Regioselective sulfation of Artemisia sphaerocephala polysaccharide: Solution conformation and antioxidant activities in vitro

The relationship between polysaccharide structure and its antioxidant activity needs to be systematically elucidated

Polysaccharides have a wide range of applications due to their excellent antioxidant activity. However, the low purity and unclear structure of polysaccharides have led some researchers to be skeptical about the antioxidant activity of polysaccharides. The current reports on the structure-activity relationship of polysaccharides are sporadic, so there is an urgent need to systematically summarize the antioxidant effects of polysaccharides with clear structures and the relationships between the structures to provide a scientific basis for the development and application of polysaccharides. This paper will systematically elucidate the structure-activity relationship of antioxidant polysaccharides, including the molecular weight, monosaccharide composition, glycosidic linkage, degree of branching, advanced conformation and chemical modification. For the first time, the antioxidant activity of polysaccharides is related to their chemical structure through histogram and radar map, and further studies using principal component analysis and cluster analysis. We critically discussed how the source, chemical structure and chemically modified groups of polysaccharides significantly contribute to their antioxidant activity and summarized the current research status and shortcomings of the structure-activity relationship of antioxidant polysaccharides. This review provides a theoretical basis and new perspective for further research on the structure-activity relationship of antioxidant polysaccharides and the development of natural antioxidants.

Polysaccharides from Platycodon grandiflorum: A review of their extraction, structures, modifications, and bioactivities

Platycodon grandiflorum (P. grandiflorum) has long been used as a food and traditional herbal medicine. As a food, P. grandiflorum is often transformed into pickles for consumption, and as a traditional Chinese medicine, P. grandiflorum clears the lung, nourishes the pharynx, dispels phlegm, and discharges pus. Polysaccharides are among the main active components of P. grandiflorum. Recent literature has described the preparation, identification, and pharmacological activity of these polysaccharides. Studies have shown that these polysaccharides exhibit a variety of significant biological effects in vitro and in vivo, such as immune stimulation and antioxidant, anti-liver injury, anti-apoptosis and antitumour effects. However, there is no systematic summary of the related research articles on P. grandiflorum polysaccharide, which undoubtedly brings some difficulties to the future research. The purpose of this review is to comprehensively describe research progress on the extraction, purification, structural characterization, modification, and biological activity of P. grandiflorum polysaccharides. The shortcomings of recent research are summarized, further research on their biological activity is proposed to provide new reference value for the application of P. grandiflorum polysaccharides in drugs and health products in the future.

The exopolysaccharides produced by Leuconostoc mesenteroides XR1 and its effect on silk drawing phenomenon of yoghurt

Yoghurt fermented by Leuconostoc mesenteroides XR1 from Kefir grains was found to produce a unique silk drawing phenomenon. This property was found to be associated with the exopolysaccharides (EPS), X-EPS, produced by strain XR1. In order to better understand the mechanism that produced this phenomenon, the X-EPS was extracted, purified and characterized. The molecular weight and monosaccharide composition were determined by size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS) and ion chromatography (IC) analysis, respectively. The results showed that its molecular weight was 4.183 × 106 g/mol and its monosaccharide composition was glucose, and glucuronic acid, with the contents of 567.6148 and 0.2096 μg/mg, respectively. FT-IR and NMR analyses showed that X-EPS was an α-pyranose polysaccharide and was composed of 92.22 % α-(1 → 6) linked d-glucopyranose units and 7.77 % α-(1 → 3) branching. Furthermore, it showed a chain-like microstructure with branches in atomic force microscopy (AFM) and scanning electron microscopy (SEM) experiments. These results suggested that the unique structure of X-EPS, gave the yoghurt a strong viscosity and cohesiveness, which resulted in the silk drawing phenomenon. This work suggested that X-EPS holds the potential for food and industrial applications.

Structural characterization and antagonistic effect against P-selectin-mediated function of SFF-32, a fucoidan fraction from Sargassum fusiforme

ETHNOPHARMACOLOGICAL RELEVANCE

Sargassum fusiforme (Harvey) Setchell, or Haizao, has been used in traditional Chinese medicine (TCM) since at least the eighth century a.d. S. fusiforme is an essential component of several Chinese formulas, including Haizao Yuhu Decoction, used to treat goiter, and Neixiao Lei Li Wan used to treat scrofuloderma. The pharmacological efficacy of S. fusiforme may be related to its anti-inflammatory effect.

AIM OF THE STUDY

To determine the structural characteristics of SFF-32, a fucoidan fraction from S. fusiforme, and its antagonistic effect against P-selectin mediated function.

MATERIALS AND METHODS

The primary structure of SFF-32 was determined using methylation/GC-MS and NMR analysis. Surface morphology and solution conformation of SFF-32 were determined by scanning electron microscopy (SEM), Congo red test, and circular dichroic (CD) chromatography, respectively. The inhibitory effects of SFF-32 against the binding of P-selectin to HL-60 cells were evaluated using flow cytometry, static adhesion assay, and parallel-plate flow chamber assay. Furthermore, the blocking effect of SFF-32 on the interaction between P-selectin and PSGL-1 was evaluated using an in vitro protein binding assay.

RESULTS

The main linkage types of SFF-32 were proven to →[3)-α-l-Fucp-(1→3,4)-α-l-Fucp-(1]2→[4)-β-d-Manp-(1→3)-d-GlcAp-(1]2→4)-β-d-Manp-(1→3)-β-d-Glcp-(1→4)-β-d-Manp-(1→2,3)-β-d-Galp-(1→4)-β-d-Manp-(1→[4)-α-l-Rhap-(1]3→. The sulfated unit or terminal xylose residues were attached to the backbone through the C-3 of some fucose residues and terminal xylose residues were attached to C-3 of galactose residues. Moreover, SFF-32 disrupted P-selectin-mediated cell adhesion and rolling as well as blocked the interaction between P-selectin and its physiological ligand PSGL-1 in a dose-dependent manner.

CONCLUSIONS

Blocking the binding between P-selectin and PSGL-1 is the possible underlying mechanism by which SFF-32 inhibits P-selectin-mediated function, which demonstrated that SFF-32 may be a potential anti-inflammatory lead compound.

Effects of ultrasound on the degradation kinetics, physicochemical properties and prebiotic activity of Flammulina velutipes polysaccharide

The controllable ultrasonic modification was hindered due to the uncertainty of the relationship between ultrasonic parameters and polysaccharide quality. In this study, the ultrasonic degradation process was established with kinetics. The physicochemical properties and prebiotic activity of ultrasonic degraded Flammulina velutipes polysaccharides (U-FVPs) were investigated. The results showed that the ultrasonic degradation kinetic models were fitted to 1/M_t-1/M₀ = kt. When the ultrasonic intensity increased from 531 to 3185 W/cm², the degradation proceeded faster. The decrease of polysaccharide concentration contributed to the degradation of FVP, and the fastest degradation rate was at 60 °C. Ultrasound changed the solution conformation of FVP, and partially destroyed the stability of the triple helix structure of FVP. Additionally, the viscosity and gel strength of FVP decreased, but its thermal stability was improved by ultrasound. Higher ultrasonic intensity led to larger variations in physicochemical properties. Compared with FVP, U-FVPs could be more easily utilized by gut microbiota. U-FVPs displayed better prebiotic activity by promoting the growth of Bifidobacterium and Brautella and inhibiting the growth of harmful bacteria. Ultrasound could be effectively applied to the degradation of FVP to improve its physicochemical properties and bioactivities.

Recent advances in antiviral activities and potential mechanisms of sulfated polysaccharides

Natural polysaccharides derived from plants, fungi and animals are well known as ideal functional products with multiple biological activities and few side effects. Among them, natural occurring sulfated polysaccharides and those from synthetic origin are increasingly causing more attention worldwide, as they have been proved to possess broad-spectrum antiviral activities. The focus of this review is on analyzing the current state of knowledge about the origin of sulfated polysaccharides, more importantly, the potential connection between the structure and their antiviral mechanisms. Sulfated polysaccharide may interfere with a few steps in the virus life cycle (i.e. adsorption, invasion, transcription and replication) and/or improve the host antiviral immune response. Moreover, their antiviral activity was affected by degree of substitution, substitution position, molecular weight, and spatial conformation. This review may provide approach for the development of novel and potent therapeutic agents.

Effect of steam explosion pretreatment on the structure and bioactivity of Ampelopsis grossedentata polysaccharides

Steam explosion (SE) was a friendly environmentally pretreatment method. In this study, the effect of steam explosion (SE) pretreatment on structure and α-glucosidase inhibitory activity of Ampelopsis grossedentata polysaccharides was evaluated. Two novel polysaccharides (AGP and AGP-SE) were extracted, isolated, purified and analyzed by NMR, FT-IR and methylation. The results indicated that AGP mainly consisted of Rha, Xyl, Glc, and Ara with a molecular weight of 2.74 × 10³ kDa and AGP-SE mainly consisted of Man, Ara, and Gal with a molecular weight of 2.14 × 10³ kDa. Furthermore, the backbone of AGP and AGP-SE were mainly composed of 5)-Araf-(1→, -Glcp-(1→, 6)-Glcp-(1→, 6)-Galp-(1→, 3,6)-Manp-(1→, and 2,3,6)-Glcp-(1→. Finally, we demonstrated that all polysaccharides exhibited obviously α-glucosidase inhibition activity and mixed type inhibition. AGP-SE had better α-glucosidase inhibition activity and the binding affinity KD on α-glucosidase by using Surface Plasmon Resonance (SPR) than AGP. Overall, SE pretreatment is an effective method for extracting polysaccharide and provides a new idea into the improvement of biological activity.

Evaluation of replica exchange with repulsive scaling approach for docking glycosaminoglycans

Glycosaminoglycans (GAGs), long linear periodic anionic polysaccharides, are key molecules in the extracellular matrix (ECM). Therefore, deciphering their role in the biologically relevant context is important for fundamental understanding of the processes ongoing in ECM and for establishing new strategies in the regenerative medicine. Although GAGs represent a number of computational challenges, molecular docking is a powerful tool for analysis of their interactions. Despite the recent development of GAG-specific docking approaches, there is plenty of room for improvement. Here, replica exchange molecular dynamics with repulsive scaling (REMD-RS) recently proved to be a successful approach for protein-protein complexes, was applied to dock GAGs. In this method, effective pairwise radii are increased in different Hamiltonian replicas. REMD-RS is shown to be an attractive alternative to classical docking approaches for GAGs. This work contributes to setting up of GAG-specific computational protocols and provides new insights into the nature of these biological systems.

Ultrasound irradiation alters the spatial structure and improves the antioxidant activity of the yellow tea polysaccharide

In this study, the impact of ultrasound irradiation on the structural characteristics and antioxidant properties of yellow tea polysaccharides with different molecular weights (Mw) were investigated. Native yellow tea polysaccharide containing YTPS-3N, YTPS-5N and YTPS-7N were prepared through precipitation with ethanol at various concentrations of 30%, 50%, and 70%, respectively, and irradiated with high intensity ultrasound (20 kHz) for 55 min to yield yellow tea polysaccharide including YTPS-3U, YTPS-5U and YTPS-7U. The molecular weight (Mw) of YTPS-3N (from 37.7 to 15.1 kDa) and YTPS-5N (from 14.6 to 5.2 kDa) sharply decreased upon ultrasound irradiation, coincidentally particle size (Zavg) was also significantly reduced for YTPS-3N (40%), YTPS-5N (48%) and YTPS-7N (54%). The high-performance liquid chromatography and Fourier transform-infrared spectroscopy analysis revealed a partial degradation of native yellow tea polysaccharide treated with ultrasound, though the monosaccharide composition was not altered. Furthermore, changes in morphology and the breakdown of native yellow tea polysaccharide upon irradiation was confirmed with the circular dichroism spectrum, atomic force and scanning electron microscopy. As a consequence, irradiation of yellow tea polysaccharide increased free radical scavenging activity with YTPS-7U exhibiting the highest levels of 2, 2-diphenyl-1-picrylhydrazyl free radical, superoxide and hydroxyl radicals scavenging activity. These results suggest that the alteration of the spatial structure of yellow tea polysaccharide can enhance its antioxidant activity which is an important property for functional foods or medicines.

Purification, characterization, antioxidant, and antitumor activity of polysaccharides isolated from silkworm cordyceps

Two new water-soluble polysaccharide fractions (SCP II-1 and SCP II-2) were obtained from silkworm cordycepsusing DEAE Sepharose FF and Superose 6 columns chromatography. The characterization of their basic structure was studied by high performance liquid chromatography, high performance ion chromatography, infrared spectroscopy and atomic force microscope (AFM). The results showed that the molecular weight of SCP II-1 and SCP II-2 were 35.2 kDa and 23.4 kDa, and they were mainly composed of ribose, mannose, glucose, and galactose in molar ratio of 1.0:27.38:8.52:17.99 and 1.0:21.21:1.95:14.28, respectively. The AFM topography confirmed the highly branched chain conformation of SCP II-1, while SCP II-2 had more polymerized chain morphology. These two fractions possessed excellent antioxidant and antitumor activities, especially SCP II-1 showed better inhibition than SCP II-2. Those data suggested that purified polysaccharides from silkworm cordyceps have potential application in functional food and pharmaceutical industry. PRACTICAL APPLICATIONS: Silkworm cordyceps is cultivated on the 5th instar larvae inoculated with Cordyceps sp. and the functions of cordyceps have been reported recently. The separation and purification of silkworm cordyceps polysaccharide is helpful to better exert important biological functions. The study on the structure-function relations of polysaccharides will be useful to the application of polysaccharides in functional food and pharmaceutical industry.

A review on polysaccharides from Artemisia sphaerocephala Krasch seeds, their extraction, modification, structure, and applications

Artemisia sphaerocephala Krasch (ASK) is an important member of Compositae (Asteraceae) family. Its seeds have been widely used as traditional medicine and to improve the quality of food. Water soluble and water insoluble polysaccharides are found in the seeds of this plant. Research has been conducted on the extraction of polysaccharides, their modification and determination of their structure. To date different techniques for extraction purposes have been applied which are reviewed here. Antioxidant, antidiabetic, anti-obesogenic, antitumor, and immunomodulatory activities have been explored using in vivo and in vitro methods. Moreover, these polysaccharides have been used as packaging material and as a sensing component for monitoring the freshness of packaged food. Some experimental results have shown that the quality of foods is also improved by using them as a food additive. We have also indicated some of the potential areas that are needed to be explored.

Different extraction methods bring about distinct physicochemical properties and antioxidant activities of Sargassum fusiforme fucoidans

Fucoidan is a complex sulfated polysaccharide and an active component found in the cell wall of brown seaweeds. In the present study, fucoidans were obtained from Sargassum fusiforme using different extraction methods, including hot water (prepared fucoidan was named as WSFF), dilute hydrochloric acid (ASFF), and calcium chloride solution (CSFF). The assessments were performed on S. fusiforme fucoidans based on their chemical composition, molecular conformations, and in vitro antioxidant activities. ASFF showed the maximum extraction yield (11.24%), whereas CSFF exhibited the minimum yield (3.94%). The monosaccharide composition of WSFF, ASFF, and CSFF was similar, but the molar ratio of monosaccharide was quite different. Moreover, their molecular weight, Fourier transform infrared (FT-IR) spectrum, surface morphology, uronic acid content and degree of sulfation were distinct. The Congo red test and Circular dichroism spectroscopy analysis displayed some differences in solution conformation of these samples. Furthermore, WSFF, ASFF, and CSFF showed distinct in vitro antioxidant activities evaluated by DPPH and hydroxyl radical scavenging assays. The present study provides scientific evidence on the influences of extraction methods on the physicochemical characteristics, conformation behaviors and antioxidant activities of S. fusiforme fucoidans.

Optimization of Ultrasonic Flavonoid Extraction from Saussurea involucrate, and the Ability of Flavonoids to Block Melanin Deposition in Human Melanocytes

(1) Background: Flavonoids are the primary medicinal ingredient of Saussurea involucrate, which have significant antioxidant capacity. Optimizing the extraction of Saussurea involucrate flavonoids (SIFs) and exploring the ability to block melanin deposition caused by reactive oxygen can greatly promote the development of S. involucrate whitening products. (2) Methods: Ultrasonic extraction process was optimized using the Box-Behnken design (BBD) and response surface methodology (RSM). Then, the effect of SIFs on antioxidant activity and anti-deposition of melanin, and genes related to the melanin synthesis are studied. (3) Results: The optimal extraction procedures are as follows: the extraction time, ethanol content, and solvent ratio (v/w) are 64 min, 54%, and 54:1, respectively. The reducing activity and scavenging rates of 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide anion, hydroxyl radical, and ABTS⁺ were promoted as more S. involucrate flavonoid extract was added. The SIFs extract induced a decrease in the melanin synthesis by inhibiting the human melanoma A375 cell tyrosinase activity. SIFs also depress expression of melanin synthesis related genes. (4) Conclusions: the highest SIFs content was obtained by using 54% ethanol and 54:1 solvent ratio (v/w) for 64 min. The extract of SIFs exhibited good ability of antioxidant and anti-deposition of melanin in human melanocytes.

Structural characterization and immunostimulatory activity of a novel polysaccharide isolated with subcritical water from Sagittaria sagittifolia L

In the present study, we obtained polysaccharides from Sagittaria sagittifolia L. (SSP) with subcritical water extraction (SWE). Two water-soluble polysaccharides (SSP-W1 and SSP-S1) from the acquired SSP were isolated with DEAE-52 and Sephadex G-100. Besides, the structural characteristics and immunostimulatory activity were also investigated. The results showed that both SSP-W1 and SSP-S1 were homogeneous polysaccharides and the molecular weight was 62.03 KDa and 15.2 KDa, respectively. In addition, both SSP-W1 and SSP-S1 are heteropolysaccharides. Moreover, FT-IR analysis showed that SSP-W1 was α-pyranose polysaccharide, while SSP-S1 was a typical β-pyranose polysaccharide. Congo red staining showed that there was no triple helix structure in both SSP-W1 and SSP-S1. Furthermore, both SSP-W1 and SSP-S1 could promote the proliferation, production of NO, and secretion of TNF-α and IL-10 of macrophages RAW 264.7, significantly. Therefore, the polysaccharides extracted from Sagittaria sagittifolia L. with SWE have the potential to be used as immunoreactive agent in medicine and functional foods.

Interaction between carboxymethyl pachyman and lotus seedpod oligomeric procyanidins with superior synergistic antibacterial activity

The inhibitory effect of carboxymethyl pachyman (CMP) mixed with lotus seedpod oligomeric procyanidins (LSPC) in certain ratios against E. coli 10899 was determined. Added low concentration of LSPC could improve the antibacterial activity of CMP, and a significant synergistic effect could be observed between them, especially when the concentration of CMP was below its critical concentration (1.35 mg/mL). Then, the interaction between CMP and LSPC was characterized after mixing; the changes in spectral characteristics, thermal properties, crystallinity pattern, molecular weight, chain morphology and microrheological behaviour explained the influence of interaction on the structure of CMP and LSPC. The smaller molecular size, electrostatic interaction and stronger hydrophobic interaction might play important roles in improving the antibacterial activity of mixture. The dissociation constant (K_d) was determined to be 0.102±0.0008 mg/mL using MicroScale Thermophoresis (MST), and the micromorphology was observed by SEM. Therefore, this mixture might be an effective natural bacteriostat.

Tapping into Synchrotron and Benchtop Circular Dichroism Spectroscopy for Expanding Studies of Complex Polysaccharides and their Interactions in Anoxic Archaeological Wood

Circular dichroism (CD) (and synchrotron circular dichroism (SCD)) spectroscopy is a rapid, highly sensitive technique used to investigate structural conformational changes in biomolecules in response to interactions with ligands in solution and in film. It is a chiroptical method and at least one of the interacting molecules must possess optical activity (or chirality). In this review, we compare the capabilities of CD and SCD in the characterisation of celluloses and lignin polymers in archaeological wood. Cellulose produces a range of spectral characteristics dependent on environment and form; many of the reported transitions occur in the vacuum-ultraviolet region (< 180 nm) most conveniently delivered using a synchrotron source. The use of induced CD in which achiral dyes are bound to celluloses to give shifted spectra in the visible region is also discussed, together with its employment to identify the handedness of the chiral twists in nanocrystalline cellulose. Lignin is one target for the design of future consolidants that interact with archaeological wood to preserve it. It is reportedly achiral, but here we review several studies in which CD spectroscopy has successfully revealed lignin interactions with chiral enzymes, highlighting the potential usefulness of the technique in future research to identify new generation consolidants.

Optimization of Flavonoids Extraction Process in Panax notoginseng Stem Leaf and a Study of Antioxidant Activity and Its Effects on Mouse Melanoma B16 Cells

The Panax notoginseng (P. notoginseng) stem leaf is rich in flavonoids. However, because of a lack of research on the flavonoid extraction process and functional development of P. notoginseng stem leaf, these parts are discarded as agricultural wastes. Therefore, in this study, we intend to optimize the extraction process and develop the skin-whitening functions of P. notoginseng stem leaf extracts. The extraction process of the stem and leaf of P. notoginseng flavonoid (SLPF) is optimized based on the Box⁻Behnken design (BBD) and the response surface methodology (RSM). The optimum extraction conditions of the SLPF are as follows: the extraction time, the ethanol concentration, the sodium dodecyl sulfate (SDS) content and the liquid material ratio (v/w, which are 52 min, 48.7%, 1.9%, and 20:1, respectively. Under the optimal extraction conditions, the average total SLPF content is 2.10%. The antioxidant activity and anti-deposition of melanin of mouse B16 cells of P. notoginseng stem leaf extracts are studied. The results indicate that the EC₅₀ values of reducing activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activities, the superoxide anion removal ability, and the 2,2-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) free radical removal ability are 7.212, 2.893, 2.949, and 0.855 mg/mL, respectively. The extracts IC₅₀ values of the tyrosinase and melanin synthesis are 0.045 and 0.046 mg/mL, respectively. Therefore, the optimal processing technology for the SLPF obtained in this study not only increases its utilization rate, but also decreases material costs. The extracts from the P. notoginseng stem leaf may be developed as food or beauty products.

Impact of acidic, water and alkaline extraction on structural features, antioxidant activities of Laminaria japonica polysaccharides

This study comparatively evaluated the effects of different extraction methods on yield, structural features and antioxidant activities of Laminaria japonica (L. japonica) polysaccharides. Results showed that acid, water and alkaline extracted L. japonica polysaccharides (LJP-CA, LJP-W and LJP-A, respectively) differed significantly. Among three polysaccharides, LJP-W showed the highest viscosity with high uronic acid content and average molecular weight, whereas LJP-CA showed the lowest viscosity with low uronic acid and high sulfate content with moderate average molecular weight. LJP-CA was mainly composed of fucose, mannose and galactose, but the proportion of glucose was greatly increased in LJP-W and LJP-A. LJP-W had an even and smooth sheet-like appearance, while LJP-CA and LJP-A exhibited irregular and rough fragments or particles with stronger antioxidant activities. These results suggest that acid and alkali would propose an improved process for polysaccharide preparation from L. japonica and to exploit its potential application as a functional ingredient in food application.

The development of a Panax notoginseng medicinal liquor processing technology using the response surface method and a study of its antioxidant activity and its effects on mouse melanoma B16 cells

Panax notoginseng medicinal liquor (PML) has a long history of use in the function of blood circulation. However, the processing of PML is currently dependent on experience, which results in low efficiency and unstable quality of PML. A variety of substances of P. notoginseng have a strong ability to scavenge free radicals and antioxidant activity, but the antioxidant activity of PML has not been formally researched. The aim of the present study was to optimize the processing technology of PML and to verify the anti-oxidation and anti-deposition of melanin functions of PML. Based on the Box-Behnken design of response surface method, the PML processing parameters were established as follows: the ratio of liquid to solid 32 : 1, 53% of alcohol, and soaking time of 35 d. With elevating concentration of PML extract, the reducing force and scavenging rates of DPPH, superoxide anion, hydroxyl radical and ABTS⁺ were increased, and the inhibition rate of tyrosinase activity and the melanin synthesis ability were increased in mice melanoma B16 cells. Thus, the optimal processing technology not only shortened the processing time but also decreased the material costs. PML may be developed as food or beauty products for the functions of anti-oxidation and anti-deposition of melanin.

Optimization Extraction, Preliminary Characterization and Antioxidant Activities of Polysaccharides from Semen Juglandis

The optimization extraction process, preliminary characterization and antioxidant activities of polysaccharides from Semen Juglandis (SJP) were studied in this paper. Based on the Box-Behnken experimental design and response surface methodology, the optimal extraction conditions for the SJP extraction were obtained as follows: temperature 88 °C, extraction time 125 min and ratio of liquid to solid 31 mL/g. Under these conditions, experimental extraction yield of SJP was (5.73 ± 0.014)% (n = 5), similar to the predicted value of 5.78%. Furtherly, the purified SJP obtained from SJP extract by DEAE-52 and Sephacryl S-100 chromatography was analyzed to be rhamnose, galacturonic acid, galactose, arabinose and fucose in the molar ratio of 1:6.34:1.38:3.21:1.56. And the weight-average molecular weight and radius of gyration of the purified SJP in 0.1 M NaCl were determined to be 2.76 × 10⁴ g/mol and 122 nm by SEC-MALLS, respectively. More importantly, it exhibited appreciable antioxidant activities compared to the standard Vc, such as DPPH radical scavenging activity (IC₅₀ 0.21 mg/mL), strong reducing power, ABTS radical scavenging activity (IC₅₀ 0.29 mg/mL), and hydroxyl radical scavenging activity (IC₅₀ 0.38 mg/mL). These results indicate that SJP may be useful for developing functional health products or natural antioxidant.

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.