Dianhui Luo

Optimization of total polysaccharide extraction from Dioscorea nipponica Makino using response surface methodology and uniform design

On the base of single factor investigation, effects of extraction temperature, extraction time and ratio of water to material as well as their interactions on the yield of total polysaccharide from Dioscorea nipponica Makino were studied by uniform design and response surface methodology, respectively. The optimal process conditions were obtained by response surface methodology as follows: ratio of liquid to solid 33:1, extracting duration 134 min, and extracting temperature 95 °C, under optimized conditions, and the experimental yield 3.82% agreed closely with the predicted yield 3.9%. The tri-dimensional response surfaces were plotted by design-expert, and it was indicated that both extraction temperature and extraction time had interaction effects on the response value and there were no interaction effects of extraction time and liquid:solid ratio. Therefore, the application of response surface methodology in the extraction of total polysaccharide from D. nipponica Makino is more significant than uniform design.

Structure elucidation of a major fucopyranose-rich heteropolysaccharide (STP-II) from Sargassum thunbergii

A crude polysaccharide was extracted from the edible algae S. thunbergii. DEAE-Sepharose CL-6B column chromatography was used to separate and purify a major polysaccharide STP-II (63.75%) from the crude polysaccharide. STP-II was found to be a homogeneous polysaccharide with a single peak by high-performance size-exclusion chromatography with a Sugar KS-804 column, have a molecular weight of 550 kD, and consist mainly of fucose, xylose, galactose, glucose and glucuronic acid. The structural assignment of STP-II was carried out using Fourier transform infrared spectroscopy analysis, periodate oxidation-smith degradation, partial hydrolysis with acid, methylation analysis and nuclear magnetic resonance studies, and the repeating unit of STP-II was thus determined. The result indicated that (1→3)-linked-fucose, (1→3)-linked-xylose and (1→3)-linked-galactose formed the major components of the main-chain structure, and the branch ratios were 17.5%. The branching and terminal residues were (1→2)-linked-glucuronic acid, (1→4)-linked-glucose, (1→)-linked-xylose and (1→)-linked-4-O-acetyl-glucose, respectively.

Quantitative Structure Activity Relationship Models for the Antioxidant Activity of Polysaccharides.

In this study, quantitative structure activity relationship (QSAR) models for the antioxidant activity of polysaccharides were developed with 50% effective concentration (EC50) as the dependent variable. To establish optimum QSAR models, multiple linear regressions (MLR), support vector machines (SVM) and artificial neural networks (ANN) were used, and 11 molecular descriptors were selected. The optimum QSAR model for predicting EC50 of DPPH-scavenging activity consisted of four major descriptors. MLR model gave EC50 = 0.033Ara-0.041GalA-0.03GlcA-0.025PC+0.484, and MLR fitted the training set with R = 0.807. ANN model gave the improvement of training set (R = 0.96, RMSE = 0.018) and test set (R = 0.933, RMSE = 0.055) which indicated that it was more accurately than SVM and MLR models for predicting the DPPH-scavenging activity of polysaccharides. 67 compounds were used for predicting EC50 of the hydroxyl radicals scavenging activity of polysaccharides. MLR model gave EC50 = 0.12PC+0.083Fuc+0.013Rha-0.02UA+0.372. A comparison of results from models indicated that ANN model (R = 0.944, RMSE = 0.119) was also the best one for predicting the hydroxyl radicals scavenging activity of polysaccharides. MLR and ANN models showed that Ara and GalA appeared critical in determining EC50 of DPPH-scavenging activity, and Fuc, Rha, uronic acid and protein content had a great effect on the hydroxyl radicals scavenging activity of polysaccharides. The antioxidant activity of polysaccharide usually was high in MW range of 4000–100000, and the antioxidant activity could be affected simultaneously by other polysaccharide properties, such as uronic acid and Ara.

Structural investigation of a polysaccharide (DMB) purified from Dioscorea nipponica Makino

A water-soluble polysaccharide was isolated from the aqueous extract of Dioscored nipponica Makino. Compositional analysis, IR analysis, methylation analysis, and NMR studies ((1)H, (13)C, (1)H(1)H COSY, HSQC, and HMBC) revealed the presence of the following repeating unit in the polysaccharide:

Structure elucidation of a non-branched and entangled heteropolysaccharide from Tremella sanguinea Peng and its antioxidant activity

A crude polysaccharide was extracted from the edible fungi Tremella sanguinea Peng, and a polysaccharide TSP-II (31.56%) was separated and purified from the crude polysaccharide. TSP-II was a homogeneous polysaccharide by the high-performance size-exclusion chromatography (HPSEC), had a molecular weight of 356kD and consisted mainly of mannose, xylose, galactose and glucose at a molar ratio 5.9:2.4:1:1.1. The structural assignment of TSP-II was carried out using fourier transform infrared spectroscopy (FTIR) analysis, periodate oxidation-smith degradation, partial hydrolysis with acid, methylation analysis and nuclear magnetic resonance (NMR) studies, and the repeating unit of TSP-II was thus determined. The result indicated that →3)-α-d-Manp-(1→, →2)-α-d-Xylp-(1→, →6)-α-d-Glcp-(1→ and →3)-α-d-Galp-(1→ formed the major components of the main-chain structure, and TSP-II was a non-branched polysaccharide. Transmission electron microscopy (TEM) analysis revealed a primary non-branched and entangled state in its microstructure. TSP-II had higher scavenging activities on hydroxyl radical (EC50=0.088mg/ml) and superoxide radical (EC50=0.127mg/ml) than Vitamin C (Vc).

Structure of an entangled heteropolysaccharide from Pholidota chinensis Lindl and its antioxidant and anti-cancer properties

A major polysaccharide PCP-I was isolated and purified from Pholidota chinensis Lindl. The physicochemical and structural properties of PCP-I were studied using high-performance size-exclusion chromatography (HPSEC), gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), periodate oxidation-smith degradation, methylation-GC-MS analysis, nuclear magnetic resonance (NMR) spectroscopy and transmission electron microscopy (TEM) analysis. PCP-I was homogeneous with molecular weight (Mw) of 249kDa and composed of xylose and fucose at a molar ratio of 2.45:1. The repeating structural units of PCP-I were →3)-α-D-Xylp-(1→ and →4)-α-L-Fucp-(1→, the terminal fractions were T-D-GalAp, and TEM further revealed that PCP-I was the entangled microstructure which was composed of four non-branched single chains. Compared with Vitamin C (Vc) and 5 fluorine urine (5-Fu), PCP-I showed scavenging effects of superoxide (EC50=1.09mg/mL) and hydroxyl (EC50=0.11mg/mL) radicals equivalent to Vc, and PCP-I (IC50=69.54μg/mL) also exhibited good anti-proliferation capability for human colon cancer cell line caco-2.