Microwave-assisted solubilization and solution properties of hyperbranched polysaccharide

Effects of extrusion temperature on structure and physicochemical properties of proso millet starch

Due to its thermal stability, and high viscosity, proso millet starch has limited practical applications. Extrusion can alter the functional properties of starch by pre-gelatinization, but the specific effects of extrusion temperature on starch behavior are not clear. In this study, proso millet starch was modified using extrusion at varying temperatures (70 °C, 90 °C, 110 °C), and its structure as well as physicochemical properties were evaluated. As the extrusion temperature increased, the starch granules were gelatinized, and the particle size increased significantly. The relative crystallinity of extruded starch decreased and the short-range order was enhanced notably, but the starch still exhibited an A-type structure. Starch chains degraded, migrated, and aggregated, showing an increase in the double helix content, but there was no difference in the single helix structure with temperature. With the increase of extrusion temperature, the amorphous layer of extruded starch thickened. Moreover, the peak viscosity, breakdown viscosity and setback viscosity initially increased and then decreased, the peak temperature and enthalpy change increased. The water absorption index, water solubility and swelling power significantly decreased with increasing temperatures. The freeze-thaw stability and transparency of extruded starch decreased, and showed a downward trend with prolonged time. The above results indicate that extrusion treatment effectively modifies the thermal stability and viscosity of proso millet starch, laying a foundation for applying it different industrial applications.

Exploring the partial degradation of polysaccharides: Structure, mechanism, bioactivities, and perspectives

Polysaccharides are promising biomolecules with lowtoxicity and diverse bioactivities in food processing and clinical drug development. However, an essential prerequisite for their applications is the fine structure characterization. Due to the complexity of polysaccharide structure, partial degradation is a powerful tool for fine structure analysis, which can effectively provide valid information on the structure of backbone and branching glycosidic fragments of complex polysaccharides. This review aims to conclude current methods of partial degradation employed for polysaccharide structural characterization, discuss the molecular mechanisms, and describe the molecular structure and solution properties of degraded polysaccharides. In addition, the effects of polysaccharide degradation on the conformational relationships between the molecular structure and bioactivities, such as antioxidant, antitumor, and immunomodulatory activities, are also discussed. Finally, we summarize the prospects and current challenges for the partial degradation of polysaccharides. This review will be of great value for the scientific elucidation of polysaccharide fine structures and potential applications.

Dendrobium as a new natural source of bioactive for the prevention and treatment of digestive tract diseases: A comprehensive review with future perspectives

BACKGROUND

The incidence of diseases related to the digestive tract is on the rise, with many types of complex etiologies. Dendrobium nobile Lindl. is a famous Traditional Chinese Medicine (TCM) rich in many bioactives proven to be beneficial in several health diseases related to inflammation and oxidative stress.

PURPOSE

At present, despite the availability of various therapeutic clinical drugs used for the treatment of digestive tract diseases, resistance emergence and existence of several side effects warrant for the developing of novel drugs for improved effects on digestive tract diseases.

METHODS

"Orchidaceae", "Dendrobium", "inflammation", "digestive tract", and "polysaccharide" were used as search terms to screen the literature. The therapeutic use of Dendrobium related to digestive tract diseases relative to known polysaccharides and other bioactive compounds were derived from online databases, including Web of Science, PubMed, Elsevier, Science Direct, and China National Knowledge Infrastructure, as well as relevant information on the known pharmacological actions of the listed phytochemicals.

RESULTS

To better capitalize upon Dendrobium for preventing and treating diseases related to digestive tract, this review summarizes bioactives in Dendrobium reported of potential in digestive tract diseases management and their underlying action mechanisms. Studies revealed that Dendrobium encompasses diverse classes including polysaccharides, phenolics, alkaloids, bibenzyls, coumarins, phenanthrene and steroids, with polysaccharide as the major class. Dendrobium exerts various health effects on a variety of disease related to the digestive tract. Action mechanisms involve antioxidant, anti-inflammatory, anti-apoptotic, antioxidant, anticancer, alongside the regulation of some key signaling pathways.

CONCLUSION

Overall, Dendrobium appears as a promising TCM source of bioactives that has the potential to be further developed into nutraceuticals for digestive tract diseases compared to current drug treatments. This review highlights for Dendrobium potential effects with future perspectives for needed future research to maximize the use of bioactive compounds from Dendrobium for digestive tract disease treatment. A compile of Dendrobium bioactives is also presented alongside methods for their extraction and enrichment for potential incorporation in nutraceuticals.

Interaction between β-glucans and gut microbiota: a comprehensive review

Gut microbiota (GMB) in humans plays a crucial role in health and diseases. Diet can regulate the composition and function of GMB which are associated with different human diseases. Dietary fibers can induce different health benefits through stimulation of beneficial GMB. β-glucans (BGs) as dietary fibers have gained much interest due to their various functional properties. They can have therapeutic roles on gut health based on modulation of GMB, intestinal fermentation, production of different metabolites, and so on. There is an increasing interest in food industries in commercial application of BG as a bioactive substance into food formulations. The aim of this review is considering the metabolizing of BGs by GMB, effects of BGs on the variation of GMB population, influence of BGs on the gut infections, prebiotic effects of BGs in the gut, in vivo and in vitro fermentation of BGs and effects of processing on BG fermentability.

The endosperm microstructure, physical, thermal properties and specific milling energy of spelt (Triticum aestivum ssp. spelta) grain and flour

Previous research has shown that the endosperm microstructure and physical properties of grain have significance in grain processing and in the development of processing machines. The aim of our study was to analyze the endosperm microstructure, physical, thermal properties, and specific milling energy of organic spelt (Triticum aestivum ssp. spelta) grain and flour. Image analysis combined with fractal analysis was used to describe the microstructural differences of the endosperm of spelt grain. The endosperm morphology of spelt kernels was monofractal, isotropic, and complex. A higher proportion of Type-A starch granules resulted in an increased proportion of voids and interphase boundaries in the endosperm. Changes in the fractal dimension were correlated with kernel hardness, specific milling energy, the particle size distribution of flour, and the starch damage rate. Spelt cultivars varied in size and shape of the kernels. Kernel hardness was a property that differentiated specific milling energy, particle size distribution of flour, and starch damage rate. Fractal analysis may be considered as a useful tool for evaluating milling processes in the future.

Production and Characterization of Durvillaea antarctica Enzyme Extract for Antioxidant and Anti-Metabolic Syndrome Effects

In this study, three enzyme hydrolysate termed Dur-A, Dur-B, and Dur-C, were produced from Durvillaea antarctica biomass using viscozyme, cellulase, and α-amylase, respectively. Dur-A, Dur-B, and Dur-C, exhibited fucose-containing sulfated polysaccharide from chemical composition determination and characterization by FTIR analyses. In addition, Dur-A, Dur-B, and Dur-C, had high extraction yields and low molecular weights. All extracts determined to have antioxidant activities by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), and ferrous ion-chelating methods. All extracts were also able to positively suppress the activities of key enzymes involved in metabolic syndrome: angiotensin I-converting enzyme (ACE), α-amylase, α-glucosidase, and pancreatic lipase. In general, Dur-B exhibited higher antioxidant and higher anti-metabolic syndrome effects as compared to the other two extracts. Based on the above health promoting properties, these extracts (especially Dur-B) can be used as potential natural antioxidants and natural anti-metabolic syndrome agents in a variety of food, cosmetic, and nutraceutical products for health applications.

Bioactive polysaccharides and oligosaccharides from garlic (Allium sativum L.): Production, physicochemical and biological properties, and structure-function relationships

Garlic is a common food, and many of its biological functions are attributed to its components including functional carbohydrates. Garlic polysaccharides and oligosaccharides as main components are understudied but have future value due to the growing demand for bioactive polysaccharides/oligosaccharides from natural sources. Garlic polysaccharides have molecular weights of 1 × 10³ to 2 × 10⁶  Da, containing small amounts of pectins and fructooligosaccharides and large amounts of inulin-type fructans ((2→1)-linked β-d-Fruf backbones alone or with attached (2→6)-linked β-d-Fruf branched chains). This article provides a detailed review of research progress and identifies knowledge gaps in extraction, production, composition, molecular characteristics, structural features, physicochemical properties, bioactivities, and structure-function relationships of garlic polysaccharides/oligosaccharides. Whether the extraction processes, synthesis approaches, and modification methods established for other non-garlic polysaccharides are also effective for garlic polysaccharides/oligosaccharides (to preserve their desired molecular structures and bioactivities) requires verification. The metabolic processes of ingested garlic polysaccharides/oligosaccharides (as food ingredients/dietary supplements), their modes of action in healthy humans or populations with chronic conditions, and molecular/chain organization-bioactivity relationships remain unclear. Future research directions related to garlic polysaccharides/oligosaccharides are discussed.

Seed coat mucilages: Structural, functional/bioactive properties, and genetic information

Seed coat mucilages are mainly polysaccharides covering the outer layer of the seeds to facilitate seed hydration and germination, thereby improving seedling emergence and reducing seedling mortality. Four types of polysaccharides are found in mucilages including xylan, pectin, glucomannan, and cellulose. Recently, mucilages from flaxseed, yellow mustard seed, chia seed, and so on, have been used extensively in the areas of food, pharmaceutical, and cosmetics contributing to stability, texture, and appearance. This review, for the first time, addresses the similarities and differences in physicochemical properties, molecular structure, and functional/bioactive properties of mucilages among different sources; highlights their structure and function relationships; and systematically summarizes the related genetic information, aiming with the intent to explore the potential functions thereby extending their future industrial applications.

Phosphorylation of levan by microwave-assisted synthesis enhanced anticancer ability

Levan is an exopolysaccharide produced by Bacillus licheniformis (strain FRI MY-55) that shows promising pharmacological activity. Phosphorylation is a chemical modification that can increase the biological and antioxidant properties of levan. In this study, levan was phosphorylated by microwave-assisted synthesis to achieve a degree of substitution of 0.29. The hydroxyl radical scavenging activity of microwave-assisted phosphorylated levan (microwave P) increased significantly (6-fold) over native levan; this activity was only slightly lower than vitamin C. Other free radical scavenging and reducing power tests revealed that Microwave P activity was increased by 30-40%. Microwave P inhibited the proliferation of HCT-116 and A549 cancer cell lines more readily than native levan with an IC₅₀ of 1.03 mg/mL and 1.38 mg/mL for HCT-116 and A549 cells, respectively. Cells treated with native levan and its derivatives remained in the sub-G1 phase according to cell cycle analysis, whereas Microwave P treatment increased the proportion of cells undergoing apoptosis. Furthermore, Microwave P effectively upregulated pro-apoptosis marker Bax and downregulated anti-apoptosis marker Bcl-2, in addition to inducing the expression of caspase-9 and caspase-3. These findings show that levan phosphorylated via microwave-assisted synthesis showed increased antioxidant and antitumor activity over native levan or levan phosphorylated via traditional long-term heating. In particular, Microwave P possesses antiproliferative activity and can induce apoptosis through mitochondrial pathways in cancerous cells.

Chain conformation of an acidic polysaccharide from green tea and related mechanism of α-amylase inhibitory activity

An acidic tea polysaccharide (TPSA) isolated from green tea was fractionated using a precipitation-fractionation method into seven fractions with different molecular weights. TPSA was characterized as a hyperbranched polysaccharide with a globular homogeneous conformation by analysis of solution parameters of each fraction using static light scattering and viscosity analyses. Observation by transmission electron microscopy confirmed that TPSA occurred as globular homogeneous particles with size in the range of 20-40 nm. To simulate the branched chain segments of TPSA, four model molecules were designed based on chemical structure of TPSA. Molecular docking analysis indicated that the branched chain segments of TPSA similar to the TPSA-4 model molecule showed preferential binding to α-amylase to form the TPSA/α-amylase complex through hydrogen bonding interactions. Circular dichroism spectroscopy showed that the structure of α-amylase was not significantly affected by TPSA. The mechanism of α-amylase inhibitory activity of TPSA was simulated by molecular docking analysis. The branched chain segments of TPSA similar to the TPSA-4 model molecule likely act as a potential competitor to the starch substrate to inhibit the activity of α-amylase.

A comparative study of sulfated tara gum: RSM optimization and structural characterization

Interest in galactomannans and its derivatives as a functional health supplement is growing based on physicochemical properties. In this work, the optimized conditions of sulfated tara gum (STG) with a maximum DS of 0.66 by box-behnken design (BBD) were obtained as following: ratio of chlorosulfonic acid/pyridine 3:1, reaction time 4 h and reaction temperature 40 °C. The structure features of STG such as the degree of substitution (DS), substitution position, weight average molar mass (M_W), monosaccharide components and chain conformation were investigated. Decreasing of M_W, the increasing of Z-average radius of gyration (〈S²〉_Z^1/2) and specific volume for gyration (SV_g) were obtained by SEC-MALLS. In addition, the structural properties of four sulfated galactomannans were comparatively investigated and analyzed based on our earlier reports of sulfated fenugreek gum, guar gum and locust bean gum. A conclusion was drown that higher galactose branch could enhance steric hindrance, which was inferred as one of the significant factors for the derivatization efficiency, thus affecting the DS, M_W and conformational transition of sulfated galactomannans. This study will provide valuable information for further research on the comparison of bioactivities and medical application of galactomannans family.

Synergistic effects of acetylated distarch adipate and sesbania gum on gelatinization and retrogradation of wheat starch

The synergistic effects of the combination of acetylated distarch adipate and sesbania gum (C-ADA-SG) with the ratio of 5:0, 4:1, 2.5:2.5, 1:4, 0:5, accounting for 5% (w/w) of the starch on gelatinization and retrogradation properties of wheat starch (WS) were studied. Scanning Electron Microscopy (SEM) showed that the microstructure of gelatinized WASs (WS added with C-ADA-SG) tended to be smoother. Based on the results of Rapid Visco-Analyzer (RVA) and Differential Scanning Calorimetry (DSC), the pasting characteristics of WS were affected and the gelatinization process was retarded by C-ADA-SG. After seven-day storage at 4 °C, compared to WS, the gel firmness, syneresis, retrogradation enthalpy, and the relative crystallinity of WASs clearly decreased by 17.47-44.36 g, 11.16-17.93%, 0.22-0.80 J·g^-1, and 4.06-8.61%, respectively. However, the band ratio 1639:1157 cm^-1 by FTIR and loss tangent (tan δ) value were increased with C-ADA-SG addition. Meanwhile, X-Ray Diffraction (XRD) reflected that native WS showed A-type crystal structure, which transferred to B + V type after retrogradation. Furthermore, Low-Field Nuclear Magnetic Resonance (LF-NMR) declared that C-ADA-SG increased the water mobility and limited the diffusion and seepage of water during storage. Generally, ADA and SG produced a synergistic effect on retarding the gelatinization and retrogradation of WS.

Structural Features, Modification, and Functionalities of Beta-Glucan

Β-glucan is a strongly hydrophilic non-starchy polysaccharide, which, when incorporated in food, is renowned for its ability to alter functional characteristics such as viscosity, rheology, texture, and sensory properties of the food product. The functional properties of β-glucans are directly linked to their origin/source, molecular weight, and structural features. The molecular weight and structural/conformational features are in turn influenced by method of extraction and modification of the β-glucan. For example, whereas physical modification techniques influence only the spatial structures, modification by chemical agents, enzyme hydrolysis, mechanical treatment, and irradiation affect both spatial conformation and primary structures of β-glucan. Consequently, β-glucan can be modified (via one or more of the aforementioned techniques) into forms that have desired morphological, rheological, and (bio)functional properties. This review describes how various modification techniques affect the structure, properties, and applications of β-glucans in the food industry.

Microwave assisted extraction and characterization of polysaccharide from waste jamun fruit seeds

The intention of current work is to recover/extract polysaccharide from jamun fruit seeds (waste) by microwave assisted solid-liquid extraction (MAE) technique using four-factor (microwave power (MWP), pH, time (MWT) and solid to liquid (SL) ratio) five-level central composite rotatable experimental design (CCRED). The observed data was evaluated by statistically and a mathematical model (polynomial) was developed to predict the polysaccharide yield. Numerical optimization technique is used to attain the ideal optimal condition (microwave power of 515 w, pH of 3.2, MWT of 3.1 min and SL ratio of 1:15 g/ml) to retrieve maximal yield of polysaccharide and attained optimal condition was experimentally validated. The experimental yield of polysaccharide (4.71 ± 0.02%) was matched with predicted value (4.72%). Physico-chemical properties of the polysaccharide extracted at optimal condition was investigated. Fourier Transform Infrared Spectroscopy (FTIR) evaluation were carried out in this study to characterize the polysaccharide. Scanning Electron Microscopy (SEM) was also utilized to reveal the morphology of raw and extracted plant sample.

A Concise Review on the Molecular Structure and Function Relationship of β-Glucan

β-glucan is a non-starch soluble polysaccharide widely present in yeast, mushrooms, bacteria, algae, barley, and oat. β-Glucan is regarded as a functional food ingredient due to its various health benefits. The high molecular weight (Mw) and high viscosity of β-glucan are responsible for its hypocholesterolemic and hypoglycemic properties. Thus, β-glucan is also used in the food industry for the production of functional food products. The inherent gel-forming property and high viscosity of β-glucan lead to the production of low-fat foods with improved textural properties. Various studies have reported the relationship between the molecular structure of β-glucan and its functionality. The structural characteristics of β-glucan, including specific glycosidic linkages, monosaccharide compositions, Mw, and chain conformation, were reported to affect its physiochemical and biological properties. Researchers have also reported some chemical, physical, and enzymatic treatments can successfully alter the molecular structure and functionalities of β-glucan. This review article attempts to review the available literature on the relationship of the molecular structure of β-glucan with its functionalities, and future perspectives in this area.

Gastrodia elata Blume Polysaccharides: A Review of Their Acquisition, Analysis, Modification, and Pharmacological Activities

Gastrodia elata Blume (G. elata) is a valuable Traditional Chinese Medicine (TCM) with a wide range of clinical applications. G. elata polysaccharides, as one of the main active ingredients of G. elata, have interesting extraction, purification, qualitative analysis, quantitative analysis, derivatization, and pharmacological activity aspects, yet a review of G. elata polysaccharides has not yet been published. Based on this, this article summarizes the progress of G. elata polysaccharides in terms of the above aspects to provide a basis for their further research and development.

Features of the hemicellulose structure of some species of regional raw materials and products of their enzymatic hydrolysis

Nowadays, it is recognized that a lot of polysaccharides are biologically active. It is well known that these biomolecules show the highest level of their activity if they are water-soluble preparations, their molecular weight being 15–25 kDa, and if they preserve the supramolecular structure of carbohydrates. Basing on the fact that β-glucans of mushrooms are characterized by the antitumor, anticoagulant, anti-inflammatory, and immunomodulatory activities, it is important to determine whether regional raw material contains polysaccharides of a similar structure, and to define the conditions for their fragmentation to obtain products with a given molecular weight. The purpose of the work was to characterize the features of the structure of the hemicellulose complex of the Agaricus bisporous and Pleurotus ostreatus and products of their limited enzymatic hydrolysis. To determine the primary structure of hemicellulose polysaccharides, the 1H-NMR spectra of the samples were registered. It has been shown that β-D-(1→3)/β-(1→6)-glucan dominates in the hemicellulose of Pleurotus ostreatus. Among the hemicelluloses in the Agaricus bisporis, the main polysaccharide was galactoglucan. Its main chain consisted of β-D-glucopyranose residues interconnected with (1→3)-glucosidic bonds. The positions of O-6 monosaccharide are joined by the side branches in the form of β-D-glucopyranoses and the terminal residues of β-D-galactopyranoses. The hemicelluloses of Pleurotus ostreatus also contain manogalactan. Complexes of hemicelluloses of both types of mushrooms contain linear α-(1→3)-glucan in small quantities. It has been studied how the molecular-weight distribution of products of limited hydrolysis of hemicelluloses depends on the conditions of their treatment with the enzyme with β-(1→3)-glucanase activity. The maximum accumulation of a fraction with a given molecular weight of 15–25 kDa was observed at a ratio of E:S = 1:45 and treatment time of 21 hours. A specific reaction with congo red has proved there is a triple helical conformation of the main chain of the polysaccharide for this fraction of carbohydrates, so the supramolecular structure of the molecule is preserved.  

β-Glucans: Relationships between Modification, Conformation and Functional Activities

β-glucan is a type of polysaccharide which widely exists in bacteria, fungi, algae, and plants, and has been well known for its biological activities such as enhancing immunity, antitumor, antibacterial, antiviral, and wound healing activities. The conformation of β-glucan plays a crucial role on its biological activities. Therefore, β-glucans obtained from different sources, while sharing the same basic structures, often show different bioactivities. The basic structure and inter-molecular forces of polysaccharides can be changed by modification, which leads to the conformational transformation in solution that can directly affect bioactivity. In this review, we will first determine different ways to modify β-glucan molecules including physical methods, chemical methods, and biological methods, and then reveal the relationship of the flexible helix form of the molecule chain and the helix conformation to their bioactivities. Last, we summarize the scientific challenges to modifying β-glucan's conformation and functional activity, and discuss its potential future development.

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.

Optimization extraction, characterization and antioxidant activities of pectic polysaccharide from tangerine peels

Response surface methodology (RSM) was employed to optimize the microwave-assisted extraction (MAE) process of pectic polysaccharide (TPPs) from tangerines peel. The optimal extraction conditions were as follows: microwave power 704 W, extraction temperature 52.2 °C, and extraction time 41.8 min Under these conditions, the experimental yield was 19.9 ± 0.2%. The purified pectic polysaccharide TPPs-2-1 was successfully obtained by anion-exchange and gel filtration chromatography. TPPs-2-1, linked mainly by α-glycosidic bonds, consisted of galacturonic acid (GalA), arabinose (Ara), galactose (Gal), rhamnose (Rha), glucose (Glc) and mannose (Man) with the average molecular weight of 17.8 kDa, and had typical IR spectra characteristic of pectic polysaccharides. Antioxidant activities were investigated on the basis of ferric-reducing antioxidant power (FRAP), hydroxyl radical (OH), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and superoxide radical (O2(-)) scavenging assay. TPPs-2-1 exhibited significant antioxidant activity in a concentration-dependent manner and might be exploited as effective natural antioxidant applied in functional food and medicine.

Polysaccharide Modification through Green Technology: Role of Endodextranase in Improving the Physicochemical Properties of (1→3)(1→6)-α-D-Glucan

The structure and properties of bioengineered (1→3)(1→6)-α-D-glucan subjected to endodextranase treatment were investigated. Upon enzyme treatment, OD220 and Mw decreased substantially during the first 60 min and thereafter slowed as the modification progressed. Compared to the native glucan, the modified sample solution had a lighter opalescent, bluish-white color. The morphological analysis revealed that bioengineered glucan produced quite a few small particles after hydrolysis. The molecular weight distribution curve gradually shifted to the low Mw region with a significant broadening distribution, and the chain hydrolysis reaction followed a combination of zeroth- and first-order processes. The NMR results showed some specific α-1,6 linkages of glucan chains were cleaved with enzyme treatment. The viscosity of modified glucan solution was markedly reduced, and the Newtonian plateaus were also observed at high shear rates (10-100 1/s). The above results suggested that the modified (1→3)(1→6)-α-D-glucan showed a tailor-made solution character similar to that of arabic gum and would be used as a novel food gum substitute in the design of artificial carbohydrate-based foods.

Effects of drying methods on physicochemical and immunomodulatory properties of polysaccharide-protein complexes from litchi pulp

Dried litchi pulp has been used in traditional remedies in China for many years to treat various diseases, and the therapeutic activity has been, at least partly, attributed to the presence of bioactive polysaccharides. Polysaccharide-protein complexes from vacuum freeze-(VF), vacuum microwave-(VM) and heat pump (HP) dried litchi pulp, which were coded as LP-VF, LP-VM and LP-HP, were comparatively studied on the physicochemical and immunomodulatory properties. LP-HP had a predominance of galactose, while glucose was the major sugar component in LP-VF and LP-VM. Compared with LP-VF and LP-VM, LP-HP contained more aspartate and glutamic in binding protein. LP-HP also exhibited a stronger stimulatory effect on splenocyte proliferation at 200 μg/mL and triggered higher NO, TNF-α and IL-6 secretion from RAW264.7 macrophages. Different drying methods caused the difference in physicochemical properties of polysaccharide-protein complexes from dried litchi pulp, which resulted in significantly different immunomodulatory activity. HP drying appears to be the best method for preparing litchi pulp to improve its immunomodulatory properties.

Solution properties and in vitro anti-tumor activities of polysaccharides from longan pulp

The solution properties of four fractions (LPI-IV) from crude longan pulp polysaccharides (LP3) were analyzed by size-exclusion chromatography combined with laser light scattering, viscometry, complex formation with Congo red, and atomic force microscopy. Their radii of gyration (z)(½) were 43.3, 62.6, 43.2 and 77.3 nm, exponents of (z)(½) = k M(w)(v) were 0.04, 0.50, 0.52 and 0.02, and intrinsic viscosities ([η]) were 9.945, 25.38, 308.2 and 452.1 mL/g, respectively. Moreover, the dependence of [η] on M(w) was established to be [η] = 5.3 × 10⁻²M(w)⁰·⁶¹ (mL/g). LPI had both a sphere-like conformation and a triple-helix structure, and LPII-IV existed as flexible chains. LP3, LPI, LPII and LPIII all exhibited direct inhibitory effects on A549, HeLa and HepG2 cells in a positive dose-dependent manner in the range of 50-400 µg/mL. The activities of LPIII, especially the inhibition of HepG2 cell proliferation, were stronger than those of others, which may be partly related to its flexible conformation. The present results support the cancer therapeutic potential of longan polysaccharides.

Microbial short-chain fatty acid production and extracellular enzymes activities during in vitro fermentation of polysaccharides from the seeds of Plantago asiatica L. treated with microwave irradiation

Effects of microwave irradiation on microbial short-chain fatty acid production and the activites of extracellular enzymes during in vitro fermentation of the polysaccharide from Plantago asiatica L. were investigated in this study. It was found that the apparent viscosity, average molecular weight, and particle size of the polysaccharide decreased after microwave irradiation. Reducing sugar amount increased with molecular weight decrease, suggesting the degradation may derive from glycosidic bond rupture. The polysaccharide surface topography was changed from large flakelike structure to smaller chips. FT-IR showed that microwave irradiation did not alter the primary functional groups in the polysaccharide. However, short-chain fatty acid productions of the polysaccharide during in vitro fermentation significantly increased after microwave irradiation. Activities of microbial extracellular enzymes xylanase, arabinofuranosidase, xylosidase, and glucuronidase in fermentation cultures supplemented with microwave irradiation treated polysaccharide were also generally higher than those of untreated polysaccharide. This showed that microwave irradiation could be a promising degradation method for the production of value-added polysaccharides.