Preparation, structural characterization and bioactivities of Se-containing polysaccharide: A review

Effect of chitosan oligosaccharide-conjugated selenium on improving immune function and blocking gastric cancer growth

Selenium (Se) is a potential chemopreventive or chemotherapeutic agent against malignant tumor. Selenium-oligosaccharides are important selenium source of dietary supplementation. Due to the insufficient natural production, it is therefore urgent to develop selenium-oligosaccharides by artificial synthesis. Chitosan, the N-deacetylated derivative of chitin, has been applied widely in biomedical field, owing to its nontoxicity, hydrophilicity, biocompatibility, and biodegradation. While chitosan is water insoluble at neutral pH, limiting its application in physiological conditions. Chitosan oligosaccharide (COS), the hydrolysate of chitosan, is readily soluble in water because of the shorter chain lengths of the oligomers and the free amino groups in the D-glucosamine units. This study was aimed at preparing COS-conjugated selenium (COS-Se) and examining the toxicity and ability on improving immune function and blocking gastric cancer growth. Our results demonstrated that COS-Se displayed directly co-mitogenic and mitogenic actions on mouse splenocytes proliferation in vitro. Besides, COS-Se treatment could effectively elevate phagocytosis and increase the secretion of anti-inflammatory cytokine in mouse peritoneal macrophages. Further in vivo experiments showed that COS-Se exhibited immuno-enhancing effects through promoting the phagocytic index, spleen index and thymus index with no obvious toxicity to Kunming mice. Moreover, COS-Se inhibited proliferation and metastasis of human gastric cancer cells, with non-toxic effects on the normal fibroblast cells in vitro. COS-Se supplementation could significantly repress the growth of gastric adenocarcinoma through reducing levels of CD34, vascular endothelial growth factor and matrix metalloproteinase-9 of nude mice. In conclusion, COS-Se was non-toxic and showed great potential as a functional food ingredient in cancer prevention.

The characterization and biological activities of synthetic N, O-selenized chitosan derivatives

Synthetic selenium polysaccharides with potential bioactivity have drawn great interest due to the SeO bonds existing in the structure. Herein, N, O-selenized N-(2-carboxyethyl) chitosan (sNCCS) was synthesized through carboxyethylation and selenylation. Various characterizations were performed to identify the structure of sNCCS, indicating that SeO bonds were formed both at the C-6 hydroxyl groups and the introduced C-2 carboxyethyl groups. The highest yield and selenium content of all sNCCS reached 84.5% and 1.553 mg/g, respectively. In vitro evaluation exhibited that sNCCS has excellent bile acid binding capacity, which was 1.63, 2.00, and 2.55-fold higher than that of N-(2-carboxyethyl) chitosan (NCCS). Moreover, it was found that higher selenium content could significantly enhance the antioxidant properties of sNCCS. Importantly, no obvious cytotoxic effect had been observed on Caco-2 cells. Taken together, sNCCS with desirable biological activity and non-cytotoxicity might be considered as an effective ingredient in the fields of food or medicine.

Acid site-regulated solid acids for polysaccharide Se-functionalization: Structural explanations for high reactivity

In this work, the application of acid site-regulated solid acids in Se-functionalization of polysaccharide is evaluated for the first time, which aimed to further improve reaction efficiency and realize environmentally friendly chemistry. A series prepared M_xO_y/HZSM-5 catalysts possesses standard crystal structure, large specific surface area, pore volume, aperture as well as strong acidity. An efficient substitution of seleno-group on polysaccharide backbone is promoted by regulating the acid site of solid acids (Se content up to 15,170.49 μg/g) compared with the conventional Se-functionalization method (1703 μg/g). Strong Lewis and Brønsted acid sites lead to the driving forces toward low molecular mass polysaccharide fragments, but the deletion of main monosaccharide components is not observed. In summary, it is proved that solid acid can be employed in acid-dependent polysaccharide Se-functionalization which will promote useful in expanding our understanding of how to further develop polysaccharide resources.

Selenium enrichment improves anti-proliferative effect of oolong tea extract on human hepatoma HuH-7 cells

Selenium (Se)-enriched tea is attracting increasing interests due to its significantly improved health benefits. This study was to investigate the anti-proliferative effects of Se-enriched oolong tea against human hepatoma HuH-7 cells. Compared with regular oolong tea extract (TE, 0.04 μg selenium/g), Se-enriched oolong tea extract (Se-TE, 0.51 μg selenium/g) exhibited more prominent anti-proliferative effect against HuH-7 cells with an IC₅₀ of 203.1 μg/mL, mainly due to the synergistic effects of organic selenium and tea polyphenols. Our results found that Se-TE increased intracellular ROS production, arrested the cell cycle at G2/M phase, and thus induced cell apoptosis. In addition, western blotting assay revealed the increased expressions of the p53, Bax, caspase 3, and a reduction of Bcl-2 and CDK2, resulting in Se-TE-induced apoptosis. The improved anti-proliferative effect makes Se-enriched oolong tea extract a promising health-promoting ingredient in food industry.

Characterization of selenium-containing polysaccharide from Spirulina platensis and its protective role against Cd-induced toxicity

Herein, selenium-containing polysaccharide from Spirulina platensis (Se-SPP) was prepared and its structural characteristics and protective role against Cd-induced toxicity in vivo and in vitro were investigated. Se-SPP was alkali-extracted from selenium-containing Spirulina platensis which was cultured in Zarrouk medium supplemented with Na₂SeO₃. The contents of carbohydrate, protein, uronic acid, sulfate and elements (including Se, C, H, O, N, and S) as well as the monosaccharide composition, molecular weight, surface morphology and FT-IR spectra of Se-SPP was compared to that of selenium-free polysaccharide (SPP). The results revealed that SPP and Se-SPP were both high-molecular-weight heteropolysaccharide with similar molecular weight and monosaccharide composition but significantly different selenium content, indicating that the covalently-bonding of a small amount of selenium did not destroy the original structure of polysaccharide. Furthermore, CdCl₂ was utilized to build Cd-intoxicated cells model in vitro and rats model in vivo respectively. Then, the protective effect of Se-SPP against cadmium-induced toxicity was assessed. The results demonstrated that Se-SPP treatment provided significant protection against Cd-induced toxicity, which was superior compared to that of SPP or Na₂SeO₃ alone. The enhancement of protective role may be affected by the covalently-bonding of selenium to polysaccharide.

Evaluation of antidiabetic activity of Pleurotus pulmonarius against streptozotocin-nicotinamide induced diabetic wistar albino rats

The current research aims to evaluate the antidiabetic properties of Pleurotus pulmonarius, an edible basidiomycetes mushroom fungi in diabetic induced wistar albino rats. Mycelial Hot Water Extracts (HWE) and Acetone Extracts (AE) of Pleurotus pulmonarius was orally administrated to STZ-NA induced (55 mg/kilogram body weight) diabetic wistar albino rats at a concentration of 200 and 400 mg/kg for 4 weeks. The outcomes revealed that the HWE of Pleurotus pulmonarius resulted in a significant (p < 0.001) reduction in blood glucose level. A noteworthy (p < 0.001) reduction in serum lipid profile and elevation in High-Density Lipoprotein Cholesterol (HDL-C) after administration with HWE, also demonstrating the protective effects of HWE in diabetes-related complications. Besides all antidiabetic parameters, pathological morphology of the pancreas, liver and kidney are regularised. This observation indicated that HWE of Pleurotus pulmonarius possessed higher antidiabetic activity than AE. Besides, HWE also promoted a significant control of alpha amylase enzyme in a concentration-dependent manner with a maximum activity of 99.23% inhibition at 1000 µg/ml. The outcomes of the present study indicated that the HWE possesses a potential antidiabetic activity both in vitro and in vivo. Thus, it can be used as a nontoxic complementary drug in the controlling of diabetes and related complications, thus providing scientific authentication of its use as an antidiabetic agent.

Characterization of selenium-containing polysaccharides isolated from selenium-enriched tea and its bioactivities

Two novel selenium polysaccharide fractions (SeTPS-1 and SeTPS-2) were isolated purified, characterized from Se-enriched tea. The results showed that the molecular weights and Se content of SeTPS-1 and SeTPS-2 were 1.7 × 10⁴ Da, 1.3 × 10⁴ Da, and 23.50 μg/g and 13.47 μg/g, respectively. SeTPS-1 and SeTPS-2 had absorption spectra typical of selenium esters. SeTPS-1 was composed of glucose and galactose at a molar ratio of 80.1:2.3, respectively, while SeTPS-2 was composed of arabinose, glucose, galactose and galacturonic acid with a molar ratio of 2.04: 48.83: 3.21: 1.30, respectively. Both SeTPS-1 and SeTPS-2 adopted a random coil conformation. Importantly, in vitro assessment of the antioxidant capacity revealed that SeTPS-1 is a more potent antioxidant compared to SeTPS-2. Both compounds were effective at reducing DNA damage induced by H₂O₂. The promising data suggesting that these compounds confer natural protection against DNA-damaging agents, thereby contributing to the functional food qualities of tea.

Structural features, selenization modification, antioxidant and anti-tumor effects of polysaccharides from alfalfa roots

Hot water extraction and chromatographic purification methods were used to extract and purify two polysaccharides (RAPS-1 and RAPS-2) from the roots of alfalfa. Subsequently, RAPS-2 was modified using the HNO₃/Na₂SeO₃ method to obtain Se-RAPS-2. The structural features, antioxidant and in vitro anti-tumor activities of the three polysaccharides were evaluated. The structural analysis revealed that RAPS-1 (Mw = 10.0 kDa) was composed of rhamnose, xylose, arabinose, galacturonic acid, mannose and glucose, whereas RAPS-2 (Mw = 15.8 kDa) consisted of rhamnose, xylose, galacturonic acid, mannose, glucose and galactose. RAPS-1 contained 1 → 2, 1 → 4, 1 → 3, and 1 → 6 or 1 → glycosidic bonds; however, while RAPS-2 lacked 1 → 4 glycosidic linkages. The molecular weight of Se-RAPS-2 was 11.0 kDa less than that of RAPS-2. The results of activities demonstrated that Se-RAPS-2 displayed superior antioxidant activity and inhibitory effect in HepG2 cells than RAPS-1 and RAPS-2.

Research progress on the biological activities of selenium polysaccharides

Selenium polysaccharides, an important organic selenium product, possess better antioxidant, antitumour, immune regulation, hypoglycaemic, and heavy metal removal activities than that of either polysaccharides or inorganic selenium.

Preparation, characterization, antioxidant and antiglycation activities of selenized polysaccharides from blackcurrant

An ultrasound-assisted enzymatic method was used to extract the polysaccharides from blackcurrant fruits (BP), and then a nitric acid-sodium selenite method was employed to prepare twelve kinds of selenized blackcurrant polysaccharides (SBPs). Among them, SBP-1, SBP-2 and SBP-3 with different selenium contents of 250 ± 11, 312 ± 15 and 643 ± 24 μg g⁻¹, displayed relatively higher 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) scavenging activities than the others. After treating with a Sepharose-6B chromatography column, the purified blackcurrant polysaccharide (PBP) and three selenized polysaccharides (PSBP-1, PSBP-2, PSBP-3) with high purity were obtained. Compared with PBP, PSBPs possessed a larger absolute value of zeta potential (ZP) and smaller particle size, indicating the positive influence of selenized modification on physical stability of polysaccharides. Ultraviolet (UV), Fourier transform infrared (FT-IR) and circular dichroism (CD) spectra confirmed that selenium had been introduced onto the polysaccharide structure. X-ray diffraction (XRD) and I₂–KI reaction results indicated that selenized modification did not cause an obvious change in crystal form and branch structure of blackcurrant polysaccharides. In addition, PSBPs were superior to PBP in antioxidant and antiglycation capacities, and the bioactivities of PSBPs were significantly improved in positive correlation with selenium content. This study suggested that PSBPs may be a potential selenium source and serve as functional food and medicine.

An ultrasound-assisted enzymatic method was used to extract the polysaccharides from blackcurrant fruits (BP), and then a nitric acid-sodium selenite method was employed to prepare twelve kinds of selenized blackcurrant polysaccharides (SBPs).

Effect of molecular weight of chitosan and its oligosaccharides on antitumor activities of chitosan-selenium nanoparticles

The antitumor activity of zero-valent selenium (Se⁰) nanoparticles stabilized by chitosan and its oligosaccharides having molecular weights 3 k, 65 k, and 600 k Da, was investigated. The nanoparticles stabilized with high molecular weight chitosan not only released selenium more easily compared with low molecular weight chitosan, but were also taken up by HepG2 cells more easily through electrostatic effect. Moreover, these were more efficient in inhibiting HepG2 cell viability. High ROS levels of cancer cells could easily induce selenium release from these nanoparticles, and oxidize the less toxic Se⁰ to highly toxic Se⁴⁺. The latter could not only consume antioxidant enzymes, but also cause mitochondrial dysfunction and cell apoptosis. Study of antitumor efficacy and side effect on a HepG2 xenograft BALB/c nude mice model exhibited that CS-Se⁰NPs had a higher selectivity for cancer cells; however, their effect on normal cells, which have relatively lower ROS levels, was limited.

Hypoglycemic and hypolipidemic activities of Grifola frondosa polysaccharides and their relationships with the modulation of intestinal microflora in diabetic mice induced by high-fat diet and streptozotocin

This study aimed to investigate the hypoglycemic and hypolipidemic activities of polysaccharides from Grifola frondosa (GFP) in diabetic mice induced by high-fat diet (HFD) and streptozotocin (STZ). Results showed that oral administration of GFP markedly reduced the serum levels of fasting blood glucose (FBG), oral glucose tolerance (OGT), cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C), and significantly decreased the hepatic levels of TC, TG and free fatty acids (FFA). Meanwhile, high-dose of GFP supplementation (900 mg/kg day) also showed powerful effects on moderating the composition of intestinal microflora in diabetic mice, especially altering the functionally relevant intestinal microbial phylotypes. Spearman's correlation network analysis revealed that key microbial phylotypes responding to GFP intervention were strongly correlated with the glucose and lipid metabolic disorders associated parameters. Moreover, GFP treatment regulated mRNA expression levels of the genes responsible for hepatic glucose and lipid metabolism. It is noteworthy that GFP treatment markedly increased mRNA expression of cholesterol 7α-hydroxylase (CYP7A1) and bile salt export pump (BSEP), suggesting an enhancement of bile acids (BAs) synthesis and excretion in liver. These findings demonstrated that GFP could prevent hyperglycemia and hyperlipidemia in diabetic mice by altering gut microbiota and regulating hepatic glycolipid metabolism related genes, and therefore could be used as potential functional food ingredients for the prevention or treatment of hyperglycemia and hyperlipidemia.

Polysaccharides of mushroom Pleurotus spp.: New extraction techniques, biological activities and development of new technologies

The biodiversity of mushrooms Pleurotus spp. is impressive due to its complexity and diversity related to the composition of chemical structures such as polysaccharides, glycoproteins and secondary metabolites such as alkaloids, flavonoids and betalains. Recent studies of polysaccharides and their structural elucidation have helped to direct research and development of technologies related to pharmacological action, production of bioactive foods and application of new, more sophisticated extraction tools. The diversity of bioactivities related to these biopolymers, their mechanisms and routes of action are constant focus of researches. The elucidation of bioactivities has helped to formulate new vaccines and targeted drugs. In this context, in terms of polysaccharides and the diversity of mushrooms Pleurotus spp., this review seeks to revisit the genus, making an updated approach on the recent discoveries of polysaccharides, new extraction techniques and bioactivities, emphasising on their mechanisms and routes in order to update the reader on the recent technologies related to these polymers.

Grifola frondosa polysaccharides ameliorate lipid metabolic disorders and gut microbiota dysbiosis in high-fat diet fed rats

The purpose of this study was to assess the potential effects of polysaccharides from edible mushroom Grifola frondosa (GFP) on lipid metabolic disorders and gut microbiota dysbiosis, and elucidate their possible regulatory mechanisms on lipid and cholesterol metabolism in high-fat diet (HFD)-exacerbated hyperlipidemic and hypercholesterolemic rats. Results showed that oral administration of GFP markedly alleviated dyslipidaemia through decreasing the serum levels of total triglycerides, total cholesterol, and free fatty acids, and significantly suppressing hepatic lipid accumulation and steatosis. Besides, the excretion of fecal bile acids was also promoted by oral administration of GFP. Metagenomic analysis revealed that GFP supplementation (400 mg kg-1 day-1) resulted in significant structure changes on gut microbiota in HFD-fed rats, in particular modulating the relative abundance of functionally relevant microbial phylotypes compared with the HFD group. Key microbial phylotypes responding to GFP intervention were identified to strongly correlate with the lipid metabolism disorder associated parameters using the correlation network based on Spearman's correlation coefficient. Serum and hepatic lipid profiles were found positively correlated with Clostridium-XVIII, Butyricicoccus and Turicibacter, but negatively correlated with Helicobater, Intestinimonas, Barnesiella, Parasutterella, Ruminococcus and Flavonifracter. Moreover, GFP treatment (400 mg kg-1 day-1) regulated the mRNA expression levels of the genes responsible for hepatic lipid and cholesterol metabolism. Oral supplementation of GFP markedly increased the mRNA expression of cholesterol 7α-hydroxylase (CYP7A1) and bile salt export pump (BSEP), suggesting an enhancement of bile acid (BA) synthesis and excretion from the liver. These findings illustrated that GFP could ameliorate lipid metabolic disorders through modulating specific gut microbial phylotypes and regulating hepatic lipid and cholesterol metabolism related genes, and therefore could be used as a potential functional food ingredient for the prevention or treatment of hyperlipidemia.