Effect of preliminary processing, method of drying and storage temperature on the level of antioxidants in kale (Brassica oleracea L. var. acephala) leaves

The levels of vitamin C, polyphenol constituents and Trolox equivalent antioxidant activity (TEAC) were analyzed in raw kale leaves, blanched leaves and dried leaves obtained using air and freeze-drying methods. 100 g of raw kale leaves contained 683 mg vitamin C and 2236 mg polyphenols (identified using the HPLC method); the level of antioxidative activity was 71 μM Trolox/1 g dry matter. Compared with the raw material, blanching before drying brought about significant decreases of 15% in vitamin C, 32% in polyphenols and13% in TEAC. After 12-month storage, air-dried material retained 30-37% polyphenols; 43-57% vitamin C; and 41-50% of the initial TEAC level; the corresponding values for freeze-dried material were 40-47%; 50-65% and 54-66% depending on the type of sample. Freeze-dried kale leaves contained higher levels of antioxidants than air-dried material: polyphenols, vitamin C and TEAC were respectively 36%, 15%and 33% higher.     

Level of Vitamin C,Polyphenols, and Antioxidant and Enzymatic Activity in Three Varieties of Kale (Brassica Oleracea L. Var. Acephala) at Different Stages of Maturity

The aim of this present study was to determine the level of vitamin C, L-ascorbic acid, polyphenols, antioxidant activity, peroxidase, polyphenol oxidase, and catalase in the leaves of three varieties of kale at different stages of maturity. Average values per 100 g of fresh matter were 102 mg of vitamin C (of which L-ascorbic acid constituted 97%) and 359 mg polyphenols; antioxidant activity was measured at 48.9% RSA (17.6 μM Trolox/g kale). Redbor₁ c.v. variety contained the highest levels of the analyzed constituents. Compared with the first stage of maturity, plants at the second stage showed increases of 6% in vitamin C; 28% in polyphenols; and 12% in antioxidant activity, whereas plants at the third stage showed 5, 48, and 22% increased values, respectively. Average POD activity was 7.58 ΔA/min/g, PPO 1.64 ΔA/min/g, and CAT 7.93 mg H₂O₂/min/g. PPO activity increased with the age of the plant. No consistent correlation was found between the stage of growth and the other enzymes.     

The amino acid composition of kale (Brassica oleracea L. var. acephala), fresh and after culinary and technological processing

The aim of the investigation was to evaluate the level of amino acids and the quality of protein in fresh and cooked leaves of kale and in two types of frozen product prepared for consumption after 12-months storage at −20 °C. Kale blanched before freezing (the traditional method) was cooked after refrigerated storage, while that cooked before freezing (the modified method) was defrosted and heated in a microwave oven. Both fresh and processed leaves of kale were a good source of amino acids. In all the samples, glutamic acid, proline and aspartic acid were the dominant, while lysine and leucine were the limiting amino acids. Cooked leaves contained 78% of the total amino acid content found in fresh leaves, while the traditional and modified frozen products contained 76% and 78%, respectively. The proportion of essential amino acids in total amino acids was 44% and 43%, respectively for fresh and cooked leaves and 46% for the frozen products. The lowest EAA index was found for the traditional frozen product (99); it was higher for the remaining samples, which were broadly similar to each other (105–106).     

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.     

Changes in vitamin C content and antioxidant capacity of raw and germinated cowpea (Vigna sinensis var. carilla) seeds induced by high pressure treatment

The effect of high pressure treatment on the vitamin C content and antioxidant capacity of raw and germinated cowpea seeds (Vigna sinensis var. carilla) at 300, 400 and 500 MPa for 15 min at room temperature has been investigated. A considerable amount of vitamin C was detected in germinated cowpeas, but the vitamin was not detected in raw seeds. An increase on the antioxidant capacity (TEAC) in cowpea sprouts was also observed (58–67%). High pressure treatment (HP) slightly modified vitamin C content and TEAC and, after pressurization at 500 MPa, the decrease was more pronounced, although the germinated seeds submitted to this HP treatment still provided a high amount of vitamin C (15–17 mg/100 g d.m.) and the antioxidant capacity was 26–59% higher than that of the raw cowpeas. The HP process can provide minimally processed fresh-like sprouts of high quality.     

Determination of total phenolic content and antioxidant capacity of onion (Allium cepa) and shallot (Allium oschaninii) using infrared spectroscopy

Total phenolic content (TPC) and total antioxidant capacity (TAC) of four onion varieties (red, white, yellow and sweet) and shallot from selected locations (Washington, Idaho, Oregon, Texas and Georgia) were determined using Fourier transform infrared (FT-IR) spectroscopy (4000–400 cm⁻¹). The Folin–Ciocalteu (F–C) assay was used to quantify TPC and three assays were used to determine TAC, including 2,2-diphenyl-picrylhydrazyl (DPPH) assay, Trolox equivalent antioxidant capacity (TEAC) assay and ferric reducing antioxidant power (FRAP) assay. Partial least squares regression (PLSR) with cross-validation (leave-one-out) was conducted on onion and shallot extracts (n = 200) and their corresponding F–C, DPPH, TEAC and FRAP values were employed to obtain four independent calibration models for predicting TPC and TAC for the extracts. Spectra from an extra 19 independent extracts were used as an external validation set for prediction. A correlation of r > 0.95 was obtained between FT-IR predicted and reference values (by F–C, DPPH, TEAC and FRAP assay) with standard errors of calibration (SEC) and standard errors of cross-validation (SECV) less than 2.85, 0.35 and 0.45 μmol Trolox/g FW of extracts for TEAC, FRAP and DPPH assay, respectively; and 0.36 mg gallic acid/g FW of extracts for the F–C assay. In addition, cluster analysis (principal component analysis (PCA)) and discriminant function analysis (DFA) could differentiate varieties of onions and shallot based upon infrared spectral features. Loading plots for the various chemometrics models indicated that hydroxyl and phenolic functional groups were most closely correlated with antioxidant capacity. The use of mid-infrared spectroscopy to predict the total antioxidant capacity of vegetables provides a rapid and precise alternative to traditional wet chemistry analysis.     

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%.     

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.     

The optimisation of extraction of antioxidants from potato peel by pressurised liquids

Response Surface Methodology was used to optimise the solid–liquid extraction and Pressurised Liquid Extraction of polyphenols from industrially generated potato peel. Efficiency of extraction was optimised by measuring antioxidant activity, phenol content and the level of caffeic acid. Conditions for optimal antioxidant activity as measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were 75% ethanol, 80 °C and 22 min with solid–liquid extraction, resulting in an optimum activity of 352 mg Trolox Equivalents/100 g DW potato peel. In comparison, the use of Pressurised Liquid Extraction resulted in an optimum activity of 339 mg Trolox Equivalents/100 g DW potato peel at 70% ethanol and 125 °C. Therefore the use of Pressurised Liquid Extraction did not enhance extraction in comparison to solid–liquid extracts, but using aqueous ethanol as extraction solvent recovered a higher level of polyphenols than when using 100% methanol.     

Phenolic compounds content and antioxidant activity in pomace from selected red grapes (Vitis vinifera L. and Vitis labrusca L.) widely produced in Brazil

The phenolic compounds content and antioxidant activity of pomace from the vinification of grape varieties widely produced in Brazil (Cabernet Sauvignon, Merlot, Bordeaux and Isabel) were investigated with a view to their exploitation as a potential source of natural antioxidants. Cabernet Sauvignon grape pomace was found to have the highest content of total phenolic compounds (74.75 mg gallic acid equivalent (GAE)/g), the highest antioxidant activity (determined using the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging methods; 485.42 and 505.52 μMol Trolox equivalent antioxidant capacity (TEAC)/g, respectively), and the highest reducing power (determined using the FRAP method; 249.46 μMol TEAC/g). The Bordeaux variety showed the highest oxidation inhibition power (41.13%), determined using the β-carotene/linoleic acid method and the highest content of total anthocyanins (HPLC; 29.17 mg/g). Catechin was the most abundant non-anthocyanic compound identified in the grape pomace (150.16 mg/100 g) for all varieties. In this study, pomaces of the red wine vinification of Cabernet Sauvignon and Bordeaux varieties showed the highest potential as a source of antioxidant compounds and natural colourants, respectively.     

Effects of binary solvent extraction system,extraction time and extraction temperature on phenolic antioxidants and antioxidant capacity from mengkudu (Morinda citrifolia)

An investigation into the effects of ethanol concentration (0–100%, v/v), extraction time (20–120 min) and extraction temperature (25–65 °C) on the extraction of phenolic antioxidants from mengkudu (Morinda citrifolia) was performed using a single-factor experiment. Total phenolic content (TPC) and total flavonoid content (TFC) assays were used for determination of phenolic compounds. Antioxidant capacity was evaluated by measuring the scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radicals. Experimental results showed that extraction conditions had significant effect on extraction of phenolic compounds and antioxidant capacities. The optimised conditions were 40% ethanol for 80 min at 65 °C, with values of 919.95 mg GAE/100 g DW for TPC, 472.73 mg CE/100 g DW for TFC, 791.71 μmol TEAC/100 g DW for ABTS and 1928.5 μmol TEAC/100 g DW for DPPH. TPC was significantly correlated with DPPH under the effects of ethanol concentration (r = 0.932) and extraction time (r = −0.938).     

Mate (Ilex paraguariensis St. Hilaire) saponins induce caspase-3-dependent apoptosis in human colon cancer cells in vitro

Saponins are naturally occurring metabolites associated with several health benefits. The objective was to quantify and purify saponins from mate dry leaves, and to assess their anti inflammatory and apoptotic mechanisms in human colon cancer cells in vitro. Matesaponins were extracted with methanol from dry leaves, partially purified and quantified. Leaves contained 10–15 mg/g dry weight total saponins, predominantly matesaponins 1 and 2. HPLC and LC/ESI-MS-MS identified saponins in six preparative chromatographic fractions (A, B, C, D, E, and F). Major matesaponins were identified as 1 [M–H]⁻ = 911 and 2 [M–H]⁻ = 1057, with trace amounts of 3 [M–H]⁻ = 1073, 4 [M–H]⁻ = 1219, and 5 [M–H]⁻ = 1383. Fractions D, E, and F significantly inhibited iNOS (IC₃₅ = 36.3, 29.5, 43.7 μM), PGE₂ (IC₃₅ = 23.1, 22.3, 11.7 μM) and COX-2 (IC₃₅ = 45.7, 32.4, 17.0 μM). Fraction F reduced nuclear translocation of nuclear factor-κB subunits p50 (49.8%) and p65 (49.0%) and induced apoptosis through suppression of Bcl-2 and increased Bax protein expressions and activated caspase-3 activity. Saponins in leaves of mate prevent inflammation and colon cancer in vitro.     

Effect of hydrothermal treatment on the antioxidant properties of broccoli (Brassica oleracea var. botrytis italica) florets

In the extracts of fresh raw and frozen broccoli, caffeic, ferulic, sinapinic acids and kaempferol were identified. Boiling reduced the amounts of caffeic acid and kaempferol in both samples. The concentration of polyphenols was 2.69 mg/g fresh mass and 0.96 mg/fresh mass in fresh raw broccoli and frozen raw broccoli, respectively. Boiling significantly decreased the amounts of phenolic compounds in fresh broccoli (1.58 mg/g of fresh mass). In the case of frozen broccoli, boiling increased the concentration of polyphenols by 38%. Fresh broccoli extract neutralized free radicals by 19.87%. Boiling significantly reduced its antiradical activity (to 15.06%). Samples of frozen broccoli had a 27.06% antiradical ability. Boiling did not change the antiradical activity in frozen broccoli case. Hydrothermal processing significantly influenced on the ability of the extracts to inhibit the decolorization of β-carotene emulsion. The extract of fresh broccoli had a higher activity when uncooked. Boiling seemed to increase this activity in the case of frozen broccoli samples. The results of the studies on the ability of broccoli extracts to inhibit linoleic acid autooxidation were ambiguous and depended on the method applied. No correlation was found between the content of phenolic compounds and the antioxidant activity of the extracts, regardless of the experimental variant and technique used.     

Comparison of nutritional and nutraceutical properties in cultivated fruits of Fragaria vesca L. produced in Italy

Individual sugars, organic acids, total polyphenols, vitamin C and antiradical activity (as measured by DPPH method) were quantified in cultivated Fragaria vesca berries, comparing different varieties (Regina delle Valli, Alpine, Sara and Valitutto) and different environments with regard to altitude. Cultivar effect mainly influenced the concentration of total polyphenols and antiradical activity which are strongly correlated (R² = 0.91; P = 0.001); conversely, altitude seemed to exert an influence in sugar and organic acid composition. The comparison of the general quality of the most diffused cultivar of F. vesca (Regina delle Valli and Alpine) evidenced that both cultivars have the same nutritional properties, whereas Regina delle Valli is better than Alpine from the point of view of total polyphenolic content (716 vs 471 mg catechin/100 g fresh weight) and radical scavenging activity (301 vs 219 ml DPPH solution/100 g fresh weight), thus resulting more attractive from the health protecting attributes point of view. F. vesca berries showed also a concentration of sugars, citric acid, malic acid and total polyphenols much higher than those reported in literature for Fragaria x ananassa.     

The antioxidant activity of selected cruciferous vegetables subjected to aquathermal processing

Kale (Brassica oleracea var. Acephala), broccoli (Brassica oleracea var. botrytis italica), Brussels sprouts (Brassica oleracea L. var. gemmifera) and green and white cauliflower (Brassica oleracea var. botrytis) were used to determine their contents of antioxidising agents: vitamin C, carotenoids and polyphenols. The examined vegetables were found to contain between 40.6 and 107 mg/100 g FW of vitamin C, from 0.04 to 2.7 mg/100 g FW of carotenoids, and from 144 to 773 mg/100 g FW of polyphenols. Cauliflower was found to contain the smallest amount of these compounds and kale the largest. The antioxidant activity of the vegetables was determined on the basis of their ability to extinguish the ABTS free radical. The aquathermal processes to which the vegetables were subsequently subjected reduced their antioxidant activity, mainly due to escape of vitamin C and polyphenols into the water environment. These losses were largest in the case of leafy or highly fragmented vegetables.     

Composition and availability of soluble and insoluble oxalates in raw and cooked taro (Colocasia esculenta var. Schott) leaves

Taro (Colocasia esculenta var. Schott) is a major staple food crop in parts of Asia and the Pacific Islands and is grown as a minor crop in New Zealand. Soluble, insoluble and total oxalate content of young and older leaves were determined by HPLC following hot water (80 °C) and hot (80 °C) acid (0.2 mol/L HCL) extractions. Young taro leaves contained 589 ± 35.8 mg total oxalates/100 g fresh weight (FW) while older taro leaves contained (443 ± 15.0 mg total oxalates/100 g FW). Soluble oxalates were 74% of the total oxalate content of the young and old leaves.     

Total and individual carotenoids and phenolic acids content in fresh,refrigerated and processed spinach (Spinacia oleracea L.)

The carotenoid and phenolic acid contents in fresh, stored and processed (blanched, frozen and boiled) spinach were comparatively determined by spectrophotometric and HPLC analyses. The major carotenoids identified after HPLC analysis in saponified samples were lutein (37–53 μg/kg), β-carotene (18–31 μg/kg), violaxanthin (9–23 μg/kg) and neoxanthin (10–22 μg/kg). These carotenoids were all affected by storage and/or heating. The content of carotenoids was best preserved after storage for one day at 4 °C.     

Effect of ionising radiation on polyphenolic content and antioxidant potential of parathion-treated sage (Salvia officinalis) leaves

The γ-irradiation effects on polyphenolic content and antioxidant capacity of parathion-pretreated leaves of Salvia officinalis plant were investigated. The analysis of phenolic extracts of sage without parathion showed that irradiation decreased polyphenolic content significantly (p < 0.05) by 30% and 45% at 2 and 4 kGy, respectively, compared to non-irradiated samples. The same trend was observed for the Trolox equivalent antioxidant capacity (TEAC), as assessed by the anionic DPPH and cationic ABTS radical-scavenging assays. The antioxidant potential decreased significantly (p < 0.01) at 2 and 4 kGy, by 11–20% and 40–44%, respectively. The results obtained with a pure chlorogenic acid solution confirmed the degradation of phenols; however, its TEAC was significantly (p < 0.01) increased following irradiation. Degradation products of parathion formed by irradiation seem to protect against a decline of antioxidant capacity and reduce polyphenolic loss. Ionising radiation was found to be useful in breaking down pesticide residues without inducing significant losses in polyphenols.     

A novel approach of LED light radiation improves the antioxidant activity of pea seedlings

Influence of light-emitting diode (LED) light on antioxidant activity of radiated pea seedlings was first studied using red (625–630 nm) and blue (465–470 nm) LED lights as light sources in an attempt to determine and compare the changes in chlorophyll and β-carotene contents, and Trolox equivalent antioxidant capacity (TEAC, μM). After radiation for 96 h, comparing to white light group, red light radiated seedlings displayed significant (p < 0.05) increases in stem length and leaf area, while blue light radiation significantly (p < 0.05) increased the stem length and seedling weight. Chlorophyll in leaves increased rapidly when seedlings were radiated by blue light but no significant (p > 0.05) difference was observed among light radiated seedlings after 96-h cultivation. β-Carotene content of LED radiated leaves was significantly (p < 0.05) higher in red light (54.47 ± 2.35 μg/g) group than in the others. TEAC value of ethanol and acetone extracts (50 mg/mL) of 240 pieces of red light radiated seedlings cultured for 96 h reached 106.48 and 81.68 μM, respectively, were higher than the other treatments. In conclusion, the contribution of red light to significant β-carotene expression and antioxidant activity for nutrition and health benefits and blue light to seedling weight and chlorophyll induction of radiated pea seedlings are emphasized.