Baotang Zhao

A comparison study on microwave-assisted extraction of Artemisia sphaerocephala polysaccharides with conventional method: Molecule structure and antioxidant activities evaluation

The conventional extraction methods for polysaccharides were time-consuming, laborious and energy-consuming. Microwave-assisted extraction (MAE) technique was employed for the extraction of Artemisia sphaerocephala polysaccharides (ASP), which is a traditional Chinese food. The extracting parameters were optimized by Box-Behnken design. In microwave heating process, a decrease in molecular weight (M(w)) was detected in SEC-LLS measurement. A d(f) value of 2.85 indicated ASP using MAE exhibited as a sphere conformation of branched clusters in aqueous solution. Furthermore, it showed stronger antioxidant activities compared with hot water extraction. The data obtained showed that the molecular weights played a more important role in antioxidant activities.

Structure-antioxidant relationships of sulfated galactomannan from guar gum.

Sulfated polysaccharides exerted potential biological property which was relative to degree of sulfation (DS), M(w), substitution position and chain conformation. In the present study, commercial guar gum was purified and its sulfated derivates with different DS and M(w) were synthesized. FT-IR and 13C NMR analysis indicated that C-6 substitution was predominant in sulfated samples compared with other positions. In the sulfation reaction, a sharp decrease in M(w) was observed. The d(f) values from 1.92 to 2.85 indicated that the -SO3H groups led to the relatively expanded conformation of sulfated polysaccharides. Antioxidant assays showed that sulfated polysaccharides had better antioxidant activities. The data obtained in in vitro models indicated that high DS and low M(w) showed the best antioxidant capacities.

Synthesis of selenium-containing polysaccharides and evaluation of antioxidant activity in vitro.

Selenium (Se) is an essential trace element for human beings and many other forms of life. Organic Se from natural foods has higher bioavailability and is safer than inorganic Se species. In the present study, selenium-containing derivatives of Artemisia sphaerocephala polysaccharide with the highest Se content of 1703 μg/g were synthesized using H(2)SeO(3)/HNO(3) and BaCl(2) as a catalyst. The effects of the ratio of HNO(3) concentration and reaction temperature were investigated. Results of Raman and (13)C NMR spectroscopy indicated that C-6 substitution was predominant in selenized polysaccharide. A sharp decrease in M(w) was observed in the selenized reaction due to the acid environment. The in vitro antioxidant results suggest that selenium-containing polysaccharide should be applied as a novel selenium source in dietary supplements, with potent antioxidant properties.

Selenylation modification can enhance antioxidant activity of Potentilla anserina L. polysaccharide.

Potentilla anserina L. polysaccharide had been selenizingly modified by nitric acid-selenious acid method with microwave-assistant. The optimal reaction parameters on selenylation modification were time 116 min, temperature 63°C, microwave power 190 W and the actual value of selenium content was 2690.1±7.2 μg/g. The scavenging ability of DPPH, OH and superoxide radicals, the metal chelating ability and reducing power in vitro were compared by antioxidant assay taking the non-modified PAP as a control. The results showed that selenylation modification could significantly enhance the antioxidant activity of SePAP and SePAP could be used as a potential antioxidant.

Catalytic synthesis of sulfated polysaccharides. II: comparative studies of solution conformation and antioxidant activities.

Sulfated derivatives of Artemisia sphaerocephala polysaccharide (ASP) with high degree of substitution (DS) were synthesized using 4-dimethylaminopyridine (DMAP)/dimethylcyclohexylcarbodiimide (DCC) as catalyst. Size exclusion chromatography combined with multi-angle laser light scattering (SEC-LLS) results showed a decrease in fractal dimension (df) values of sulfated ASP (SASP). Compared to ASP and SASP with low DS (0.51-1.01), SASPcata2 exhibited an internal structure between rigid rod and random coil with a DS of 1.24. DS had greater influence on its conformation in aqueous solution. Circular dichroism (CD), methylene blue (MB) and Congo red (CR) spectrophotometric method and atomic force microscopy (AFM) results confirmed that the degradation of ASP and SO3H groups improved significantly the stiffness of the chains due to the electrostatic effect. Furthermore, antioxidant experiments revealed that high DS could enhance the scavenging activities of radicals and reducing power of SASP in vitro. The extended chain conformation was beneficial to enhance the biological activity of sulfated polysaccharides.

Structure and antioxidant activities of sulfated guar gum: Homogeneous reaction using DMAP/DCC catalyst

It was essential to understand the chemical structure of polysaccharides for further research and biochemical or medical application of this natural biopolymer. In the present study, sulfated derivatives of guar gum with high degree of sulfation (DS) were synthesized using 4-dimethylaminopyridine (DMAP)/dimethylcyclohexylcarbodiimide (DCC) as catalyst in homogeneous conditions. The effects of the ratio of chlorosulfuric acid to pyridine, the content of catalyst and reaction temperature were investigated. Results of FT-IR, (1)H and (13)C NMR indicated that C-6 substitution was predominant in sulfated polysaccharide. In the sulfation reaction, a sharp decrease in M(W) was observed. The enhanced antioxidant activities of sulfated polysaccharides were not a function of a single factor but a combination of high DS and low molecule weight.

Regioselective synthesis of sulfated guar gum: Comparative studies of structure and antioxidant activities

We reported here a new synthesis of C-2 and C-3 sulfated guar gum (SRSGG) with low degree of substitution (DSS) of 0.58, employing triphenylchloromethane (TrCl) as a protected precursor. The yield and DSTr (calculated from the weight of triphenylmethanol) of triphenylmethylated GG (GGTr) was 165.6% and 0.71, respectively. In addition, low ratio (1:4) of chlorosulfuric acid to pyridine (1:4) was chosen in sulfation reaction since the protecting group was slightly sensitive to acid. Results of FT-IR and (13)C NMR spectroscopy indicated that C-2 and C-3 substitution was predominant but not fully sulfated in SRSGG. Size-exclusion chromatograph combined with multi-angle laser photometer (SEC-LLS) showed a decrease in molecular weight in the reaction. This might be due to the degradation in sulfation and deprotection process. Finally, we investigated the effect of structure features on the antioxidant activities in vitro. Vitro antioxidant experiments revealed that the regioselective sulfation at C-2 and C-3 and low molecular weight afforded strong antioxidant activities showing a much higher scavenging abilities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical than that by the known C-6-sulfated derivative. The antioxidant activities of sulfated polysaccharides were not a function of a single factor but a combination of molecular weight, DSS and substitution positions.

Purification, structure and anti-oxidation of polysaccharides from the fruit of Nitraria tangutorum Bobr.

In this paper, polysaccharides were extracted from the fruits of Nitraria tangutorum Bobr. (NTWP) using a hot water extraction method and extraction conditions were optimized by RSM. The optimal conditions were determined as follows: extraction time 7 h, extraction temperature 60 °C, ratio of water to raw material 15 : 1, and with these conditions, the yield was 14.01 ± 0.11%. After purification using DEAE-cellulose column and Sephadex G-200 column, NTWP-II was successfully obtained. The results of GC-MS and SEC-LLS analysis suggested that monosaccharide composition of NTWP-II was composed of Rha, Ara, Man, Glc and Gal with the molar ratio of 1.14 : 2.5 : 3.00 : 2.69 : 5.28 and Mw, Mw/Mn and Rz 2.29 × 105, 1.32, 15.22. The detailed structure of NTWP-II was characterized by FT-IR, NMR. Based on these analyses, the structure of the repeating unit of NTWP-II was established.