Juan Kan

In vitro and in vivo antioxidant activity of ethanolic extract of white button mushroom (Agaricus bisporus).

The antioxidant activities of ethanolic extract from edible mushroom Agaricus bisporus (A. bisporus) were evaluated by various methods in vitro and in vivo. In antioxidant assays in vitro, ethanolic extract of A. bisporus was found to have strong reducing power, superoxide radical, hydroxyl radical and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, and moderate hydrogen peroxide scavenging activity. In antioxidant assays in vivo, mice were administered with ethanolic extract of A. bisporus via gavage for 30 consecutive days. As a result, administration of ethanolic extract significantly enhanced the activities of antioxidant enzymes in serums, livers and hearts of mice. In addition, the total phenolic content in the extract determined by Folin-Ciocalteu method was 6.18mg of gallic acid equivalents per gram of dry weight. The main phenolic compounds in ethanolic extract analyzed by ultra-high performance liquid chromatography tandem mass spectrometry were determined as gallic acid, protocatechuic acid, catechin, caffeic acid, ferulic acid and myricetin. These results suggested that ethanolic extract of A. bisporus had potent antioxidant activity and could be explored as a novel natural antioxidant.

Free radical mediated grafting of chitosan with caffeic and ferulic acids: structures and antioxidant activity.

In this study, two water soluble chitosan derivatives were synthesized by grafting caffeic acid (CA) and ferulic acid (FA) onto chitosan via a free radical mediated method. The structural characterization, antioxidant activity in vitro and in vivo of chitosan derivatives were determined. Results showed that the UV-vis absorption peaks of chitosan derivatives shifted toward longer wavelengths. FT-IR spectroscopy exhibited the typical phenolic characteristics within 1450-1600 cm(-1). (1)H NMR spectroscopy showed new peaks of phenyl protons at 6.2-7.6 ppm. (13)C NMR spectroscopy showed additional peaks between 110 and 150 ppm assigned to the C=C of phenolic groups. These results all confirmed the successful grafting of CA and FA onto chitosan backbones. The chitosan derivatives had decreased thermal stability and crystallinity as compared to chitosan. In vitro assays showed that the antioxidant activity decreased in the order of CA-g-chitosan>FA-g-chitosan>chitosan. Moreover, administration of the chitosan derivatives could significantly increase antioxidant enzymes activities and decrease malondialdehyde levels in both serums and livers of d-galactose induced aging mice. Our results indicated the potential of CA-g-chitosan and FA-g-chitosan in the development of novel antioxidant agents.

Preparation, characterization and antioxidant activity of phenolic acids grafted carboxymethyl chitosan

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 CC stretching within 1450-1650 cm(-1). NMR spectroscopy of the grafted copolymers showed new peaks at 6.2-7.6 ppm 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.

Synthesis of chitosan-gallic acid conjugate: structure characterization and in vitro anti-diabetic potential.

In this study, chitosan grafted copolymer with gallic acid (GA) was synthesized by a novel and efficient free radical mediated method. The optimal grafting conditions, structural characterization, α-glucosidase and α-amylase inhibitory activities of chitosan grafted copolymers were investigated. Results showed that the maximum grafting ratio (128.3 mg GA equivalents/g) was obtained at 12 h with 5 g/L chitosan, 16 g/L GA, 2 g/L ascorbic acid and 0.2 M hydrogen peroxide. UV-vis, Fourier-transform infrared and nuclear magnetic resonance spectroscopy all confirmed the successful grafting of GA onto chitosan. The conjugation of GA onto chitosan probably occurred between amine (C-2), hydroxyl groups (C-3 and C-6) of chitosan and carboxyl groups of GA, forming amide and ester linkages, respectively. Differential scanning calorimetry and X-ray diffraction spectra indicated that GA grafted chitosan (GA-g-chitosan) had decreased thermal stability and crystallinity as compared to chitosan. Notably, GA-g-chitosan showed increased α-glucosidase and α-amylase inhibitory activity with the increase of grafting ratio. These results indicated the potential of GA-g-chitosan in the development of an effective anti-diabetic agent.

Extraction, characterization and in vitro antioxidant activity of polysaccharides from black soybean

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 6.4h 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.

Synthesis, characterization and in vitro anti-diabetic activity of catechin grafted inulin

In this study, a novel biological macromolecule with strong in vitro anti-diabetic activity was developed by grafting catechin onto inulin via a free radical mediated method. The characterization, α-glucosidase and α-amylase inhibitory activities of catechin grafted inulin (catechin-g-inulin) were investigated. Results showed that the grafting ratio of catechin-g-inulin was 124.8 mg CAE/g. UV-vis spectrum of catechin-g-inulin exhibited a new band at 280 nm, attributing to B ring of catechin moiety. FT-IR spectrum of catechin-g-inulin showed new absorption bands between 1540 and 1418 cm(-1), attributing to CC stretching vibration of catechin moiety. (1)H NMR spectrum of catechin-g-inulin preserved all the characteristic proton signals of inulin and partial signals of catechin. These all confirmed the successful grafting copolymerization. Conjugation probably occurred between OH of inulin (C-6) and H-6/H-8 of catechin (A ring). Catechin-g-inulin also exhibited increased thermal stability and crystallinity as compared to inulin. Moreover, in vitro anti-diabetic assays showed the α-glucosidase inhibitory activity decreased in the order of catechin-g-inulin>catechin>acarbose>inulin, and α-amylase inhibitory activity decreased in the order of catechin-g-inulin>acarbose>catechin>inulin. These indicated the potential of catechin-g-inulin in the development of a novel effective anti-diabetic agent.

Antioxidant and protective effect of inulin and catechin grafted inulin against CCl4-induced liver injury

In this study, the antioxidant activity and hepatoprotective effect of inulin and catechin grafted inulin (catechin-g-inulin) against carbon tetrachloride (CCl4)-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 H2O2, 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 CCl4 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 CCl4 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 CCl4-induced acute liver injury.

Protocatechuic acid grafted onto chitosan: Characterization and antioxidant activity

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 279.69mg 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 292nm. As compared to CS, PA-g-CS exhibited a decreased band at 1596cm(-1) and a new band at 1716cm(-1), suggesting the formation of amide and ester linkages between PA and CS. New proton signals at δ6.77-7⋅33ppm 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.

Structure, physical property and antioxidant activity of catechin grafted Tremella fuciformis polysaccharide.

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.

Synthesis, characterization, bioactivity and potential application of phenolic acid grafted chitosan: A review

In recent years, increasing attention has been paid to the grafting of phenolic acid onto chitosan in order to enhance the bioactivity and widen the application of chitosan. Here, we present a comprehensive overview on the recent advances of phenolic acid grafted chitosan (phenolic acid-g-chitosan) in many aspects, including the synthetic method, structural characterization, biological activity, physicochemical property and potential application. In general, four kinds of techniques including carbodiimide based coupling, enzyme catalyzed grafting, free radical mediated grafting and electrochemical methods are frequently used for the synthesis of phenolic acid-g-chitosan. The structural characterization of phenolic acid-g-chitosan can be determined by several instrumental methods. The physicochemical properties of chitosan are greatly altered after grafting. As compared with chitosan, phenolic acid-g-chitosan exhibits enhanced antioxidant, antimicrobial, antitumor, anti-allergic, anti-inflammatory, anti-diabetic and acetylcholinesterase inhibitory activities. Notably, phenolic acid-g-chitosan shows potential applications in many fields as coating agent, packing material, encapsulation agent and bioadsorbent.