Hot Water-soluble Polysaccharides Research Articles

Physicochemical, rheological properties and in vitro hypoglycemic activities of polysaccharide fractions from peach gum

In this study, peach gum was sequentially extracted by water at 25 °C, 95 °C and 0.1 M NaOH, obtaining room temperature water-soluble (PG-WE), hot water-soluble (PG-HWE), and alkali-soluble (PG-AE) polysaccharide fractions. These three kinds of polysaccharide fractions exhibited a similar arabinogalactan structure according to FTIR spectrum and monosaccharide composition. However, their molecular weight and chain conformation were different based on high-performance size exclusion chromatography analysis, which resulted in different rheological behavior. PG-WE and PG-HWE presented non-Newtonian behavior, and the apparent viscosity of PG-WE was higher than that of PG-HWE at concentrations of 2.0 % and 3.0 % (w/w). Dynamic sweep tests showed that PG-HWE solutions behaved as viscous fluids, while PG-WE solutions tended to form gel-like structures at concentrations higher than 2 % (w/w). Furthermore, PG-WE showed significant in vitro inhibition against α-glucosidase activity in a dose-dependent manner and reduced the fluorescence of α-glucosidase through dynamic quenching mechanism.

Chemical Characterization and In Vitro Anti-Cancer Activities of a Hot Water Soluble Polysaccharide from Hulless Barley Grass.

Hulless barley grass may confer many health benefits attributed to its bioactive functional components, such as polysaccharides. Here, a hot water soluble polysaccharide was extracted from hulless barley grass, and its chemical characterization and in vitro anti-cancer activities were investigated. The yield of hulless barley grass polysaccharide (HBGP) was 2.3%, and the purity reached 99.1% with a polydispersity index (PDI) of 1.11 after purification by a diethylaminoethyl cellulose (DE-32) column and an S-400 high resolution (HR) column. The molecular weight and number-average molecular weight of HBGP were 3.3 × 104 and 2.9 × 104 Da, respectively. The monosaccharide composition of HBGP included 35.1% galactose, 25.6% arabinose, 5.5% glucose, and 5.3% xylose. Based on infrared spectrum analysis, HBGP possessed pyranose and galactose residues. In addition, this water-soluble polysaccharide showed significant cell proliferation inhibitory effects against cancer cell lines HT29, Caco-2, 4T1, and CT26.WT in a dose-dependent manner, especially for HT29 (the half-inhibitory concentration IC50 value = 2.72 mg/mL). The results provide a basis for the development and utilization of hulless barley grass in functional foods to aid in preventing cancer.

Cinnamomum burmannii decoction: A thickening and flavouring ingredient

Cinnamon is a spice widely used as a flavouring agent in foodstuffs. Despite its commercial availability and low cost, C. burmannii aqueous extracts obtained by decoction originate high viscous solutions (1545 cP) when compared with C. verum (51 cP), preventing its broad use by food industry. Following the hypothesis that cinnamon polysaccharides are responsible for this viscosity, in this work, the hot water-soluble polysaccharides from C. burmannii were structurally characterized, using C. verum for comparison. The results showed that C. burmannii had a higher content of branched arabinoxylans in relation to C. verum. The hot water-soluble polysaccharides from C. verum comprised also glucans, arabinogalactans, and pectic polysaccharides. The partial mild acid-hydrolysis performed to C. burmannii allowed to reach a viscosity value near to the C. verum solutions, keeping the characteristic aroma profile of cinnamon by the predominance of cinnamaldehyde and other varietal compounds, namely mono and sesquiterpenoids. Therefore, C. burmannii can be used as flavouring and thickening agent, whereas low viscosity products can be obtained by a partial acid-hydrolysis, contributing to its wide application in food industry.

Anti-inflammatory and antioxidant activity of the hot water-soluble polysaccharides from Anacyclus pyrethrum (L.) Lag. roots

Ethnophamacological relevancethe roots of Anacyclus pyrethrum (L.) Lag. (Family: Asteraceae) are used in Algeria to treat respiratory infections, to cure chronic head and nostrils catarrh, and to clear the brain by stimulating the free flow of nasal mucous. They contain a high quantity of hot water-soluble polysaccharides. Aims of the studyThe study aims to evaluate the antioxidant and anti-inflammatory activity of polysaccharides extracted from Anacyclus pyrethrum roots (APPS). Materials and methodsThe APPS were extracted using boiling water, separated from proteins by the Sevag method then precipitated with 90% ethanol. The antioxidant effect of crude APPS was evaluated using FRAP assay. To investigate the anti-inflammatory potential, mice were treated with crude polysaccharides (25, 50, and 100 mg/kg, i.p.) for 3 days (14th, 15th, and 16th day of the experimentation). Respiratory inflammation was induced by HDM (House Dust Mite), mice were sensitized intranasally with 25 μg HDM suspended in 10 μl NaCl (5 μl/nostril) on days 0 and 7 then challenged with 5 μg HDM on days 14, 15, and 16. Mice were sacrificed 24 h after the last challenge. The number of immune cells in the blood in NL (Nasal Liquid) and in BAL (Broncho Alveolar Liquid) was enumerated, the spleen was removed to calculate the relative spleen weight and to count splénocytes, lungs histopathological examination was carried out to confirm the protective effect of APPS. Structural characterization of APPS was identified using FTIR (Fourier-Transform Infrared Spectroscopy) and SEM (Scanning Electron Microscopy). ResultsThe crude APPS possessed reducing power. In vivo assay, treatment with APPS causes a decrease in the number of blood leucocytes at all doses on the one hand, and in the relative spleen weight and splénocytes number on the other hand except at the dose of 50 mg/kg in which an enhancement of the number of splénocytes and immune cells in NL and BAL was significant. The histopathological examination showed clear protection of lung tissue damaged by HDM, after treatment with APPS mainly, at the dose of 50 mg/kg. ConclusionOur data clearly showed antioxidant and anti-inflammatory activity of APPS on HDM-challenged mice induced lungs inflammation by equilibrating the inflammatory reaction mostly, with an optimal dose of 50 mg/kg.

In vitro immunomodulatory activity of water-soluble glucans from fresh and dried Longan (Dimocarpus longan Lour.)

Longan (Dimocarpus longan Lour.) is a seasonal tropical fruit used by Chinese medicine in both fresh and dried pulp forms. Their polysaccharides have been reported to have biological activity. However, their composition and immune activity have not yet been disclosed. To fulfil this aim, hot water-soluble polysaccharides of fresh and dried longan pulp were fractionated according to their molecular weight by ultrafiltration (10, 50, 100 kDa cut off). The main polysaccharides recovered were 1,6-linked glucans branched at O-3 (4–8%), O-2 (1%), O-2,4 (0.1%), and O-3,4 (0.1%). The drying process promotes the solubility of the polysaccharides. These glucans from fresh and dried longan pulp have immunomodulatory activity, shown by in vitro phagocytosis, NO, TNF-α, and IL-6 macrophages production assays. They showed also to inhibit the inflammatory response induced by LPS. The immunological activity of these glucans seems to have different responses dependent on their molecular weight, related to the immune regulatory pathways.

Conformational, antioxidant and antibacterial properties of polysaccharides extracted from edible mushrooms of Pleurotus species

Polysaccharide fractions were extracted from three species of edible mushroom belonging to genus Pleurotus: P. florida, P. ostreatus and P. sajor-caju. The cold water, hot water and alkali soluble polysaccharides were precipitated using ethanol. Fractions thus obtained were characterized for presence of specific functional group by vibrational spectroscopy. Spectra of all fractions showed occurrence of several intense overlapped IR bands in the region of 1200-900 cm−1 (mainly C-C and C-O stretching vibrations in pyranoid rings) indicating the presence of polysaccharides as the major component. The (1→3, 1→6) linked β-conformation of the glucans was marked by presence of characteristic IR peaks and spectral similarity with a standard (1→3, 1→6) β-D-glucan in all the fractions. The antioxidant activity of the β-glucan extracts was observed to be variable among the three species. The P. ostreatus NaOH soluble glucans showed the maximum DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity amongst all. The extracted β-glucans exhibited moderate antagonism towards human pathogenic bacteria Yersinia enterocolitica and Salmonella typhi.

Polysaccharides from lichen Xanthoria parietina: 1,4/1,6-α-d-glucans and a highly branched galactomannan with macrophage stimulating activity via Dectin-2 activation

Hot-water soluble polysaccharides H-1-3 and H-2-1 were isolated from the thalli of the lichen Xanthoria parietina (L.) Th. Fr. and purified by ion exchange and gel permeation chromatography. Structure elucidation was mainly based on 2D-NMR and nano-ESI-Q-TOF MS/MS experiments.H-1-3 (13.7 kDa) was shown to be linear α-glucan with α-d-Glcp-(1 → [→[4)-α-d-Glcp-(1]2 → [6)-α-d-Glcp-(1]3 → 4)]n core backbone. The (1,4)- and (1,6)-α-d-Glcp linkages were in a 2:3 M ratio.H-2-1 (525 kDa) was characterized as a complex branched β-galacto-α-mannan with →[6)-α-d-Manp-(1 → [2,6)-α-d-Manp-(1]2 → [2)-α-d-Manp-(1]2→]n core units and main side chains of (1,3)-β-d-Galf linked at O-6 to →2)-α-d-Manp-(1→, together with minor terminal units of 1,4/1,6-α-D -Glcp units attached to the core chain at O-6 position and α-L-Rhap linked to Galf side chain at O-2 position (Manp: Galf: Glcp: Rhap linkage ratio = 9:3:2:1).H-2-1 exerted strong immunoactivity in vitro and activated murine RAW macrophages 264.7 towards significantly increased phagocytosis, TNF-α and IL-1β secretion. These effects are due to an interaction of the galactomannan with the transmembrane pattern-recognition protein Dectin-2 of the macrophages.

Cytotoxic, Antitumor and Immunomodulatory Effects of the Water-Soluble Polysaccharides from Lotus (Nelumbo nucifera Gaertn.) Seeds.

Lotus is an edible and medicinal plant, and the extracts from its different parts exhibit various bioactivities. In the present study, the hot water–soluble polysaccharides from lotus seeds (LSPS) were evaluated for their cancer cell cytotoxicity, immunomodulatory and antitumor activities. LSPS showed significant inhibitory effects on the mouse gastric cancer MFC cells, human liver cancer HuH-7 cells and mouse hepatocarcinoma H22 cells. The animal studies showed that LSPS inhibited tumor growth in H22 tumor-bearing mice with the highest inhibition rate of 45.36%, which is comparable to that induced by cyclophosphamide (30 mg/kg) treatment (50.79%). The concentrations of white blood cells were significantly reduced in cyclophosphamide-treated groups (p < 0.01), while LSPS showed much fewer side effects according to the hematology analysis. LSPS improved the immune response in H22 tumor-bearing mice by enhancing the spleen and thymus indexes, and increasing the levels of serum cytokines including tumor necrosis factor-α and interleukin-2. Moreover, LSPS also showed in vivo antioxidant activity by increasing superoxide dismutase activity, thus reducing the malondialdehyde level in the liver tissue. These results suggested that LSPS can be used as an antitumor and immunomodulatory agent.

308 - Antitumor and Immunomodulatory Activities of the Hot Water-Soluble Polysaccharides from Lotus (Nelumbo Nucifera Gaertn.) Seeds

Lotus (Nelumbo nucifera Gaertn.) seeds have a very long history as a traditional medicine in China, being used in folk remedies as cooling, diuretic, antiemetic, anti-inflammatory and anticancer agents. In the present study, the hot water-soluble polysaccharides from lotus seeds (LSPS) were evaluated for their cancer cell cytotoxicity, immunomodulatory and antitumor activities. The extraction yield of LSPS in hot water was 0.95%. Therefore, the development of a LSPS-enriched food additive or functional food is needed. LSPS showed significant toxicity on MFC cells and HuH-7 cells with dose-dependent manners. The animal studies showed that LSPS inhibited tumor growth in H22 tumor-bearing mice with the highest inhibition rate of 45.36%, which is comparable to that induced by cyclophosphamide (30 mg/kg) treatment (50.79%). LSPS administration improved the immune response in H22 tumor-bearing mice by increasing the spleen and thymus indexes, and enhancing the levels of serum cytokines, including TNF-α and IL-2. Moreover, LSPS also exhibited in vivo antioxidant activity by increasing SOD activity, thus reducing MDA content in the liver tissue.

Do assorted approaches aid in estimation of uronic acids? Case studies on Tinospora sinensis polysaccharides

Polysaccharides containing uronic acids are of immense biological significance. Colorimetric methods using different chromogens have been explored for uronic acid estimation in polysaccharides but these methods counter numerous difficulties, when neutral sugars are present in substantial amount. The uronic acid content of cold water-soluble polysaccharide (CWSP) and hot water-soluble polysaccharide (HWSP) isolated from Tinospora sinensis, widely known for marked therapeutic significance has been studied. The uronic acid was quantitatively estimated by spectrophotometric methods using carbazole, 3-phenylphenol and 3,5-dimethylphenol (DMP) vis-a-vis gas–liquid chromatography (GLC) analysis. Galacturonic acid in CWSP and HWSP was estimated as 1.41% and 1.20% respectively. The findings bring to light, the efficacy of chromogens and also reveal to what extent, they could be relied upon. The results also indicated higher specificity and selectivity of DMP over carbazole and 3-phenylphenol. However, GLC analysis despite time consuming remains the finest method for precise estimation of uronic acids. Further, GLC analysis of alditol acetates indicated the monosugar composition of l-rhamnose, l-arabinose, d-mannose, d-galactose and d-glucose in molar ratio 0.178, 0.259, 0.140, 1.045 and 98.377 in CWSP and l-rhamnose, l-arabinose, d-xylose, d-mannose, d-galactose and d-glucose in molar ratio 0.608, 0.628, 0.978, 0.227, 0.111 and 97.448 in HWSP respectively.

Optimized extraction of polysaccharides from Cymbopogon citratus and its biological activities

In this study the extraction of hot water soluble polysaccharides (HWSPs) from Cymbopogon citratus using hot water decoction was discussed. Response surface methodology (RSM) based on a three level, three variable central composite rotatable design (CCRD), was employed to obtain best possible combination of extraction time (X1: 30–180min), extraction temperature (X2: 70–100°C) and water to the raw material ratio (X3: 10–60) for maximum HWSPs extraction. The optimum extraction conditions were as follows: extraction time was around 113.81min, extraction temperature at 99.66°C and the ratio of water to raw material was 33.11g/mL. Under these conditions, the experimental yield was 13.24±0.23%, which is well in close agreement with the value predicted by RSM model yield (13.19%). The basic characterization of HWSPs was determined by using the FTIR. These preliminary in vitro biological studies indicated that lemongrass polysaccharides were useful for anticancer therapy.

Studies on Tinospora cordifolia monosugars and correlation analysis of uronic acids by spectrophotometric methods and GLC

Cold water-soluble (CWSP) and hot water soluble polysaccharides (HWSP) from Tinospora cordifolia stems were isolated and purified in 2.99% and 1.99% yield respectively. Complete hydrolysis followed by paper chromatography and GLC analysis indicated the presence of l-rhamnose, l-arabinose, d-xylose, d-mannose, d-galactose and d-glucose in molar ratio of 0.857, 1.106, 0.727, 0.526, 0.708 and 95.763 in CWSP and 0.697, 0.777, 2.048, 0.777, 0.292 and 95.408 in HWSP. The uronic acid content in the polysaccharide has been studied extensively using assorted approaches. It was quantitatively estimated by GLC analysis and spectrophotometric methods using carbazole, m-hydroxydiphenyl and 3,5-dimethylphenol as colorimetric reagents. GLC analyses indicated galacturonic acid content of 3.06% and 5.16% in CWSP and HWSP respectively. Estimation of uronic acid using 3,5-dimethylphenol corroborated the above analysis. The study resulted in composition of constituent monosugars of CWSP and HWSP and co-relation analysis of uronic acid content, leading to an unambiguous structural analysis.

Cell proliferative effect of polyxyloses extracted from the rhizomes of wild turmeric, Curcuma aromatica

Hot water-soluble crude polysaccharides were extracted from the rhizomes of wild turmeric, Curcuma aromatica Salisb. (Zingiberaceae), using dry grinding, boiling water extraction, and then ethanol precipitation. The crude polysaccharide extract was then fractionated by DEAE-cellulose ion exchange column chromatography, and subsequently further purified by Superdex G-200 gel filtration column chromatography, giving two relatively abundant polysaccharide fractions, called P11 and P21, and a much less common fraction P22 obtained in insufficient amounts for further analysis. The two main polysaccharide fractions were evaluated for monosaccharide composition by acid hydrolysis and high performance liquid chromatography (HPLC), whilst the molecular weight and functional groups were determined by gel permeable chromatography (GPC) and FT-IR, respectively. Fractions P11 and P21 were found to be polyxyloses with molecular weight-averages of 469,171 and 157,665 Da, respectively. P11 (100 μg/mL) could significantly induce human gingival fibroblast cells proliferation by 30%, while P21 (100 μg/mL) could significantly inhibit gingival fibroblast cells proliferation by 92%. The in vitro human primary gingival fibroblast cell proliferation in cell culture at a concentration of 100 μg/mL.

Facile preparation of Chaetomorpha antennina based porous polysaccharide–PMMA hybrid material by radical polymerization under microwave irradiation

A hybrid material was prepared from the hot water soluble sulphated polysaccharide of the green seaweed Chaetomorpha antennina (CMsps) and polymethyl methacrylate (PMMA) by radical polymerization in aqueous medium under microwave irradiation. An insoluble material was formed with the progress of the polymerization. The product was characterized by the IR spectrum and elemental analysis, as well as by acid hydrolysis followed by mass spectrum of the hydrolysate of the hybrid CMsps–PMMA for confirming the insertion of PMMA. Comprehensive characterization of the product included TGA, XRD, ESI-MS and BET surface analysis. The hybrid material was porous, and formed gel in water–DMSO mixture. It had the crystallinity index of 0.122, and had BET pore diameter of 3.71 nm, a size which is far larger than the molecular diameters of common natural gases and zeolites (0.5–1.0 nm). This material may be useful in the domain of certain adsorption and catalytic applications.

Cytochemical changes in the developmental process of Nostoc sphaeroides (cyanobacterium)

There are several apparent developmental stages in the life cycle of Nostoc sphaeroides Kutzing, an edible cyanobacterium found mainly in paddy fields in central China. The cytochemical changes in developmental stages such as hormogonia, aseriate stage, filamentous stage and colony in N. sphaeroides were examined using fluorescent staining and colorimetric methods. The staining of acidic and sulfated polysaccharides increased with development when hormogonia were used as the starting point. Acidic polysaccharides (AP) were most abundant at the aseriate stage and then decreased, while the sulfated polysaccharides (SP) were highest at the colony stage. Quantitatively, along the developmental process from hormogonia to colony, total carbohydrates first increased, then became stable, and then reached their highest level at the colony stage, while reducing sugars were highest at the hormogonia stage and then decreased sharply once development began. SP were not detectable in the hot water soluble polysaccharides (HWSP), and hormogonia had the lowest content of AP, while old colonies had the highest. The AP content of the aseriate stage, filamentous stage and young colony stage were very similar. The evolutionary relationships reflected in the developmental stages of N. sphaeroides are discussed.

Immunomodulatory effect of Antrodia camphorata mycelia and culture filtrate

Aim of the study Antrodia camphorata, a precious folkloric medicinal mushroom, has been used to treat tumorigenic diseases in Taiwan. This study was to investigate the innate immunity augmentation effects of different fractions prepared from hot water extracts of submerged cultured Antrodia camphorata (AC). Materials and methods The cytokine induction potency of AC fraction in diluted peripheral blood culture was measured by ELISA. The effects of AC fraction on phagocytic activity and CD11b expression were measured by the ingestion of FITC-labeled Escherichia coli and by labeling with PE-labeled CD11b monoclonal antibody, respectively, using flow cytometry. The molecular mass of hot water-soluble polysaccharides and content of adenosine in AC fraction were determined by gel permeation chromatography (GPC) and HPLC, respectively. Results The mycelia fraction, Fr. M II, and culture filtrate fractions, Fr. E II and Fr. E III, showed the strongest TNF-α and IL-6 induction effect as a function of their concentration. These fractions (20 μg/ml) also showed marked activity in enhancing phagocytosis in human polymorphonuclear neutrophils (PMN) and monocytes. In parallel, the expression of CD11b, an early marker of PMN activation, was also up-regulated dose-dependently. Composition analysis suggested that immunomodulatory effect of mycelia is mainly attributed to the 10–20 kDa polysaccharides and adenosine. Conclusions These results provide evidences that Antrodia camphorata can modulate innate immunity and may serve as an adjuvant for tumor treatment.

Immunostimulatory and Anti-inflammatory Polysaccharides from Tripterygium wilfordii.: Comparison with Organic Extracts

The organic extracts of Tripterygium wilfordii. Hook F. (Celastraceae) have been used in the treatment of inflammatory and autoimmune diseases for many years in China, although they also possess significant toxicity. These extracts are anti-inflammatory and immunosuppressive in nature, suppressing lipopolyscacharide (LPS)-stimulated upregulation of NF kappa B gene expression. In the current study, an ethyl acetate (EA) extract and a crude hot water soluble polysaccharide (PS) fraction from T. wilfordii. were compared. Both fractions were effective in reducing LPS-stimulated NO accumulation in cultured RAW 267.4 macrophages in a dose-dependent manner (IC50 values of 1.7 and 32.1 μ g/mL for EA and PS, respectively). The LC50 of EA (19.8–22.3 μ g/mL) was significantly greater than that of PS, which exhibited no apparent cytotoxicity toward either macrophages or EAhy 926 endothelial cells (up to 10 mg/mL). We also showed that PS was able to stimulate NO production by untreated macrophages in a dose-dependent manner. Thus, depending on the experimental condition of cultured macrophages, a crude PS fraction of T. wilfordii. may exhibit immunostimulatory or anti-inflammatory effects. This unique property, together with its relatively low level of toxicity, supports further investigation of its role in diseases in which inflammation and immunomodulation are critical.

Metabolism of Labeled Exogenous Glucose in Fiber Flax Tissues

A labeled glucose solution was introduced into cut fiber flax plants (45-50 cm high) using a special unit under a pressure of 0.1 atm for 30 min, 1, and 2 h. The highest quantities of labeled carbon were revealed in the woody tissue. Sucrose made up a considerable proportion in low molecular weight products of [ [2-14C]-glucose transformation (23.5%). Metabolism of labeled glucose in the leaves exposed to sunlight yielded a set of metabolites similar to products of 14CO2 photoassimilation. In the shade, the pattern of 14C distribution in labeled compounds of the water/alcohol soluble fraction remained similar in mature leaves, while in juvenile leaves, 14C content decreased in sucrose and increased in organic and amino acids. In the shade, the incorporation of 14C into starch and hot water soluble polysaccharides increased at the expense of the acetone fraction (lipids and pigments), water/salt soluble proteins, and cellulose. Low light conditions increased the radioactivity ratio of sparingly soluble (KOH and Triton X-100 soluble) proteins to albumins and globulins. We propose that the synthesis of components of the photosynthetic apparatus in juvenile leaves is directly powered by photosynthesis and the photosynthesis of glucose and the polymers compete for ATP energy. Appearance of sucrose in the woody tissue is due to its release from the phloem to the stem apoplast and the radial transfer to the xylem, where it is transported to the upper shoot with the transpiration flow.

Purification and characterization of complement-activating acidic polysaccharides from the fruits of Capsicum annuum.

Hot water-soluble crude polysaccharide (HCAP-0) that was obtained from the fruits of Capsicum annuum showed potent anti-complementary activity. The activity was unchanged by pronase digestion, but decreased by periodate oxidation. The HCAP-0 was fractionated by DEAE ion-exchange chromatography to give two major fractions, HCAP-II and III. These two fractions were finally purified by gel filtration to give HCAP-IIa, HCAPIIIa1, and IIIa2 fractions that had high anti-complementary activities. The HCAP-IIIa1 and IIIa2 consisted of homogeneous polysaccharides. The anti-complementary activities were unaffected by treatment with polymyxin B, indicating that the modes of complement activation were not due to preexisting lipopolysaccharide. The molecular weight and sugar content of HCAP-IIIa2 had potent anti-complementary activity. The highest yields were 55 kDa and 75.9%, and the molar ratio of galactose (Ara:Gal, 1.0:4.6) was higher than other sugars. The crossed immuno-electrophoresis showed that both classical and alternative pathways were activated by HCAP-IIIa2.

Salt tolerance of Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crust, was enhanced by exogenous carbohydrates

Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l −1 NaCl or 0.2 mol l −1 NaCl plus 100 mg l −1 sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity ( Fv/ Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l −1 NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions.