Immunologically active O6-branched (1-->3)-beta-glucan from the lichen Thamnolia vermicularis var. subuliformis

Antibacterial mechanism of the methanol extract of Thamnolia subuliformis (Ehrh.) W. Culb against Staphylococcus aureus

Thamnolia subuliformis (Ehrh.) W. Culb is a species of lichen with edible and medicinal applications in China. Our previous studies demonstrated that the methanol extract of Thamnolia subuliformis (METS) exhibits broad antibacterial activity and stability against foodborne pathogens. This study aimed to investigate the antibacterial mechanism of METS against Staphylococcus aureus using nontargeted metabolomics, focusing on cell wall and membrane damage. The results revealed that the minimum inhibitory concentration (MIC) was 0.625 mg ml-1 and that METS had good biosafety at this concentration. METS caused significant damage to the cell wall and membrane integrity, based on both morphological observation by electron microscopy and the leakage of alkaline phosphatase, protein, and nucleic acid in the cell cultures. Treatment with METS at the MIC disrupted the lipid metabolism of S. aureus, causing a decrease in the metabolism of various phospholipids and sphingolipids in the cell membrane and an increase in the ratio of saturated fatty acids to unsaturated fatty acids. Moreover, it influenced intracellular amino acid and energy metabolism. These results shed light on the antibacterial mechanism of METS against S. aureus while also serving as a reference for the further development of natural antibacterial compounds derived from Thamnolia subuliformis.

Lichens: An update on their ethnopharmacological uses and potential as sources of drug leads

ETHNOPHARMACOLOGICAL RELEVANCE

Lichens, a unique symbiotic association between an alga/cyanobacterium and a fungus, produce secondary metabolites that are a promising source of novel drug leads. The beauty and importance of lichens have not been adequately explored despite their manifold biological activities such as anticancer, antimicrobial, antioxidant, anti-inflammatory, analgesic, antipyretic and antiparasitic.

AIM OF THE STUDY

The present review collates and discusses the available knowledge on secondary metabolites and biological activities of lichens (in vitro and in vivo).

MATERIALS AND METHODS

Using relevant keywords (lichens, secondary metabolites, bioactivity, pharmacological activities), five electronic databases, namely ScienceDirect, PubMed, Google Scholar, Scopus and Recent Literature on Lichens, were searched for past and current scientific contributions up until May 2022. Literature focusing broadly on the bioactivity of lichens including their secondary metabolites were identified and summarized.

RESULTS

A total of 50 review articles and 189 research articles were searched. Information related to antioxidant, antimicrobial, anti-inflammatory, anticancer and insecticidal activities of 90 lichen species (from 13 families) and 12 isolated metabolites are reported. Over 90% of the studies comprised in vitro investigations, such as bioassays evaluating radical scavenging properties, lipid peroxidation inhibition and reducing power, cytotoxicity and antimicrobial bioassays of lichen species and constituents. In vivo studies were scarce and available only in fish and rats. Most of the studies were done by research groups in Brazil, France, Serbia, India and Turkey. There were relatively few reports from Asia and Africa despite the ubiquitous nature of lichens and the high occurrence in these continents.

CONCLUSION

Secondary metabolites from lichens are worthy of further investigation in terms of their potential therapeutic applicability, including better understanding of their mechanism(s) of action. This would be of great importance in the search for novel drugs.

Plant/algal polysaccharides extracted by microwave: A review on hypoglycemic, hypolipidemic, prebiotic, and immune-stimulatory effect

Microwave-assisted extraction (MAE) is an emerging technology to obtain polysaccharides with an extensive spectrum of biological characteristics. In this study, the hypoglycemic, hypolipidemic, prebiotic, and immunomodulatory (e.g., antiinflammatory, anticoagulant, and phagocytic) effects of algal- and plant-derived polysaccharides rich in glucose, galactose, and mannose using MAE were comprehensively discussed. The in vitro and in vivo results showed that these bioactive macromolecules with the low digestibility rate could effectively alleviate the fatty acid-induced lipotoxicity, acute hemolysis, and dyslipidemia status. The optimally extracted glucomannan- and glucogalactan-containing polysaccharides revealed significant antidiabetic effects through inhibiting α-amylase and α-glucosidase, improving dynamic insulin sensitivity and secretion, and promoting pancreatic β-cell proliferation. These bioactive macromolecules as prebiotics not only improve the digestibility in gastrointestinal tract but also reduce the survival rate of pathogens and tumor cells by activating macrophages and producing pro-inflammatory biomarkers and cytokines. They can effectively prevent gastrointestinal disorders and microbial infections without any toxicity.

Anti-Inflammatory Effects of Antarctic Lichen Umbilicaria antarctica Methanol Extract in Lipopolysaccharide-Stimulated RAW 264.7 Macrophage Cells and Zebrafish Model

Umbilicaria antarctica (UA) is a member of the family Umbilicariaceae. To the best of our knowledge, no studies on its anti-inflammatory effects have been reported yet. In the present study, we examined its ability to suppress inflammatory responses and the molecular mechanisms underlying these abilities using lipopolysaccharide- (LPS-) stimulated RAW 264.7 cells and a zebrafish model of inflammation. We investigated the effects of UA on the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) in LPS-stimulated RAW 264.7 cells. To explore the anti-inflammatory mechanisms of UA, we measured the mRNA and protein expression of proinflammatory mediators in LPS-stimulated RAW 264.7 cells using quantitative RT-PCR and western blot analyses, respectively. UA significantly inhibited the production of NO, PGE₂, interleukin- (IL-) 6, and tumor necrosis factor- (TNF-) α in the LPS-stimulated RAW 264.7 cells. It also suppressed the mRNA and protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor- (NF-) κB activation in LPS-stimulated RAW 264.7 cells and tail pin-cutting-induced zebrafish model. Collectively, these findings indicate that UA significantly inhibits LPS-stimulated inflammatory responses. These effects were considered to be strongly associated with the suppression of NF-κB activation. Overall, our results demonstrate that UA extract exerts strong anti-inflammatory activities in in vitro and in vivo models and suggest that UA may be an effective novel therapeutic agent for the treatment of inflammatory diseases.

3D biofilms: in search of the polysaccharides holding together lichen symbioses

Stable, long-term interactions between fungi and algae or cyanobacteria, collectively known as lichens, have repeatedly evolved complex architectures with little resemblance to their component parts. Lacking any central scaffold, the shapes they assume are casts of secreted polymers that cement cells into place, determine the angle of phototropic exposure and regulate water relations. A growing body of evidence suggests that many lichen extracellular polymer matrices harbor unicellular, non-photosynthesizing organisms (UNPOs) not traditionally recognized as lichen symbionts. Understanding organismal input and uptake in this layer is key to interpreting the role UNPOs play in lichen biology. Here, we review both polysaccharide composition determined from whole, pulverized lichens and UNPOs reported from lichens to date. Most reported polysaccharides are thought to be structural cell wall components. The composition of the extracellular matrix is not definitively known. Several lines of evidence suggest some acidic polysaccharides have evaded detection in routine analysis of neutral sugars and may be involved in the extracellular matrix. UNPOs reported from lichens include diverse bacteria and yeasts for which secreted polysaccharides play important biological roles. We conclude by proposing testable hypotheses on the role that symbiont give-and-take in this layer could play in determining or modifying lichen symbiotic outcomes.

Digestibility of sulfated polysaccharide from the brown seaweed Ascophyllum nodosum and its effect on the human gut microbiota in vitro

Sulfated polysaccharides from marine algae exhibit various bioactivities with potential benefits for human health and well-being. In this study, the in vitro digestibility and fermentability of polysaccharides from the brown seaweed Ascophyllum nodosum (AnPs) were examined, and the effects of AnPs on gut microbiota were determined using high-throughput sequencing technology. Salivary amylase, artificial gastric juice, and intestinal juice had no effect on AnPs, but the molecular weight of AnPs and reducing sugar decreased significantly after fermentation by gut microbiota. AnPs significantly modulated the composition of the gut microbiota; in particular, they increased the relative abundance of Bacteroidetes and Firmicutes, suggesting the potential for AnPs to decrease the risk of obesity. Furthermore, the total SCFA content after fermentation increased significantly. These results suggest that AnPs have potential uses as functional food components to improve human gut health.

Digestion under saliva, simulated gastric and small intestinal conditions and fermentation in vitro of polysaccharides from the flowers of Camellia sinensis induced by human gut microbiota

In the present study, digestion under saliva, simulated gastric and small intestinal conditions and fermentation in vitro of polysaccharides from the flowers of Camellia sinensis (TFPS) by human gut microbiota were investigated. The results indicated that human saliva and simulated gastric and intestinal juices had no effect on TFPS, while TFPS could be utilized by human fecal microbiota, which was proved from the decreased molecular weight and lower content of total or reducing sugars after fermentation under anaerobic conditions. It was found that pH in the fermentation system decreased, and the production of short-chain fatty acids was significantly enhanced. Furthermore, in vitro fermentation of TFPS altered the composition of gut microbiota, specifically in elevating the ratio of Bacteroidetes to Firmicutes and enriching Prevotella. The present results suggest that TFPS has the potential to be developed as functional foods to modify gut microbiota.

Structure Elucidation of a Polysaccharide from Umbilicaria esculenta and Its Immunostimulatory Activity

Umbilicaria esculenta has been used as a tonic food in China for several centuries owing to its pleasant flavor and health benefits. In this study, a water soluble polysaccharide, which we designated as UP2, with an average molecular weight of 3.33 × 105 Da, was isolated from U. esculenta cultivated in the Huangshan Mountain, by consecutive hot water extraction and anion-exchange chromatography. Gas chromatography analysis indicated that UP2 contained three kinds of monosaccharides, including mannose, glucose, and galactose at a molar ratio of 1.7:1.0:1.2. Linkage analysis of UP2 revealed the presence of (1 → 6)-linked glucosyl, (1 → 3,6)-linked glucosyl, t-linked galactosyl, (1 → 6)-linked galactosyl and (1 → 6)-linked mannosyl at a molar ratio of 0.7:4.6:4.1:2.2:9.1. Structural analysis determined that UP2 possessed a backbone consisting of (1 → 6)-linked β-D-glucopyranosyl and (1 → 6)-linked α-D-mannopyranosyl residues, which substituted at the O-3 position of (1 → 6)-linked β-D-glucopyranosyl residues by branches of (1 → 6)-linked α-D-galactopyranosyl and 1-linked β-D-galactopyranosyl residues. Immunostimulatory activity analysis showed that UP2 could stimulate the proliferation of RAW264.7 cells in a dose-dependent manner, and all the samples (20-500 μg/mL) were found to enhance nitric oxide production. The highest phagocytic activity of UP2 was observed at 200 μg/mL. Thus, UP2 may be a potential source of biological and pharmacological agents.

Bioactivities, isolation and purification methods of polysaccharides from natural products: A review

Polysaccharides play multiple roles and have extensive bioactivities in life process and an immense potential in healthcare, food and cosmetic industries, due to their therapeutic effects and relatively low toxicity. This review describes their major functions involved in antitumor, anti-virus, and anti-inflammatory bioactivities. Due to their enormous structural heterogeneity, the approaches for isolation and purification of polysaccharides are distinct from that of the other macromolecules such as proteins, etc. Yet, to achieve the homogeneity is the initial step for studies of polysaccharide structure, pharmacology, and its structure-activity relationships. According to the experiences accumulated by our lab and the published literatures, this review also introduces the methods widely used in isolation and purification of polysaccharides.

Dietary administration of laminarin improves the growth performance and immune responses in Epinephelus coioides

This study was conducted to evaluate the effects of laminarin on the growth performance, immunological and biochemical parameters, as well as immune related genes expression in the grouper, Epinephelus coioides. One hundred and eight fish were randomly divided into four groups (45 groupers/group). Blank control group was fed with the basal diet, while low, medium and high doses of laminarin groups were fed with the basal diet supplemented with 0.5%, 1.0%, and 1.5% laminarin, respectively, for 48 days. The immunological and biochemical parameters in blood were investigated. The mRNA levels of IL-1β, IL-8, and TLR2 in midgut were also evaluated by quantitative real-time PCR. Dietary laminarin supplementation significantly improved the specific growth rate and the feed efficiency ratio of the fish. The level of TP and the activity of LZM, CAT and SOD were higher than that of the control. The levels of UREA and CREA as well as the activity of ALP were lower than of the control. There was no significant difference in the levels of ALT and AST between control groups and treated groups. In addition, dietary laminarin supplementation decreased the levels of C3 and C4. The expression of immune response genes IL-1β, IL-8, and TLR2 showed significant increases (P < 0.05) in groupers fed low dose (0.5%) and medium dose (1.0%) of laminarin compared with the blank control. These results suggest that laminarin modulates the immune response and stimulates growth of the fish.

Glucomannan and branched (1→3)(1→6) β-glucan from the aposymbiotically grown Physcia kalbii mycobiont

Cultures of the mycobiont Physcia kalbii were obtained from germinated ascospores and cultivated on Sabouraud-Sucrose-agar medium. Alkaline extraction of freeze-dried mycelia provided a branched (1→3),(1→6)-β-glucan and a glucomannan, whose chemical structure was determined by monosaccharide composition, methylation, controlled Smith degradation and NMR spectroscopic analysis. The β-glucan had a (1→3)-linked β-glucopyranosyl backbone, partially substituted (approx. 50% of the units) at O-6. The side chains were formed by 6-O- (∼82%) and 2,6-O-linked-β-Glcp units, while the non-reducing ends were formed by β-glucopyranosyl residues. The glucomannan had (1→6)-linked α-Manp units in the main chain, almost all being substituted at O-2 by α-Manp and α-Glcp units. This glucomannan could be a typical polysaccharide of lichens from the family Physciaceae.

Does aposymbiotically cultivated fungus Ramalina produce isolichenan?

The main α-glucan synthesized by lichens of the genera Ramalina in the symbiotic state is isolichenan. This polysaccharide was not found in the aposymbiotically cultivated symbionts. It is still unknown if this glucan is produced by the mycobiont only in the presence of a photobiont, in a lichen thallus, or if the isolichenan suppression is influenced by the composition of culture medium used in its aposymbiotic cultive. Consequently, the latter hypothesis is tested in this study. Cultures of the mycobiont Ramalina complanata were obtained from germinated ascospores and cultivated on 4% glucose Lilly and Barnett medium. Freeze-dried colonies were defatted and their carbohydrates extracted successively with hot water and aqueous 10% KOH, each at 100 °C. The polysaccharides nigeran, laminaran and galactomannan were liberated, along with a lentinan-type β-glucan and a heteropolysaccharide (Man : Gal : Glc, 21 : 28 : 51). Nevertheless, the α-glucan isolichenan was not found in the extracts. It follows that it was probably a symbiotic product, synthesized by the mycobiont only in this particular microenvironment, in the presence of the photobiont in the lichen thallus. A discussion about polysaccharides found in the symbiotic thallus as well as in other aposymbiotic cultivated Ramalina mycobionts is also included.

Dendritic cell activation by glucan isolated from umbilicaria esculenta

Background

Lichen-derived glucans have been known to stimulate the functions of immune cells. However, immunostimulatory activity of glucan obtained from edible lichen, Umbilicaria esculenta, has not been reported. Thus we evaluated the phenotype and functional maturation of dendritic cells (DCs) following treatment of extracted glucan (PUE).

Methods

The phenotypic and functional maturation of PUE-treated DCs was assessed by flow cytometric analysis and cytokine production, respectively. PUE-treated DCs was also used for mixed leukocyte reaction to evaluate T cell-priming capacity. Finally we detected the activation of MAPK and NF-κB by immunoblot.

Results

Phenotypic maturation of DCs was shown by the elevated expressions of CD40, CD80, CD86, and MHC class I/II molecules. Functional activation of DCs was proved by increased cytokine production of IL-12, IL-1β, TNF-α, and IFN-α/β, decreased endocytosis, and enhanced proliferation of allogenic T cells. Polymyxin B, specific inhibitor of lipopolysaccharide (LPS), did not affect PUE activity, which suggested that PUE was free of LPS contamination. As a mechanism of action, PUE increased phosphorylation of ERK, JNK, and p38 MAPKs, and enhanced nuclear translocation of NF-κB p50/p65 in DCs.

Conclusion

These results indicate that PUE induced DC maturation via MAPK and NF-κB signaling pathways.

Enzymatic method to measure β-1,3-β-1,6-glucan content in extracts and formulated products (GEM assay)

An enzymatic method to measure β-glucan content (GEM assay) is applicable in a variety of matrices. The method is composed of swelling the sample with KOH and initial digestion with a lyticase, which is followed by treatment with a mixture of exo-1,3-β-d-glucanase and β-glucosidase that converts the β-glucan to glucose. The glucose generated by the enzymatic hydrolysis is measured by another enzymatic method. The method is shown to be accurate and precise. The method is selective and applicable to both highly branched and unbranched β-1,3-glucans.

Polysaccharides present in cultivated Teloschistes flavicans symbiosis: comparison with those of the thallus

The chemical structures of polysaccharides present in aposymbiotically cultured myco- and photobionts of the lichen Teloschistes flavicans were determined, in order to compare them with those previously found in the intact thallus. The mycobiont was cultured on a solid Lilly and Barnett medium and the resulting colonies were freeze dried, defatted, and their polysaccharides were extracted successively with 2%, 10% and 30% aq. KOH, each at 100 degrees C. The extracts were neutralized (HOAc) and fractionated, giving rise to three homogeneous fractions, PFSK2 from 2% KOH, which contained a (1-->4),(1-->6)-linked alpha-glucan (1:1 ratio, pullulan), fraction PK10 from 10% KOH extraction, which was a linear (1-->3)-linked linear beta-glucan (laminaran), and fraction PK30 from 30% KOH extraction, being a branched (1-->3),(1-->6)-linked beta-glucan. The photobiont (Trebouxia sp. de Puymaly) was cultured in liquid nutrient medium, and after purification, a linear (1-->5)-linked beta-galactofuranan was characterized. The galactofuranan and the laminaran were not present in the symbiotic thallus, in contrast to the glucans, showing that the mycobiont alone produces them without participation of the photobiont.

Immunomodulating polysaccharides from the lichen Thamnolia vermicularis var. subuliformis

Three heteroglycans Ths-4, Ths-5 and thamnolan and a beta-glucan, Ths-2, isolated from the lichen Thamnolia vermicularis var. subuliformis were tested for in vitro immunomodulating activities and shown to have various influences on the immune system. All the polysaccharides except Ths-4 caused a stimulation of rat spleen cell proliferation. In contrast, Ths-4 caused cell death early in the culture, probably due to over-stimulation. Moreover, the galactofuranomannans, Ths-4, Ths-5 and the beta-glucan Ths-2, induced rat spleen cells to secrete IL-10 significantly above background levels. In addition, Ths-4 and Ths-5 stimulated significant TNF-alpha secretion by rat peritoneal macrophages. The galactofuranomannans Ths-4 and Ths-5 have similar structures apart from the molecular weight. Thus, it may be concluded that the molecular size might influence the potency but not the pattern of activity for Ths-4 and Ths-5. The galactofuranorhamnan thamnolan had less mitogenic effect than Ths-5 and Ths-2 and neither induced IL-10 secretion by rat spleen cells nor TNF-alpha secretion by peritoneal macrophages to significant levels. This shows that thamnolan with its unusual galactofuranorhamnan structure differs from the other Thamnolia polysaccharides in its immunomodulatory activity.

Immunostimulatory polysaccharides from Chlorella pyrenoidosa. A new galactofuranan. measurement of molecular weight and molecular weight dispersion by DOSY NMR

Fractionation of the hot water extract of Chlorella pyrenoidosa was performed using a combination of ethanol precipitation, size exclusion chromatography, and anion exchange chromatography. One fraction contained a new polysaccharide, and this compound was shown to be a 1-->2-linked beta-d-galactofuranan from its 1D and 2D (1)H and (13)C NMR spectra, with a molecular weight of 15 kDa from DOSY NMR measurements. A number of other fractions were shown to have the same repeating unit as the previously identified arabinogalactan. However, arabinogalactans from different fractions were shown by DOSY NMR to have different molecular weights, which ranged from 27 to 1020 kDa. Agreement with molecular weights measured for some of these fractions by SEC-MALS was very good, further confirming the relationship established by Viel et al. between molecular weights of neutral polysaccharides and self-diffusion coefficients. The smaller molecular weight polysaccharides, the galactofuranan and the 27 and 50 kDa arabinogalactans, were shown to be close to monodisperse by analysis of the distributions of the self-diffusion coefficients for the polymers. The larger arabinogalactans had considerable variation in their molecular weights (188 +/- 109 kDa and 1020 +/- 370 kDa). Only the two larger arabinogalactans showed immunostimulatory activity.

Structural characterisation of novel lichen heteroglycans by NMR spectroscopy and methylation analysis

Two galactofuranomannans, Ths-4 and Ths-5, were isolated from the lichen, Thamnolia vermicularis var. subuliformis, using ethanol fractionation and anion-exchange and size-exclusion chromatography. The average molecular weights of Ths-4 and Ths-5 were estimated to be 19 and 200 kDa, respectively. Structural characterisation of Ths-4, Ths-5 and their partially hydrolysed derivatives was performed by methanolysis and methylation analysis. The intact and partially hydrolysed Ths-4 was further analysed using NMR spectroscopy (1D, COSY, NOESY, TOCSY, HSQC and HMBC). According to the data obtained, the heteroglycans Ths-4 and Ths-5 have similar structures, but have large differences in molecular weight. The structure is composed of 3-O-linked and 5-O-linked galactofuranosyl chains linked to a mannan core. The mannan core consists of a main chain of alpha-(1-->6)-linked mannopyranosyl residues, substituted at O-2 with either a single alpha-mannopyranosyl unit or an alpha-Manp-(1-->2)-alpha-Manp-(1-->2)-alpha-Manp group in the ratio of approximately 1:3, respectively. The polysaccharides have idealised repeating blocks as is shown.

Immunomodulating effects of lichen-derived polysaccharides on monocyte-derived dendritic cells

Many naturally occurring polysaccharides from fungi and lichens have been found to have immunomodulating activity. However, the majority of these studies have focused on their effects on the innate arm of the immune system. Although dendritic cells (DCs) belong to the innate immune system, they play an important role as a bridge between the innate and the adaptive immune response. In this study, the effects of 11 chromatographically purified and well-characterised lichen polysaccharides (of different structural types) on the maturation of DCs were tested by analysing the secretion of IL-12p40 and IL-10 by human monocyte-derived dendritic cells in vitro. Four of the polysaccharides upregulated IL-10 secretion by the dendritic cells, as compared with unstimulated cells, the beta-glucans lichenan and Ths-2 and the heteroglycans Pc-4 and thamnolan. IL-12p40 secretion was significantly upregulated by the beta-glucan lichenan and the heteroglycans Pc-2, Pc-4, thamnolan and Ths-4, while the mature dendritic cells stimulated with the heteroglycan Pc-1 secreted significantly less IL-12p40 than the unstimulated cells. Proportional index (PI) was used to determine the relationship between the IL-12p40 and IL-10 secretion. The PI of all the beta-glucans, i.e. lichenan, pustulan and Ths-2, and the heteroglycan thamnolan was significantly lower than the PI observed for the unstimulated cells, which was mainly due to increased IL-10 secretion. Therefore, these polysaccharides could be considered suitable candidates in tolerance and anti-inflammatory studies, as IL-10 is one of the major cytokines involved in tolerance and anti-inflammatory responses.

A β-d-glucan isolated from the fruiting bodies of Hericium erinaceus and its aqueous conformation

HEP3, a beta-D-glucan slightly soluble in water, was isolated from the alkaline extract of the fruiting bodies of Hericium erinaceus. Its chemical structure was investigated by methylation analysis, periodate oxidation, Smith degradation and by IR and NMR spectroscopy. It was shown to have a main chain composed of beta-(1-->3)-linked D-glucopyranosyl residues, with single unit glucosyl branches attached to O-6 of every third backbone residue. Viscometry and Congo red reaction indicated that HEP3 has a highly ordered hydrogen-bond dependent conformation in aqueous solution, which collapses in strong alkaline solution.

Effects of lichen heteroglycans on proliferation and IL-10 secretion by rat spleen cells and IL-10 and TNF-alpha secretion by rat peritoneal macrophages in vitro

Four polysaccharides Pc-1, Pc-2, Pc-3 and Pc-4 were isolated from water and alkali extracts of the lichen Peltigera canina using ethanol fractionation, gel filtration and preparative HP-GPC. The monosaccharide composition was determined by methanolysis and GC and showed mannose and galactose as the predominating structural units. The mean M(r) was determined by HP-GPC. The heteroglycans were tested for in vitro immunomodulating activities and showed mitogenic activity in rat spleen cell proliferation assay and stimulated IL-10 secretion. In rat peritoneal macrophages, the heteroglycans stimulated TNF-alpha secretion, but not IL-10 secretion. These results indicate that the polysaccharides influence cells of the immune system both from the innate and the adaptive systems.

Glucans of lichenized fungi: significance for taxonomy of the genera Parmotrema and Rimelia

The glucans of lichenized fungi are an important class of polysaccharides with structural and chemotaxonomic roles. The water-insoluble glucans of the genus Parmotrema (P. austrosinense, P. delicatulum, P. mantiqueirense, P. schindleri, and P. tinctorum) and those of Rimelia (R. cetrata and R. reticulata), were investigated in order to evaluate the significance in chemotyping, with nigeran [(1-->3),(1-->4)-alpha-glucan] and lichenan [(1-->3),(1-->4)-beta-glucan] characterized using (1)H and (13)C NMR, methylation analysis, and controlled Smith degradations. Results from all species were similar, suggesting that glucan chemistry does not support separation of Rimelia from Parmotrema.