Effect of Cooking on Isoflavones,Phenolic Acids,and Antioxidant Activity in Sprouts of Prosoy Soybean (Glycine max)

Soy sprouts possess health benefits and is required to be cooked before consumption. The effects of cooking on the phenolic components and antioxidant properties of soy sprouts with different germination days were investigated. A food‐grade cultivar Prosoy with a high protein content was germinated for 1, 2, 3, 5, and 7 d and cooked till palatable for 20, 20, 5, 5, and 7 min, respectively. Total phenolic content (TPC), total flavonoids content (TFC), condensed tannins content (CTC), individual phenolic acids, isoflavones, DPPH, ferric‐reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) of raw and cooked sprouts were measured. Cooking caused significant losses in phenolic content and antioxidant activities, and maximum loss was on day 3 > 5 > 7, including TPC (32%, 23%, and 15%), TFC (50%, 44%, and 20%), CTC (73%, 47%, and 12%), DPPH (31%, 15%, and 5%), FRAP (34%, 25%, and 1%), and ORAC (34%, 22%, 32%), respectively. Cooking caused significant losses in most individual phenolic acid, benzoic group, cinnamic group, total phenolic composition, individual isoflavones, and total isoflavones. The losses of phenolic acids such as gallic, protocatechuic, hydroxybenzoic, syringic, chlorogenic, or sinapic acids during cooking were not compensated by the increases in trihydroxybenzoic, vanillic or coumaric acids on certain days of germination. Cooking caused minimal changes in phenolic acid composition of day 1 and 2 sprouts compared to 3, 5, and 7 d sprouts.     

Phenolic Compounds and Antioxidant Capacities of 10 Common Edible Flowers from China

The free and bound phenolic compounds in 10 common Chinese edible flowers were investigated using reversed phase high‐performance liquid chromatography. Their antioxidant capacities were evaluated using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical‐scavenging activity, 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) radical‐scavenging activity, oxygen radical absorption capacity (ORAC), ferric reducing antioxidant power (FRAP), and cellular antioxidant activity (CAA). Free factions were more prominent in phenolic content and antioxidant capacity than bound fractions. Paeonia suffruticosa and Flos lonicerae showed the highest total phenolic content (TPC) 235.5 mg chlorogenic acid equivalents/g of dry weight and total flavonoid content 89.38 mg rutin equivalents/g of dry weight. The major phenolic compounds identified were gallic acid, chlorogenic acid, and rutin. P. suffruticosa had the highest antioxidant capacity in the DPPH, ABTS, and ORAC assays, which were 1028, 2065, 990 μmol Trolox equivalents/g of dry weight, respectively, whereas Rosa chinensis had the highest FRAP value (2645 μmol Fe²⁺ equivalents /g of dry weight). The P. suffruticosa soluble phenolics had the highest CAA, with the median effective dose (EC₅₀) 26.7 and 153 μmol quercetin equivalents/100 g of dry weight in the phosphate buffered saline (PBS) and no PBS wash protocol, respectively. TPC was strongly correlated with antioxidant capacity (R = 0.8443 to 0.9978, P < 0.01), which indicated that phenolics were the major contributors to the antioxidant activity of the selected edible flowers.     

Phenolic compositions and antioxidant activities of Maya nut (Brosimum alicastrum): Comparison with commercial nuts

The goal of the present study was to investigate the antioxidant activity and total phenolic content (TPC) of Maya nut (Brosimum alicastrum) in comparison with commercially available nuts (i.e. walnut, almond, and peanut). Results indicated that Maya nut had the highest TPCs among these nuts. Maya nut also possessed strong 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and 2.2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activities and ferric reducing antioxidant power (FRAP) (p < 0.05) as compared to walnut, almond, and peanut. Five phenolic acids (gallic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, and p-coumaric acid) and one flavonoid ((-)-epicatechin) were identified and the phenolic content ranged from 6.5 to 326.2 µg/g.     

Effect of processing on the antioxidant activity of millet grains

Millets are generally dehulled and subjected to a hydrothermal treatment before consumption, thus the hulls can be used as a potential source of antioxidants. Several millet grains, namely kodo, finger (Ravi), finger (local), proso, foxtail, little and pearl millet were studied. Antioxidant activities of phenolic extracts obtained from whole grains, as well as their corresponding dehulled and cooked grains and hulls were studied for their total phenolic content (TPC), radical scavenging capacity, and antioxidant activity in a β-carotene/linoleate emulsion. The phenolics present in whole grains were identified and quantified using HPLC and HPLC/MS and results were expressed as total for each of the phenolic groups. The TPC ranged from 2 to 112 μmol ferulic acid equivalents/g defatted meal. All varieties exhibited effective inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, peroxyl and superoxide radicals. Dehulling and cooking affected the TPC and radical scavenging and antioxidant activities of the grains, depending on the variety. In general, the antioxidant activity of phenolic extracts was in the order of hull > whole grain > dehulled grain > cooked dehulled grain With the exception of the two finger millet varieties, hulls of other millet grains had high TPC, thus demonstrating their superior antioxidant activity. Hydroxybenzoic acids, hydroxycinnamic acids and flavonoids in whole grains were identified as contributors to the observed effects. Therefore, dehulling of grain and hydrothermal treatments affect the phenolic content and antioxidant potential of millet grains.     

Flavonoid constituents and antioxidant capacity in flowers of different Zhongyuan tree penoy cultivars

Flavonoid components in flowers of 48 Zhongyuan tree penoy cultivars were identified by means of a hyphenated technique of HPLC coupled with a photodiode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESIMS). The total phenolic content (TPC) was determined by Folin–Ciocalteu method and the antioxidant activity with both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. About 14 flavonoids including five anthocyanins, three flavonol glycosides and six flavone glycosides were described. Apigenin-pento-hexoside and Apigenin-hexo-glucuronide were reported for the first time. TPC, expressed as gallic acid content, varied between 3.97 and 21.73 mg/g fresh weight. Antioxidant activity varied among the cultivars (7.66–31.36 and 4.80–17.87 mg ascorbic acid equivalents/g fresh weight for DPPH and FRAP assays, respectively) and highly corresponded with TPC.     

Changes in bioactive compounds and antioxidant activity during convective drying of murta (Ugni molinae T.) berries

Murta (Ugni molinae T.) berries were air‐dried at five temperatures (40, 50, 60, 70 and 80 °C), and the changes in β‐carotene, phenolic acids, total phenolic and flavonoid contents and antioxidant capacities (DPPH and ORAC) were investigated. The berries showed a high content of β‐carotene, which decreased during drying temperature between 40 °C and 80 °C. Free and bound phenolic acids were also determined, showing gallic acid to be the prevalent phenolic acid. Total phenolic and flavonoid contents in the dried berries showed a higher decrease at lower temperature due to longer drying time. The radical‐scavenging activity also showed higher antioxidant activity at higher drying temperatures (70–80 °C) than at lower drying temperatures (40–50 °C). Total phenolic content (TPC) and flavonoids showed good correlation with antioxidant capacity. Murta berries proved to be an excellent source of antioxidants and bioactive compounds and are therefore a potential ingredient for new functional food products.     

Antioxidant Activities and Phenolic Compounds of Several Tissues of Pawpaw (Asimina triloba [L.] Dunal) Grown in Korea

Pawpaw (Asimina triloba [L.] Dunal) possesses antioxidant compounds and strong inhibitors of cancer cells, and is widely cultivated in North America, Canada, and Korea. We analyzed the total phenolic and total flavonoid contents (TPC and TFC, respectively) of pawpaw plants grown in Korea and the antioxidant activities of their roots, twigs, leaves, and fruit with respect to 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) radical scavenging activity, 2,2′‐azino‐bis diammonium salt (ABTS) radical scavenging activity, ferrous (Fe²⁺) chelating ability, and nitrite scavenging activity. Pearson's correlation analyses revealed a linear correlation between TPC and antioxidant activities (r² >0.69). Root methanol extracts had higher TPC and antioxidant activities than other extracts, which was also consistent with those from the phenolic compounds found in those extracts. Therefore, antioxidant activities seem to depend on the TPC of each pawpaw tissue and pawpaw roots might be useful as a natural source of natural antioxidants.     

Reprocessing effect on the quality of domestically cooked (boiled/stir-fried) frozen vegetables

This was a study of the effect on quality parameters of reprocessing (blanching at 97 °C for increasing times+freezing) prior to domestic cooking (boiling or stir-frying) of frozen green peas (cv. Mastim) and beans (cvs. Paloma and Moncayo). The results were compared with those of frozen control samples directly boiled or stir-fried. Kramer shear was the most suitable mechanical test for evaluating the effect of reprocessing on mechanical behaviour in both boiled and stir-fried frozen vegetables. Reprocessing significantly affected the mechanical behaviour of both green bean varieties with both cooking methods. Reprocessed products were softer than those supplied by the industry, and softening was significantly greater the longer the blanching time. The colour was more uniform and homogeneous in boiled than in stir-fried reprocessed vegetables; colour parameters showed that reprocessing affected the colour of stir-fried samples more significantly than that of boiled samples. In all the studied vegetables, less chlorophyll and more ascorbic acid were retained when samples were stir-fried than when they were boiled, although chlorophyll and ascorbic acid decreased with increasing reprocessing time in both cooking methods. In the two frozen green bean varieties in particular, SEM microphotographs confirmed the results of mechanical tests, indicating that with both cooking methods, the mechanical parameters were lower in the reprocessed samples than in the controls. The shortest reprocessing procedure (blanching at 97 °C for 2, 3 min+freezing), as a compromise among quality parameters, could shorten the time required for domestic stir-frying of frozen green peas and boiling or stir-frying of frozen green beans.     

Antioxidant properties of commercial, regular- and whole-wheat spaghetti

Whole grains contain more vitamins, minerals, natural antioxidants and dietary fibre than regular, refined grain products. Therefore, consumption of whole grain products is associated with beneficial health effects. The present investigation evaluated the antioxidant properties of 10 samples of regular- and whole-wheat spaghetti that are commercially available. The methods employed were total phenolic content (TPC), 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging activity, oxygen radical absorbance capacity (ORAC) and ferulic acid content by HPLC analysis. The effects of cooking on the antioxidant properties of spaghetti were also studied. Whole wheat spaghetti exhibited significantly higher levels of total phenolic content (1389 μg/g) than regular wheat spaghetti (865 μg/g); however, TPC in both regular and whole wheat spaghetti was 48–78% of the original content after cooking. There were no significant differences in ORAC values (34.3–100.4 μmol Trolox equivalents/g) or DPPH scavenging activity (1.0–2.3 μmol Trolox equivalents) among whole wheat and regular spaghetti. Whole wheat spaghetti (234 μg/g) had significantly higher content of ferulic acid than regular spaghetti (p < 0.05). TPC and ferulic acid content were found to be good indicators of the antioxidant capacity of spaghetti with both indices demonstrating the superiority of whole wheat over regular pasta products. The current findings on spaghetti add to the mounting evidence on the potential health benefits to be derived from consuming whole grain products.     

Antioxidant and tyrosinase inhibitory activities of different parts of guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.)

The antioxidant and the tyrosinase inhibitory activities of 4 different solvents (acetone, ethanol, methanol, and water) for preparation of extracts from guava (branch, fruit, leaf, and seed) were evaluated by measuring total phenolic contents (TPC), DPPH radical scavenging activity, ABTS radical scavenging activity, reducing power (RP), and tyrosinase inhibitory activity. The extracts of branch and leaf showed relatively higher antioxidant properties than those of fruit and seed. The highest TPC (141.28 mg/g gallic acid equivalents), DPPH radical scavenging activity (IC₅₀=34.01 μg/mL), ABTS radical scavenging activity (IC₅₀=3.23 μg/mL), and RP (IC₅₀= 75.63 μg/mL) were found in acetone extract of leaf, while water extract of seed had the lowest antioxidant activity. The tyrosinase inhibitory activity of ethanol extract from guava leaf was 69.56%, which was the highest activity among the extracts. These results indicate that useful bioactive substances exist in the guava branch as well as leaf extracts.     

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.     

Bioaccessibility and antioxidant activity of phenolic compounds in cooked pulses

The aim of this study was to evaluate the bioaccessibility of polyphenols and antioxidant activity in cooked pulses and to study the effect of cooking on their total phenolic content (TPC) and antioxidant capacity. Cooked faba beans showed the highest TPC, followed by soybeans and lentils or peas. TPC ranged from 10.4 ± 0.2 to 52.9 ± 0.3 mg/100 g and was positively correlated with antioxidant activity. Cooking resulted in increased TPC and antioxidant activity of the methanolic extracts, caused by cell disruption and improved extraction of polyphenols. Although polyphenols were lost in the cooking water, boiled legumes had more polyphenols than those resulting cooking broths. In vitro gastrointestinal digestion resulted in increased TPC and antioxidant capacity of the extracts. Soybeans showed the highest amount of bioaccessible polyphenols. The release of phenolics from cooked legumes was mainly achieved during the intestinal phase. Literature data may underestimate the TPC and antioxidant capacity of pulses.     

Characterisation and comparison of phenols,flavonoids and isoflavones of soymilk and their correlations with antioxidant activity

To investigate the relationship between bioactive compounds and antioxidant property, total phenolic content (TPC), total flavonoid content (TFC), individual and total isoflavone content of soymilk and their correlations with oxygen‐radical‐absorbing capacity (ORAC), ferric reducing antioxidant power (FRAP) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging capacity values were evaluated and compared. Results showed that TPC, TFC, isoflavones (including concentration and profiles) and antioxidation activity significantly varied among ten tested soybean cultivars. Significant correlations were established between DPPH and TFC (r = 0.553, P < 0.01), DPPH and TPC (r = 0.753, P < 0.01), FRAP and TFC (r = 0.599, P < 0.01) and FRAP and TPC (r = 0.616, P < 0.01). Positive linear correlations were found between subtotal, total isoflavones and ORAC. Unlike other isoflavone monomers, aglycone isoflavones correlated positively with DPPH and FRAP significantly. DPPH well correlated with FRAP, whereas neither DPPH nor FRAP correlated with ORAC. TPC, TFC, individual and total isoflavone values are potentially useful for soymilk antioxidant activity assessment.     

Influence of heating on the polyphenolic content and antioxidant activity of grape seed flour

Abstract: The production of grape seed flour (GSF) from a waste product generated during winemaking, is of interest in product development applications due to its potential health benefits. However, before GSF can used in baking as a source of additional antioxidants, research on its heat stability is required. The overall objective of this study was to assess changes in phenolic content and antioxidant activity of GSF during heating. Merlot GSF was heated at 5 temperatures (120 to 240 °C) for 0 to 90 min. At each time/temperature combination, total phenolic content (TPC), total flavanoid content (TFC), Trolox equivalent antioxidant capacity (TEAC), 2,2 diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging, and ferric ion reducing antioxidant power (FRAP) of the extracts were determined. Specific polyphenolic compounds, including catechin, gallocatechin, epicatechin, and gallic acid were also measured. Results showed that when Merlot GSF was heated to ≥180 °C, significant decreases in the TPC and antioxidant activity, measured using FRAP, DPPH, and TEAC, were observed. Longer heating times also caused a reduction in antioxidant capability. Catechin and epicatechin content decreased with increasing heating temperature while gallocatechin and gallic acid content increased. Both catechin and epicatechin content had strong positive correlations (r > 0.91) with TPC and TFC, as well with FRAP and TEAC, suggesting that the GSF antioxidant activity is related to the presence of these particular compounds. Overall, while a decrease in antioxidant content was observed during heating, this occurred at higher baking temperatures. Thus GSF may be suitable for use as an ingredient in baked goods to bolster antioxidant content. Practical Application: In order for Merlot grape seed flour (GSF) to be used in baking as a source of additional antioxidant compounds, the impact of heating on the polyphenolic compounds in the GSF needed to be examined. Thermal treatment of Merlot GSF caused significant decreases in the TPC, antioxidant power, and specific polyphenolic compounds when heated ≥180 °C. Thus while antioxidant content decreased with higher heating temperatures, this occurred at higher baking temperatures. Thus, GSF may be suitable for use as an ingredient in baked goods to bolster antioxidant content.     

Phenolic Profiles,Antioxidant Activities,and Neuroprotective Properties of Mulberry (Morus atropurpurea Roxb.) Fruit Extracts from Different Ripening Stages

The present work investigated the phenolic profiles (including nonanthocyanin and anthocyanin phenolics), antioxidant activities, and neuroprotective potential of mulberry fruit (MF) (Morus atropurpurea Roxb.) grown in China at different ripening stages. High‐performance liquid chromatography‐tandem mass spectrometry method (HPLC‐MS/MS) was used to identify and quantify the phenolic compounds. The antioxidant capacity, total phenolic content (TPC), total flavonoid content (TFC), and total monomeric anthocyanin content (TAC) were determined using spectrophotometric methods. The neuroprotective effects of MFs at different ripening stages were investigated using Aβ_25‐35‐treated PC12 cells as the cellular model of Alzheimer's disease. Of the 19 phenolic compounds characterized from the MF extracts, the contents of rutin and anthocyanins increased and that of chlorogenic acid decreased significantly with maturity. At the fully ripened stage, MF extracts showed the highest amounts of TPC (11.23 mg gallic acid equivalents/g fresh weight), TFC (15.1 mg rutin equivalents/g fresh weight), and TAC (1177 mg cyanidin 3‐O‐glucoside equivalents/100 g fresh weight). Meanwhile, antioxidant activity of MF extracts at this stage was highest according to ABTS (an IC50 value of 4.11 μg/mL) and DPPH (an IC50 value of 10.08 μg/mL) assays. Cellular assays revealed increased cell viability in cells treated with the ripe MF extracts; compared with the control groups, the ripening fruits also increased the antioxidant enzyme levels in PC12 cells. Together, these results suggest that the antioxidant activities and neuroprotective properties of ripening MFs are related to the contents and types of phenolic compounds that are present in the fruits.     

Optimization of phenolic compound recovery and antioxidant activity of light and dark dried fig (Ficus carica L.) varieties

The optimum conditions for extraction of total phenolic contents (TPC) and for enhancing the antioxidant activity from light and dark dried figs were determined. The effects of the solvent nature (acetone, ethanol, methanol, or water), solvent concentration (20–80%), acetic acid concentration (0–2%), extraction temperature (25–70°C), extraction time (0.5–4 h), sample to solvent ratio (1/25–1/100), and number of extractions (1, 2, and 3) were determined. The TPC was used to identify antioxidant compounds. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used to evaluate antioxidant activity. All extraction parameters had significant effects (p<0.05) on the TPC and the antioxidant activities. The best conditions were obtained with double extraction using 60% acetone without acidification, at 40°C for 120 min, and with a 1/75 solid to solvent ratio. These conditions resulted in TPC concentrations of 469.46 (light variety) and 399.79 mg of gallic acid (GAE)/100 g (dark variety), and antioxidant activities of 96.47 and 102.28 mg of GAE/100 g, respectively.     

Antioxidant and <Emphasis Type="Italic">α</Emphasis>-glucosidase inhibitory activities of different solvent extracts of skullcap (<Emphasis Type="Italic">Scutellaria baicalensis</Emphasis>)

In this study, different solvent extracts of skullcap (Scutellaria baicalensis) were assayed for their total phenol content (TPC), antioxidant activity [determined as DPPH radical scavenging activity, superoxide dismutase (SOD)-like activity, oxygen radical absorbance capacity (ORAC) assay, and comet assay], and α-glucosidaseinhibitory activity. The TPC of skullcap ranged from 9.06 mg/g gallic acid equivalents (GAE) for acetone extract (AE) to 91.8 mg/g GAE for methanol extract (ME). AE, which had a low TPC, exhibited the highest DPPH radical scavenging activity and SOD-like activity. TPC positively correlated with the ORAC assay (r=0.96, p<0.001). All skullcap extracts significantly reduced the hydrogen peroxide-induced DNA damage in human leukocytes. ME with a high TPC and ORAC value showed the highest α-glucosidase inhibition. The difference in the biological activities of the extracts may be due to the differences in their chemical structure or polarity. Therefore, the results obtained indicate that might be a potential source of compounds with health-protective effects. ME, in particular, might be a prospective therapeutic agent for diabetes.     

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.     

Evaluation of antioxidant activities and total phenolic contents of typical malting barley varieties

Fourteen typical malting barley varieties from China were evaluated for their DPPH radical, ABTS radical cation and superoxide anion radical scavenging activities, reducing power, metal chelating activities, and total phenolic contents (TPC). All barley samples exhibited significant antioxidant activities determined by different assays, and contained significant levels of phenolic compounds. Gan4 and Wupi1 barley exhibited the highest DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power. Gan4 and Humai16 barley showed the highest TPC, whereas the highest superoxide anion radical scavenging activity and metal chelating activity were found in Huaimai19 and Ken3 barley, respectively. The Pearson correlation analysis revealed that the TPC showed strong correlations with DPPH radical scavenging activity, ABTS radical cation scavenging activity, and reducing power (P < 0.01), whereas its correlations with superoxide anion radical scavenging activity and metal chelating activity were poor (P > 0.05). Moreover, DPPH radical scavenging activity, ABTS radical cation scavenging activity and reducing power were well positively correlated with each other (P < 0.01). Principal component analysis (PCA) was applied to understand the interrelationships among the measured antioxidant activity evaluation indices, and to gain an overview of the similarities and differences among the 14 barley varieties.     

Phenolic contents and antioxidant activities of bitter gourd (Momordica charantia L.) leaf, stem and fruit fraction extracts in vitro

Bitter gourd (Momordica charantia L.) has long been regarded as a food and medicinal plant. We investigated the antioxidant activity of the water extract of leaf, stem and fruit fractions by several in vitro systems of assay, namely DPPH radical-scavenging activity, hydroxyl radical-scavenging activity, β-carotene–linoleate bleaching assay, ferric reducing/antioxidant power (FRAP) assay and total antioxidant capacity. Total phenolic content was measured by Folin–Ciocalteu reagent. Identification of phenolic compounds was achieved using HPLC with the UV-diode array detection. The extracts of different fractions were found to have different levels of antioxidant activity in the systems tested. The leaf extract showed the highest value of antioxidant activity, based on DPPH radical-scavenging activity and ferric reducing power, while the green fruit extract showed the highest value of antioxidant activity, based on hydroxyl radical-scavenging activity, β-carotene–linoleate bleaching assay and total antioxidant capacity. The predominant phenolic compounds were gallic acid, followed by caffeic acid and catechin. The present study demonstrated that the water extract fractions of bitter gourd have different responses with different antioxidant methods. Total phenol content was shown to provide the highest association with FRAP assay in this present study (R² = 0.948).