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In this study, novel chitosan (CS) based active films were developed by grafting natural phenolic antioxidant of protocatechuic acid (PA) onto chitosan backbones. The physicochemical, mechanical and antioxidant properties of three PA grafted CS (PA-g-CS) films with different grafting ratios were characterized. The transparent PA-g-CS films exhibited yellowish color with thickness ranging from 44.1 to 48.6 μm. By contrast with CS film, PA-g-CS films with medium and high grafting ratios showed decreased moisture content, water vapor permeability; however, increased water solubility and tensile strength. The barrier to UV light of CS film could be improved by grafting with PA. An increase in the total color difference was observed for PA-g-CS films, indicating PA-g-CS films were more colored. Among four kinds of films tested, PA-g-CS film with medium grafting ratio exhibited the highest tensile strength (45.7 MPa) and elongation at break (5.05%). According to thermogravimetric analysis, the maximum rates of weight loss for PA-g-CS films appeared at 291.8–294.0 °C. Antioxidant activity assays showed that PA-g-CS films had both dose-dependent and time-dependent scavenging activity on DPPH radical. Our results suggest that PA-g-CS films are expected to serve as novel antioxidant food packaging materials. [ABSTRACT FROM AUTHOR]

In this study, protocatechuic acid (PA) was grafted onto chitosan (CS) by a carbodiimide mediated cross-linking reaction. The structural characterization, physical property and antioxidant activity of PA grafted CS (PA-g-CS) was investigated. As results, three copolymers with different grafting ratios (61.64, 190.11 and 279.69 mg PAE/g) were obtained by varying the molar ratios of reaction substrates. PA-g-CS showed the same UV absorption peaks as PA at 258 and 292 nm. As compared to CS, PA-g-CS exhibited a decreased band at 1596 cm −1 and a new band at 1716 cm −1 , suggesting the formation of amide and ester linkages between PA and CS. New proton signals at δ 6.77–7⋅33 ppm were observed on 1 H NMR spectrum of PA-g-CS, assigning to the methine protons of PA. Signals at δ 150.8–116.6 ppm on 13 C NMR spectrum of PA-g-CS was assigned to the aromatic ring carbon of PA moieties. All the structural information confirmed the successful grafting of PA onto CS. SEM observation showed CS had a smooth surface, while PA- g -CS had a rough surface. TGA revealed the thermal stability of PA-g-CS was lower than CS. Antioxidant activity assays further verified the reducing power and DDPH radical scavenging activity of PA-g-CS was much higher than CS. [ABSTRACT FROM AUTHOR]

In this study, structural characterization, physical property and antioxidant activity of catechin grafted Tremella fuciformis polysaccharide (catechin-g-TPS) were investigated. Crude polysaccharides were isolated from the fruit bodies of T. fuciformis and further purified on DEAE-52 and Sepharose CL-4B chromatography to afford a main purified fraction (named TPS). The molecular weight of TPS was determined as 5.82 × 10 5 Da by HPLC. Then, the free radical mediated grafting of catechin onto TPS was achieved by using a redox system. As compared with the unmodified TPS, catechin-g-TPS showed new bands within the range of 1300–1600 cm −1 in FT-IR spectrum, and exhibited new signals at around δ 6.00 and 6.80 ppm in 1 H NMR spectrum. Thermogravimetric analysis indicated the thermal stability of catechin-g-TPS was higher than TPS. X-ray diffraction spectrum of catechin-g-TPS exhibited two sharp narrow diffraction peaks at 14.2 and 32.1°, corresponding to the crystalline peaks of catechin. Scanning electron microscopy observation revealed the surface of TPS was smooth, whereas the surface of catechin-g-TPS was much rough. These results all confirmed the successful grafting of catechin onto TPS. Moreover, catechin-g-TPS had higher 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and reducing power as compared to TPS. [ABSTRACT FROM AUTHOR]

This study aimed to compare the extraction efficiency of dynamic high pressure microfluidization-assisted extraction (DHPMAE) and other commonly used extraction methods on the antioxidant activities (AAs) of sweet potato leaves ( Ipomoea batatas L., SPL), and to identify the antioxidant compounds by HPLC-QTOF-MS 2 . Two highly consumed commercial varieties, orange-fleshed and cream-fleshed sweet potato leaves (OFL and CFL), were taken as materials. OFL was evidenced to be a better antioxidants resource than CFL due to higher polyphenols and AAs. DHPMAE had the best extraction efficiency on total phenolics and total flavonoids, with the values in OFL extract at 16.35 mg GAE/g DM and 16.51 mg RE/g DM, respectively. DHPMAE extract also exhibited the strongest DPPH· and ABTS· + scavenging ability, chelating ability and reducing power. Multiple regression analysis revealed that polyphenols played an important contribution to the AAs of SPL extracts. After successive fractionation of DHPMAE extract by chloroform, ethyl acetate, and n -butanol, the ethyl acetate fraction showed the highest total phenolic (569.38 mg GAE/g Extract) and total flavonoid (43.15 mg RE/g Extract) content, as well as the highest AAs. HPLC-QTOF-MS 2 analysis of the ethyl acetate fraction resulted in identifying 37 compounds including 20 phenolic acids, 12 flavonoids, 3 organic acids, 1 nucleoside and 1 ester, and 20 of them were firstly detected in SPL. Caffeoylquinic acid derivatives and flavonoids were the most abundant antioxidant compounds. The presented results suggested that DHPM might be a promising assisted technology in extracting polyphenols from plants, and SPL could be utilized for the development of functional food. [ABSTRACT FROM AUTHOR]

Dynamic high pressure microfluidization (DHPM)-assisted extraction (DHPMAE) of lotus ( Nelumbo nucifera ) leaves polysaccharides (LLPs) was optimized by response surface methodology. The optimal extraction conditions were: liquid/solid ratio of 35:1 (v/m, mL/g), processing pressure of 180 MPa, processed two times, extraction temperature of 76 °C, extraction time of 50 min. Under the optimal extraction conditions, DHPMAE produced a higher polysaccharides yield (6.31%) than leaching (2.95%). Scanning electron microscope (SEM) analysis revealed that DHPM could reduce the particles size and make the surface more unconsolidated. The LLPs prepared by both methods showed similar FT-IR spectrum, and were consisted of the same monosaccharides, including rhamnose, fucose, arabinose, xylose, mannose, glucose and galactose. The content of each monosaccharide in extracts, however, was quite different. The average molecular weight of LLPs prepared by DHPMAE is 550 kDa, smaller than 578 kDa obtained by leaching. The LLPs prepared by DHPMAE exhibited stronger DPPH scavenging ability (IC 50 value of 0.38 mg/mL), HO scavenging ability (IC 50 value of 0.61 mg/mL) and reducing power. Therefore, DHPMAE can be a promising alternative to traditional extraction techniques for polysaccharides from plants, and lotus leaves might be a potential resource of natural antioxidants. [ABSTRACT FROM AUTHOR]

In this study, the antioxidant activity and hepatoprotective effect of inulin and catechin grafted inulin (catechin-g-inulin) against carbon tetrachloride (CCl 4 )-induced acute liver injury were investigated. Results showed that both inulin and catechin-g-inulin had moderate scavenging activity on superoxide radical, hydroxyl radical and H 2 O 2 , as well as lipid peroxidation inhibition effect. The antioxidant activity decreased in the order of Vc > catechin > catechin-g-inulin > inulin. Administration of inulin and catechin-g-inulin could significantly reduce the elevated levels of serum aspartate transaminase, alanine transaminase and alkaline phosphatase as compared to CCl 4 treatment group. Moreover, inulin and catechin-g-inulin significantly increased the levels of hepatic superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione and total antioxidant capacity, whereas markedly decreased the malondialdehyde level when compared with CCl 4 treatment group. Notably, catechin-g-inulin showed higher hepatoprotective effect than inulin. In addition, the hepatoprotective effect of catechin-g-inulin was comparable to positive standard of silymarin. Our results suggested that catechin-g-inulin had potent antioxidant activity and potential protective effect against CCl 4 -induced acute liver injury. [ABSTRACT FROM AUTHOR]

Optimization of extraction conditions, preliminary characterization and in vitro antioxidant activity of polysaccharides from black soybean (BSPS) were investigated. The results of Box-Behnken design showed that the optimal extraction conditions for BSPS were as follows: ratio of water to material of 20 ml/g, extraction time of 6.4 h and extraction temperature of 92 °C, with a corresponding yield of 2.56%. The crude BSPS were further fractionated on DEAE-52 and Sepharose CL-4B chromatography to afford three purified fractions (BSPS-1, BSPS-2 and BSPS-3). Chemical analysis showed that the three purified fractions were mainly composed of carbohydrate and uronic acid. In addition, BSPS-1 was composed of arabinose, rhamnose, galactose, glucose and mannose in the molar ratio of 1.79:1.00:2.59:26.54:1.01. BSPS-2 was composed of arabinose, rhamnose, xylose, galactose and mannose in the molar ratio of 8.10:4.80:9.15:13.38:1.00. BSPS-3 was composed of arabinose, rhamnose, galactose and mannose in the molar ratio of 16.80:3.60:33.66:1.00. The results of Fourier transform-infrared spectroscopy further confirmed the characteristic polysaccharide structures of the three purified fractions. Moreover, antioxidant assays showed crude BSPS and its purified fractions had potential superoxide anion and DPPH radical scavenging activities, and their antioxidant activity decreased in the order of crude BSPS > BSPS-3 > BSPS-2 > BSPS-1. [ABSTRACT FROM AUTHOR]

Highlights: [•] Caffeic and ferulic acids were grafted onto chitosan by a free radical mediated method. [•] Copolymers had good free radical scavenging and peroxidation inhibition effects. [•] Copolymers significantly increased antioxidant enzymes activities and decreased malondialdehyde levels in d-galactose induced aging mice. [ABSTRACT FROM AUTHOR]

Abstract: In this study, three phenolic acids including gallic acid (GA), caffeic acid (CA) and ferulic acid (FA) were grafted onto N,O-carboxymethyl chitosan (NOCC) by a free radical mediated grafting method. The grafted copolymers obtained were all water-soluble samples. UV–vis absorption peaks of the grafted copolymers shifted toward longer wavelengths. FT-IR spectroscopy of the grafted copolymers exhibited additional phenolic characteristics of the aromatic ring C C stretching within 1450–1650cm−1. NMR spectroscopy of the grafted copolymers showed new peaks at 6.2–7.6ppm assigned to the phenyl protons of phenolic acids. These results all confirmed the successful grafting of three phenolic acids to NOCC. The conjugation probably occurred at amine of NOCC and carboxyl groups of phenolic acids. The grafted copolymers exhibited decreased crystallinity as compared to NOCC and chitosan. Moreover, antioxidant activity in vitro assays showed that the antioxidant property decreased in the order of GA-g-NOCC>CA-g-NOCC>FA-g-NOCC>NOCC>chitosan. Our results suggested the potential of phenolic acids grafted NOCC for the development of effective antioxidant agents. [Copyright &y& Elsevier]

Abstract: Hemodialysis can remove uremic solutes but this treatment induces oxidative stress in uremic patients because of hemo-incompatibility. Therefore, we hypothesised that an antioxidant dialysate (a dialysate containing antioxidant(s)) would provide antioxidant defence in uremic patients during hemodialysis. Several herbal extracts were studied and measurements of antioxidant power and stability assays indicated that epigallocatechin gallate (EGCG) was the best of those tested for use as an antioxidant dialysate (EGCG dialysate). We observed that EGCG dialysate could provide the highest level of antioxidant defence at a dialysate flow rate of 500ml/min and a blood flow rate of 200ml/min. In addition, some important parameters for hemodialysis were calculated for supporting the protective role of EGCG dialysate. This is the first description of the preparation of an antioxidant dialysate. We suggest that EGCG dialysate will reduce the level of oxidative stress in hemodialysis patients, leading to a decrease of complications associated with oxidative damage. [Copyright &y& Elsevier]

AbstractUremic patients with diabetes suffer from high levels of oxidative stress due to regular hemodialysis therapy (neutrophil activation induced by hemo-incompatibility between the hemodialyser and blood) and complications associated with diabetes. Several plasma biomarkers were screened in 13 uremic diabetic patients after receiving the mixture of (–)-epigallocatechin gallate (EGCG), a major component of green tea extract, and Amla extract (AE), from Emblica officinalis, the Indian gooseberry, for 3 months. We found that oral administration of a 1:1 mixture of EGCG and AE for 3 months significantly improved antioxidant defense as well as diabetic and atherogenic indices in uremic patients with diabetes. Furthermore, no significant changes in hepatic function, renal function, or inflammatory responses were observed. These results suggest that a 1:1 combination of EGCG and AE is a safe and effective treatment for uremic patients with diabetes. [ABSTRACT FROM AUTHOR]