidant effects of phenolics obtained from Zanthoxylum piperitum leaf using in vitro model system

In order to obtain basic data for the utilisation of Zanthoxylum piperitum leaf as a functional substance in the food industry, the antioxidative and neuronal cell protective effects of silica-gel open column chromatographic fractions, obtained from Z. piperitum leaf, were examined. ABTS and FRAP assays indicated that the ZP4 fraction (eluted with methanol/chloroform, 1:4, v/v) of Z. piperitum leaf was a more potent radical-scavenger and reducing agent than the other five fractions. The ZP4 fraction also presented protective effects against H₂O₂-induced neurotoxicity in a dose-dependent manner. Therefore, our study verified that the ZP4 fraction has strong antioxidative and neuronal protective effects which are correlated with its high level of phenolics, particularly quercitrin, afzelin, and hyperoside. These phenolics of Z. piperitum leaf can be utilised as effective and safe functional food substances, i.e., natural antioxidants, and may reduce the risk of neurodegenerative disorders.     

Antioxidant activity and phenolic content of phenolic rich fractions obtained from black cumin (Nigella sativa) seedcake

The antioxidant activities of crude methanolic extract (CME) and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black cumin seedcake were investigated. DPPH radical scavenging activity, β-carotene–linoleate bleaching, and inhibition of corn oil oxidation were used to evaluate the antioxidant capacity. The total phenolics were found to be 78.8, 27.8, 32.1 and 12.1 mg gallic acid equivalents (GAE)/g in EAF, CME, WF and HF, respectively. The CME and EAF exhibited the highest DPPH followed by WF and HF. The extract/fractions showed high effect on reducing the oxidation of β-carotene. The effect of extract/fractions on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The oil peroxide and anisidine values were generally lower with addition of PRFs in comparison to a control. The predominant phenolic compounds identified by HPLC–DAD in CME and WF of black cumin seedcake were hydroxybenzoic, syringic and p-cumaric acids.     

Evaluation of the antioxidant activity of Ruellia tuberosa

The antioxidant activity of Ruellia tuberosa L. (Acanthaceae) was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay and the hydrogen peroxide-induced luminol chemiluminescence assay. The methanolic extract (ME) and its four fractions of water (WtF), ethyl acetate (EaF), chloroform (CfF), and n-hexane (HxF) were prepared and then subjected to antioxidant evaluation. The results of both methods revealed that R. tuberosa possesses potent antioxidant activity. The antioxidant activities of the different fractions tested decreased in the order of EaF > CfF > ME > WtF > HxF according to the hydrogen peroxide-induced luminol chemiluminescence assay, and results were the same with the exception of the rank order of HxF and WtF according to the DPPH free radical-scavenging assay. The results provide useful information on the pharmacological activities associated with free radicals of this traditional folk remedy.     

Antioxidant and nitric oxide inhibition activities of selected Malay traditional vegetables

The antioxidant properties and the effect on nitric oxide (NO) production, in lipopolysaccharide-activated macrophages, of 12 traditional vegetables of the Malaysian Malays, including Pithecellobium confertum, Averrhoa bilimbi, Portulaca oleracea, Solanum torvum, Solanum nigrum, Persicaria tenella, Cosmos caudatus, Pandanus amaryllifolius, Curcuma mangga, Ocimum basilicum, Anacardium occidentale and Melicope ptelefolia, were investigated. Antioxidant activity of the methanolic extracts was evaluated by measuring the production of hydroperoxide and its degradation product (malonaldehyde) resulting from linoleic acid oxidation using ferric thiocyanate and thiobarbituric acid methods, respectively. Radical-scavenging potential was also evaluated using the 1,1-diphenyl-2-picrylhydrazyl radical. Griess assay was used to assess NO-inhibitory activity of the extracts. All species, except P. confertum, S. torvum and P. amaryllifolius, showed antioxidant activity. M. ptelefolia, P. oleracea and P. tenella showed in vitro activity on NO inhibition in murine peritoneal macrophages, whereas other plants showed no significant activity.     

Antioxidant activities of phenolic rich fractions (PRFs) obtained from black mahlab (Monechma ciliatum) and white mahlab (Prunus mahaleb) seedcakes

The antioxidant activities of phenolic rich fractions (PRFs) from crude methanolic extract (CME), and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black mahlab (Monechma ciliatum) and white mahlab (Prunus mahaleb) seedcakes were investigated. The total phenolic compounds were found to be higher in white mahlab than black mahlab seedcakes. The antioxidant activity determined by the DPPH method revealed that black mahlab PRFs had the highest antioxidant activity, compared to white mahlab fractions. The presence of antioxidants in the two mahlab PRFs reduced the oxidation of β-carotene by hydroperoxides from these extracts/fractions. The effect of the two mahlab PRFs on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The CME performed better antioxidant activity in inhibiting the formation of both primary and secondary oxidation products. The qualitative and quantitative characterisation of phenolic compounds was carried out by HPLC/DAD.     

Antioxidant activity of some phenolic constituents from green pepper (Piper nigrum L.) and fresh nutmeg mace (Myristica fragrans)

Antioxidant potential of phenolic compounds from green pepper (Piper nigrum L.) and lignans from fresh mace (Myristica fragrans) were evaluated for their ability to scavenge 1,1′-diphenyl-2-picrylhydrazyl (DPPH) radical, inhibit lipid peroxidation and protect plasmid DNA damage upon exposure to gamma radiation. EC₅₀ values of the major phenolic compounds of green pepper namely, 3,4-dihydroxyphenyl ethanol glucoside, 3,4-dihydroxy-6-(N-ethylamino) benzamide and phenolic acid glycosides were found to be 0.076, 0.27 and 0.12 mg/ml, respectively, suggesting a high radical scavenging activity of these phenolics. These results were further confirmed with cyclic voltammetry. Acetone extract of nutmeg mace and its subsequent TLC isolated fractions constituted mainly of lignans as revealed by GC–MS analysis. The major compounds were tentatively identified from their mass spectral fragmentation pattern. DPPH radical scavenging capacity of the acetone extract as well as its fractions was comparatively lower than that of green pepper phenolics. In contrast, these fractions had a greater ability to inhibit lipid oxidation than phenolics from pepper as revealed by β-carotene–linoleic acid assay. A DNA protecting role of these compounds even at doses as high as 5 kGy further suggested the potential use of green pepper and fresh nutmeg mace and their extracts as a nutraceutical in preventing oxidative damage to cells.     

Antioxidant activity of cherry laurel fruit (Laurocerasus officinalis Roem.) and its concentrated juice

Cherry laurel fruit and its concentrated juice (pekmez) were examined for their antioxidant activities using different free-radical scavenging activity tests [hydrogen peroxide, superoxide radical, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical], together with reducing power and inhibition of oxidation of human low-density lipoprotein cholesterol. On a fresh weight basis, pekmez exhibited a significantly (P < 0.01) higher antioxidant activity than that of cherry laurel fruit in most cases. However, on a dry weight basis hydrogen peroxide and DPPH radical scavenging activities, and reducing power were significantly higher (P < 0.01) in cherry laurel fruit than in its pekmez, with some exceptions, thus indicating possible destruction of antioxidative compounds during pekmez production. This was also partly due to the moisture content of these two samples. On the basis of the results presented, it is suggested that the intake of cherry laurel fruit and pekmez rich in phenolics would have beneficial effects in improving amelioration of degenerative diseases caused by oxidative stress. Therefore, both cherry laurel fruit and pekmez might be considered as functional food ingredients and nutraceuticals.     

Extraction and Characterization of the Pectic Substances from Japanese Pepper (Zanthoxylum piperitum DC.) Fruit

Pectic substances were extracted from Japanese pepper (Zanthoxylum piperitum DC) fruit with hot diluted HCl (90°C, pH 2.2). The yield of the pectic substances was 8.4% (w/w) based on dry material. The contents of total carbohydrate, anhydrogalacturonic acid, ash, protein, and moisture of the pectic substances were 84.1, 66.9, 3.6, 2.7, and 9.6% (w/w), respectively. The degree of methylation was estimated to be 80.3% by using alcohol oxidase test. This indicated that the pectic substances are high methoxyl pectins and have an ability to form sugar gels. The jelly grade of the pectic substances was estimated to be 130 (USA-SAG) at standard condition. Viscosity-average molecular weight was relatively low (30.3 kDa). When the molecular weight distribution was checked by gel-permeation chromatography on Sepharose CL-4B, the elution profile of the pectic substances was highly polydispersed extending from 40 kDa (or less) to 2000 kDa.     

Antioxidant constituents in some sweet pepper (Capsicum annuum L.) genotypes during maturity

Changes in total phenolics, antioxidant activity (AOX), carotenoids, capsaicin and ascorbic acid were monitored during three maturity stages in 10 genotypes of sweet pepper. In an attempt to explain the variations during maturity stages (green, intermediate and red/yellow), the data was expressed both on fresh and dry weight basis. All the antioxidant constituents (phenolics, ascorbic acid and carotenoids) and AOX, when expressed on fresh weight basis in general, showed an overall increasing trend during maturity in all the genotypes studied. On dry weight basis, phenolic content declined in majority of the genotypes during maturity to red stage. This decline was significant (P<0.05) in Parker, Torkel, HA-1038 and Flamingo. Genotype Flamingo and Golden Summer had the highest phenolic content of 852.0 mg 100 g⁻¹ and 720.5 mg 100 g⁻¹, at their final red and yellow maturity stages, respectively. With maturation, most of the cultivars showed a declining trend with regard to capsaicin content while total carotenoids and β-carotene content increased significantly. Anupam was a promising genotype in terms of both total carotenoids and β-carotene content. Ascorbic acid content declined progressively with advancing maturity. Genotype HA-1038 had the maximum content (3030 mg 100 g⁻¹ dwb) at the green stage. AOX in general, increased with maturity and registered a 1.30-1.95fold increase from green to red stage.The study proposes the nutritional significance of consuming sweet peppers at the red maturity stage because of enhanced functional properties. Overall genotype Flamingo and Anupam represent superior genotypes for both nutrition and germplasm improvement.     

Antioxidant activity of minor components of tree nut oils

The antioxidative components of tree nut oils were extracted using a solvent stripping process. Tree nut oil extracts contained phospholipids, sphingolipids, sterols and tocopherols. The chloroform/methanol extracted oils had higher amounts of phenolic compounds than their hexane extracted counterparts. The antioxidant activity of tree nut oil minor component extracts were assessed using the 2,2-azino-bis (3-ethylbenzthiazoline sulphonate) (ABTS) radical scavenging activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, β-carotene bleaching test, oxygen radical absorbance capacity (ORAC) and photochemiluminescence inhibition assays. Results of these studies demonstrated that extracts of chloroform/methanol extracted oils possessed higher antioxidant activities than extracts of their hexane extracted counterparts. Meanwhile the extract of chloroform/methanol extracted pecan oil possessed the highest antioxidant activity.     

Antioxidant properties of papain hydrolysates of wheat gluten in different oxidation systems

Enzymatic hydrolysis was used for preparing hydrolysates from wheat gluten which is by-product during production of wheat starch. The enzyme used for the hydrolysis was papain. The hydrolysate was separated based on the molecular weight of the peptides by membrane ultrafiltration (UF) with a molecular weight cut-off of 5 kDa into permeate (P) and retentate (5-K) fractions. The antioxidative activities of the hydrolysate and its UF fractions were investigated by using the TBA method and scavenging effect of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The three fractions showed strong antioxidative activities in the linoleic acid oxidation system, and exhibited DPPH radical scavenging activity. The antioxidative activity of the P fraction was almost the same as that of vitamin E at pH 7.0. The molecular weight distribution of the P fraction was concentrated in 4.2 kDa (86.5%) after gel permeation chromatography fractionation using an HPLC system.The P and 5-K fractions had higher surface hydrophobicities (H₀) at pH7.0 compared with the hydrolysate. The resulting UF fractions were superior to the hydrolysate in terms of antioxidative activities.     

Antioxidant potency of cumin varieties—cumin, black cumin and bitter cumin—on antioxidant systems

Cumin is one of the commonly used spices in food preparations. It is also used in traditional medicine as a stimulant, a carminative and an astringent. In this study, we characterized the antioxidant activity of three commercially available cumin varieties, viz., cumin (Cuminum cyminum), black cumin (Nigella sativa) and bitter cumin (C. nigrum). The antioxidant capacity of cumin varieties was tested on Fe²⁺ ascorbate induced rat liver microsomal lipid peroxidation, soybean lipoxygenase dependent lipid peroxidation and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging methods. The total phenolic content of methanolic extracts of cumin varieties ranged from 4.1 to 53.6 mg g^–1 dry weight. Methanolic extracts of all the three varieties of cumin showed higher antioxidant activity compared with that of the aqueous extract. Among the cumin varieties, bitter cumin showed the highest antioxidant activity followed by cumin and black cumin in different antioxidant systems. IC₅₀ values of the methanolic extract of bitter cumin were found to be 0.32, 0.1 and 0.07 mg dry weight of cumin seeds on the lipoxygenase dependent lipid peroxidation system, the DPPH radical scavenging system and the rat liver microsomal lipid peroxidation system, respectively. The data also show that cumin is a potent antioxidant capable of scavenging hydroxy, peroxy and DPPH free radicals and thus inhibits radical-mediated lipid peroxidation. The high antioxidant activity of bitter cumin can be correlated to the high phenolic content among the three cumin varieties. Thus, bitter cumin with a high phenolic content and good antioxidant activity can be supplemented for both nutritional purposes and preservation of foods.     

Major chemotypes and antioxidative activity of the leaf essential oils of Cinnamomum osmophloeum Kaneh. from a clonal orchard

Essential oils of 92 cutting clones from a clonal orchard of Cinnamomum osmophloeum Kaneh. were obtained by hydrodistillation and characterised by gas chromatography–mass spectrometry. Our results showed that the yields of essential oils ranged between 0.09% and 2.65% (vol/fresh wt). The constituents of essential oils varied among samples. The major chemotypes classified in the individual cutting clones were cinnamaldehyde (50 plants, representing 50–95% of the total volatiles), linalool (1 plant, 73.3%), β-cubebene (2 plants, 59.4% and 78.7%), and cinnamyl acetate (1 plant, 61.8%). The antioxidant activities of the four chemotypes were determined using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The antioxidant activities of the essential oil decreased in the order of cinnamyl acetate > cinnamaldehyde > β-cubebene > linalool. Indigenous cinnamon oil extract showed a good free radical-scavenging capacity at all concentrations studied, except at 2 μg/ml. The scavenging activity increased with increasing concentration of the extract. The capability of the four essential oil chemotypes to reduce the stable radical, DPPH, to DPPH-H was assayed by a decrease in the IC₅₀ values of 10.4 (cinnamyl acetate type) to 29.7 (linalool type) μg/ml. These results suggest that the leaf essential oil of C. osmophloeum possesses chemical compounds with antioxidant activity which can be used as natural preservatives in food and/or by the pharmaceutical industry. Trees in this plantation which can be used for further propagation for the production of chemotypes of interest were identified.     

Antioxidant and Xanthine Oxidase Inhibitory Activities of Persicaria hydropiper

Five different polarity fractions of methanolic extract from Persicaria hydropiper, which are consumed as vegetables, were evaluated for its total phenolic content, and antioxidant activities by 1,1-diphenyl-2-picrylhydrazyl radical scavenging, ferric thiocyanate, and xanthine oxidase inhibition assays. Particularly, higher phenolic content was exhibited by butanol and ethyl acetate fractions with the values of 224.38 and 68.95 mg GAE/100 g dry extract, respectively. Both butanol and ethyl acetate fractions exhibited higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity with IC₅₀ values of 28.61 and 25.55 μg/ml. Meanwhile, both fractions also were shown to inhibit xanthine oxidase activity compared to other fractions with IC₅₀ values of 28.72 and 165.25 μg/ml. As for the ferric thiocyanate method, all the fractions except hexane fraction showed similar activity against lipid peroxidation and were comparable to butylated hydroxyl toluene, with percentage of inhibition from 95 to 98%.     

Antioxidant activities of red pepper (Capsicum annuum) pericarp and seed extracts

In this study, we examined the antioxidant activities of red pepper (Capsicum annuum, L.) pericarp and red pepper seed extracts. The extracts were evaluated by various antioxidant assays, including 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, superoxide anion radical scavenging, hydroxyl radical scavenging, [2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid)] (ABTS) radical scavenging, ferrous chelating activity, superoxide dismutase (SOD) activity and reducing power, along with the determination of total phenolic and flavonoid contents. All the extracts showed strong antioxidant activity by the testing methods. The red pepper pericarp extract exhibited strong ferrous chelating activity and high scavenging activity against free radicals, including both the hydroxyl and DPPH radicals, but it exhibited weaker scavenging activity for the superoxide anion radical and for SOD. In contrast, the red pepper seed extract exhibited strong SOD activity and high scavenging activity against the superoxide anion radical, but showed weaker ferrous chelating activity, hydroxyl radical scavenging, and DPPH radical scavenging. We observed that the reducing power level and ABTS radical scavenging activity of the red pepper seed were higher than those of the red pepper pericarp at the highest tested concentration. Most of the test results for the red pepper seed and red pepper pericarp extracts increased markedly with increasing concentration; however, the metal chelating, SOD and ABTS radical scavenging activities did not increase with the concentration. Highest total phenolic and flavonoid contents were obtained from the red pepper pericarp extracts. Overall, the red pepper seed and red pepper pericarp extracts were highly effective for the antioxidant properties assayed, with the exceptions of ferrous chelating activity, hydroxyl radical scavenging and SOD activity.     

Antioxidant activities of Sechium edule (Jacq.) Swartz extracts

The antioxidant activities (AA) of Sechium edule extracts were tested by three established in vitro methods, namely reducing power, β-carotene linoleate model and 1,1- diphenyl-2 picrylhydrazyl (DPPH) radical-scavenging. Leaf ethanolic extracts and leaf and seed water extracts showed strong inhibitory activity by β-carotene bleaching (AA values of 90%). Furthermore, these extracts exerted hydrogen-donating ability in the presence of DDPH stable radical (IC₅₀ 2 μg/ml). These extracts also showed strong reducing power by the potassium ferricyanide reduction method. Leaf and seed extracts may be exploited as biopreservatives in food applications as well as for health supplements or functional food, to aleviate oxidative stress.     

Antioxidant activity and phenolic composition of sumac (Rhus coriaria L.) extracts

Antioxidant activity and phenolic compounds of sumac extracts were investigated. Sumac was extracted in methanol and subjected to solvent–solvent partitioning to yield two fractions as ethyl acetate and aqueous. Methanol extract was further fractioned over Sephadex LH-20 column. Antioxidant activity of extracts and fractions were screened using ferric thiocyanate and DPPH radical scavenging methods. Phenolic composition of active fraction(s) was determined by HPLC–MS systems. Those fractions which exhibited strong antioxidant activity were rich in anthocyanins and hydrolysable tannins. While gallic acid was the main phenolic acid in the extracts, anthocyanin fraction contained cyanidin, peonidin, pelargonidin, petunidin, and delphinidin glucosides and coumarates. Pentagalloyl glucose was abundant in the hydrolysable tannin fraction. Effective scavenging concentration (EC₅₀) on DPPH radical was 0.70 μg/mL both in ethyl acetate and tannin fractions, and 5.33 μg/mL in anthocyanin rich fraction. Same extracts and fractions showed moderate lipid peroxidation inhibition effect compared with the synthetic antioxidants. The findings demonstrate that sumac can be used as a natural antioxidant.