A polysaccharide from Lycium barbarum L.: Structure and protective effects against oxidative stress and high-glucose-induced apoptosis in ARPE-19 cells

Size exclusion chromatography and asymmetrical flow field-flow fractionation for structural characterization of polysaccharides: A comparative review

Natural polysaccharides exhibit a wide range of biological activities, which are closely related to their structural characteristics, including their molecular weight distribution, size, monosaccharide composition, glycosidic bond types and spatial conformation, etc. Size exclusion chromatography (SEC) and asymmetrical flow field-flow fractionation (AF4), as two potent separation techniques, both harbor potential for continuous development and enhancement. This manuscript reviewed the fundamental principles and separation applications of SEC and AF4. The structural information and spatial conformation of polysaccharides can be obtained using SEC or AF4 coupled with multiple detectors. In addition, this manuscript elaborates in detail on the shear degradation of samples such as polysaccharides separated by SEC. In addition, the abnormal elution that occurs during the application of the two methods is also discussed. Both SEC and AF4 possess considerable potential for ongoing development and refinement, thereby offering increased possibilities and opportunities for polysaccharide separation and characterization.

Polysaccharides in fruits: Biological activities, structures, and structure-activity relationships and influencing factors-A review

Fruits are a rich source of polysaccharides, and an increasing number of studies have shown that polysaccharides from fruits have a wide range of biological functions. Here, we thoroughly review recent advances in the study of the bioactivities, structures, and structure-activity relationships of fruit polysaccharides, especially highlighting the structure-activity influencing factors such as extraction methods and chemical modifications. Different extraction methods cause differences in the primary structures of polysaccharides, which in turn lead to different polysaccharide biological activities. Differences in the degree of modification, molecular weight, substitution position, and chain conformation caused by chemical modification can all affect the biological activities of fruit polysaccharides. Furthermore, we summarize the applications of fruit polysaccharides in the fields of pharmacy and medicine, foods, cosmetics, and materials. The challenges and perspectives for fruit polysaccharide research are also discussed.

Preparation of Dendrobium officinale Polysaccharide by Lactic Acid Bacterium Fermentation and Its Protective Mechanism against Alcoholic Liver Damage in Mice

Dendrobium officinale polysaccharide (DP) was prepared with lactic acid bacterium fermentation to overcome the large molecular weight and complex structure of traditional DP for improving its functional activity and application range in this work. The structure was analyzed, and then the functional activity was evaluated using a mouse model of alcoholic liver damage. The monosaccharide compositions were composed of four monosaccharides: arabinose (0.13%), galactose (0.50%), glucose (24.38%), and mannose (74.98%) with a molecular weight of 2.13 kDa. The connection types of glycosidic bonds in fermented D. officinale (KFDP) were →4)-β-D-Manp(1→, →4)-β-Glcp(1→, β-D-Manp(1→, and β-D-Glcp(1→. KFDP exhibited an excellent protective effect on alcoholic-induced liver damage at a dose of 80 mg/kg compared with polysaccharide separated and purified from D. officinale without fermentation (KDP), which increased the activity of GSH, GSH-Px, and GR and decreased the content of MDA, AST, T-AOC, and ALT, as well as regulated the level of IL-6, TNF-α, and IL-1β to maintain the normal functional structure of hepatocytes and retard the apoptosis rate of hepatocytes. The results proved that fermentation degradation is beneficial to improving the biological activity of polysaccharides. The potential mechanism of KFDP in protecting alcoholic liver damage was inhibiting the expression of miRNA-150-5p and targeting to promote the expression of Pik3r1. This study provides an important basis for the development of functional foods.

Natural products for the treatment of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a chronic retinal disease that significantly influences the vision of the elderly.

PURPOSE

There is no effective treatment and prevention method. The pathogenic process behind AMD is complex, including oxidative stress, inflammation, and neovascularization. It has been demonstrated that several natural products can be used to manage AMD, but systematic summaries are lacking.

STUDY DESIGN AND METHODS

PubMed, Web of Science, and ClinicalTrials.gov were searched using the keywords "Biological Products" AND "Macular Degeneration" for studies published within the last decade until May 2023 to summarize the latest findings on the prevention and treatment of age-related macular degeneration through the herbal medicines and functional foods.

RESULTS

The eligible studies were screened, and the relevant information about the therapeutic action and mechanism of natural products used to treat AMD was extracted. Our findings demonstrate that natural substances, including retinol, phenols, and other natural products, prevent the development of new blood vessels and protect the retina from oxidative stress in cells and animal models. However, they have barely been examined in clinical studies.

CONCLUSION

Natural products could be highly prospective candidate drugs used to treat AMD, and further preclinical and clinical research is required to validate it to control the disease.

Characterization, antioxidant activity and in vitro digestion of hawthorn pectin prepared by gradient ethanol precipitation

Four modified hawthorn pectin fractions (MHPs), named MHP-30, MHP-50, MHP-70 and MHP-90, were obtained by ultrasonic-assisted pectin methyl esterase modification and gradient ethanol precipitation. The results indicated that all four MHPs were composed of galacturonic acid, galactose, xylose, arabinose, glucose and mannose in different proportions. With the increase of the ethanol concentration, the molecular weight, esterification degree and galacturonic acid content of MHPs all decreased, whereas the arabinose content and branching degree increased. The structural characterization from XRD, SEM, and FT-IR showed that four MHPs exhibited amorphous structure, similar functional groups, diverse surface morphologies. Besides, in vitro antioxidant assays confirmed that MHP-70 and MHP-90 exhibited stronger total antioxidant activities than MHP-30 and MHP-50. The results of simulated saliva-gastrointestinal digestion showed that the molecular weight of MHP-70 and MHP-90 remained stable, yielded small amounts of reducing sugars, and were resistant to digestion in the human upper digestive tract. Overall, MHP-70 and MHP-90 shown great potential as novel natural antioxidants, which are expected to be good carbon sources for the utilization of intestinal microorganisms.

Structural characterization and osteogenic differentiation-promoting activity of polysaccharide purified from Chroogomphus rutilus

Chroogomphus rutilus (CR) possesses anti-inflammatory, antioxidant, and hypoglycemic properties. However, studies are yet to evaluate the anti-osteoporotic activity of the fungi and its polysaccharides. Therefore, this study is aimed at characterizing and evaluating the anti-osteoporotic effects of a novel polysaccharide from CR. The neutral polysaccharide CRP2 extracted and purified from the fruiting body of CR had a molecular weight of 20.41 kDa. Monosaccharide composition analysis revealed that CRP2 is composed of galactose, glucose, fucose, and mannose. The backbone of CRP2 primarily consisted of →6)-α-D-Galp-(1 → residues, with specific site substitutions speculated at partial positions, such as O-CH3 substitution at H-3 position, or a branch site located at C-2, including α-L-Fucp-(1 → 6)-β-D-Glcp-(1 → and α-D-Manp-(1→. CRP2 treatment increased trabecular bone density, restored a network-shaped structure, and upregulated the expression of osteoblast differentiation markers, including runt-related transcription factor 2, osterix, osteocalcin, and osteopontin in the femoral tissue of mice with osteoporosis (OP). Additionally, CRP2 treatment suppressed the expression of tumor necrosis factor-α and interleukin-1β in the femoral tissue of mice with OP. Mechanistically, CRP2 exerted anti-OP effect by inhibiting inflammation and promoting osteogenesis through the transforming growth factor β-1/Smad pathway. Conclusively, these findings augment our understanding of the potential role of CRP2 in OP treatment.

Yucca schidigera purpurea-sourced arabinogalactan polysaccharides augments antioxidant capacity facilitating intestinal antioxidant functions

This study isolated and purified a novel homogeneous arabinogalactan polysaccharide from Yucca schidigera extract (YSE), unveiled its unique structure and explored its antioxidant function. Firstly, the antioxidant potential of YSE was demonstrated in piglet trials. A homogeneous polysaccharide with a molecular weight of 24.2 kDa, designated as Yucca schidigera polysaccharide B (YPB), was isolated and purified from YSE. The monosaccharide composition of YPB was Rha, Araf, Galp, and Glcp, whose molar percentages were 2.8 %, 11.6 %, 45.5 %, and 40.0 %, respectively. Methylation analysis combined with 1D and 2D nuclear magnetic resonance showed that YPB was a complex polysaccharide with a main glycosidic linkage pattern of →2)-α-ʟ-Rha-(1 → 3)-β-ᴅ-Galp-(1→3)-β-ᴅ-Galp-(1 → 3)-β-ᴅ-Galp-(1 → 3)-β-ᴅ-Glcp-(1→, and branched Araf and Galp fragments were connected with the main chain through →3,6)-β-ᴅ-Galp-(1→, →3,4)-β-ᴅ-Glcp-(1→, and →2,4)-α-ʟ-Rha-(1→ linkages. Following the in vitro biochemical assays of bioactive components, YPB should be the contributor to the antioxidant activity in YSE. Based on the establishment of oxidative stress model, YPB exhibited strong antioxidant capacity and activated NRF2 pathway, and then provided protection against the damage induced oxidative stress in IPEC-J2 cells and rats. Further analysis with inhibitors found that this antioxidant effect was attributed to its interaction with epidermal growth factor receptor and mannose receptor, and stimulating PI3K/AKT pathway.

Establishment of high performance liquid chromatographic fingerprint and determination of 4 kinds of phenolic acid bioactive substances of fruitless Lycium barbarum leaves from Ningxia at different harvesting periods

"Fruitless Lycium barbarum leaf (FLBL) are the leaves of a new variety of Lycium barbarum in Ningxia, which exhibit higher content of various nutrients, trace elements, and bioactive substances compared to Lycium barbarum fruits and leaves. However, the health and medicinal value as well as the by-products derived from FLBL have not received sufficient attention, and the contents of main components vary at different harvesting periods. Therefore, for the first time this study aimed to establish high-performance liquid chromatography (HPLC) fingerprints and determine the contents of four phenolic acid bioactive substances during different harvesting periods in order to provide an experimental basis for cultivation, collection, and research on FLBL. The results revealed 17 common peaks among 10 batches samples with a similarity ranging from 0.71 to 0.976. The linear relationships R2 for catechin, epicatechin-catechin, chlorogenic acid, and rutin were determined as 0.9999 each; meanwhile, the average recovery rate ranged from 93.92 % to 120.11 %, with an RSD between 0.91 % and 2.82 %. The precision, repeatability stability (24 h), and recovery rate met the requirements outlined in "Chinese Pharmacopoeia". Catechin, epicatechin, and rutin exhibited higher levels from June to August, while chlorogenic acid showed increased levels from July to September. The findings serve as a foundation for quality control measures such as identifying optimal harvest periods or facilitating development and production processes related to Ningxia FLBL."

Recent advances in medicinal and edible homologous plant polysaccharides: Preparation, structure and prevention and treatment of diabetes

Medicinal and edible homologs (MEHs) can be used in medicine and food. The National Health Commission announced that a total of 103 kinds of medicinal and edible homologous plants (MEHPs) would be available by were available in 2023. Diabetes mellitus (DM) has become the third most common chronic metabolic disease that seriously threatens human health worldwide. Polysaccharides, the main component isolated from MEHPs, have significant antidiabetic effects with few side effects. Based on a literature search, this paper summarizes the preparation methods, structural characterization, and antidiabetic functions and mechanisms of MEHPs polysaccharides (MEHPPs). Specifically, MEHPPs mainly regulate PI3K/Akt, AMPK, cAMP/PKA, Nrf2/Keap1, NF-κB, MAPK and other signaling pathways to promote insulin secretion and release, improve glycolipid metabolism, inhibit the inflammatory response, decrease oxidative stress and regulate intestinal flora. Among them, 16 kinds of MEHPPs were found to have obvious anti-diabetic effects. This article reviews the prevention and treatment of diabetes and its complications by MEHPPs and provides a basis for the development of safe and effective MEHPP-derived health products and new drugs to prevent and treat diabetes.

Separation of polysaccharides from Lycium barbarum L. by high-speed countercurrent chromatography with aqueous two-phase system

The traditional method for isolation and purification of polysaccharides is time-consuming. It often involves toxic solvents that destroy the function and structure of the polysaccharides, thus limiting in-depth research on the essential active ingredient of Lycium barbarum L. Therefore, in this study, high-speed countercurrent chromatography (HSCCC) and aqueous two-phase system (ATPS) were combined for the separation of crude polysaccharides of Lycium barbarum L. (LBPs). Under the optimized HSCCC conditions of PEG1000-K2HPO4-KH2PO4-H2O (12:10:10:68, w/w), 1.0 g of LBPs-ILs was successfully divided into three fractions (126.0 mg of LBPs-ILs-1, 109.9 mg of LBPs-ILs-2, and 65.4 mg of LBPs-ILs-3). Moreover, ATPS was confirmed as an efficient alternative method of pigment removal for LBPs purification, with significantly better decolorization (97.1 %) than the traditional H2O2 method (88.5 %). Then, the different partitioning behavior of LBPs-ILs in the two-phase system of HSCCC was preliminarily explored, which may be related to the difference in monosaccharide composition of polysaccharides. LBPs-ILs-1 exhibited better hypoglycemic activities than LBPs-ILs-2 and LBPs-ILs-3 in vitro. Therefore, HSCCC, combined with aqueous two-phase system, was an efficient separation and purification method with great potential for separating and purifying active polysaccharides in biological samples.

Structural characteristics and structure-activity relationship of four polysaccharides from Lycii fructus

At present, the structure-activity relationship of polysaccharides is a common and important focus in the fields of glycobiology and carbohydrate chemistry. To better understand the effect of specific polysaccharide structures on bioactive orientation, four homogeneous polysaccharides from Lycii fructus, one neutral along with three acidic polysaccharides, were purified, structurally characterized and comparatively evaluated on the antioxidative and anti-aging activities. The GC-MS-based monosaccharide composition analysis and methylation results showed that the LFPs had similar glycosyl types but varied proportions. Nuclear magnetic resonance (NMR) spectroscopy showed that LFPs consisted of arabinogalactan, rhamnogalacturonan and homogalacturonan structural domains. The results of the structure-activity relationship indicated that the antioxidative activity was positively correlated with the galacturonic acid (GalA) content, while the neutral multi-branched chains might be responsible for the anti-aging activity. This study is the first time to compare the principal structures and multiple biological activities of LFPs, which provided a reference for the industrial development and deep excavation of the health value of LFPs.

Two polysaccharides from Rehmannia glutinosa: isolation, structural characterization, and hypoglycemic activities

Rehmannia glutinosa (RG) as a Chinese herbal medicine can be used both in medicine and food. As the main component of RG, the polysaccharides have a hypoglycemic effect, however, the hypoglycemic activity of RG homopolysaccharides remains unknown. We isolated and purified two polysaccharides, RGP70-1-1 and RGP70-1-2 (4.9 kDa and 2.8 kDa) from RG. The structural characteristics, including monosaccharide composition, linkage, and configuration were analyzed by FT-IR, HPLC, GC-MS, NMR spectroscopy, Congo test, and SEM. RGP70-1-1 and RGP70-1-2 consist of four monosaccharides (glucose, mannose, arabinose, and galactose). RGP70-1-1 contains 14 connection modes, with the linkages including l-Araf-(1→, →3)-l-Araf-(1→, →5)-l-Araf-(1→, →3,5)-l-Araf-(1→, →2,5)-l-Araf-(1→, d-Manp-(1→, →2)-d-Manp-(1→, →4)-d-Manp-(1→, d-Galp-(1→, →4)-d-Galp-(1→, →4,6)-d-Galp-(1→, →6)-d-Glcp-(1→, →4,6)-d-Glcp-(1→, →3,6)-d-Glcp-(1→. The linkages of RGP70-1-2 is including →5)-l-Araf-(1→, →3,5)-l-Araf-(1→, →4)-d-Manp-(1→, →3,6)-d-Manp-(1→, d-Galp-(1→, →6)-d-Galp-(1→, d-Glcp-(1→, →6)-d-Glcp-(1→, →4,6)-d-Glcp-(1→. Furthermore, RGP70-1-1 and RGP70-1-2 can inhibit α-glucosidase and α-amylase. RGP70-1-1 stimulated GLP-1 secretion in STC-1 cells and was related to the up-regulation of PI3K and p-AKT protein expression. The findings revealed a natural product with potential hypoglycemic activity, which may be used as a GLP-1 secretagogue and a beneficial functional food ingredient for T2D.

Structure of a highly branched galacturonoglucan from fruits of Schisandra chinensis (Turcz.) Baill

A novel galacturonoglucan, named SCP-1, is isolated and purified from Schisandra chinensis fruits. The structure of SCP-1 is systematically investigated by a combination of monosaccharide compositions, absolute M_w, methylation analysis, partial acid hydrolysis, isoamylase degradations, and nuclear magnetic resonance spectroscopy. The structure of SCP-1 is theoretically described as follows: (i) Glc and GalA in a molar ratio of 17:3; (ii) → 4)-α-Glcp-(1→, →4,6)-α-Glcp-(1→, →3,4,6)-α-Glcp-(1→, α-Glcp-(1→, →4)-α-GalAp-6-OMe-(1→, α-GalAp-6-OMe-(1→, β-Glcp-(1→, →6-)-β-Glcp-(1 → and →3,4)-β-Glcp-(1 → in a molar ratio of 48:5:3:3:10:5:12:5:9; (iii) a repeating unit of →4)-α-Glcp-(1 → as a backbone with branched points at C-3 and C-6, substituted by different types of acidic and neutral side chains to form multiple branches; and (iv) a rigid rod configuration deduced from α value of 1.26 in Mark-Houwink equation ([η] = kM^α). Anti-tumor assay investigated the effects of SCP-1 on human HepG2 cancer cell lines in vitro. This is for the first time to report a galacturonoglucan in S. chinensis fruits.

Purification of exopolysaccharides from Lactobacillus rhamnosus and changes in their characteristics by regulating quorum sensing genes via polyphenols

To explore the effect of Lonicera caerulea fruit polyphenols (LCP) on caries-causing bacteria, strain RYX-01 with high production of biofilm and exopolysaccharides (EPS) was isolated from the oral cavity of caries patients and was identified as Lactobacillus rhamnosus by 16S rDNA analysis and morphology. The characteristics of EPS produced by RYX-01 (EPS-CK) and those produced by adding L. caerulea fruit polyphenols (EPS-LCP) were compared to reveal whether LCP reduced the cariogenicity of RYX-01 by influencing the structure and composition of EPS. The results showed that LCP could increase the content of galactose in EPS and destroy the original aggregation state of EPS-CK but had no significant effect on the molecular weight and functional group composition of EPS (p > 0.05). At the same time, LCP could inhibit the growth of RYX-01, reduce EPS and biofilm formation and inhibit the expression of quorum sensing (QS, luxS)- and biofilm formation (wzb)-related genes. Therefore, LCP could change the surface morphology, content and composition of RYX-01 EPS and reduce the cariogenic effect of EPS and biofilm. In conclusion, LCP can be used as a potential plaque biofilm inhibitor and QS inhibitor in drugs and functional foods.

A comprehensive review on the ethnobotany, phytochemistry, pharmacology and quality control of the genus Lycium in China

The Lycium genus, perennial herbs of the Solanaceae family, has been an important source of medicines and nutrient supplements for thousands of years in China, where seven species and three varieties are cultivated. Among these, Lycium barbarum L. and Lycium chinense Mill., two "superfoods", together with Lycium ruthenicum Murr, have been extensively commercialized and studied for their health-related properties. The dried ripe fruits of the genus Lycium are well recognized as functional foods for the management of various ailments including waist and knee pain, tinnitus, impotence, spermatorrhea, blood deficiency and weak eyes since ancient times. Phytochemical studies have reported numerous chemical components in the Lycium genus, categorized as polysaccharides, carotenoids, polyphenols, phenolic acids, flavonoids, alkaloids and fatty acids, and its therapeutic roles in antioxidation, immunomodulation, antitumor treatment, hepatoprotection and neuroprotection have been further confirmed by modern pharmacological studies. As a multi-functional food, the quality control of Lycium fruits has also attracted attention internationally. Despite its popularity in research, limited systematic and comprehensive information has been provided on the Lycium genus. Therefore, herein, we provide an up-to-date review of the distribution, botanical features, phytochemistry, pharmacology and quality control of the Lycium genus in China, which will provide evidence for further in-depth exploration and comprehensive utilization of Lycium, especially its fruits and active ingredients in the healthcare field.

Purification, structure identification and immune activity of a neutral polysaccharide from Cynanchum Auriculatum

The crude polysaccharides CAPS and CAP of Cynanchum Auriculatum, which were prepared by degrading starch by single-enzymatic method (α-amylase) and double-enzymatic method (α-amylase and glucoamylase) respectively, were compared. CAP had good water solubility and higher non-starch polysaccharide content. A homogeneous neutral polysaccharide CAPW, with the degree of acetylation about 17 %, was obtained from CAP by anion exchange column chromatography. Its detailed structure was identified by various methods. CAPW, with the weight average molecular weight of 8.4 kDa, was composed of mannose, glucose, galactose, xylose, and arabinose in a molar ratio of 1.27:1.00:0.25:0.10:1.16. The backbone included β-1,4-Manp, β-1,4,6-Manp, β-1,4-Glcp and β-1,4,6-Glcp residues, with branches at the O-6 position of β-1,4,6-Manp and β-1,4,6-Glcp residues, consisting of α-T-Araf, α-1,5-Araf, α-1,2,5-Araf, α-1,3,5-Araf, T-Xylp,1,4-Xylp, β-T-Manp and β-T-Galp residues. In vitro immunological experiments suggested that CAP-W improved the phagocytic ability of macrophages, stimulated the release of NO, TNF-α and IL-6 from RAW264.7 cells, promoted the expression of NF-κB and caused nuclear translocation of NF-κB p65.

Serum metabolomics combined with 16S rRNA sequencing to reveal the effects of Lycium barbarum polysaccharide on host metabolism and gut microbiota

Gut microbes and microbial metabolites derived from polysaccharides mediate beneficial effects related to polysaccharides consumption. Lycium barbarum polysaccharide (LBP) is the main bioactive components in L. barbarum fruits and possesses considerable health-promoting effects. In the present study, we aimed to investigate whether LBP supplementation influenced host metabolic responses and gut microbiota in healthy mice, and to identify bacterial taxa associated with the observed beneficial effects. Our results indicated that mice supplied with LBP at 200 mg/kg BW showed lower serum total cholesterol (TC), triglyceride (TG), and liver TG levels. LBP supplementation strengthened the antioxidant capacity of liver, supported the growth of Lactobacillus and Lactococcus, and stimulated short-chain fatty acids (SCFAs) production. Serum metabolomic analysis revealed that fatty acid degradation pathways were enriched, and RT-PCR further confirmed that LBP up-regulated the expression of liver genes involved in fatty acid oxidation. The Spearman's correlation analysis indicated that some serum and liver lipid profiles and hepatic SOD activity were associated with Lactobacillus, Lactococcus, Ruminococcus, Allobaculum and AF12. Collectively, these findings provide new evidence for the potential preventive effect of LBP consumption on hyperlipidemia and nonalcoholic fatty liver disease.

Structural elucidation of a novel arabinogalactan LFP-80-W1 from Lycii fructus with potential immunostimulatory activity

Polysaccharides are the most important effective components of Lycii fructus, which has a variety of biological activities and broad application prospects in the fields of medicine and food. In this study, we reported a novel arabinogalactan LFP-80-W1 with potential immunostimulatory activity. LFP-80-W1 was a continuous symmetrical single-peak with an average molecular weight of 4.58 × 10⁴ Da and was mainly composed of arabinose and galactose. Oligosaccharide sequencing analyses and NMR data showed that the LFP-80-W1 domain consists of a repeated 1,6-linked β-Galp main chain with branches arabinoglycan and arabinogalactan at position C-3. Importantly, we found that LFP-80-W1 could activate the MAPK pathway and promote the release of NO, IL-6, and TNF-α cytokines in vitro. Therefore, our findings suggest that the homogeneous arabinogalactan from Lycii fructus, can be used as a natural immunomodulator.

Protective effects of Scoparia dulcis L. extract on high glucose-induced injury in human retinal pigment epithelial cells

Diabetic retinopathy (DR) is a major cause of vision loss in diabetic patients. Hyperglycemia-induced oxidative stress and the accumulation of inflammatory factors result in blood-retinal barrier dysfunction and the pathogenesis of DR. Scoparia dulcis L. extract (SDE), a traditional Chinese medicine, has been recently recognized for its various pharmacological effects, including anti-diabetic, anti-hyperlipidemia, anti-inflammatory, and anti-oxidative activities. However, there is no relevant research on the protective effect of SDE in DR. In this study, we treated high glucose (50 mM) in human retinal epithelial cells (ARPE-19) with different concentrations of SDE and analyzed cell viability, apoptosis, and ROS production. Moreover, we analyzed the expression of Akt, Nrf2, catalase, and HO-1, which showed that SDE dose-dependently reduced ROS production and attenuated ARPE-19 cell apoptosis in a high-glucose environment. Briefly, we demonstrated that SDE exhibited an anti-oxidative and anti-inflammatory ability in protecting retinal cells from high-glucose (HG) treatment. Moreover, we also investigated the involvement of the Akt/Nrf2/HO-1 pathway in SDE-mediated protective effects. The results suggest SDE as a nutritional supplement that could benefit patients with DR.

Structural Characteristics of Rehmannia glutinosa Polysaccharides Treated Using Different Decolorization Processes and Their Antioxidant Effects in Intestinal Epithelial Cells

Polysaccharide decolorization is a key determinant of polysaccharide structure. In this study, two purified Rehmannia glutinosa polysaccharides, RGP−1−A and RGP−2−A, were obtained after decolorization using the AB-8 macroporous resin and H₂O₂, respectively. RGP−1−A (molecular weight (Mw) = 18,964 Da) and RGP−2−A (Mw = 3305 Da) were acidic and neutral heteropolysaccharides, respectively, and were both polycrystalline in structure. FTIR analysis revealed that RGP−1−A was a sulfate polysaccharide, while RGP−2−A had no sulfate group. Experiments on IPEC-1 cells showed that RGPs alleviated oxidative stress by regulating the Nrf2/Keap1 pathway. These findings were confirmed by the upregulation of Nrf2, NQO1, and HO-1; the subsequent increase in the levels of antioxidant indicators (SOD, LDH, CAT, and MDA); and the restoration of mitochondrial membrane potential. Overall, the antioxidant capacity of RGP−1−A was significantly higher than that of RGP−2−A. These results suggest that RGPs may be a potential natural antioxidant and could be developed into functional foods.

Isolation, Structural Characterization and Macrophage Activation Activity of an Acidic Polysaccharide from Raspberry Pulp

The discovery of safe and effective plant polysaccharides with immunomodulatory effects has become a research hotspot. Raspberry is an essential commercial fruit and is widely distributed, cultivated, and consumed worldwide. In the present study, a homogeneous acidic polysaccharide (RPP-2a), with a weight-average molecular weight (Mw) of 55582 Da, was isolated from the pulp of raspberries through DEAE-Sepharose Fast Flow and Sephadex G-200 chromatography. RPP-2a consisted of rhamnose, arabinose, galactose, glucose, xylose, galacturonic acid and glucuronic acid, with a molar ratio of 15.4:9.6:7.6:3.2:9.1:54.3:0.8. The results of Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometer (GC-MS), 1D-, and 2D-nuclear magnetic resonance (NMR) analyses suggested that the backbone of RPP-2a was primarily composed of →2)-α-L-Rhap-(1→, →2,4)-α-L-Rhap-(1→, →4)-α-D-GalAp-(1→, and →3,4)-α-D-Glcp-(1→ sugar moieties, with side chains of α-L-Araf-(1→, α-L-Arap-(1→, and β-D-Galp-(1→3)-β-D-Galp-(1→ residues linked to the O-4 band of rhamnose and O-3 band of glucose residues. Furthermore, RPP-2a exhibited significant macrophage activation activity by increasing the production of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and the expression of inducible nitric oxide synthase (iNOS) and cytokines at the transcriptional level in RAW264.7 cells. Overall, the results indicate that RPP-2a can be utilized as a potential natural immune-enhancing agent.

Methyltransferase-like (METTL)14-mediated N6-methyladenosine modification modulates retinal pigment epithelial (RPE) activity by regulating the methylation of microtubule-associated protein (MAP)2

The expression of METTL14 is significantly reduced in patients with retinitis pigmentosa (RP). To clarify the significance of the N6-methyladenosine (m⁶A) RNA modification in RP, we examined phagocytosis, apoptosis, and cell cycle distribution in a human RPE cell line, ARPE-19, following lentivirus-mediated knockdown of METTL14. Differentially expressed genes and changes in m⁶A level were evaluated by RNA sequencing (RNA-seq) and methylated RNA immunoprecipitation sequencing (MeRIP-seq), respectively. The results showed that phagocytosis and proliferation were decreased whereas apoptosis was increased in RPE cells by METTL14 silencing. We found that METTL14 directly regulated m⁶A level and the expression of MAP2, as determined by RNA-seq, MeRIP-seq, MeRIP quantitative PCR, and the RNA pull-down assay. Additionally, MAP2 could bind to neuronal differentiation (NEUROD)1, a pathogenic gene in RPE-associated diseases. A family member of the YTH domain, (YTHDF)2 was recognized as an m⁶A reader of MAP2 mRNA. MAP2 overexpression had the same effects as METTL14 knockdown in RPE cells. Thus, METTL14 regulates the expression of MAP2 via the modification of m⁶A, resulting in the dysregulation of NEUROD1 and pathologic changes in RPE cells. These findings suggest that therapeutic strategies targeting the m⁶A modification of MAP2 or the METTL14/YTHDF2/MAP2/NEUROD1 signaling axis may be effective in the treatment of RPE-associated ocular diseases.