Carotenoid composition and vitamin A activity of medicinally important green leafy vegetables

Carotenoid composition of green leafy vegetables (GLVs, n = 30) with medicinal value was analyzed by HPLC; vitamin A activity (as retinol equivalent, RE) of provitamin A carotenoids was calculated. Results show that among GLVs studied, the level of β-carotene (50–130 mg/100 g dry wt) was higher in nine GLVs than other carotenoids while lutein (50–187 mg/100 g dry wt) and zeaxanthin (1–5 mg/100 g dry wt) were higher in 12 GLVs than other xanthophylls. α-Carotene was detected only in nine GLVs, ranging from 1 to 37 mg/100 g dry wt. Interestingly, Chenopodium album, Commelina benghalensis and Solanum nigrum were found to contain higher levels of both lutein and β-carotene in the range of 84–187 and 50–115 mg/100 g dry wt, respectively. The values of retinol equivalents (RE) ranged from 641 to 19101 and were higher (>10,000) in six GLVs of the 30. The results demonstrate that GLVs studied contained higher levels of RE and lutein.     

Natural essential oils as reducing agents of peroxidase activity in leafy vegetables

The effectiveness of natural essential oils eucalyptus (Eucalyptus globulus), tea tree (Melaleuca alternifolia), melisa (Melissa officinalis), roomer (Rosmarinus officinalis), clove (Syzygium aromaticum) and lemon (Citrus limonum) to reduce peroxidase activity of organic leafy vegetables extracts was evaluated. Three oil concentrations at the minimum inhibitory concentration (MIC, 2×MIC and 4×MIC) of each natural essential oils were used. Crude vegetable extracts of Swiss chard, spinach, lettuce, butter lettuce and cabbage were the source of peroxidase activity. The effectiveness of the essential oils as natural antioxidants varied with the enzyme sources. At the MIC, clove, rosemary, lemon, melisa and tea tree had the high antioxidant properties being clove more effective than the other oils.     

Nitrate-N determination in leafy vegetables: Study of the effects of cooking and freezing

Nitrate upon reduction to nitrite can cause methaemoglobinaemia or act as precursor in the endogenous formation of carcinogenic nitrosamines. The leafy vegetables are the major vehicle for the entry of nitrate into the human system. The present study was conducted to establish a flow injection analysis (FIA) technique to investigate the nitrate-N contents of four commonly consumed fresh leafy vegetables (Chinese cabbage, celery, lettuce and English cabbage) from market in Fiji. Two extraction techniques (activated carbon and alkaline extraction) were assessed to extract nitrate-N and the activated carbon extraction was preferred over alkaline extraction and applied. The recoveries of spiked nitrate-N in vegetable matrices ranged from 90.40% to 112.80% in activated carbon extraction with an average of 100.62%. The effects of cooking (boiling, baking and frying) and deep-freezing on the nitrate-N contents were also studied. Nitrate contents in selected leafy vegetables were determined by FIA coupled with Greiss protocol involving sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride as color reagents. Nitrate was determined in the linear range from 1.0 to 20.0 mg L⁻¹ with the method detection limit of 0.042 mg L⁻¹ (0.34 mg kg⁻¹). The results of the study show that nitrate contents in fresh leafy vegetables ranged from 1297 to 5658 mg kg⁻¹. Boiling reduces nitrate content by 47–56% whereas frying in Soya bean oil elevates nitrate content by as much as 159–307%. No significant change was observed in nitrate content after baking. The deep-freezing of the selected leafy vegetables shows that nitrate-N content fluctuates slightly from the original nitrate-N values over the seven day period. The FIA throughput was 38 samples h⁻¹.     

Carotenoid and chlorophyll composition of commonly consumed leafy vegetables in Mediterranean countries

Major chloroplast pigments in five leafy vegetables (chicory-Cichorium intybus, cv. ‘Anivip’ and cv. ‘Monivip’, dandelion-Taraxacum officinale, garden rocket-Eruca sativa and wild rocket-Diplotaxis tenuifolia), commonly consumed in Mediterranean countries, have been separated by high-performance liquid chromatography (HPLC) on a reversed-phase column. Three classes of pigments were identified and quantified: xanthophylls (oxygenated carotenoids), carotenes (hydrocarbon carotenoids) and chlorophylls. The contents of the pigments in the analysed leafy vegetables varied significantly. The results indicated that selected leafy vegetables were moderately rich in xanthophylls, primarily lutein (3.87–7.44 mg/100 g fwt). Other xanthophylls were detected in relatively small quantities. The provitamin A carotenoids (α- and β-carotene) were also detected, but α-carotene were not present in chicory cultivars and in dandelion. The ratio of chlorophyll a/b varied from 2.44 to 2.67 depending on the species. The highest content of all the analysed constituents was found in the garden rocket.     

Comparative Study of Antioxidant Activity of the Food Flowers of West Bengal,India

In India, many flowers are consumed as food. During the present study, 37 flowers have been analyzed for their 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and total antioxidant capacity. The flowers were found to have different levels of antioxidant properties in the systems tested. On the basis of the activity and availability, a few flowers were further studied for hydroxyl radical scavenging activity, superoxide radical scavenging activity, lipid peroxidation prevention, and DNA damage prevention properties. The correlations suggest that the total phenol contents of the flowers were responsible for the antioxidant properties of the aqueous extracts. The unweighted-pair group average dendrogram showing interrelationships between the investigated species grouped them into two high level clusters based on activity.     

Antioxidant Activities and Polyphenolic Constituents of Bitter Bean Parkia Speciosa

Bitter bean (Parkia speciosa), also known as petai, is a popular non-timber forest product. Traditionally, its fruits are consumed as vegetables and herbal medicines in Malaysia. The present study aimed to evaluate the antioxidant activities of aqueous and ethanol extracts of P. speciosa empty pods using various antioxidant assays, as well as examining their polyphenolic constituent contents. Results showed that with the exception of superoxide radical scavenging activity, ethanol extracts possessed stronger DPPH and ABTS radical scavenging, anti-lipid peroxidation, metal chelating and reducing power activities than aqueous extracts. It was found to contain a higher level of total flavonoids and total phenols than aqueous extracts. The major polyphenolic constituents present in these extracts were gallic acid, catechin, ellagic acid, and quercetin. Although aqueous extracts contained a higher level in gallic acid, its catechin, ellagic acid, and quercetin contents were lower than ethanol extracts. Taken together, the higher amount of polyphenolic compounds present in ethanol extracts could have contributed to its stronger antioxidant activities than aqueous extracts; these results also provided the chemical basis for certain health benefits claimed of P. speciosa empty pods in folk medicine and as foods.     

Antioxidant and micronutrient quality of fruit and root vegetables from the Indian subcontinent and their comparative performance with green leafy vegetables and fruits

Commonly consumed, fruit vegetables (12) and root vegetables (15) in the Indian subcontinent in cooked and uncooked states assessed for inhibition of thiobarbituric acid reactive substances (TBARS), superoxide radical scavenging activity (SOSA), ferrous iron chelating ability (FICA) and nine micronutrients, exhibited large variability in these parameters. SOSA and FICA were significantly associated (r = 0.803, p < 0.001) with each other. Inhibition of TBARS showed marginal correlation with both FICA (0.38, p < 0.05) and SOSA (0.29, p > 0.05). There were significant cooking losses for each of the assessed antioxidant capacity parameters (p < 0.05). Contents of ascorbic acid, per 100 g of cooked fruit and root vegetables were high (61.9 and 31.3% of recommended daily allowance (RDA)). However, both the food classes were not good sources of beta‐carotene, riboflavin and thiamine (1.66–5.26% RDA). When compared with our data on 30 cooked green leafy vegetables (GLV) and 30 fresh fruits, root vegetables showed significantly (p < 0.05) higher levels of zinc and selenium. Cooked root vegetables were comparable with cooked GLVs but uncooked GLVs gave the highest values for inhibition of TBARS (0.73 ± 0.21 mM vitamin E/100g). SOSA (40.7 ± 15.6 mM tannic acid/100g) and FICA (41.6 ± 14.9 mM EDTA/100g) were highest for uncooked fruit vegetables. Root vegetables had the highest levels of polyphenols (251.4 ± 107.3 mg/100g). For the present study, popular fruits and vegetables such as guava, spinach, bitter gourd (Momordica charantia), yam, ginger and beetroot, and also less common ones like bael (Aegle marmelos), kokum (Garcinia indica) and mango‐ginger (Curcuma ameda), showed potential in vitro to combat oxidative stress. Copyright © 2005 Society of Chemical Industry     

Thermophysical properties and thermal behavior of leafy vegetables packaged in clamshells

Little is known about the thermophysical properties of fresh-cut lettuce other than heat of respiration. Empirical correlations based on food composition remain the only way to estimate the thermophysical properties of fresh-cut lettuce. The objectives of this study were (i) to determine the thermophysical properties of several baby-leaf lettuce and brassica greens and (ii) to verify the measured thermophysical properties by using them in a heat transfer model and comparing the predicted product temperatures with measured product temperatures in a simulated interruption of a cold chain. Density, leaf thickness, thermal conductivity, specific heat and water activity from nine varieties of baby-leaf lettuce and brassica greens were measured. A broken cold chain was simulated in a low temperature incubator set at 10 °C for a length of time before readjustment at 2 °C. Results showed that density (1078–1112 kg m⁻³), leaf thickness (0.18–0.54 mm), thermal conductivity (0.55–0.70 W (m °C)⁻¹) and specific heat (3.1–4.3 kJ (kg °C)⁻¹) varied significantly (P < 0.05) between varieties. However, no significant differences were observed for water activity (0.959 ± 0.006). Using thermophysical properties as input in the heat transfer model, experimental and calculated temperatures were well correlated (R² = 0.98) with a root mean square error of 0.57 °C over the 10–40 mg CO₂ (kg h)⁻¹ range of respiration rate. The measured thermophysical properties adequately predicted the temperature of the baby-leaf greens during simulated broken cold chains. A sensitivity analysis performed with the heat transfer model showed that the thermal conductivity, the specific heat and the density were relatively more important on the thermal behaviour of the baby-leaf greens than the heat of respiration.     

Natural antioxidants and antioxidant capacity of Brassica vegetables: A review

Dietary antioxidants, such as water-soluble vitamin C and phenolic compounds, as well as lipid-soluble vitamin E and carotenoids, present in vegetables contribute both to the first and second defense lines against oxidative stress. As a result, they protect cells against oxidative damage, and may therefore prevent chronic diseases, such as cancer, cardiovascular disease, and diabetes. Brassica vegetables, which include different genus of cabbage, broccoli, cauliflower, Brussels sprouts, and kale, are consumed all over the world. This review focuses on the content, composition, and antioxidant capacity both lipid- and water-soluble antioxidants in raw Brassica vegetables. The effects of post-harvest storage, industrial processing, and different cooking methods on stability of bioactive components and antioxidant activity also are discussed.     

Antioxidant activity prediction and classification of some teas using artificial neural networks

In order to characterise and to classify some teas a simple, rapid and economical method based on composition, antioxidant activity and artificial neural networks (ANNs) is proposed. For these purpose two types of ANN based applications have been developed: one for predicting the antioxidant activity and a second one for establishing the class of the teas. The complex relationship between the total antioxidant activity (AA) depending on the total flavonoids content (F), total catechins content (C) and total methyl-xanthines content (MX) of commercial teas was revealed by the first designed feed-forward ANN. Secondly, using a probabilistic ANN, successful tea classification in various classes (green tea, black tea and express black tea) was also performed.     

Antioxidant properties of polar and non‐polar extracts of some tropical green leafy vegetables

BACKGROUND: The higher consumption of vegetables and fruits could be a practical approach to the management of oxidative stress. The present study sought to compare the antioxidant properties of polar and non‐polar constituents of some tropical green leafy vegetables (Struchium sparganophora, Amaranthus cruentus, Telfairia occidentalis, Ocimum gratissimum, Talinium triangulare, Cnidoscolous aconitifolius and Vernonia amygdalina). RESULTS: The polar antioxidant constituents (total phenol (3330–17 572 mg kg^?1), total flavonoid (1668–4306 mg kg^?1) and vitamin C (224–642 mg kg^?1)) were higher than the non‐polar antioxidant constituents (total phenol (703–3115 mg kg^?1), total flavonoid (130–1303 mg kg^?1) and carotenoids (132–1303 mg kg^?1)). Furthermore, the polar extracts had a significantly higher (P < 0.05) 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging ability (except T. triangulare), total antioxidant capacity, reducing power (except T. triangulare and A. cruentus) and Fe(II) chelating ability (except C. aconitifolius and S. sparganophora). However, the polar and non‐polar extract of O. gratissimum had the highest antioxidant properties while that of T. triangulare had the least antioxidant properties. CONCLUSION: The polar extract of most of the vegetables had higher antioxidant properties than the non‐polar extract, with O. gratissimum extracts having the highest antioxidant properties. Copyright © 2008 Society of Chemical Industry     

壶瓶碎米荠粗黄酮产品的抗氧化研究

以DPPH自由基、超氧阴离子自由基、羟自由基和总还原力为指标,测定体外抗氧化能力;以小鼠血清中SOD、CAT、GSH-Px活性和MDA含量为测定指标,测定体内抗氧化能力。结果显示：壶瓶碎米荠含硒粗黄酮对自由基具有一定的清除作用,在实验考察的自由基中,除超氧阴离子外其余均显示出良好的抗氧化效果且随着剂量的增加呈现出良好的线性;动物实验中壶瓶碎米荠两种粗黄酮均能提高小鼠SOD、CAT、GSH-Px活性,降低MDA含量并呈现出良好的线性效果,含硒粗黄酮抗氧化效果显著高于普通粗黄酮,与阳性对照VC效果相似。当壶瓶碎米荠含硒粗黄酮剂量达到100 mg/kg时,芦丁实验组、粗黄酮实验组小鼠体重降低,出现轻微毒害作用,而含硒粗黄酮处理组体重差异不显著,从侧面说明硒具有一定增强免疫力的效果。     

Antioxidant activity of commercial buckwheat flours and their free and bound phenolic compositions

Commercial buckwheat flours were investigated for their antioxidant activities, free, and bound phenolic compositions using spectrophotometer, LC–ESI-IT-MS, and LC–ESI-Q-TOF-MS. Farinetta flour contained the highest free and bound phenolic contents, followed by Supreme, whole buckwheat, and Fancy flour, respectively. The 50% ethanol extraction achieved significantly higher free phenolic content compared with water and absolute alcohol. The absolute ethanol extraction contained considerable more bound phenolic and flavonoid compounds. A high extraction temperature increased the phenolic contents. The optimal solvent to solids ratio was 50:1, and the optimal extraction time was 5 h for flavonoids. The spectral method was reproducible for analysing the total flavonoid contents. The LC–ESI-Q-TOF-MS studies on whole buckwheat flour showed that p-coumaric and gallic acids were found in the bound phenolics along with isoquercitrin but were not present in the free phenolic compounds. The free flavonol-glycosides were found in whole buckwheat flour but not in any other buckwheat flours.     

Antioxidant properties of several tropical fruits: A comparative study

Nine tropical fruits were analyzed for total phenol contents, ascorbic acid contents and antioxidant activities. The antioxidant activities were evaluated based on the ability of the fruit extracts to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH), reduce iron(III) to iron(II) and to bind to iron(II) ions. The results were compared to those of orange. It was found that guava, papaya and star fruit have higher primary antioxidant potential, as measured by scavenging DPPH and iron(III) reducing assays. Banana, star fruit, water apple, langsat and papaya have higher secondary antioxidant potential as measured by the iron(II) chelating experiment.     

Effect of different cooking methods on the antioxidant activity of some vegetables from Pakistan

The effects of different cooking methods (boiling, frying and microwave cooking) on the antioxidant activity of some selected vegetables (peas, carrot, spinach, cabbage, cauliflower, yellow turnip and white turnip) were assessed by measuring the total phenolic contents (TPC), reducing power and percentage inhibition in linoleic acid system. TPC (gallic acid equivalents g/100 g of dry weight) and reducing power of the methanolic extracts of raw‐, microwaved‐, boiled‐ and fried vegetables ranged 0.333–2.97, 0.52–2.68, 0.48–2.08, 1.00–2.02 and 0.391–2.24, 0.822–1.10, 0.547–1.16, 0.910–4.07, respectively. The level of inhibition of peroxidation ranged 71.4–89.0, 66.4–87.3, 73.2–89.2 and 77.4–91.3%, respectively. Antioxidant activity of the vegetables examined was appreciably affected because of varying cooking treatments. TPC of vegetables, generally, decreased by boiling, frying and microwave cooking. There was a significant (P < 0.05) increase in reducing power as a result of frying. However, boiling and microwave cooking did not affect reducing power. Inhibition of peroxidation increased by boiling and frying, whereas, in contrast it was decreased by microwave cooking. The results of the present investigation showed that all the cooking methods affected the antioxidant properties of the vegetables; however, microwave treatment exhibited more deleterious effects when compared with those of other treatments. Thus an appropriate method might be sought for the processing of such vegetables to retain their antioxidant components at maximum level.     

Antioxidant activity of methanolic extracts from some grains consumed in Korea

The objectives of this study were to determine antioxidant activity of the methanolic extracts from some grains and to investigate relationships between antioxidant activities and antioxidant contents in the extracts. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activities, inhibitory effect on lipid peroxidation, chelating activity and reducing power have been used to investigate the relative antioxidant activities of the extracts from grains. The concentrations of total polyphenolics and carotenoids in the extracts were measured by spectrophotometric methods and vitamin E analysis was carried out by HPLC. The methanolic extracts prepared from red sorghum and black rice showed significantly higher antioxidant activities and contained higher polyphenolic contents than other grains such as white rice, brown rice, mungbean, foxtail millet, prosomillet, barley, and adlay. Polyphenolic compounds were the major naturally occurring antioxidants in grains. The correlation coefficient between total polyphenolic content and ABTS radical cation scavenging activity in the extracts was >0.99. However, no relationship was found between antioxidant activities and carotenoids and vitamin E derivatives.     

Evaluation of Free Radical Scavenging Activity and Antioxidant Potential of a Few Popular Green Leafy Vegetables of Malaysia

In this study, phenolic contents and antioxidant activity of five popular green leafy vegetables of Malaysia—Kangkung, Kucai, Di Huang Miao, Ubi Keledek, and Yaw Mak Choy—were evaluated. Methanol, acetone, and distilled water were the solvent systems used for extraction. The antioxidant capacity of the extracts was evaluated using ferric reducing antioxidant potential assay and the free radical scavenging capacity was evaluated using the DPPH· radical-scavenging assay. The total flavonoids, flavonols, and tannins were also quantified. The efficacy of the three solvents used for extraction differed significantly for both the levels of antioxidants and free radical scavenging activity. In general, methanol was the best of the three solvents for extraction of antioxidants. The results of this study will be useful for health conscious consumers, and they will provide a basis for future exploration of these green leafy vegetables as potential sources of natural antioxidants for food and nutraceutical applications.     

Anti-oxidant activity and total phenolic content of some Asian vegetables

The anti-oxidant activity of extracts from 36 vegetables was evaluated by using a model system consisting of β-carotene and linoleic acid. The total phenolics of the extracts was determined spectrophotometrically according to the Folin–Ciocalteau procedure and ranged from 34 to 400 mg (100 g)⁻¹ on a fresh weight basis. Mint, aonla, black carrots, chenopodium, fenugreek, kachnar and ginger had high phenolic contents. The anti-oxidant activity expressed as per percent inhibition of oxidation ranged from a high of 92% in turmeric extracts to a low of 12.8% in long melon. Other vegetables found to have high anti-oxidant activity (>70%) were kachnar, aonla, ginger, fenugreek, mint, beetroot, black carrots, Brussels sprouts, broccoli, lotus stem, yam, coriander and tomato. Anti-oxidant activity correlated significantly and positively with total phenolics ( r ²=0.6578, P  < 0.05). The results indicate that vegetables containing high phenolics may provide a source of dietary anti-oxidants.