Enzymatic purification and structure characterization of glucuronoxylan from water extract of Cassia obtusifolia seeds

Cassiae Semen: A comprehensive review of botany, traditional use, phytochemistry, pharmacology, toxicity, and quality control

ETHNOPHARMACOLOGICAL RELEVANCE

Cassiae Semen, belonging to the family Leguminosae, is derived from the dry mature seeds of Cassia obtusifolia L. or Cassia tora L. and has long been used as a laxative, hepatoprotective, improve eyesight, and antidiabetic complications medicine or functional food in Asia.

AIMS OF THE REVIEW

This review summarizes the integrated research progress of botany, traditional uses, phytochemistry, pharmacology, toxicity, and quality control of Cassiae Semen. Additionally, the emerging challenges and possible developing directions are discussed as well.

MATERIALS AND METHODS

The information on Cassiae Semen was collected from published scientific materials, including ancient books of traditional Chinese Medicine; Ph.D. and M. Sc. dissertations; monographs on medicinal plants; pharmacopoeia of various countries and electronic databases, such as PubMed, Web of Science, ACS, Science Direct, J-STAGE, Springer link, Taylor, CNKI and Google Scholar, etc. RESULTS: First, the traditional uses and plant origins of Cassiae Semen are outlined. Secondly, approximately 137 compounds, including anthraquinones, naphthopyranones, naphthalenes, flavones, polysaccharides and other compounds, have been isolated and identified from Cassia obtusifolia L. and Cassia tora L. Third, the pharmacological activities and mechanisms of crude extract of Cassiae Semen and its main bioactive compounds are summarized. Moreover, the processing, toxicity, and quality control are introduced briefly.

CONCLUSIONS

Cassiae Semen is a frequently used Chinese Materia Medica with pharmacological effects that mainly affect the digestive system, cardiovascular systems and nervous system. This review summarized its botany, traditional uses, phytochemistry, and pharmacology, it also exhibited recent scientific research advances and gaps, which provide a deeper insight into the understanding and application of Cassiae Semen. In future research on Cassiae Semen, more attention should be given to the pharmacological activities of naphthopyranones and polysaccharides and the mechanism of action for improving eye diseases. Meanwhile, it is essential to focus on strengthening the study on the pharmacokinetics research and the safety evaluation of related health products research.

Recent advances in medicinal and edible homologous polysaccharides: Extraction, purification, structure, modification, and biological activities

110 kinds of traditional Chinese medicines can be used for medicine and food from Chinese pharmacopoeia in 2021. With the deepening of research in recent years, medicinal and edible homologous (MEH) traditional Chinese medicines have great development and application prospects in many fields. Polysaccharides are one of the major and representative pharmacologically active macromolecules in traditional Chinese medicines with MEH. Moreover, traditional Chinese medicines with MEH have become the main source of natural polysaccharides with safety, high efficiency, and low side effects. Increasing researches have confirmed that MEH polysaccharides (MEHPs) have multiple biological activities both in vitro and in vivo methods, such as antioxidant, immunomodulatory, anti-tumor, anti-aging, anti-inflammatory, hypoglycemic, hypolipidemic activities, and regulating intestinal flora. Additionally, different raw materials, extraction, purification, and chemical modification methods result in differences in the structure and biological activities of MEHPs. The purpose of the present review is to provide comprehensively and systematically reorganized information in the extraction, purification, structure, modification, biological activities, and potential mechanism of MEHPs to support their therapeutic effects and health functions. New valuable insights and theoretical basis for the future researches and developments regarding MEHPs were proposed in the fields of medicine and food.

Isolation, NMR characterization and bioactivity of a (4-O-methyl-α-D-glucurono)-β-D-xylan from Campomanesia xanthocarpa Berg fruits

Hemicellulose-type polysaccharides were isolated from Campomanesia xanthocarpa fruits by alkaline extraction and submitted to fractionation processes giving rise to eluted (GE-300) and retained (GR-300) fractions. GE-300 presented a mixture of galactoglucomannans (GGM) and glucuronoxylans (MGX), while the GR-300 fraction is composed only of MGX. In this way, the chemical structure of MGX, investigated by 1D ¹H, ¹³C and 2D ¹H-¹³C HSQC, ¹H-¹H COSY and ¹H-¹³C HMBC NMR spectroscopy, revealed that the chemical structure of polysaccharide is a (4-O-methyl-α-D-glucurono)-D-xylan. Deep and precise NMR chemical shift determination of clean and specific ¹H NMR glycosyl units were developed by 1D TOCSY and 1D NOESY analysis. This approach demonstrated unequivocally that 4-O-methyl-α-D-glucopyranosyl uronic acid group is linked to O-2 of a (1 → 4)-β-D-xylan in the main chain. Furthermore, MGX scavenged DPPH radical (0.5 to 1.0 mg mL^-1) and was not cytotoxic to human dermal fibroblasts at concentrations up to 1.0 mg mL^-1, as demonstrated by neutral red and crystal violet assays, evidencing in vitro biocompatibility. The structure elucidation of GR-300 together with its bioactivity assessment contributed to better understand the chemical characteristics of C. xanthocarpa hemicelluloses and may provide structural basis for future structure-property studies.

Structure–immunomodulatory activity relationships of dietary polysaccharides

Polysaccharides are usually composed of more than ten monosaccharide units, which are connected by linear or branched glycosidic bonds. The immunomodulatory effect of natural polysaccharides is one of the most important bioactive function. In this review, molecular weight, monosaccharide (including galactose, mannose, rhamnogalacturonan-I arabinogalactan and uronic acid), functional groups (namely sulfate, selenium, and acetyl groups), types of glycoside bond connection (including β-1,3-D-glucosyl, α-1,4-D-glucosyl, β-1,4-D-glucosyl, α-1,6-D-glucosyl, β-1,4-D-mannosyl, and β-1,4-D-Xylopyranosyl), conformation and the branching degrees are systematically identified as their contribution to the immunostimulatory activity of polysaccharides. At present, studies on the structure-activity relationships of polysaccharides are limited due to their low purity and high heterogeneity. However, it is an important step in providing useful guidance for dietary supplements with polysaccharides. The chemical structures and the process of immune responses induced are necessary to be discussed. Polysaccharides may bind with the cell surface receptors to modulate immune responses. This review mainly discusses the structure-activity relationship of dietary polysaccharides.

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Structure - activity relationships of polysaccharides with immune-enhancing effect are proposed.

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Polysaccharides with the higher molecular weight are helpful to improve immunity.

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Higer galactose, mannose, rhamnogalacturonan-I, arabinogalacta,n and uronic acid contents have immunoregulation.

Phytochemistry, Ethnopharmacological Uses, Biological Activities, and Therapeutic Applications of Cassia obtusifolia L.: A Comprehensive Review

Cassia obtusifolia L., of the Leguminosae family, is used as a diuretic, laxative, tonic, purgative, and natural remedy for treating headache, dizziness, constipation, tophobia, and lacrimation and for improving eyesight. It is commonly used in tea in Korea. Various anthraquinone derivatives make up its main chemical constituents: emodin, chrysophanol, physcion, obtusifolin, obtusin, au rantio-obtusin, chryso-obtusin, alaternin, questin, aloe-emodin, gluco-aurantio-obtusin, gluco-obtusifolin, naphthopyrone glycosides, toralactone-9-β-gentiobioside, toralactone gentiobioside, and cassiaside. C. obtusifolia L. possesses a wide range of pharmacological properties (e.g., antidiabetic, antimicrobial, anti-inflammatory, hepatoprotective, and neuroprotective properties) and may be used to treat Alzheimer's disease, Parkinson's disease, and cancer. In addition, C. obtusifolia L. contributes to histamine release and antiplatelet aggregation. This review summarizes the botanical, phytochemical, and pharmacological features of C. obtusifolia and its therapeutic uses.

Isolation and structure characterization of glucuronoxylans from Dolichos lablab L. hull

Polysaccharides were extracted by hot water and alkali in sequence from Dolichos lablab L. hull, and further purified by ion-exchange and gel columns. Hot water extracted D. lablab hull polysaccharide (DLHP) was rich in glucuronoxylan and pectin, and alkali extracted polysaccharide (DLHAP) mostly embraced glucuronoxylan. The structures of purified glucuronoxylans from DLHP and DLHAP were mainly analyzed by HPAEC-PAD, methylation combined with GC-MS, NMR and SEC-MALLS. DLHP-1 was identified as acetylated glucuronoxylan containing →4)-β-Xylp-(1→ backbone with substitution at O-2 site by α-GlcpA/4-O-methyl-α-GlcpA. The molar ratio of β-Xylp to α-GlcpA was 6.9:1, and acetylation was mainly at O-3 site of β-Xylp with acetylation degree of 21.5%. DLHP-1 and DLHP-2 had similar physicochemical properties, except for molecular weight (M_w). DLHAP-1 was the non-methylated glucuronoxylan almost without acetylation, and it had the molar ratio of β-Xylp to α-GlcpA of 5.6:1. Besides, DLHP-1 (M_w of 20.0 × 10³ g mol^-1) adopted semi-flexible chain, while DLHAP-1 (M_w of 15.4 × 10³ g mol^-1) showed flexible chain. These results provided a structural basis for study on polysaccharides from D. lablab hull, which was benefit for understanding biological activities and developing functional food or pharmaceuticals of D. lablab.

Polysaccharides extracted from Cassia seeds protect against high glucose-induced retinal endothelial cell injury

INTRODUCTION

To investigate the protect effect of polysaccharides extract from cassia seeds (CSPE) on human retinal endothelial cells (HRECs) in hyperglycemia environment.

METHODS

The same amount of human retinal endothelial cells (HRECs), respectively, inoculated in vitro were divided into normal group (Con group), hyperglycemia group (H-Glu group), and different concentration of cassia polysaccharides extract (CSPE) combined with high glucose medium group (CSPE group). HRECs in Con group were cultured routinely. The cell in H-Glu group was treated with high glucose, in which the concentration of glucose in the medium was 30 mM. HRECs in CSPE group were treated with different concentrations of CSPE combined with high glucose. Enhanced cell counting kit-8(CCK8) assay was used to measure the HRECs cell survival rate in different groups. The generation of reactive oxygen species (ROS) in different group was measured by flow cytometry. The real-time quantitative PCR analysis was used for determining intracellular heme oxygenase-1 (HO-1) mRNA levels. Western Blot was applied to test the change of proteins, such as HO-1- and NF-E2-related factor 2 (Nrf2) protein.

RESULTS

The cell survival rate of the H-Glu group was significantly lower than that of the Con group (P < 0.05). When the concentration of CSPE was 100 mg/ml in CSPE group, the HRECs cell survival rate was significantly lower than that of the Con group (P < 0.05), and there was no significant difference with H-Glu group. When the concentration of CSPE in CSPE group was between 50 µg/ml and 1 × 10⁴ µg/ml, the survival rate of HRECs cells showed no significant difference compared with that of H-Glu group and Con group. However, when the concentration of CSPE in CSPE group was between 2.5 and 40 µg/ml, the HRECs cell survival rate was significantly higher than that of H-Glu group (P < 0.05) with a concentration-independent, and there was no significant difference between CSPE group and Con group. The ROS production was lowest in the CSPE group and was lower in Con group than in the H-Glu group. The contents of HO-1 mRNA (P < 0.05), HO-1 and Nrf2 protein were lower in the H-Glu group than in the CSPE and Con group, and there was no significant difference between the CSPE group and H-Glu group.

CONCLUSIONS

A certain concentration range of CSPE can increase the expression of the downstream protein HO-1 and negatively regulate the production of ROS by upregulating the expression of Nrf2, thus protecting human retinal endothelial cells from oxidative damage caused by high glucose.

Extraction and characterization of xylan from sugarcane tops as a potential commercial substrate

Xylan is the major hemicellulose present in sugarcane stem secondary cell walls. Xylan is composed of xylose backbone with a high degree of substitutions, which affects its properties. In the present study, the xylan from sugarcane tops (SCT) was extracted and characterized. Compositional analysis of xylan extracted from SCT (SCTx) displayed the presence of 74% of d-xylose residues, 16% of d-glucuronic acid residues and 10% of l-arabinose. High performance size exclusion chromatographic analysis of SCTx displayed a single peak corresponding to a molecular mass of ∼57 kDa. The Fourier transform infrared spectroscopic analysis of SCTx displayed the peaks corresponding to those obtained from commercial xylan. FESEM analysis of SCTx showed the granular and porous surface structure. Differential thermogravimetric analysis (DTG) of SCTx displayed two thermal degradation temperatures (T_d) of 228°C, due to breakdown of the side chains of glucuronic acid and arabinose and 275°C, due to breakdown of xylan back bone. The presence of arabinose and glucuronic acid as a side chains was confirmed by the DTG and thermogravimetric analysis. The CHNS analysis of SCTx showed the presence of only carbon and hydrogen supporting its purity. The recombinant xylanase (CtXyn11A) from Clostridium thermocellum displayed a specific activity of 1394 ± 51 U/mg with SCTx, which was higher than those with commercial xylans. The thin layer chromatography and electrospray ionization mass spectroscopy analyses of CtXyn11A hydrolysed SCTx contained a series of linear xylo-oligosaccharides ranging from degree of polymerization 2-6 and no substituted xylo-oligosaccharides because of the endolytic activity of enzyme. The extracted xylan from SCT can be used as an alternative commercial substrate and for oligo-saccharide production.

Acacia Xylan as a Substitute for Commercially Available Xylan and Its Application in the Production of Xylooligosaccharides

Over the past two decades, birchwood and beechwood xylans have been used as a popular substrate for the characterization of xylanases. Recently, major companies have discontinued their commercial production. Therefore, there is a need to find an alternative to these substrates. Xylan extraction from Acacia sawdust resulted in 23.5% (w/w) yield. The extracted xylan is composed of xylose and glucuronic acid residues in a molar ratio of 6:1 with a molecular mass of ∼70 kDa. The specific optical rotation analysis of extracted xylan displayed that it is composed of the d-form of xylose and glucuronic acid monomeric sugars. The nuclear magnetic resonance analysis of extracted xylan revealed that the xylan backbone is substituted with 4-O-methyl glucuronic acid at the O2 position. Fourier transform infrared analysis confirmed the absence of lignin contamination in the extracted xylan. Xylanase from Clostridium thermocellum displayed the enzyme activity of 1761 U/mg against extracted xylan, and the corresponding activity against beechwood xylan was 1556 U/mg, which confirmed that the extracted xylan could be used as an alternative substrate for the characterization of xylanases.

Extraction Optimization, Structural Characterization, and Antioxidant Activities of Polysaccharides from Cassia Seed (Cassia obtusifolia)

In order to explore Cassia seed polysaccharides (CSPs) as natural antioxidants for application in the functional-food industry, microwave-assisted extraction (MAE) was optimized for the extraction of CSPs by using a response surface methodology. Furthermore, the chemical structures and antioxidant activities of CSPs extracted by MAE and hot water extraction were investigated and compared. The maximum extraction yield of CSPs extracted by MAE (8.02 ± 0.19%) was obtained at the optimized extraction parameters as follows: microwave power (415 W), extraction time (7.0 min), and ratio of water to raw material (51 mL/g). Additionally, the contents of the uronic acids, molecular weight, ratio of constituent monosaccharides, intrinsic viscosities, and degrees of esterification of CSPs were significantly affected by the MAE method. Moreover, CSPs exhibited remarkable 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS, 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl DPPH, nitric oxide, and hydroxyl radical scavenging activities as well as reducing power. The high antioxidant activities observed in CSPs extracted by MAE could be partially attributed to its low molecular weights and high content of unmethylated galacturonic acid. Results indicate that the MAE method could be an efficient technique for the extraction of CSPs with high antioxidant activity, and CSPs could be further explored as functional food ingredients.

Effect of Lactobacillus plantarum NCU116 Fermentation on Asparagus officinalis Polysaccharide: Characterization, Antioxidative, and Immunoregulatory Activities

Lactic acid fermentation represents a novel method to produce bioactive functional ingredients, including polysaccharides. In this work, a selected lactic acid bacteria strain NCU116 was used to ferment Asparagus officinalis (asparagus) pulps. Two polysaccharides were subsequently separated from both unprocessed and fermented asparagus pulps, namely, asparagus polysaccharide (AOP) and fermented-AOP (F-AOP). The physicochemical and bioactive properties of AOP and F-AOP were characterized and investigated. High-performance anion-exchange chromatography showed that fermentation increased the proportions of rhamnose, galacturonic acid, and glucuronic acid in polysaccharides by 46.70, 114.09, and 12.75‰, respectively. High-performance size-exclusion chromatography revealed that fermentation decreased the average molecular weight from 181.3 kDa (AOP) to 152.8 kDa (F-AOP). Moreover, the fermentation reduced the particle size and changed the rheology property. In vitro, F-AOP displayed superior free radical scavenging properties compared to AOP, using 2,2-diphenyl-1-picryhydrazyl, hydroxyl, and superoxide anion radical scavenging assays. In vivo, F-AOP administration dose-dependently promoted a gradual shift from Th17-dominant acute inflammatory response (IL-17 and RORγt) to Th1-dominant defensive immune response (IFN-γ and T-bet). These results indicated that the Lactobacillus plantarum NCU116 fermentation was practical and useful to obtain promising bioactive polysaccharides.

Polysaccharide from fermented Momordica charantia L. with Lactobacillus plantarum NCU116 ameliorates type 2 diabetes in rats

The influence of Lactobacillus plantarum-fermentation on the structure and anti-diabetic effects of Momordica charantia polysaccharides were evaluated. High-fat diet and streptozotocin-induced type 2 diabetic rats were administrated with polysaccharides from fermented and non-fermented Momordica charantia (FP and NFP) for 4 weeks. Fermentation affected the physicochemical characterization, monosaccharide composition, molecular weight, and viscosity of Momordica charantia polysaccharides. Treatment with FP significantly ameliorated hyperglycemia, hyperinsulinemia, hyperlipidemia, and oxidative stress in diabetic rats compared with NFP. Moreover, the diversity and abundance of gut microbiota (Lactococcus laudensis and Prevotella loescheii) in diabetic rats were notably increased by treatment with FP in comparison to NFP. Meanwhile, FP-treated diabetic rats exhibited more colonic short-chain fatty acids (SCFAs) and lower pH values than that in NFP-treated rats. Overall, Lactobacillus plantarum-fermentation could enhance the anti-diabetes effects of Momordica charantia polysaccharides in rats by modifying the structure of polysaccharides to optimize gut microbiota and heighten the production of SCFAs.