Chemical reactions on polysaccharides

Zero birefringence films of pullulan ester derivatives

High-performance films with almost zero-birefringence and zero-wavelength dispersion were succeeded to prepare from pullulan esters derivatives (PLEs) without any additives. Optical transmittance analysis, birefringence measurement of PLE cast film and hot stretched films, and infrared dichroism analysis were conducted to characterize optical properties of PLE films comparing with cellulose triacetate which is commercially used as low-birefringence in optical devices. The aims of this study, characterization of optical properties of pullulan esters, can develop a deep understanding of the fundamental knowing and applicability of polysaccharides. Accordingly, authors believe this paper will open the gate for researches in the application of polysaccharides.

Sulfonation and Antioxidative Evaluation of Polysaccharides from Pleurotus Mushroom and Streptococcus thermophilus Bacteria: A Review

Human beings are equipped with antioxidant defense systems to neutralize free radicals as free radicals could damage macromolecules, subsequently resulting in serious diseases. Researchers have been attracted to search for potential natural antioxidants to reduce oxidative damage. Pleurotus and Streptococcus thermophilus have been chosen as sources of sustainable bioactive compounds that have been consumed for thousands of years. Polysaccharides are important bioactive components produced by Pleurotus mushrooms and Streptococcus thermophilus bacteria. Additionally, there is a continued interest in sulfonation of crude polysaccharides from both sources, since sulfonation has been found to improve or create new bioactive properties in polysaccharides. Both crude and sulfated polysaccharides with good antioxidant capacities have great potential for the further development as commercial products. This review focuses on characterization, sulfonation methods, and antioxidant capacity evaluations of polysaccharides from Pleurotus and S. thermophilus. Common antioxidant capacity assays, including the mechanisms underlying each assay, and various experimental procedures are also discussed.

Physicochemical characteristics and bioactivities of the exopolysaccharide and its sulphated polymer from Streptococcus thermophilus GST-6

Exopolysaccharide (EPS) produced by Streptococcus thermophilus GST-6 in skim milk was extracted and purified. The EPS was composed of glucose and galactose in a molar ratio of 1.80:1.03 with identical primary structure to the EPS from S. thermophilus ST1 reported previously. The purified EPS was sulphated at a sulphonation degree of 0.26±0.03, and presence of sulphate groups in the sulphated EPS (SEPS) was confirmed. Microstructural studies demonstrated a porous web with coarse surface for the EPS while the SEPS appeared as stacked flakes with relatively uniform shapes. Sulphonation of the EPS slightly decreased its degrading temperature from 234.6°C to 232.5°C. The DPPH, superoxide and hydroxyl radicals scavenging activities of the EPS were significantly (P<0.05) improved after sulphonation. The SEPS also showed stronger inhibitory activity than the EPS against Eschericia coli, Salmonella typhimurium and Staphylococcus aureus.

In Vitro Anti-tumor Effects of Chemically Modified Polysaccharides from Cherokee Rose Fruit

Cherokee rose fruit (CRF) is a Chinese traditional herb which has been used in medicine for hundreds of years. The anti-tumor activity of CRF polysaccharides (CRFPs) has not yet been evaluated. To study the in vitro anti-tumor effects of CRFP and its derivatives, native CRFP was isolated from CRF by hot water extraction, and its molecular weight analyzed with gel filtration chromatography was 227,000 Da. Native CRFP was sulfated with ClSO3H-DMF and carboxymethylated with monochloroacetic acid in alkaline aqueous medium. The resulting derivatives were isolated and labeled as SF-CRFP and CM-CRFP, respectively. The in vitro inhibition rates of CRFP and its derivatives for tumor cells SKVO (human ovarian cancer cell), HepG2 (human hepatoma cell), and LoVo (human colon cancer cell) were evaluated, the result showed that native CRFP exhibited no significant inhibition effect on the three tumor cells even at a concentration of 50 μg/ml, but sulfation and carboxymethylation substantially enhanced the anti-tumor activities of CRFP in a dose-dependent way. SF-CRFP at the dose of 50 μg/ml displayed a significant inhibitory effect on SKVO, HepG2, and LoVo, with the viability rates of 33.6%, 44.8%, and 43.2%, respectively. It has a dosage-dependence inhibition on tumor growth in this model, with IC50 for SKVO, HepG 2, and LoVo being 21 μg/ml, 36 μg/ml, and 49 μg/ml, respectively. CM-CRFP showed a specific inhibition on HepG2 with a viability rate of 12.2%, with an IC50 of 17 μg/ml, while it had hardly any anti-tumor effect on SKVO cells. Thus, chemical modifications of CRFPs by sulfation and carboxymethylation effectively improved their anti-tumor properties.

Molecular mass and antitumor activities of sulfated derivatives of alpha-glucan from Poria cocos mycelia

Two kinds of water-insoluble (1-->3)-alpha-D-glucan samples, ab-PCM3-I and ac-PCM3-I, isolated from different Poria cocos mycelia were sulfated, to produce two series of water-soluble derivatives ab-PCM3-I-S1-S5 and ac-PCM3-I-S1-S5, respectively. The derivatives having different weight-average molecular mass (Mw) were produced by changing reaction temperature and time as well as molar ratios between chlorosulfonic acid and number of hydroxyl groups in the glucan. The degrees of substitution (DS) of the sulfated derivatives were analyzed by elemental analysis (EA) to be 0.39-0.67 for ab-PCM3-I-S and 0.73-0.96 for ac-PCM3-I-S, respectively. The Mw and the intrinsic viscosity ([eta]) of the samples ab-PCM3-I-S and the ac-PCM3-I-S were measured by size exclusion chromatography combined with laser light scattering (SEC-LLS) and viscometry in phosphate buffer solution (PBS) at 37 degrees C. The results indicated that their Mw ranged from 2.0 to 11.3 x 10(4) for the samples ab-PCM3-I-S, and 4.7 to 40.0 x 10(4) for the samples ac-PCM3-I-S. Moreover, the antitumor activities of the sulfated derivatives ab-PCM3-I-S and ac-PCM3-I-S against Sarcoma 180 tumor cell tested both in vitro and in vivo are significantly higher than those of the native alpha-D-glucans. Therefore, a moderate range of molecular mass from 2.0 x 10(4) to 40.0 x 10(4), relatively high chain stiffness and good water solubility of the sulfated derivatives are beneficial to the enhancement of their antitumor activities.

Current knowledge on biosynthesis, biological activity, and chemical modification of the exopolysaccharide, pullulan

The article presents an overview of the latest advances in investigations of the biosynthesis, molecular properties, and associated biological activity of pullulan. The literature survey on the pullulan biosynthesis is intended to illustrate how the great variety of environmental conditions as well as variability in strain characteristics influences the metabolic pathways of the pullulan formation and effects structural composition of the biopolymer. Molecular properties of pullulan as alpha-(1-->4)- and alpha-(1-->6)-glucan are discussed in terms of similarities with amylose and dextran structures, and an emphasis is made on the inherent biological activity of pullulan molecules. The author also attempts to summarize the concepts, options, and strategies in chemical modification of the biopolymer and to delineate future prospects in designing new biologically active derivatives.

Chain conformation of sulfated derivatives of β-glucan from sclerotia of Pleurotus tuber-regium

Six water-insoluble (1-->3)-beta-D-glucan fractions TM8-1 to TM8-6 with weight-average molecular mass Mw ranging from 5.76 to 77.4x10(4) obtained from the sclerotia of Pleurotus tuber-regium were sulfated to produce the water-soluble fractions S-TM8-1 to S-TM8-6 with Mw from 6.0 to 64.8x10(4). The degree of substitution (DS) of S-TM8 fractions was analyzed by elemental analysis (EA) to be 1.14-1.74. The 13C NMR results indicated that the C-6 was fully substituted, and C-2, C-4 were partially substituted by the sulfo-groups. The Mw and the intrinsic viscosity [eta] of the S-TM8 fractions were measured, respectively, by size-exclusion chromatography combined with laser light scattering (SEC-LLS), LLS and viscometry in phosphate buffer solution (PBS) at 37 degrees C. The dependences of [eta] and radius of gyration <s2>z(1/2) on Mw for the S-TM8 samples were found to be [eta]=1.89x10(-2) Mw(0.70) (cm3/g) and <s2>z(1/2)=1.12x10(-4) Mw(0.81) (nm) in the Mw range tested. Based on current theories for a wormlike chain model, the molar mass per unit contour length ML and persistence length q of the S-TM8 were calculated to be 990 nm(-1) and 8.5 nm, respectively. The relatively higher q value suggested a more expanded flexible chain of S-TM8 in PBS. The water-solubility and relatively expanded chain conformation of the STM8 fractions were considered to be significant to their antiviral activity.

Chemical modification, characterization and structure-anticoagulant activity relationships of Chinese lacquer polysaccharides

A natural lacquer polysaccharide with complex branches was separated into two fractions, LPH (MW 16.9x10(4)) and LPL (MW 6.85x10(4)). Results of 13C NMR and FT-IR indicated they had the same structure. The treatment of LPL with sodium periodate led to a partial cut-off of side chains with 4-O-methyl-D-glucuronic acid in the terminal. These polysaccharides were sulfated in the presence of Py*SO3/DMSO. Depending on the reaction conditions, the products showed a different degree of sulfation (DS) ranging from 0.57 to 1.57 and different molecular weights ranging from 1.71x10(4) to 3.49x10(4). FT-IR analysis showed the equatorial primary OH at O-6 and the axial secondary OH at O-4 were sulfated. Activated partial thromboplastin time (APTT), prothrombin time and thrombin time (TT) assays showed the sulfated polysaccharides could prolong APTT and TT, but not TP. These activities strongly depended on the DS, the molecular weights (MW) and the branching structure of polysaccharides. DS of above 0.8 was essential for anticoagulant activity. The anticoagulant activity increased with the DS and the molecular weights. The molecular weights played a more important role. The branching structure of polysaccharides increased the activities. In our studies, the sulfated polysaccharides with the DS of 1.15 and the highest MW of 3.49x10(4) had the best blood anticoagulant activities.