Chemical structure and gel properties of carrageenans from algae belonging to the Gigartinaceae and Tichocarpaceae, collected from the Russian Pacific coast

The chemical and gel characteristics of carrageenans isolated from the most abundant algal species growing on the Russian Pacific coast – Chondrus pinnulatus, C. armatus and Iridaea cornucopiae belonging to the Gigartinaceae and Tichocarpus crinitus from the Tichocarpaceae were investigated. The polysaccharides were identified by FTIR and NMR spectroscopy as predominantly κ-carrageenans with traces of ι-type (Gigartinaceae) and κ / β-type repeating structures (Tichocarpaceae) together with a small quantity of λ-carrageenan (10%). The chemical structure and the hydrodynamic properties play a determinant role on the rheology of these carrageenans. κ-Carrageenans from the Gigartinaceae displayed good gelling properties. The highest gel strength was obtained from C. pinnulatus (1232.7 Pa) at a 2.5% polymer concentration, while carrageenans from the Tichocarpaceae formed very weak gels (77.4 Pa) at the same concentration. Optimum gel characteristics were found with 1.0–2.0% KCI concentrations for kappa- carrageenans from Gigartinaceae and 0.75% for T. crinitus. The flow curves of λ-carrageenans solutions from the Gigartinaceae were similar, all between 20 and 65 °C, and characteristic of conformational disordered ‘random coil’ polysaccharides. Carrageenans from T. crinitus displayed the properties of ’random coil' only at high temperatures. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bioconversion of red seaweed galactans: a focus on bacterial agarases and carrageenases

Agars and carrageenans are 1,3-α-1,4-β-galactans from the cell walls of red algae, substituted by zero (agarose), one (κ-), two (ι-), or three (λ-carrageenan) sulfate groups per disaccharidic monomer. Agars, κ-, and ι-carrageenans auto-associate into crystalline fibers and are well known for their gelling properties, used in a variety of laboratory and industrial applications. These sulfated galactans constitute a crucial carbon source for a number of marine bacteria. These microorganisms secrete glycoside hydrolases specific for these polyanionic, insoluble polysaccharides, agarases and carrageenases. This article reviews the microorganisms involved in the degradation of agars and carrageenans, in their environmental and taxonomic diversity. We also present an overview on the biochemistry of the different families of galactanases. The structure–function relationships of the family GH16 β-agarases and κ-caraggeenases and of the family GH82 ι-carrageenases are discussed in more details. In particular, we examine how the active site topologies of these glycoside hydrolases influence their mode of action in heterogeneous phase. Finally, we discuss the next challenges in the basic and applied field of the galactans of red algae and of their related degrading microorganisms.     

Hybridity of carrageenans water- and alkali-extracted from Chondracanthus chamissoi, Mazzaella laminarioides, Sarcothalia crispata, and Sarcothalia radula

Carrageenans water- and alkali-extracted from Chondracanthus chamissoi, Mazzaella laminarioides, Sarcothalia crispata, and Sarcothalia radula were degraded by Pseudoalteromonas carrageenovora κ-carrageenase and Alteromonas fortis ι-carrageenase. The composition of the high molecular weight fraction (i.e., enzyme-resistant fraction) as well as the standard and hybrid oligosaccharide content highlighted differences between the species-specific carrageenans in terms of composition and distribution of the carrabiose moieties. Inspection of the distribution of μ- and ν-carrabiose, the biosynthetic precursors of κ- and ι-carrabiose, revealed their localization in κ-carrabiose- or ι-carrabiose-rich segments, respectively.     

Carrageenophyte identification by second-derivative Fourier transform infrared spectroscopy

The second-derivative mode of the Fourier transform I.R. spectra of dried algal material has been applied to distinguish the carrageenans-producingStenogramme interrupta from the isomorphous speciesRhodymenia howeana. Spectra of the tetrasporophyteS. interrupta showed bands assigned to a -carrageenan type polysaccharide, while the gametophytic and cystocarpic plants showed the characteristic absorptions of -and -carrageenans. Results were confirmed by hot water extraction of samples of the three nuclear phases ofS. interrupta and characterization of the extracts by chemical analysis.Author for correspondence     

Enhanced immunostimulatory and antitumor activity of different derivatives of κ-carrageenan oligosaccharides from <Emphasis Type="Italic">Kappaphycus striatum</Emphasis>

Chemical modification of carbohydrates can lead to differences in their biological activities. We previously showed that κ-carrageenan oligosaccharides from Kappaphycus striatum have antitumor and immunomodulation effects on S180-bearing mice. In this study, we tested the hypothesis that different chemical modifications of carrageenan oligosaccharides enhance their activities. The mice inoculated with S180 cell suspension were treated p.o. with carrageenan oligosaccharides and their sulfated, acetylated, and phosphorylated derivatives (50, 100, and 200 μg g⁻¹) for 14 days. Transplantable tumor inhibition rate and macrophage phagocytosis, quantitative hemolysis of sheep red blood cells, lymphocyte proliferation, the activity of natural killer cells, production of interleukin-2, and tumor necrosis factor-α were also analyzed. As expected, treatment with different κ-carrageenan oligosaccharides derivatives resulted in an increase in tumor inhibition rate and macrophage phagocytosis and cellular immunity, especially on spleen lymphocyte proliferation. The sulfated derivative at the dose 200 μg g⁻¹ per day showed the highest antitumor activity with the 54.12% tumor weight inhibition and elicited an increase in nature killer cells activity up to 76.1% on S180-bearing mice, which were both significantly higher than the unmodified oligosaccharides. It suggested that chemical modification (especially sulfation) of carrageenan oligosaccharides can enhance their antitumor effect and boost their antitumor immunity.     

Antioxidant activities of sulfated polysaccharides from brown and red seaweeds

The in vitro antioxidant activities of the following six sulfated polysaccharides were investigated: iota, kappa and lambda carrageenans, which are widely used in the food industry, fucoidan (homofucan) from the edible seaweed Fucus vesiculosus and fucans (heterofucans) F0.5 and F1.1 from the seaweed Padina gymnospora. With respect to the inhibition of superoxide radical formation, fucoidan had an IC₅₀ (the half maximal inhibitory concentration) of 0.058 mg·mL⁻¹, while the IC₅₀ for the kappa, iota and lambda carrageenans were 0.112, 0.332 and 0.046 mg·mL⁻¹, respectively. All of the samples had an inhibitory effect on the formation of hydroxyl radicals. The results of peroxidation tests showed that fucoidan had an IC₅₀ of 1.250 mg·mL⁻¹ and that the kappa, iota and lambda carrageenans had an IC₅₀ of 2.753 and 2.338 and 0.323 mg·mL⁻¹, respectively. Fucan fractions showed low antioxidant activity relative to fucoidan. These results clearly indicate the beneficial effect of algal polysaccharides as antioxidants.     

Characterization of Carrageenan Extracted from <Emphasis Type="Italic">Hypnea bryoides</Emphasis> in Oman

Carrageenophyte red seaweed from Oman, Hypnea bryoides, extracted using three different processes: an aqueous, a mild alkaline, and a more vigorous alkaline extraction was investigated. The resulting extract precipitated by alcohol was subject to chemical and rheological measurements. The total carbohydrate [ranged from 36.78 to 41.65 g/100 g], and ash [39.04 to 43.11 g/100 g] were the most abundant components in H. bryoides and contrary to the two, lipid content was found at a minimum [ranging from 2.95 to 3.38 g/100 g]. Alkali treatment with NaOH allowed complete conversion of kappa (κ) carrageenan form as detected by FTIR analysis. Total yield by alkali treatments gave higher yields (33%) compared with aqueous treatments (12%). However, subsequent aqueous treatment produced mixed carrageenan (μ and κ) with higher molecular weight compared with the alkali treatments which produced single carrageenan form (κ) with molecular weight of 4.1 × 10⁵ Da. The effects of thermal history on gel–sol and sol–gel transition were investigated by differential scanning calorimeter (DSC) and rheology on a pure sample and 1.5% κ-carrageenan mixture added with 30 mM KCl. Transition temperatures from DSC and rheology showed comparable results and were in good agreement with those previously reported.     

Agars from Gelidium rex (Gelidiales,Rhodophyta)

Gelidium rex grows in the rocky intertidal of central Chile. Extraction of vegetative G. rex with water at 95 °C yielded 17.9% of agar with a gel strength value of 590 g cm^–2. The gel strength increased up to 1272 g cm^–2 when the alga was treated with alkali prior to extraction. Cystocarpic and tetrasporic thalli of G. rex were extracted with distilled water at 95 °C, affording soluble polysaccharides in 36.0% and 15.7% yield respectively. Polysaccharides of both life history phases were fractionated by chromatography on DEAE Sephadex. Elution with distilled water gave fractions devoid of sulfate; the fraction from cystocarpic plants contained 45.5% of 3,6-anhydrogalactose whereas the neutral fraction from tetrasporic plants contained 40.0% of 3,6-anhydrogalactose. Further elution with 0.1, 0.4, 0.8 and 1.5 molar aqueous solutions of KCl afforded four fractions for each polysaccharide. Chemical analysis of these fractions showed that the agars from cystocarpic and tetrasporic Gelidium rex are mixtures of related polysaccharides that range from neutral polymers to highly sulfated galactans.     

Carrageenans, sulphated polysaccharides of red seaweeds, differentially affect Arabidopsis thaliana resistance to Trichoplusia ni (cabbage looper)

Carrageenans are a collective family of linear, sulphated galactans found in a number of commercially important species of marine red alga. These polysaccharides are known to elicit defense responses in plant and animals and possess anti-viral properties. We investigated the effect of foliar application of ι-, κ- and λ-carrageenans (representing various levels of sulphation) on Arabidopsis thaliana in resistance to the generalist insect Trichoplusia ni (cabbage looper) which is known to cause serious economic losses in crop plants. Plants treated with ι- and κ-carrageenan showed reduced leaf damage, whereas those treated with λ- carrageenan were similar to that of the control. In a no-choice test, larval weight was reduced by more than 20% in ι- and κ- carrageenan treatments, but unaffected by λ-carrageenan. In multiple choice tests, carrageenan treated plants attracted fewer T. ni larvae by the fourth day following infestation as compared to the control. The application of carrageenans did not affect oviposition behaviour of T. ni. Growth of T. ni feeding on an artificial diet amended with carrageenans was not different from that fed with untreated control diet. ι-carrageenan induced the expression of defense genes; PR1, PDF1.2, and TI1, but κ- and λ-carrageenans did not. Besides PR1, PDF1.2, and TI1, the indole glucosinolate biosynthesis genes CYP79B2, CYP83B1 and glucosinolate hydrolysing QTL, ESM1 were up-regulated by ι-carrageenan treatment at 48 h post infestation. Gas chromatography-mass spectrometry analysis of carrageenan treated leaves showed increased concentrations of both isothiocyanates and nitriles. Taken together, these results show that carrageenans have differential effects on Arabidopsis resistance to T. ni and that the degree of sulphation of the polysaccharide chain may well mediate this effect.     

CARRAGEENANS FROM AUSTRALIAN REPRESENTATIVES OF THE FAMILY CYSTOCLONIACEAE (GIGARTINALES, RHODOPHYTA), WITH DESCRIPTION OF CALLIBLEPHARIS CELATOSPORA SP. NOV., AND TRANSFER OF AUSTROCLONIUM TO THE FAMILY ARESCHOUGIACEAE

Ten Australian representatives from seven of the 10 genera presently constituting the family Cystocloniaceae have been analyzed for their cell-wall galactans. Included in our survey are the monotypic Australian-endemic genera Austroclonium , Gloiophyllis , Erythronaema , and Stictosporum , one species of Craspedocarpus , three species of Rhodophyllis , and two species of Calliblepharis . As one of the species of the latter genus is endemic to Western Australia and presently undescribed, we illustrate its habit and anatomical features in formally proposing to name it Calliblepharis celatospora Kraft, sp. nov. All the species surveyed essentially produce typical iota (ι)-carrageenans, with the exception of Austroclonium . The sulfated galactans from Austroclonium predominantly contain the repeating units of ι-, alpha (α)-, and 6'-O-methylated ι- and α-carrageenans; whether these exist as discrete polysaccharides or a complex hybrid structure was not resolved. Thus, Austroclonium carrageenans resemble the polysaccharides from Rhabdonia , Areschougia , and Erythroclonium . Although these latter three genera are currently included in the large gigartinalean family Solieriaceae, all produce significantly different carrageenans from Solieria itself and related genera such as Eucheuma , Kappaphycus , Betaphycus , Sarcodiotheca , Agardhiella , Sarconema , and Callophycus . In consideration of these findings, as well as of significant anatomical similarities, we provisionally recommend reestablishment of the family Rhabdoniaceae Kylin (as the family Areschougiaceae J. Agardh) for Rhabdonia , Areschougia , Erythroclonium , and Austroclonium.     

Chemical characterization of cell-wall polysaccharides from tank-cultivated and wild plants ofDelesseria sanguinea (Hudson) Lamouroux (Ceramiales,delesseriaceae): culture patterns and potent anticoagulant activity

Tank cultivation ofDelesseria sanguinea was investigated in order to manipulate conditions for vegetative growth and to provide biomass for the analysis of cell wall polysaccharides. Seasonality is subject to short-day photoperiodic control. Night-break or long-day conditions prevented fertility in tetrasporophytes and gametophytes and triggered outgrowth of new blades. Long-day illuminations allowed a 1% daily growth rate. Seawater temperature below 13 °C was necessary for inducing formation of new blades. Both wild and cultivated ofD. sanguinea plants contained a non gelling sulfated heteropolysaccharide composed of a galactosyl backbone branched with xylosyl residues. The hot water extract at neutral pH displayed the highest anticoagulant activity (5 μg ml^-1 polysaccharide concentration in APTT clotting assay). No obvious differences were found in polysaccharide chemical composition and properties between gametophytes and sporophytes or between cultivated and wild plants.     

Hyper-production and Characterization of the ι-Carrageenase Useful for ι-Carrageenan Oligosaccharide Production from a Deep-sea Bacterium, <Emphasis Type="Italic">Microbulbifer thermotolerans</Emphasis> JAMB-A94<Superscript>T</Superscript>, and Insight into the Unusual Catalytic Mechanism

A gene of unknown function from the genome of the agar-degrading deep-sea bacterium Microbulbifer thermotolerans JAMB-A94^T was functionally identified as a ι-carrageenase gene. This gene, designated as cgiA, is located together with two β-agarase genes, agaA and agaO in a cluster. The cgiA gene product is 569 amino acids and shares 29% identity over 185 amino acids with the ι-carrageenase from Zobellia galactanivorans Dsij DSM 12802. Recombinant, cgiA-encoded ι-carrageenase (55 kDa) was hyper-produced in Bacillus subtilis. The recombinant enzyme shows maximal activity at 50°C, the highest reported optimal temperature for a carrageenase. It cleaved β-1,4 linkages in ι-carrageenan to produce a high ratio of ι-carrageenan tetramer, more than 75% of the total product, and did not cleave the β-1,4 linkages in κ- or λ-carrageenan. Therefore, this enzyme may be useful for industrial production of ι-carrageenan oligosaccharides, which have demonstrated antiviral potential against diverse viruses. Furthermore, we performed site-directed mutagenesis on the gene to identify the catalytic amino acid residues. We demonstrated that a conserved Glu351 was essential for catalysis; however, this enzyme lacked a catalytic Asp residue, which is generally critical for the catalytic activity of most glycoside hydrolases.     

Use of enzymatic cell wall degradation for improvement of protein extraction from Chondrus crispus,Gracilaria verrucosa and Palmaria palmata

The effect of polysaccharidases (κ-carrageenase, β-agarase, xylanase, cellulase) on the protein extraction from three rhodophytes has been studied. The kinetic parameters (apparent V _m, apparent K _m) and the optimum activity conditions (pH, temperature) of each enzyme were determined by using pure substrates. All the tested enzymes possess Michaelis Menten mechanism with estimated substrate saturating concentrations of 8 000 mg l⁻¹(carrageenan) for κ-carrageenase, 8 000 mg l⁻¹ (agar) for β-agarase, 5000 mg l⁻¹ (xylane) for β-xylanase and 6 000 mg l⁻¹ (carboxymethylcellulose) for cellulase. The optimum activity conditions are pH 6.5–6.8 at 45°C for carrageenase, pH 6–6.5 at 55°C for agarase, pH 5 at 55°C for xylanase and pH 3.8 at 50°C for cellulose. Different alga/enzymes couples (κ-carrageenase/Chondrus crispus, β-agarase/Gracilaria verrucosa, β-xylanase/Palmaria palmata) were tested under the optimum activity conditions. Alga/cellulase + specific enzyme (e.g. Chondrus crispus/carrageenase + cellulase) systems were also studied at the optimum activity conditions of a specific enzyme (e.g. carageenase). The use of the only cellulose was also tested on each alga. Except for Palmaria palmata, the highest protein yields were observed with the procedures using cellulase coupled with carrageenase or agarase for an incubation period limited to 2 h. The Chondrus crispus/carrageenase + cellulose and Gracilaria verrucosa/agarase + cellulase systems gave ten-fold and three-fold improvements, respectively, in protein extraction yield as compared to the enzyme-free blank procedure. The combined action of xylanase and cellulose on protein extraction from Palmaria palmata does not significantly improve protein yield. The best overall protein yield for P. palmata is for P. palmata/xylanase with a 14-h incubation time. This study shows the interest in the use of a polysaccharidase mixture for improving protein extractibility from certain rhodophytes. This biotechnology approach, adapted from procedures for protoplast production or enzymatic liquefaction of higher plants, could be tested as an alternative method to obtain proteins from seaweeds of nutritional interest.     

Seasonal variation of carrageenans in tetrasporic,cystocarpic and ‘sterile’ stages of Gigartina skottsbergii S. et G. (Rhodophyta,Gigartinales)

Cystocarpic and sterile plants of Gigartina skottsbergii produce -carrageenans, while tetrasporophytes produce -carrageenans. No seasonal variation in the carrageenan yields in the three stages was evident. Yields were clearly higher in cystocarpic (34.1–64.7%) and sterile samples (32.3–71.8%) than in tetrasporic plants (10.1–34.0%). Chemical characteristics of the polysaccharides for any stage are the same throughout the year.The authors are Research Members of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.The authors are Research Members of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.     

A κ-carrageenan derived oligosaccharide prepared by enzymatic degradation containing anti-tumor activity

Depolymerization of -carrageenan was performed using carrageenase isolated from the cell-free medium of a culture of marine Cytophaga sp. MCA-2. The low-molecular-weight carrageenans after ultrafiltration and lyophilization were sulfonated with formamide-chlorosulfonic acid. The anti-tumor activity of the products with different molecular weight was determined by using Sarcoma 180 tumor in mouse. A carrageenan oligosaccharide with a molecular weight of 1726, administered orally at a dose of 100 mg kg^–1 mouse markedly inhibited tumor formation. However, the anti-tumor activity of high-sulfonated carrageenan was much less than that of the non-sulfonated or light-sulfonated preparation. The activities of the latter products on superoxide dismutase and catalase were enhanced considerably, which suggests that carrageenan oligosaccharide was effective in promoting the antioxidation ability and eliminating danger from free radicals. The preparations showed special effects on immunological regulation, especially the phagocytosis ratio and phagocytosis index of macrophage, which might be beneficial for the anti-tumor activity. Although no anti-tumor activity of this product was detected in vitro, suggesting that its activity differs between in vitro and in vivo, this 1726 molecular weight product provides a potent clinical use in tumor treatment.     

Inhibition of galectin-3 mediated cellular interactions by pectic polysaccharides from dietary sources

Pectic polysaccharides from dietary sources such as Decalepis hamiltonii—swallow root (SRPP), Hemidesmus indicus (HPP), Nigella sativa—black cumin (BCPP), Andrographis serpyllifolia—(APP), Zingiber officinale—ginger (GRPP) and, citrus pectin (CPP) were examined for galectin inhibitory activity. Inhibition of (a) galectin-3 of MDA-MB-231 cells induced hemagglutination of red blood cells; (b) galectin-3 mediated interaction between normal/metastatic human buccal cells (NBC)/(MBC) and; (c) invasion of MDA-MB-231 and MBC in the invasive chamber was assessed. Results indicated that SRPP inhibited hemagglutination at Minimum Inhibitory Concentration (MIC) of 1.86 μg ml⁻¹ equivalent of carbohydrate as apposed to those of BCPP (130 μg ml⁻¹), APP (40 μg ml⁻¹), HPP (40 μg ml⁻¹) and CPP (25 μg ml⁻¹). GRPP even at concentration >1–6 mg ml⁻¹ did not inhibit agglutination. Also SRPP showed ∼15 and 2 fold potent anti hemagglutination activity relative to that of galectin-3 specific sugars—galactose (MIC-27.1 μg ml⁻¹) and lactose (MIC-4.16 μg ml⁻¹) respectively. Further, SRPP at 10 μg ml⁻¹ inhibited agglutination of NBC by galectin-3 of MDA-MB-231 cells. Modified swallow root pectic polysaccharide (MSRPP) of 50 kDa retained anti hemagglutination activity (MIC of 1.03 μg ml⁻¹) and inhibited MDA-MB-231 and MBC invasion by 73 and 50% with an IC₅₀ of 136 and 200 μg ml⁻¹ respectively. Both SRPP and MSRPP induced apoptosis up to 80% at 100 μg ml⁻¹ concentration by activating ∼2 and 8 folds of Caspase-3 activity. Sugar composition analysis and its correlation with the galectin inhibitory property indicated that pectic polysaccharides with higher arabinose and galactose content—arabinogalactan inhibited hemagglutination significantly.     

DIFFERENTIAL LOCALIZATION OF CARRAGEENAN GELLING SEQUENCES IN KAPPAPHYCUS ALVAREZII VAR. TAMBALANG (RHODOPHYTA) WITH FITC-CONJUGATED CARRAGEENAN OLIGOSACCHARIDES1

The ability of kappa (κ) and iota (ι) carrageenans to form gels is dependent upon the regular repeat of disaccharide units along the carbohydrate chain. Short, chemically- and enzymatically-purified fragments of κ and ι carrageenan were conjugated to fluorescein and used as specific hybridization probes for localization of κ and ι carrageenan gelling sequences within the cells walls and intercellular matrices of Kappaphycus alvarezii (Doty) Doty. The probes label cell walls and intercellular matrices under ionic conditions appropriate for gelation of κ and ι carrageenans. The distribution of κ and ι carrageenans in the matrix and cell walls of K. alvarezii was determined with respect to cell type (epidermis, cortex, medulla, and central axis) and age. The κ-probe labels the cell walls of all cell types except epidermal in both young and old tissues. In contrast, the ι-probe labels the cell walls of the epidermis in both young and old tissue and the cell walls of the thylles only in old tissue. Both probes label intercellular matrix material; however, ι-probe labelling is very much weaker than κ-probe labelling. The results indicate that FITC-conjugated carrageenan oligosaccharides are useful tools that provide information on gelling subunit distribution.     

Second-derivative Fourier transform infrared spectra of seaweed galactans

The Fourier transform infrared spectra of agar, agarose, -, -, and -carrageenan, and ofChondrus canaliculatus, Iridaea ciliata, I. membranacea, I. laminarioides andGracilaria chilensis polysaccharides were recorded in the 4000–400 cm^-1 region. The bands in the second derivative mode are sharper and more bands are resolved than in the normal spectra.Agar, agarose andG. chilensis phycocolloids exhibit diagnostic bands at 790 and 713 cm^-1. -, - and -carrageenans, and native carrageenan-type polysaccharides fromC. canaliculatus andIridaea species exhibit bands at around 1160, 1140, 1100, 1070, 1040, 1008, 610, and 580 cm^-1. Therefore, FT-IR spectroscopy in the second-derivative mode may be applied to differentiate between agar- and carrageenan-types seaweed galactans.     

Effects of polysaccharides from <Emphasis Type="Italic">Morchella conica</Emphasis> on nitric oxide production in lipopolysaccharide-treated macrophages

Morchella conica is a species of rare edible mushroom whose multiple medicinal functions have been proven. However, reports barely mention the mechanisms of these functions. In this study, the effects of two polysaccharides from M. conica (PMCs) on nitric oxide (NO) production in lipopolysaccharide (LPS)-treated macrophages were investigated. The results showed that 50–200 μg/ml of the extracellular polysaccharide (EPMC) and 25–200 μg/ml of the intracellular polysaccharide (IPMC) significantly inhibited NO production. Accordingly, the signal mechanisms were also explored. It was found that 100 μg/ml of EPMC and 25 μg/ml of IPMC could efficiently down-regulate the inducible nitric oxide synthase (iNOS) expression and nuclear factor-κB (NF-κB) DNA-binding activity and up-regulate heme oxygenase 1 (HO-1) expression. Moreover, by using a HO-1 inhibitor NaPP to treat the cells, the PMC-inhibited NO production and iNOS expression, rather than NF-κB activation, were released partially, indicating that HO-1 probably medicates the inhibition of PMCs on iNOS and NO. Besides, EPMC also significantly suppressed the phosphorylation of p38 mitogen-activated protein kinase (p38), c-jun N-terminal kinase, mitogen-activated protein kinase kinase 4, and expression of NF-κB inducing kinase, while IPMC seemed to show no regular effect on p38. In conclusion, PMCs inhibited NO production in LPS-induced macrophages through regulating a series of signal pathways, suggesting that PMCs play a potential role on immunomodulation and treating related diseases.     

Stimulation effect of carrageenan on enzymatic defense system of sweet basil against Cuscuta campestris infection

Sweet basil is an important medicinal plant used especially for therapeutical potentials. Sweet basil is a common host for Cuscuta campestris, which has a negative effect on infected plants. Therefore, natural friendly control of C. campestris seems to be useful. It has been shown that carrageenans can act as elicitors of plant defense responses. In this work, the effect of κ-carrageenans on protection against C. campestris and suppression of its invasion in basils were studied. Basils were sprayed with a solution of κ-carrageenan (1?g?L^?1), once a week, three times in total. Infection of basils with C. campestris was performed two days after the last carrageenan treatment. C. campestris stem and the leaves of basils were collected two weeks after C. campestris inoculation for biochemical studies. Treatment with carrageenan significantly increased shoot length and leaf area of basil and decreased C. campestris infestation by about 26%. The content of malondialdehyde, other aldehydes, hydrogen peroxide and lipoxygenase (LOX) activity increased significantly in basils parasitized by C. campestris. There were significant differences in phenylalanine ammonia lyase (PAL), catalase (CAT), superoxide dismutase (SOD) and peroxidase activity of parasitized basils by C. campestris compared with healthy basils. Carrageenan treatment of basils caused a significant increase in H₂O₂ content and the activity of PAL, CAT and SOD, but not of malondialdehyde, other aldehydes content and LOX, polyphenol oxidase (PPO) and peroxidases activity. The activated enzymatic defense system (PAL, PPO, CAT, SOD and peroxidase) in carrageenan-treated basils have a vital role in alleviating oxidative stress damage in infected plants, by removing excess reactive oxygen species and inhibiting LOX activity and lipid peroxidation that was observed in this study. Our results showed that the application of κ-carrageenan-induced beneficial effects in plants, with regard to growth stimulation and the activation of enzymatic defense system. Thus, carrageenan was recommended as a natural biostimulator for protection of plants against C. campestris.