Root Polysaccharide Research Articles

α-Glucosidase inhibitory activity and structural characterization of polysaccharide fraction from Rhynchosia minima root

Rhynchosia minima root, a renowned traditional Chinese medicinal herb, has been shown to exhibit multiple therapeutic activities. In this study, the α-glucosidase inhibitory activity of R. minima root polysaccharide fractions (PRM1, PRM3 and PRM5) is evaluated. PRM3 displays an excellent inhibitory activity with an IC50 value of 8.85mg/mL, which is similar to that of acarbose, a positive control compound that has been applied for the control of postprandial hyperglycemia. PRM3 is a homogeneous fraction with an average molecular weight of 97.3kDa. The results of methylation analysis, periodate oxidation and nuclear magnetic resonance (NMR) spectra reveal that the repeating units of PRM3 are mainly composed of (1→3,4)-α-Arap, (1→4,6)-β-Galp, (1→2,4)-β-Rhap, (1→3,4)-β-GalpA, T-α-Araf and T-α-Galp residues. Moreover, triple helix stereo-configuration has been proven to exist in PRM3. In summary, the strong α-glucosidase inhibitory activity and unique structural feature of PRM3 suggest that it could have a potential application in functional foods.

CDNA Isolation and Functional Characterization of UDP-d-glucuronic Acid 4-Epimerase Family from Ornithogalum caudatum.

d-Galacturonic acid (GalA) is an important component of GalA-containing polysaccharides in Ornithogalum caudatum. The incorporation of GalA into these polysaccharides from UDP-d-galacturonic acid (UDP-GalA) was reasonably known. However, the cDNAs involved in the biosynthesis of UDP-GalA were still unknown. In the present investigation, one candidate UDP-d-glucuronic acid 4-epimerase (UGlcAE) family with three members was isolated from O. caudatum based on RNA-Seq data. Bioinformatics analyses indicated all of the three isoforms, designated as OcUGlcAE1~3, were members of short-chain dehydrogenases/reductases (SDRs) and shared two conserved motifs. The three full-length cDNAs were then transformed to Pichia pastoris GS115 for heterologous expression. Data revealed both the supernatant and microsomal fractions from the recombinant P. pastoris expressing OcUGlcAE3 can interconvert UDP-GalA and UDP-d-glucuronic acid (UDP-GlcA), while the other two OcUGlcAEs had no activity on UDP-GlcA and UDP-GalA. Furthermore, expression analyses of the three epimerases in varied tissues of O. caudatum were performed by real-time quantitative PCR (RT-qPCR). Results indicated OcUGlcAE3, together with the other two OcUGlcAE-like genes, was root-specific, displaying highest expression in roots. OcUGlcAE3 was UDP-d-glucuronic acid 4-epimerase and thus deemed to be involved in the biosynthesis of root polysaccharides. Moreover, OcUGlcAE3 was proposed to be environmentally induced.

Hairy root induction and polysaccharide production of medicinal plant Callerya speciosa Champ.

A reliable and efficient hairy root induction system for the important medicinal plant Callerya speciosa was established by optimizing several parameters that affected the efficiency of Agrobacterium rhizogenes-mediated transformations. Four strains, A4, LBA9402, R1601 and C58C1, and four types of explants, hypocotyls, cotyledons, leaves and excised stems, were examined and the highest rate of transformation (68.3 %) was obtained in cotyledons using strain LBA9402. Therefore, the optimum co-cultivation time and acetosyringone (AS) concentration were evaluated for LBA9402-infected cotyledons and determined to be 2 days and 100 µM AS, respectively, resulting in 64.4 and 66.7 % hairy root transformation efficiency rates, respectively. Transgenic hairy root lines were confirmed by PCR amplification and Southern blot. The growth trend of hairy roots was “slow-quick-slow” and peaked after 30 days of culturing, with increases of 11-fold and 11.4-fold of fresh and dry weights respectively, compared with initial inoculation. Hairy roots showed the ability to synthesize polysaccharides. The effects of different media Murashige and Skoog (MS), ½ MS, WPM and B5, and carbon sources, sucrose, glucose, fructose and maltose on the growth and polysaccharide production of hairy roots were also studied. The ½ MS medium was found to be superior, resulting in the highest accumulation of biomass (10.9 g L−1 fresh weight and 1.1 g L−1 dry weight), the maximum growth index (9.96) and polysaccharide content (22.56 mg g−1 dry weight). Sucrose at 30 g L−1 was optimal for both biomass accumulation and polysaccharide production.

Polysaccharide extraction from Sphallerocarpus gracilis roots by response surface methodology

The extraction process of Sphallerocarpus gracilis root polysaccharides (SGRP) was optimized using response surface methodology with two methods [hot-water extraction (HWE) and ultrasonic-assisted extraction (UAE)]. The antioxidant activities of SGRP were determined, and the structural features of the untreated materials (HWE residue and UAE residue) and the extracted polysaccharides were compared by scanning electron microscopy. Results showed that the optimal UAE conditions were extraction temperature of 81°C, extraction time of 1.7h, liquid-solid ratio of 17ml/g, ultrasonic power of 300W and three extraction cycles. The optimal HWE conditions were 93°C extraction temperature, 3.6h extraction time, 21ml/g liquid-solid ratio and three extraction cycles. UAE offered a higher extraction yield with a shorter time, lower temperature and a lower solvent consumption compared with HWE, and the extracted polysaccharides possessed a higher antioxidant capacity. Therefore, UAE could be used as an alternative to conventional HWE for SGRP extraction.

Isatis indigotica root polysaccharides as adjuvants for an inactivated rabies virus vaccine

Adjuvants can enhance vaccine immunogenicity and induce long-term enhancement of immune responses. Thus, adjuvants are important for vaccine research. Polysaccharides isolated from select Chinese herbs have been demonstrated to possess various beneficial functions and excellent adjuvant abilities. In the present study, the polysaccharides IIP-A-1 and IIP-2 were isolated from Isatis indigotica root and compared with the common vaccine adjuvant aluminum hydroxide via intramuscular co-administration of inactivated rabies virus rCVS-11-G into mice. Blood was collected to determine virus neutralizing antibody (VNA) titers and B and T lymphocyte activation status. Inguinal lymph node samples were collected and used to measure B lymphocyte proliferation. Splenocytes were isolated, from which antigen-specific cellular immune responses were detected via ELISpot, ELISA and intracellular cytokine staining. The results revealed that both types of polysaccharides induce more rapid changes and higher VNA titers than aluminum hydroxide. Flow cytometry assays revealed that the polysaccharides activated more B lymphocytes in the lymph nodes and more B and T lymphocytes in the blood than aluminum hydroxide. Antigen-specific cellular immune responses showed that IIP-2 strongly induced T lymphocyte proliferation in the spleen and high levels of cytokine secretion from splenocytes, whereas aluminum hydroxide induced proliferation in only a small number of lymphocytes and the secretion of only small quantities of cytokines. Collectively, these data suggest that the polysaccharide IIP-2 exhibits excellent adjuvant activity and can enhance both cellular and humoral immunity.

Fractionation and evaluation of proteins in roots of Echinacea purpurea (L.) Moench.

Echinacea purpurea (L.) Moench, a member of the Asteraceae family, is a plant rich in flavonoids, essential oils, phenolic compounds, saponins, polysaccharides and glycoproteins. The aim of the study was to evaluate the protein content in dried roots of Echinacea purpurea (L.) Moench after homogenization of roots with liquid nitrogen, extraction in 0.01 mol L-1 phosphate-buffered saline (PBS) and purification followed by fractionation of proteins using gel filtration chromatography. Total concentration of proteins was measured using the Bradford method, and evaluation of the molecular mass of proteins was accomplished by applying the SDS-PAGE gel electrophoresis. The Bradford assay revealed that the highest concentration of proteins in fractions collected after gel filtration chomatography was 4.66-6.07 mg mL-1. Glycoproteins, alkamides and polysaccharides in roots of Echinacea purpurea (L.) Moench are chemical compounds that are responsible for their immunomodulatory properties. However, information about the difference of protein contents in fresh and dried roots of E. purpurea is insufficient.

Development and Validation of an Express Method for Assay of Water-Soluble Polysaccharides in Common Burdock (Arctium lappa L.) Roots

An express method was developed for assay of water-soluble polysaccharides in common burdock (Arctium lappa L.) roots, with an analysis time of 3 h. The method was validated in terms of reproducibility, accuracy, and linearity, and this demonstrated that the method was accurate on reproduction, correct, and had a quite strictly linear relationship between the weight of the precipitate and the weight of the material analyzed using gravimetric determination of water-soluble polysaccharides in common burdock roots. The method can be used for rapid analysis of the quality of common burdock root and for the industrial production of inulin from this raw material.

Thermal stress resistance and aging effects of Panax notoginseng polysaccharides on Caenorhabditis elegans

Panax notoginseng attract public attention due to their potential biomedical properties and corresponding health benefits. The present study investigated the anti-aging and thermal stress resistance effects of polysaccharides from P. notoginseng on Caenorhabditis elegans. Results showed polysaccharides had little scavenging ability of reactive oxygen species (ROS) in vitro, but significantly extended lifespan of C. elegans, especially the main root polysaccharide (MRP) which prolongs the mean lifespan of wild type worms by 21%. Further study demonstrated that the heat stress resistance effect of polysaccharides on C. elegans might be attributed to the elevation of antioxidant enzyme activities (both superoxide dismutase (SOD) and catalase (CAT)) and the reduction lipid peroxidation of malondialdehyde (MDA) level. Taken together, the results provided a scientific basis for the further exploitation of the mechanism of longer lifespan controlled by P. notoginseng polysaccharides on C. elegans. The P. notoginseng polysaccharides might be considered as a potential source to delay aging.

Effects of Bush Sophora Root polysaccharide and its sulfate on immuno-enhancing of the therapeutic DVH

Bush Sophora Root polysaccharide (BSRPS) and its sulfate, sulfated Bush Sophora Root polysaccharide (sBSRPS), possess the antiviral activities against duck hepatitis A virus. However their antiviral mechanisms are still not clear. This paper reported their immuno-enhancing roles in the therapeutic effects for duck virus hepatitis (DVH). The effects of BSRPS and sBSRPS on stimulating lymphocyte proliferation were investigated by MTT methods. After that, ducklings were challenged with DHAV and treated with BSRPS and sBSRPS. Meanwhile, the total antibody (Ab), cytokines including interferon gamma (IFN-γ), hepatocyte growth factor (HGF), interleukin (IL)-2, IL-6 and IL-8 were determined by enzyme-linked immuno sorbent assay methods. The results showed that BSRPS owned a fine hepatoprotective effect with stable HGF producing ability. Sulfated modification was able to increase the proliferation rates of B and T lymphocytes and the secretions of total Ab, IFN-γ and IL-2, as comparison with those of BSRPS group. In summary, both of them exhibited immuno-enhancing effects on the therapeutic effects for DVH, and the capacity of sBSRPS was stronger than that of BSRPS.

Anti-duck virus hepatitis mechanisms of Bush Sophora Root polysaccharide and its sulfate verified by intervention experiments

In our previous study, Bush Sophora Root polysaccharide (BSRPS) and its sulfate (sBSRPS) exhibited anti-duck virus hepatitis (DVH) abilities as well as anti-oxidative and immuno-enhancement effects. The aim of this paper was to ulteriorly investigate the exact anti-DVH mechanisms of BSRPS and sBSRPS by intervention experiments. Hinokitiol and FK506 were used as the pro-oxidant and immunosuppressant, respectively. The dynamic deaths, oxidative and immune evaluation indexes and hepatic pathological change scores were detected. When was intervened by hinokitiol, sBSRPS still possessed therapeutic effect while BSPRS was useless. Under the condition of immunosuppression, BSRPS lost a part role in treating DVH; however such a role of sBSRPS completely exhausted. These results suggested both anti-oxidative and immuno-enhancement effects of BSRPS played roles in healing DVH, and the former was more crucial; unlike BSRPS, only immuno-enhancement ability of sBSRPS was imperative for its curative effect on DVH.

Stimulation and suppression of innate immune function by American ginseng polysaccharides: biological relevance and identification of bioactives.

Polysaccharides constituting about 10% by weight of ginseng root are known to stimulate the immune system but have recently been shown to also suppress induced proinflammatory responses. Our study aims to determine whether American ginseng root polysaccharides (AGRPS) stimulates basal innate immune function and at the same time can suppress response to lipopolysaccharide (LPS) induced proinflammatory response. An in vitro mechanistic study was used to identify the bioactive fraction(s) responsible for AGRPS immunomodulatory effects. The ex vivo and in vivo immunomodulatory effects after oral administration of AGRPS extract was studied in adult rats by measuring cultured alveolar macrophage production of NO and changes of plasma cytokine level, modification of LPS proinflammatory immune response by AGRPS extract was also examined. To identify the bioactive fraction(s) responsible for AGRPS extract immunomodulatory effects, the immunobioactivities of the extract fractions (isolated by ion exchange and size exclusion chromatography) was investigated in an in vitro mechanistic study. Culture of alveolar macrophages obtained from AGRPS extract treated rats resulted in an increase of ex vivo production of NO and also reduced alveolar macrophage responsiveness to ex vivo LPS challenge. Oral treatment with AGRPS extract elevated plasma TNF-α concentration in vivo. This treatment also suppressed LPS induced elevation of plasma TNF-α in vivo. AGRPS extract immunostimulatory and immunosuppressive effects were mediated primarily by acid PS and its species with molecular weights ≥ 100 kDa and 50-100 kDa. AGRPS extract exerted immunostimulation and suppressed LPS immune response under basal and LPS induced proinflammatory conditions respectively.

A RG-II type polysaccharide purified from Aconitum coreanum alleviates lipopolysaccharide-induced inflammation by inhibiting the NF-κB signal pathway.

Korean mondshood root polysaccharides (KMPS) isolated from the root of Aconitum coreanum (Lévl.) Rapaics have shown anti-inflammatory activity, which is strongly influenced by their chemical structures and chain conformations. However, the mechanisms of the anti-inflammatory effect by these polysaccharides have yet to be elucidated. A RG-II polysaccharide (KMPS-2E, Mw 84.8 kDa) was isolated from KMPS and its chemical structure was characterized by FT-IR and NMR spectroscopy, gas chromatography–mass spectrometry and high-performance liquid chromatography. The backbone of KMPS-2E consisted of units of [→6) -β-D-Galp (1→3)-β-L-Rhap-(1→4)-β-D-GalpA-(1→3)-β-D-Galp-(1→] with the side chain →5)-β-D-Arap (1→3, 5)-β-D-Arap (1→ attached to the backbone through O-4 of (1→3,4)-L-Rhap. T-β-D-Galp is attached to the backbone through O-6 of (1→3,6)-β-D-Galp residues and T-β-D-Ara is connected to the end group of each chain. The anti-inflammatory effects of KMPS-2E and the underlying mechanisms using lipopolysaccharide (LPS) - stimulated RAW 264.7 macrophages and carrageenan-induced hind paw edema were investigated. KMPS-2E (50, 100 and 200 µg/mL) inhibits iNOS, TLR4, phospho-NF-κB–p65 expression, phosphor-IKK, phosphor-IκB-α expression as well as the degradation of IκB-α and the gene expression of inflammatory cytokines (TNF-α, IL-1β, iNOS and IL-6) mediated by the NF-κB signal pathways in macrophages. KMPS-2E also inhibited LPS-induced activation of NF-κB as assayed by electrophorectic mobility shift assay (EMSA) in a dose-dependent manner and it reduced NF-κB DNA binding affinity by 62.1% at 200µg/mL. In rats, KMPS-2E (200 mg/kg) can significantly inhibit carrageenan-induced paw edema as ibuprofen (200 mg/kg) within 3 h after a single oral dose. The results indicate that KMPS-2E is a promising herb-derived drug against acute inflammation.

Bush Sophora Root polysaccharide and its sulfate can scavenge free radicals resulted from duck virus hepatitis

In order to study the antioxidant effect of Bush Sophora Root polysaccharide (BSRPS) and its sulfate on anti-duck virus hepatitis (DVH), sulfated Bush Sophora Root polysaccharide (sBSRPS) was prepared by chlorosulfonic acid–pyridine method. Ducklings were fed with BSRPS and sBSRPS after challenged DHAV. Death was monitored, evaluation indexes of peroxidative and hepatic injury at the initial (4th and 8th hour) and later (54th hour) stages were detected. The results showed a fine treatment effect of BSRPS and sBSRPS. Visual hepatic pathological injury severities were less serious after the treatment. At the initial stage, free radical levels in all groups were the same, and BSRPS and sBSRPS reduced the hepatic injury through inhibiting virus replication. At the later stage, mass free radicals were detected in VC group while free radical levels in BSRPS and sBSRPS groups were significantly lower than VC group. The antioxidant effect of BSRPS and sBSRPS might alleviate the hepatic injury.

Comparison of Bush Sophora Root polysaccharide and its sulfate's anti-duck hepatitis A virus activity and mechanism

In order to research the sulfating modification in enhancing the anti-duck hepatitis A virus (DHAV) activity of Bush Sophora Root polysaccharide (BSRPS), sulfated Bush Sophora Root polysaccharide (sBSRPS) was prepared by chlorosulfonic acid–pyridine method. KBr pellets method was applied to analyze their different structures. Anti-DHAV activity was studied by duck embryonic hepatocytes culture in vitro and artificial inoculation method in vivo. Direct immunofluorescence method and Real-time PCR were applied to study the antiviral mechanism of adsorption, replication and release in vitro and the dynamic change of virus content of blood in vivo. The results showed at the most effective content, sBSRPS (7.813μg/mL) could inhibit both replication and release of DHAV in vitro, BSRPS (500μg/mL) only inhibit replication. The relative expression of DHAV gene at the 8thh and the mortality rate of sBSRPS group were significantly reduced. These results indicated sBSRPS performed more effectively in anti-DHAV activity than BSRPS.

Effects of dietary Astragalus polysaccharide and Astragalus membranaceus root supplementation on growth performance, rumen fermentation, immune responses, and antioxidant status of lambs

The aim of this study was to investigate effects of dietary Astragalus membranaceus root (AMT) and Astragalus polysaccharide (APS) supplementation on growth performance, blood metabolites, rumen fermentation, immune responses and antioxidant status of weaned lambs. Twenty-four male Ujumqin weaned lambs (a local breed) with average age of 60±10.3d and similar genetic background were randomly assigned to one of three treatments for a 30d feeding period. Treatments consisted of the lambs’ basal diets with addition of: (1) nothing (control), (2) 15g/kg APS or (3) 50g/kg AMT of the diet (dry matter (DM) basis). Blood samples were collected at day 0 and 30 and ruminal fluid samples at day 0, 15 and 30. Results showed that APS supplementation increased DM intake of lambs (P=0.003), but that average daily gain, feed efficiency and apparent digestibility of nutrients did not differ among treatments. Concentrations of ammonia N (P=0.004) and total volatile fatty acids (P=0.005) were affected by an interaction between treatment and feeding time. Both APS and AMT feeding increased propionic acid (P=0.025) which resulted in a reduction in the acetic acid to propionic acid ratios in ruminal fluid (P=0.014). Feeding APS and AMT increased total antioxidant capacity (P<0.001) and total superoxide dismutase activities (P<0.001), and decreased cortisol levels (P<0.001) in plasma. However, blood plasma metabolites such as blood urea N, high and low density lipoprotein–cholesterol, triglyceride, glucose and total protein, which are reflective of animal metabolism, were not affected by APS and AMT feeding. Only dietary AMT supplementation affected immune responses, including increased immunoglobulin M production (P<0.001) and lymphocyte numbers (P=0.024) in whole blood. Results suggest that APS and AMT feeding mainly improved antioxidant capacity and affected rumen fermentation patterns of lambs, while AMT supplementation affected immunity, but both additives failed to improve apparent digestibility of nutrients in weaned lambs.

A quantitative assay for total fructans in burdock (Arctium spp.) roots

A quantitative assay of the total content of polysaccharides (fructans) in burdock roots in fructose equivalent has been elaborated. Extraction of free carbohydrates and polysaccharides has been studied using spectrophotometry and quantitative HPTLC. The optimal parameters for extracting the target group of compounds have been determined. Metrological analysis of the elaborated assay has been performed. It has been shown that the detection error does not exceed 3%.

In vitro immunomodulatory effects of Astragalus verus Olivier. (black milkvetch): an immunological tapestry in Kurdish ethnomedicine

Astragalus verus Olivier., Fabaceae, has been used as an immunopromoting remedy in Kurdish ethnomedicine. Here, phagocytic (nitroblue tetrazolium (NBT) dye reduction and lysosomal enzyme activity of mouse splenocyte), (co)mitogenic (mouse splenocyte reduction of methyl thiazolyl tetrazolium (MTT)), and antioxidative (nitrite-induced methemoglobin formation) activities of A. verus extracts and chemical compositions of their essential oils (gas chromatography–mass spectrometry) were investigated. All aqueous (AQ), acetone (AC), and methanol (ME) extracts of aerial parts and root polysaccharide extract (PS) enhanced phagocytic activity compared with the control. The phagocytic activities assayed by lysosomal enzyme activity were in agreement with the values obtained by NBT reduction test and followed the order AQ > PS > AC > ME. All A. verus extracts showed enhanced mitogenic activities compared with the control; however, the AQ extract at 200 μg/mL showed maximum mitogenic activity by 311% compared with the control. The stimulation index values obtained by lipopolysaccharide comitogenic activity were roughly in agreement with the values obtained by concanavalin A comitogenic activity and followed the order AQ > PS > AC > ME. The AQ extract showed profound antioxidant activity while other extracts did not show an acceptable antioxidant activity. The main components isolated from the essential oil of A. verus were thymol in AQ, n-hexadecanoic acid, 1,2-benzenedicarboxylic acid, diisooctyl ester, and phytol in both ME and AC and tetradecane, pentadecane, hexadecane, and phenol,2,4-bis(1,1-dimethylethyl) in PS. The results clearly showed that A. verus could be employed as an immunopromoting remedy; however, more advanced researches are requested to develop a promised pharmaceutical drug from A. verus in the future.

Optimisation of extraction conditions for polysaccharides from the roots of Isatis tinctoria L. by response surface methodology and their in vitro free radicals scavenging activities and effects on IL-4 and IFN-γ mRNA expression in chicken lymphocytes

Response surface methodology along with Box-Behnken design was firstly applied to optimize the extraction conditions for the polysaccharides from the roots of Isatis tinctoria L. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis. The 3-D response surface and the contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimal conditions were extraction temperature (X1) 99.5°C, extraction time (X2) 3.75h and ratio of water to raw material (X3) 11.84 (v/w). Under these conditions, the maximal observed value extraction yield of Isatis root polysaccharides (IRPSs) was (11.19±0.04)%, which was agreed with predicted value 11.17%. Pharmacological experiments indicated that IRPS have an appreciable ABTS radical scavenging ability in vitro and could increase IL-4 and IFN-γ mRNA expression in chicken lymphocytes obtaining maximum promoted effects of 70% and 115%, respectively. This study may facilitate a deeper understanding of IRPS to provide theoretical references.

Separation of 1-phenyl-3-methyl-5-pyrazolone derivatives of traditional Chinese medicine oligosaccharides by capillary zone electrophoresis

A simple and practical capillary zone electrophoretic (CZE) method has been developed for the separation of traditional Chinese medicine oligosaccharides according to their relative molecular masses (M(r)). To optimize the conditions of the method, the concentration and pH value of the running buffer, and the applied voltage were evaluated. The optimized conditions were as follows: 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of the oligosaccharides were separated with 50 mmol/L phosphate buffer (pH 2.5) as running buffer and the voltage was 15 kV. The detection was performed with an ultraviolet detector at 245 nm. An uncoated fused-silica capillary of 50 microm i. d. and 38/48 cm length (effective length/total length) was employed, and a hydrodynamic pressure injection (10 cm x 2 s) was applied. In order to examine the practicability of the method for the analysis of actual traditional Chinese medicine oligosaccharide samples, a complex sample consisting of some usual monosaccharides and oligosaccharides degraded from beta-cyclodextrin was separated under the electrophoretic conditions. And then, the method was applied to the analysis of the controlled degradation products of Indigowoad Root polysaccharide. The results indicated that the oligosaccharide sample could fully be separated from low to high M(r). This method is efficient and practical. In addition, the separation hypothesis of PMP derivatives of monosaccharides and oligosaccharides in pH 2.5 running buffer is also discussed, which would be helpful for us to understand the unusual migration of the PMP derivatives of rhamnose and mannose.

Nitric oxide enhances aluminum tolerance by affecting cell wall polysaccharides in rice roots

Nitric oxide (NO) is a key signal molecule involved in many physiological processes in plants. To study the mechanisms of exogenous NO contribution to alleviate the aluminum (Al) toxicity, roots of rice (Oryza sativa) seedlings pre-treated with sodium nitroprusside (SNP, a NO donor) were used to investigate the effect of Al in this study. Results indicated that NO alleviated the lipid peroxidation induced by Al and promoted the root elongation, whereas butylated hydroxyanisole (BHA), an efficient lipophilic antioxidant, alleviated the lipid peroxidation only. Rice seedling roots pre-treated with SNP followed by Al treatment had lower contents of pectin and hemicellulose, lower Al accumulation in root tips and cell walls, higher degree of methylation of pectin and lower wall Al-binding capacity than the roots with Al treatment only. Therefore, the decreased Al accumulation in the cell walls of rice roots is likely to be the reason for the NO-induced increase of Al tolerance in rice, and it seems that exogenous NO enhanced Al tolerance in rice roots by decreasing the contents of pectin and hemicellulose, increasing the degree of methylation of pectin, and decreasing Al accumulation in root cell walls.