Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues

The extracts from kinnow peel, kinnow seeds, litchi pericarp, litchi seeds, grape seeds, and banana peel were screened for total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC), 1,1 diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, as well as reducing power. Kinnow peel extract exhibited the highest reducing power, TEAC, and DPPH free radical scavenging activity, whereas, the phenolic content of 37.4 mg GAE/g-dw was highest for grape seed extract. Banana peel extract with a low TPC showed the lowest reducing power, TEAC as well as DPPH free radical scavenging activity among the fruit residue extracts examined in the present study. Correlation analysis between the reducing power and DPPH radical scavenging ability; reducing power and ABTS radical scavenging activity; and ABTS and DPPH radical scavenging abilities showed a high degree of correlation (r² = 0.85-0.91). However, r² of 0.36, 0.66, and 0.49 between TPC and DPPH radical scavenging activity; TPC and reducing power; and TPC and ABTS radical scavenging ability, respectively, indicated that some non-phenolic compounds also contributed to the total antioxidant activity in fruit residue extracts examined in this study. To the best of our knowledge, this is the first paper presenting comprehensive data on TPC, reducing power, and antioxidant activity for the six fruit residues. This study demonstrated that kinnow peel, litchi pericarp, litchi seeds, and grape seeds, can serve as potential sources of antioxidants for use in food and pharmaceutical industry.     

Antioxidative and functional properties of protein hydrolysate from defatted skipjack (Katsuwonous pelamis) roe

Antioxidative and functional properties of protein hydrolysate from defatted skipjack (Katsuwonous pelamis) roe, hydrolysed by Alcalase 2.4 L (RPH) with different degrees of hydrolysis (DH) at various concentrations were examined. As DH increased, the reduction of DPPH, ABTS radicals scavenging activities and reducing power were noticeable (p < 0.05). The increases in metal chelating activity and superoxide scavenging activity were attained with increasing DH (p < 0.05). However, chelating activity gradually decreased at DH above 30%. All activities except superoxide anion radical scavenging activity increased as the concentration of hydrolysate increased (p < 0.05). Hydrolysis using Alcalase could increase protein solubility to above 80% over a wide pH range (2–10). The highest emulsion ability index (EAI) and foam stability (FS) of hydrolysates were observed at low DH (5%) (p < 0.05). Concentrations of hydrolysates determined interfacial properties differently, depending on DH. The molecular weight distribution of RPH with 5%DH (RPH5) was determined using Sephadex G-75 column. Two major peaks with the molecular weight of 57.8 and 5.5 kDa were obtained. Fraction with MW of 5.5 had the strongest metal chelating activity and ABTS radical scavenging activity. The results reveal that protein hydrolysates from defatted skipjack roe could be used as food additives possessing both antioxidant activity and functional properties.     

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.     

橄榄酚类提取物的抗氧化性能

为进一步开发利用橄榄中的酚类物质,文中通过测定橄榄酚类提取物的铁离子还原能力、亚铁离子螯合能力,及对2,2'-氨基-二(3-乙基-苯并噻唑啉-6-磺酸)自由基(ABTS+.)、1,1-二苯-2-苦基苯肼自由基(DPPH.)、羟基自由基(.OH)和超氧阴离子自由基(O2-.)的清除能力,以考察橄榄酚类提取物的体外抗氧化性能,并与食品抗氧化剂丁基羟基茴香醚(BHA)和Vc进行对比。结果表明:橄榄酚类提取物具有较好的体外抗氧化性能,其ABTS+.、DPPH.清除率分别高达99%和95%以上,.OH、O2-.清除率可达50%左右,铁离子还原力约1 700μmol/L Trolox,亚铁离子螯合率最高为14.9%。且提取物ABTS+.、DPPH.和.OH清除能力及铁离子还原能力均强于BHA和Vc,而O2-.清除能力强于BHA但弱于Vc。另外,橄榄酚类粗提物和纯化物相同浓度下的ABTS+.、DPPH.、.OH清除能力和铁离子还原能力相当(P>0.05),而其O2-.清除能力和亚铁离子螯合能力表现有所差异。     

Antioxidant activities of squid protein hydrolysates prepared with papain using response surface methodology

Squid protein hydrolysates (SPH) were prepared from the Indian squid Loligo duvauceli using papain. Response surface methodology (RSM) was used for optimization of hydrolysis conditions, including temperature, time, and the enzyme-substrate ratio using DPPH radical scavenging activity as a response. The amino acid composition of SPH was compared with raw squid muscle. In vitro antioxidant activities were evaluated based on reducing power, metal chelation, ABTS, hydroxyl radical, and superoxide anion radical scavenging assays. SPH exhibited good ABTS radical scavenging activities of 96.50±0.90%, superoxide anion radical scavenging activities of 96.4±0.89%, reducing powers of 0.71±0.02, moderate hydroxyl radical scavenging activities of 64.03±2.11%, and metal chelating activities of 52.04±1.02%. In vivo antioxidant activities determined using a sardine minced model system showed 42% reduction in formation of secondary oxidative products as thiobarbituric acid reactive substances (TBARS), almost equivalent to reduction by ascorbic acid of 41.42% at 400 ppm.     

Polyphenol contents and in vitro antioxidant activities of lyophilised aqueous extract of kiwifruit (Actinidia deliciosa)

The aim of this study was to determine the antioxidant potency and total phenolic and flavonoid contents of kiwifruit (Actinidia deliciosa) in vitro by analysing the radical scavenging activity of lyophilised water extract from kiwifruit (LEK) for 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picryl-hydrazyl (DPPH), N,N-dimethyl-p-phenylenediamine (DMPD), and superoxide anion radical (O₂⁻) as well as the total reducing power by FRAP and CUPRAC assays and the metal chelating activities. LEK showed efficient radical scavenging activity with DPPH, ABTS, DMPD, and O₂⁻ radicals; ferric (Fe³⁺) and cupric (Cu²⁺) ion reducing power and metal chelating activities. Moreover, the amounts of phenolic compounds, such as caffeic acid, ferulic acid, syringic acid, ellagic acid, catechol, pyrogallol, p-hydroxy benzoic acid, vanillin, p-coumaric acid, gallic acid, quercetin, ??-tocopherol and ascorbic acid, in LEK were quantified by LC-MS-MS. The results show that pyrogallol (2070.0 mg/kg LEK) is the main phenolic compound responsible for the antioxidant and radical scavenging activities of LEK. Finally, total phenolic and flavonoid contents were determined as gallic acid (GAE) and quercetin equivalents (QE). The GAE and QE values in LEK were 16.67 ± 2.83 ??g GAE/mg and 12.95 ± 0.52 ??g QE/mg, respectively. The results suggest that consumption of kiwifruit (A. deliciosa) can be beneficial effects due to its antioxidant properties.     

Antioxidant properties of dried product of ‘haba-nori’, an edible brown alga, Petalonia binghamiae (J. Agaradh) Vinogradova

Dried ‘haba-nori’ Petalonia binghamiae, a brown alga, is a traditional food in the fisheries towns in Japan. To determine the antioxidant properties of the dried P. binghamiae, assays for antioxidant activities, including ferrous-reducing power, ferrous ion chelating, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging and scavenging of a superoxide anion radical-generated by non-enzymatic system were tested in this study. A water extract solution contained total phenols at about 75 μmol phloroglucinol equivalents/g dry sample and showed strong antioxidant activities in the reducing power, DPPH radical and superoxide anion radical scavenging assays. The antioxidant activities were detected in high-molecular (>100 kDa), 10–30 kDa, and low-molecular (<5 kDa) fractions and were correlated with, not only phenolic compounds, but also brown compounds. The radical- scavenging activities were increased by heat treatment at 121 °C for 1 h. These results suggest that P. binghamiae is both a useful seafood and a healthy food with antioxidant activity.     

丝瓜花不同溶剂提取物抗氧化活性及其酚类成分分析

以无水乙醇、70%乙醇、40%乙醇和水分别对丝瓜花进行提取,并测定各提取物中总酚、总黄酮含量,采用DPPH·清除能力、超氧化物自由基清除能力、FRAP抗氧化能力和亚铁离子螯合能力等方法评价其抗氧化活性,通过HPLC分析其中酚类成分。结果表明,70%和40%乙醇提取物总酚及总黄酮含量较高,而且DPPH·清除活性、FRAP还原力最强,40%乙醇提取物、水提物分别具有最强的超氧阴离子自由基清除活性和亚铁离子螯合能力。总酚含量与DPPH·清除活性之间存在较强的相关性(R²=0.8688)。HPLC分析检出提取物中9种酚类化合物,其中含量最高的为杨梅素。试验结果说明,70%乙醇、40%乙醇可能是丝瓜花抗氧化性物质提取的较好溶剂。结果表明丝瓜花是一种较好的抗氧剂资源。     

老山芹全株及其不同部位酚类物质含量及抗氧化能力分析

比较老山芹及其不同部位（嫩叶、茎）甲醇提取物总多酚、总黄酮含量,测定5 种抗氧化指标（铁还原能力、超氧阴离子自由基清除能力、羟自由基清除能力、1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力、2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS）阳离子自由基清除能力）,研究其体外抗氧化活性间的差异。结果表明：老山芹嫩叶总多酚含量为30.51 mg/g,分别为全株植物与嫩茎的1.25、1.78 倍;老山芹嫩叶总黄酮含量为28.92 mg/g,分别为全株植物与嫩茎的1.34、4.00 倍。在抗氧化能力测定实验中,铁还原能力、超氧阴离子自由基清除能力、羟自由基清除能力排序均为嫩叶＞全株植物＞嫩茎＞对照组（VC）;ABTS阳离子自由基清除能力排序为嫩叶＞全株植物＞对照组（Trolox）＞嫩茎;DPPH自由基清除能力排序为嫩叶＞嫩茎＞对照组（VC）＞全株植物。老山芹及不同部位甲醇提取物对超氧阴离子自由基、羟自由基清除能力较强,对DPPH自由基、ABTS阳离子自由基清除能力次之,铁还原能力较弱。     

羟脯氨酸小肽的体外抗氧化活性

羟脯氨酸作为胶原蛋白的特征成分,其在肽序列中可使胶原衍生低聚肽对肽酶或蛋白酶产生高度抗性,口服后经过胃肠消化吸收至血液中仍能以肽的形式存在。羟脯氨酸小肽可在肠上皮细胞膜部位被完整吸收,并在血浆达到较高的水平,具有良好的吸收率和生物利用度以及更稳定、高效的生物活性。本实验以15 条羟脯氨酸小肽为研究对象,采用1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基、2,2’-联氮双(3-乙基苯并噻唑啉-6-磺酸)（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonicacid),ABTS）阳离子自由基、超氧阴离子自由基和羟自由基4 种体外方法对其抗氧化活性进行评价。结果表明：在15 条羟脯氨酸小肽中,Leu-Hyp的DPPH自由基清除率最高,为23.6%;Leu-Hyp、Ile-Hyp的ABTS阳离子自由基清除率最高,分别为57.8%和57.7%;其他小肽的DPPH自由基和ABTS阳离子自由基清除能力均较低,清除率均小于15%或不具有ABTS阳离子自由基清除能力。浓度为3 mmol/L时,15 条小肽的羟自由基和超氧阴离子自由基清除能力均较强,清除率分别可达30%～50%和60%～80%。综上,本实验所选15 条羟脯氨酸小肽均具有一定的羟自由基和超氧阴离子自由基清除能力,其中Leu-Hyp、Ile-Hyp的体外抗氧化性最好。     

澳洲坚果青皮不同极性溶剂分步提取物功能成分与抗氧化活性及其相关性分析

采用80%（体积分数,下同）乙醇超声提取澳洲坚果青皮,依次用石油醚、氯仿、乙酸乙酯、正丁醇4 种不同极性溶剂对其提取物进行分步萃取,剩余为水溶解物,分别得到80%乙醇提取物、石油醚提取物、氯仿提取物、乙酸乙酯提取物、正丁醇提取物与水溶解物6 种溶剂提取物,测定其总酚、黄酮、多糖等主要功能成分质量分数与抗氧化活性,并分析其相关性。结果表明：总酚和黄酮质量分数在澳洲坚果青皮乙酸乙酯提取物中均最高,分别为（40.36±0.48）%与（41.68±0.93）%,多糖质量分数在正丁醇提取物中最高,为（22.08±2.09）%。澳洲坚果青皮不同极性溶剂分步提取物具有较强的2,2’-联氮-双-3-乙基苯并噻唑啉-6-磺酸（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid),ABTS）阳离子自由基清除能力与较高的还原力,对1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基与超氧阴离子自由基拥有一定的清除能力。其中,乙酸乙酯提取物对DPPH自由基、ABTS阳离子自由基的清除能力最强,还原力最高,其半抑制浓度（half maximal inhibitory concentration,IC50）分别为0.67、0.05、0.09 mg/mL。正丁醇提取物对超氧阴离子自由基的清除能力最强,其IC50为0.08 mg/mL,相同质量浓度下优于芦丁。通过对各指标进行皮尔逊相关性分析得出,澳洲坚果青皮不同极性溶剂分步提取物对DPPH自由基清除能力、ABTS阳离子自由基清除能力与还原力均与其总酚、黄酮、多糖质量分数呈极显著正相关（P＜0.01）,对超氧阴离子自由基的清除能力与其多糖质量分数呈极显著正相关（P＜0.01）。应用多元回归分析建立了澳洲坚果青皮不同极性溶剂分步提取物DPPH自由基清除能力（Y1）、超氧阴离子自由基清除能力（Y2）、ABTS阳离子自由基清除清除能力（Y3）、还原力（Y4）与其功能成分（总酚（X1）、黄酮（X2）、多糖（X3）与皂苷及其他成分（X4））质量分数之间的线性回归方程,分别为Y1＝7.634 4－0.071 0X1＋0.170 2X2＋0.227 6X3－0.013 3X4、Y2＝29.024 5－0.405 0X1＋0.320 0X2＋0.597 2X3、Y3＝40.305 6＋0.188 8X1＋0.030 4X4与Y4＝0.298 2＋0.004 5X2＋0.006 0X3。结论：研究为开发利用澳洲坚果青皮资源提供一定的技术依据。     

Evaluation of reducing power and radical scavenging activities of water and ethanol extracts from sumac (Rhus coriaria L.)

The purpose of this study was to determine the reducing power, metal chelating, and radical scavenging capabilities of water and ethanol extracts of sumac (Rhus coriaria L.), comparatively. The water and ethanol extracts of sumac were evaluated for their radical scavenging activities by means of the DPPH and DMPD assays. Water extract of sumac (R. coriaria L.) scavenged radicals effectively with EC₅₀ values of 36.4 ??g/ml for DPPH free radical and 44.7 ??g/ml for DMPD cation radical. Similarly, the total reducing power of water extract was found higher than ethanol extract in both potassium ferricyanide reduction (FRAP) and cupric ions reduction capacity methods (CUPRAC). 2,2′-Bipyridine was used to determine the metal chelating activity and the result of water extract was found higher than ethanol extract. Total phenolic and total flavonoid contents of both extracts were studied as well. The values of water extract were found to be higher than that of ethanol extract. The present study found that water extracts of sumac (R. coriaria L.) have effective antioxidant and radical scavenging activities as compared to ethanol extracts.     

Determination of antioxidative potential of lichen Usnea ghattensis in vitro

The study was aimed at evaluating the antioxidant activities of extract of Usnea ghattensis. The antioxidant activity, reducing power, superoxide anion radical scavenging and free radical scavenging activities were studied. The antioxidant activity increased with the increasing amount of extracts (2-20 mg/ml) added to the linoleic acid emulsion. Lipid peroxidation upto 73.3% was inhibited by the extract of 20 mg/ml and 39.2% by α-tocopherol at the same concentration. These effects were statistically significant (r²=0.876,P<0.01) when compared with control. However, the extract had no significant effect on superoxide anion scavenging by the PMS/NADH-NBT method. Like antioxidant activity, the reducing power and free radical scavenging activity of extract depends on concentration and increasing with increased amount of sample. The reducing power and DPPH radical-scavenging activity of U. ghattensis extract were found greater than the BHA and BHT. The results obtained in the present study indicate that U. ghattensis is a potential source of natural antioxidant.     

Antioxidant and antimicrobial activities of Smilax china L. leaf extracts

Antioxidant and antimicrobial activities of Smilax china L. leaf extracts obtained with methanol, ethanol, acetone, and water were investigated. Antioxidant activity was evaluated by determining the DPPH radical scavenging activity, ABTS radical scavenging activities, total phenol content (TPC), and reducing power (RP). The highest DPPH, ABTS radical scavenging activity, and RP were found in the ethanol extract, which also showed the highest TPC (105.81±0.48 μg gallic acid equivalents/mL). The antimicrobial activity of all the extracts against foodborne microorganisms was determined by paper disc method. All the extracts inhibited the growth of Listeria monocytogenes, Staphylococcus aureus, and Salmonella Typhimurium, however, no antimicrobial activity was observed against Escherichia coli O157:H7. The results indicated that Smilax china L. possessed antioxidant and antimicrobial substances, and suggested that the ethanol extract can be applied into food and cosmetic industry.     

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.     

Assessment of in vitro antioxidant capacity and polyphenolic composition of selected medicinal herbs from Leguminosae family in Peninsular Malaysia

Determination of total phenolic (TPC), flavonoid and anthocyanin contents, and various antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging, ferric reducing power, ferrous ion chelating and lipid peroxidation inhibition) of leaves and flowers of Bauhinia kockiana, Caesalpinia pulcherrima and Cassia surattensis were performed in this study. The B. kockiana flower was found to possess the highest TPC (8280 ± 498 mg GAE/100 g), free radical scavenging activity (ascorbic acid equivalents 14,600 ± 2360 mg AA/100 g) and reducing ability (72.4 ± 8.7 mg GAE/g). Rutin and chlorogenic acid were detected in the plants, where the C. pulcherrima leaf contained the highest amount of rutin (669 ± 26 mg/100 g), while minute amounts of chlorogenic acid were detected in C. surattensis leaf (9.13 ± 0.44 mg/100 g). The C. pulcherrima leaf displayed the highest ferrous ion chelating and lipid peroxidation inhibition activities. Positive correlation was observed between TPC and various antioxidant activities.     

Antioxidative activity of Mungoong,an extract paste,from the cephalothorax of white shrimp (Litopenaeus vannamei)

The antioxidative activity of Mungoong, an extract paste, from the cephalothorax of white shrimp (Litopenaeus vannamei) was studied. Extraction media were shown to affect the antioxidative activity and properties of resulting extracts from Mungoong. Distilled water exhibited the highest efficacy in extracting the antioxidants from Mungoong, as evidenced by the highest ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picryl hydrazyl) radical scavenging activity as well as ferric reducing activity power (FRAP), compared with distilled water/ethanol mixture (1:1, 1:2 and 2:1) and ethanol. UV-absorbances at both 280 and 295 nm (A₂₈₀, A₂₉₅), browning intensity (A₄₂₀) and fluorescence intensity were also highest in the extract using distilled water. ABTS and DPPH radical scavenging activity and FRAP of water extract, increased linearly with increasing concentration. Good correlation between ABTS and DPPH radical scavenging activity; DPPH radical scavenging activity and FRAP; ABTS radical scavenging activity and FRAP were observed, suggesting that antioxidants in the extract, possessed the capability of scavenging the radicals together with reducing power. Antioxidants in the water extract from Mungoong showed high stability over the wide pH ranges (2–11) and temperature up to 100 °C, in which the activity of more than 80% remained. MALDI-TOF analysis revealed that water extract contained the peptides having the mass ranges of m/z 400–1000 and 4000–7000.     

Effect of ultrafine grinding on hydration and antioxidant properties of wheat bran dietary fiber

Wheat bran dietary fiber (DF) powders was prepared by ultrafine grinding, whose effects were investigated on the composition, hydration and antioxidant properties of the wheat bran DF products. The results showed that ultrafine grinding could effectively pulverize the fiber particles to submicron scale. As particle size decrease, the hydration properties (water holding capacity, water retention capacity and swelling capacity) of wheat bran DF were significantly (p < 0.05) decreased and a redistribution of fiber components from insoluble to soluble fractions was observed. The antioxidant activities of wheat bran and DF before and after grinding were in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion-chelating activity, reducing power and total phenolic content (TPC). Compared with DF before and after grinding, micronized insoluble DF showed increased chelating activity, reducing power and TPC yet decreased DPPH˙ radical scavenging activity. Positive correlations were detected between chelating activity, reducing power and TPC.     

Antioxidant activity of stem and root extracts of Rhubarb (Rheum ribes): An edible medicinal plant

The antioxidant activity of chloroform and methanol extract of roots and stems of Rhubarb (Rheum ribes L.), which are used for medicinal purposes and also its fresh stems and petioles are consumed as vegetable, was studied. The antioxidant potential of both extracts of roots and stems were evaluated using different antioxidant tests, namely total antioxidant (lipid peroxidation inhibition activity), DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging, superoxide anion radical scavenging, ferric reducing power, and cupric reducing power (CUPRAC), and metal chelating activities. Total antioxidant activity was also measured according to the β-carotene bleaching method, and all four extracts exhibited stronger activity than known standards, namely butylated hydroxytoluene (BHT) and α-tocopherol. Particularly, higher activity was exhibited by roots with 93.1% and 84.1% inhibitions of chloroform and methanol extracts, while 82.2% and 82.0% inhibitions by stem extracts, respectively. However, both methanol extracts exhibited higher DPPH radical scavenging activity than the corresponding chloroform extracts, moreover, methanol extract of the stems showed better activity than BHT. In addition, both root extracts showed more potent superoxide anion radical scavenging activity than BHT, and comparable with well known radical scavenger l-ascorbic acid. Except chloroform extract of the roots, the other three extracts exhibited better metal chelating activity than quercetin. Also, total phenolic and flavonoid contents in both extracts of the roots and stems of R. ribes were determined as pyrocatechol and quercetin equivalents, respectively.     

Antioxidant and free radical scavenging activities of pigments extracted from molasses alcohol wastewater

The pigments from molasses alcohol wastewater were extracted by the macroporous resin adsorption method. The antioxidant and free radical scavenging activities of these pigments were also investigated. The adsorptive characteristics of five macroporous resins including HPD-600, HPD-500, D301-R, NKA-II and D296-R were studied and the results showed that the macroporous resin HPD-600 was most appropriate for extracting the pigments from molasses alcohol wastewater. The antioxidant and free radical scavenging activities of pigments extracted from alcohol wastewater were evaluated using nitrate, hydroxyl radical, superoxide anion radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) in vitro model systems. The pigment extract exhibited a concentration-dependent radical scavenging activity in all the systems. Meanwhile, scavenging activity of pigment extract in the DPPH system was found to be significantly (P < 0.05) higher than that in other systems and the 50% inhibitory concentration (IC₅₀ value) was about 0.07 mg/ml. The scavenging effect of pigment extract on superoxide anion radical was very weak with IC₅₀ value greater than 10 mg/ml.