Xiaoxiong Zeng

Purification, antitumor and antioxidant activities in vitro of polysaccharides from the brown seaweed Sargassum pallidum

Supercritical CO2 extraction, ultrasonic-aid extraction and membrane separation technology were applied to prepare Sargassum pallidum polysaccharides (SP). Three main fractions, SP-1, SP-2 and SP-3, were obtained by membranes of 1.0×10(-4)mm pore size and normal molecular-weight cut-off of 50kDa. The resulting three preparations were further purified by DEAE Cellulose-52 chromatography to afford seven polysaccharide fractions. Furthermore, the antitumor and antioxidant activities, in vitro, of the polysaccharide fractions were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical-scavenging assay, respectively. SP-3-1 and SP-3-2 showed significantly higher antitumor activity against the HepG2 cells, A549 cells, and MGC-803 cells. SP-3 had the highest sulfate content (22.6%). These results indicate that the higher antitumor activity of SP-3-1 and SP-3-2 from SP-3 with lower molecular weights may be related to their molecular weights and sulfate contents. The antioxidant activities of SP-1, SP-2 and SP-3 were low at the tested concentration.

Optimization of Fabrication Parameters To Produce Chitosan−Tripolyphosphate Nanoparticles for Delivery of Tea Catechins

This work investigated the polyanion-initiated gelation process in fabricating chitosan-tripolyphosphate (CS-TPP) nanoparticles intended to be used as carriers for delivering tea catechins. The results demonstrated that the particle size and surface charge of CS-TPP nanoparticles could be controlled by fabrication conditions. For preparation of CS-TPP nanoparticles loaded with tea catechins, the effects of modulating conditions including contact time between CS and tea catechins, CS molecular mass, CS concentration, CS-TPP mass ratio, initial pH value of CS solution, and concentration of tea catechins on encapsulation efficiency and the release profile of tea catechins in vitro were examined systematically. The study found that the encapsulation efficiency of tea catechins in CS-TPP nanoparticles ranged from 24 to 53%. In addition, FT-IR analysis showed that the covalent bonding and hydrogen bonding between tea catechins and CS occurred during the formation of CS-TPP nanoparticles loaded with tea catechins. Furthermore, studies on the release profile of tea catechins in vitro demonstrated that the controlled release of tea catechins using CS-TPP nanoparticles was achievable.

Effect of ultrasound on different quality parameters of apple juice.

Fresh apple juice treated with ultrasound (for 0, 30, 60 and 90 min, at 20 °C, 25 kHz frequency) was evaluated for different physico-chemical, Hunter color values, cloud value, antioxidant capacity, scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical, ascorbic acid, total phenolics, flavonoids, flavonols and microbial characteristics. No significant effect of sonication was observed on pH, total soluble solids (°Brix) and titratable acidity of apple juice. Sonication significantly improved ascorbic acid, cloud value, phenolic compounds, antioxidant capacity, DPPH free radical scavenging activity and differences in Hunter color values. Moreover, significant reduction in microbial population was observed. Findings of the present study suggested that sonication treatment could improve the quality of apple juice. It may successfully be employed for the processing of apple juice with improved quality and safety from consumers health point of view.

Grafting of gallic acid onto chitosan enhances antioxidant activities and alters rheological properties of the copolymer.

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and β-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in β-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries.

Preliminary characterization, antioxidant activity in vitro and hepatoprotective effect on acute alcohol-induced liver injury in mice of polysaccharides from the peduncles of Hovenia dulcis

The fresh fleshy peduncles of Hovenia dulcis have been used as a food supplement and traditional herbal medicine for the treatment of liver diseases and alcoholic poisoning for more than a millennium. The objectives of the present study, therefore, were to determine the antioxidant activity of polysaccharides from the peduncles of H. dulcis (HDPS) and to evaluate its hepatoprotective effect on acute alcohol-induced liver injury in mice. HDPS, prepared by hot water extraction, ethanol precipitation and treatment of macroporous resin, was found to be non-starch polysaccharide and mainly composed of galactose, arabinose, rhamnose and galacturonic acid. In in vitro antioxidant assay, HDPS exhibited high superoxide radical scavenging activity, strong inhibition effect on lipid peroxidation and a medium ferrous ion-chelating activity. For hepatoprotective activity in vivo, the administration of HDPS significantly decreased the serum levels of alanine aminotransferase and aspartate aminotransferase, significantly decreased the liver level of malondialdehyde and remarkably restored the liver activities of superoxide dismutase and glutathione peroxidase in alcohol-induced liver injury mice. The results suggested that HDPS had a significant protective effect against acute alcohol-induced liver injury possibly via its antioxidant activity to protect biological systems against the oxidative stress.

Preparation, preliminary characterization, antioxidant, hepatoprotective and antitumor activities of polysaccharides from the flower of tea plant (Camellia sinensis)

In the present study, the crude polysaccharides from the flowers of tea plant (Camellia sinensis) (TFPS) were prepared with hot water and further fractionated on a DEAE-52 cellulose chromatography to afford three purified fractions of TFPS-1, TFPS-2 and TFPS-3. Then, their preliminary structures, antioxidant and antitumor activities in vitro and hepatoprotective activity in vivo were investigated. Compared with TFPS-2 and TFPS-3, TFPS-1 had relative higher content of sulfate and relative complicated monosaccharide composition. In addition, TFPS-1 and TFPS-3 showed relative stronger antioxidant activity and inhibitory activity on the growth of human gastric cancer BGC-823 cells. For hepatoprotective activity in vivo, we demonstrated that crude TFPS significantly prevented the increase of serum alanine aminotransferase and aspartate aminotransferase levels, reduced the formation of malondialdehyde and enhanced the activities of superoxide dismutase and glutathione peroxidase in carbon tetrachloride-induced liver injury mice. The results suggested that TFPS should be a potent natural polymer with antioxidant, hepatoprotective and antitumor activities.

Sonication enhances polyphenolic compounds, sugars, carotenoids and mineral elements of apple juice

A study was initiated with the objective of evaluating the effects of sonication treatment on quality characteristics of apple juice such as polyphenolic compounds (chlorogenic acid, caffeic acid, catechin, epicatechin and phloridzin), sugars (fructose, glucose and sucrose), mineral elements (Na, K, Ca, P, Mg, Cu and Zn), total carotenoids, total anthocyanins, viscosity and electrical conductivity. The fresh apple juice samples were sonicated for 0, 30 and 60 min at 20 °C (frequency 25 kHz and amplitude 70%), respectively. As results, the contents of polyphenolic compounds and sugars significantly increased (P<0.05) but the increases were more pronounced in juice samples sonicated for 30 min whereas, total carotenoids, mineral elements (Na, K and Ca) and viscosity significantly increased (P<0.05) in samples treated for 60 min sonication. Losses of some mineral elements (P, Mg and Cu) also occurred. Total anthocyanins, Zn and electrical conductivity did not undergo any change in the sonicated samples. Findings of the present study suggest that sonication technique may be applied to improve phytonutrients present naturally in apple juice.

Effective enzymatic synthesis of lactosucrose and its analogues by β-D-galactosidase from Bacillus circulans.

In the present study, beta-d-galactosidase from Bacillus circulans was proved to be a suitable biocatalyst for the production of lactosucrose (beta-d-Galp-(1-->4)-alpha-d-Glcp-(1-->2)-beta-d-Fruf, I) and its analogues from lactose and sucrose. During the hydrolysis of lactose, the formation of four transfer products was followed by high performance liquid chromatography with refraction index detector. In addition, the transfer products were isolated from the reaction mixture and identified to be I, beta-d-Galp-(1-->3)-alpha-d-Glcp-(1-->2)-beta-d-Fruf (II), beta-d-Galp-(1-->4)-beta-d-Galp-(1-->4)-alpha,beta-d-Glcp (III), and beta-d-Galp-(1-->4)-beta-d-Galp-(1-->4)-alpha-d-Glcp-(1-->2)-beta-d-Fruf (IV) by mass spectrometry with an electrospray ionization source and nuclear magnetic resonance spectroscopy. The order for the production of the transfer products was III > I > IV > II in the initial stage of the reaction, and the same relationship was also observed for the hydrolytic rates of transfer products. Furthermore, the effects of synthetic conditions including reaction temperature, reaction time, concentration of substrate, molar ratio of donor/acceptor, and enzyme concentration on the formation of transfer products were examined. We found that the optimal synthetic conditions were different for the production of I and II. Under the optimal conditions, the amount of total transfer products kept increasing during the early 4 h incubation, and a maximum yield of 146 g/L for total transfer products was obtained at 4 h of reaction.

Thermosonication as a potential quality enhancement technique of apple juice.

Enzymatic browning and microbial growth lead to quality losses in apple products. In the present study, fresh apple juice was thermosonicated using ultrasound in-bath (25 kHz, 30 min, 0.06 W cm(-3)) and ultrasound with-probe sonicator (20 kHz, 5 and 10 min, 0.30 W cm(-3)) at 20, 40 and 60°C for inactivation of enzymes (polyphenolase, peroxidase and pectinmethylesterase) and microflora (total plate count, yeast and mold). Additionally, ascorbic acid, total phenolics, flavonoids, flavonols, pH, titratable acidity, (°)Brix and color values influenced by thermosonication were investigated. The highest inactivation of enzymes was obtained in ultrasound with-probe at 60°C for 10 min, and the microbial population was completely inactivated at 60°C. The retention of ascorbic acid, total phenolics, flavonoids and flavonols were significantly higher in ultrasound with-probe than ultrasound in-bath at 60°C. These results indicated the usefulness of thermosonication for apple juice processing at low temperature, for enhanced inactivation of enzymes and microorganisms.

Bioactive peptides/chitosan nanoparticles enhance cellular antioxidant activity of (-)-epigallocatechin-3-gallate.

(-)-Epigallocatechin-3-gallate (EGCG), one representative of the well-studied chemopreventive phytochemicals but with low bioavailability, was encapsulated in monodispersed nanoparticles that were assembled from bioactive caseinophosphopeptide (CPP) and chitosan (CS). The encapsulation efficiency of EGCG in CS-CPP nanoparticles ranged from 70.5 to 81.7%; meanwhile, the in vitro release of EGCG from CS-CPP nanoparticles was in a controllable manner. The EGCG-loaded CS-CPP nanoparticles exerted stronger activity of scavenging free radical than the free EGCG (p < 0.01) in the cellular antioxidant activity assay. Furthermore, cellular uptake of the EGCG-loaded CS-CPP nanoparticles was confirmed by the green fluorescence inside the human hepatocellular caricinoma (HepG2) cells, which was considered to play an important role in the improvement of the antioxidant activity of the nanoencapsulated EGCG. The results suggested that encapsulation of EGCG using CS-CPP nanoparticles should be a potential approach to enhance its antioxidant activity in biological systems.