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A structural study of the cell wall polysaccharides of Myrmecia biatorellae, the symbiotic algal partner of the lichenized fungus Lobaria linita was carried out. It produced a cold-water insoluble rhamnogalactofuranan, with a (1→3)-linked β-d-galactofuranosyl main-chain, substituted at O-6 by single units of β-d-Galf, or by side-chains of 2-O- and 2,4-di-O-linked α-l-Rhap units. The structure of the polysaccharide was established by chemical and NMR spectroscopic analysis., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

A structural study of the cell wall polysaccharides of Myrmecia biatorellae, the symbiotic algal partner of the lichenized fungus Lobaria linita was carried out. It produced a rhamnogalactofuranan, with a (1→6)-β-D-galactofuranose in the main-chain, substituted at O-2 by single units of β-D-Galf, α-L-Rhap or by side chains of 2-O-linked β-D-Galf units. The structure of the polysaccharide was established by chemical and NMR spectroscopic analysis, and is new among natural polysaccharides. Moreover, in a preliminary study, this polysaccharide increased the lethality of mice submitted to polymicrobial sepsis induced by cecal ligation and puncture, probably due to the presence of galactofuranose, which have been shown to be highy immunogenic in mammals., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The antischistosomal activity of the sulfated polysaccharide α-D-glucan (Glu.SO(4)) extracted from Ramalina celastri was evaluated after encapsulation into liposomes (Glu.SO(4)-LIPO) in Schistosoma mansoni-infected mice. The effect of treatment with Glu.SO(4) and Glu.SO(4)-LIPO (10 mg/kg) on egg elimination, worm burden and hepatic granuloma formation was assessed using female albino Swiss mice, 35-40 days of age, weighing 25 ± 2 g, infected with 150 cercariae/animal (Biomphalaria glabrata, BH strain). Four groups (N = 10) were studied, two controls (empty liposomes and NaCl) and two treated groups (Glu.SO(4)-LIPO and Glu.SO(4)) using a single dose. Parasitological analysis revealed that Glu.SO(4)-LIPO was as efficient as Glu.SO(4) in reducing egg elimination and worm burden. Treatment with free Glu.SO(4) and Glu.SO(4)-LIPO induced a statistically significant reduction in the number of granulomas (62 and 63%, respectively). Lectin histochemistry showed that wheat germ agglutinin intensely stained the egg-granuloma system in all treated groups. On the other hand, peanut agglutinin stained cells in the control groups, but not in the treated groups. The present results suggest a correlation between the decreasing number of hepatic egg-granulomas and the glycosylation profile of the egg-granuloma system in animals treated with free Glu.SO(4) or Glu.SO(4)-LIPO.

A structural study of the carbohydrates from Trebouxia sp., the algal symbiont of the lichen Ramalina gracilis demonstrated a galactofuranan-rich heteropolysaccharide, which was predominated by (1-->5)-linked galactofuranosyl units with side-chains in position 6 on approximately 11.0% of the units. The side-chains have very complex branched structures. This polysaccharide showed cell eliciting activity on peritoneal macrophages in vitro at all concentrations tested (1-150 microg/mL), and at 150 microg/mL an increase of 60% of macrophage activation in comparison to the control group was observed. A potential role of these carbohydrates in lichen recognition process is also discussed.

A structural study of the carbohydrates from the aposymbiotically cultured Asterochloris sp., the algal symbiont of the lichen Cladina confusa was carried out for the first time. A xylorhamnogalactofuranan was purified and was predominated by (1-->3)-linked galactofuranosyl units with sidechains in position 6 on approximately 6.4% of the units. The sidechains have galactofuranosyl units 5-O and 6-O-substituted, as well rhamnopyranosyl units 2-O, 3-O and 2,3-di-O-substituted. Xylose was detected only as nonreducing end units, together with galactofuranosyl units. Amylose and a beta-(1-->4)-xylan were also present. These polysaccharides have not been found in the symbiotic thallus of C. confusa, which contained only glucans, galactomannoglucan and galactoglucomannan. A potential role of these carbohydrates in lichen recognition proccess is also discussed.

A light microscopic and molecular analysis of photobionts in Ramalina and Cladonia from coastal habitats of Brazil is presented. A Bayesian phylogenetic analysis of ITS rDNA sequences suggests a Trebouxia lineage which is preferentially tropical in geographic distribution. This highly diverse clade also includes the morphological similar species Trebouxia higginsiae and galapagensis. Within the predominantly tropical clade of Trebouxia we distinguish several subclades, three of which are represented in our samples of Ramalina species. Since sexuality has not been recognized in coccal lichenised photobionts until recently, we cannot apply a biological species concept, but when compared with the sequence diversity between known species we conclude that several new species need to be described in this clade. The mutually exclusive presence of other Trebouxia lineages in temperate samples of Ramalina suggests an evolution towards higher selectivity in this genus. A strictly tropical lineage is not conspicuous in the photobionts of the genus Asterochloris sampled from Cladonia so far.

Two homogeneous galactomannan fractions were isolated from the lichen, Roccella decipiens, one (FP) containing Man and Gal in an 81:19 molar ratio and the other (RFS), having Man, Gal, and Glc in a 43:56:1 molar ratio. FP consisted of a main chain with (1-->4)-linked alpha-D-Manp units, most of which were substituted at O-2 with side chains consisting of nonreducing end-, 2-O- and 6-O-substituted alpha-Manp units. The latter appeared to be substituted by single-unit beta-D-Galf nonreducing ends. RFS contained a similar alpha-D-Manp core structure, but with side chains containing nonreducing end, 5-O-, 6-O-, and 5,6-di-O-substituted beta-D-Galf units. Such polysaccharide structures have not been previously reported.

Fatty acid components, in both the free and combined form of the intact tropical lichen Teloschistes flavicans, and its isolated photobiont and mycobiont, were analyzed by GC-MS of derived methyl esters. Its rDNA analysis confirmed that the isolated cultured symbionts belong to the genera Trebouxia and Teloschistes, respectively. The fatty acid composition of the lichen did not correspond to those found in the isolated symbionts, suggesting that the fatty acid metabolism is markedly influenced by the symbiosis. Differences in the fatty acid composition in the lichen were observed during the summer (27 degrees C), when the main fatty acids were saturated and in the winter (22 degrees C) when an increase of unsaturated fatty acids occurred. Similar differences of composition were also observed for the cultured mycobiont at different temperatures. The increase in the unsaturation level at low temperatures would maintain the membrane fluidity. Our results are the first on the fatty acids of a tropical lichen and suggest that it is sensitive to small temperature variations, which influences its saturated and unsaturated fatty acid composition.

Galactoglucomannans were isolated from the lichenized fungi of the genus Parmotrema (Parmotrema austrosinense, Parmotrema delicatulum, Parmotrema mantiqueirense, Parmotrema schindlerii, and Parmotrema tinctorum and that of Rimelia (Rimelia cetrata and Rimelia reticulata) via successive hot alkaline extraction and precipitation with Fehling solution. The structure of each polysaccharide was investigated using 13C NMR and HSQC-DEPT spectroscopy, methylation analysis, and HPSEC-MALLS. The galactoglucomannans had a (1-->6)-linked main chain of alpha-Manp units, substituted preferentially at O-2 and O-4 by alpha-Galp and beta-Galp nonreducing end-units, respectively. The C-1 region of the 13C NMR spectra of these heteropolysaccharides is typical of the lichen species, and is an additional tool in lichenized fungi classification.

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.

A galactoglucomannan (GGM), isolated from the lichen Cladonia ibitipocae, consisted of a (1-->6)-linked main chain of alpha-mannopyranose units, substituted by alpha- and beta-D-galacto (alpha- and beta-D-Galp)-, beta-D-gluco (beta-D-Glcp)- and alpha-D-mannopyranosyl (alpha-D-Manp) groups, and was sulfated giving a sulfated polysaccharide (GGM-SO4) with 42.2% sulfate corresponding to a degree of substitution of 1.29. NMR studies indicated that after sulfation, the OH-6 groups of galactopyranosyl and mannopyranosyl units were preferentially substituted. GGM-SO4 was investigated in terms of its in vitro anticoagulant and in vivo antithrombotic properties. Those of the former were evaluated by its activated partial thromboplastin (APTT) and thrombin time (TT), using pooled normal human plasma, and compared with that of 140 USP units mg(-1) for a porcine intestinal mucosa heparin. Anticoagulant activity was detected in GGM-SO4, but not in GGM. The in vivo antithrombotic properties of GGM-SO4 were evaluated using a stasis thrombosis model in Wistar rats, intravenous administration of 2 mg kg(-1) body weight totally inhibiting thrombus formation. It caused dose-dependent increases in tail transection bleeding time. The results obtained showed that this sulfated polysaccharides is a promising anticoagulant and antithrombotic agent.

A structural characterization of polysaccharides extracted from the aposymbiotically cultured photobiont of the lichen Ramalina gracilis was carried out in order to compare them with those previously found in the symbiotic thallus. The photobiont was isolated from thallus fragments, following the method of Yamamoto, and cultivated in a liquid nutrient medium. Freeze-dried cells were defatted, and the polysaccharides extracted successively with water and aq. 10% KOH, each at 100 degrees C. After purification, the soluble fractions provided a polysaccharide containing a (1-->5)-linked beta-galactofuranosyl backbone, substituted in a small proportion at O-6 by beta-Galf units. Amylose was also found, as insoluble material obtained on freeze-thawing of the alkaline extract. These polysaccharides have not been found in the symbiotic thallus of Ramalina gracilis, which contained only water-soluble (isolichenan) and insoluble glucans (nigeran and laminaran), and galactomannan. Surprisingly, the galactofuranan has similarities with those found in some fungal cell walls.

Mycobiont isolation experiments were performed on six species of Ramalina from Brazil: R. celastri, R. complanata, R. dendriscoides, R. gracilis, R. peruviana and R. sprengelii. This study aimed to optimize the culture conditions and nutrient requirements of the selected mycobionts. The aposymbiotic R. complanta was successfully isolated from ascospores, while aposymbiotic R. peruviana was obtained from thallus fragments. In R. peruviana the production of secondary metabolites was investigated under aposymbiotical growth conditions using HPLC. When cultivated on solid medium, this mycobiont produced the typical chemosyndrome (sekikaic acid and satellite compounds), found in the voucher lichen thallus. When cultivated in liquid medium (immersed in malt yeast medium in the absence of agar), only one, the major lichen substance, sekikaic acid, was synthesized by the fungus. In addition, atranorin was formed, but was not detected in any of the voucher specimens. Red pigments were found in solid and liquid cultures. These were separated into two compounds, but could not be fully identified. R. celastri spores germinated, but did not form mycelia. R. dendriscoides, R. gracilis and R. sprengelii were not successfully cultivated in aposymbiotic conditions, although eight different culture media were tested.

Several structurally different glucans (alpha- and beta-) and galactomannans were characterized as components of four species of the genus Ramalina, namely R. dendriscoides, R. fraxinea, R. gracilis and R. peruviana. Freeze-thawing treatment of hot aqueous extracts furnished as precipitates (PW) linear alpha-D-glucans of the nigeran type, with regularly distributed (1-->3)- and (1-->4)-linkages in a 1:1 ratio. The supernatants (SW) contained alpha-D-glucans with (1-->3)- and (1-->4)-linkages in a molar ratio of 3:1. The lichen residues were then extracted with 2% aq. KOH, and the resulting extracts submitted to the freeze-thawing treatment, giving rise to precipitates (PK2) of a mixture of alpha-glucan (nigeran) and beta-glucan, which were suspended in aqueous 0.5% NaOH at 50 degrees C, dissolving preferentially the beta-glucan. These were linear with (1-->3)-linkages (laminaran). The mother liquor of the KOH extractions (2% and 10% aq. KOH) was treated with Fehling's solution to give precipitates (galactomannans). The galactomannans are related, having (1-->6)-linked alpha-D-mannopyranosyl main chains, substituted at O-4 and in a small proportion at O-2,4 by beta-D-galactopyranosyl units. Despite the different habitats of these lichenized fungi, all species studied in this investigation have a similar pool of polysaccharides.

The cultured photobiont Trebouxia sp. of Ramalina celastri was successively extracted at 100 degrees C with hot water, 2% aqueous KOH, and 10% aqueous KOH to give polysaccharide-containing fractions A (2.9%), B (3.9%), and C (0.9% yield) respectively. The intact biont contained 3.8% amylose, which was present in each fraction, and was identified by a blue color formed with iodine solution. In fraction A, and following retrogradation from aqueous solution, it was characterized by (13)C-NMR spectroscopy. Fraction B was treated with alpha-amylase to give a water-soluble fraction consisting mainly of beta-mannose-containing polysaccharides (1.5% yield), whose main component had dn/dc 0.162 and M(r) 17 kDa. Fraction C was subjected to freeze-thawing and the precipitate was treated with alpha-amylase to give a resistant, linear, low molecular mass (1-->4)-linked beta-xylan. The beta-D-mannopyranan preparation contained mainly of 3-O- (28%), 4-O- (11%), and 6-O-substituted Manp units (35%), with 3-O-substituted Rhap units (11%). A controlled Smith degradation provided a beta-mannan with nonreducing end- (8%), 3-O- (85%) and 6-O-substituted units, showing (1-->3)- and (1-->6)-linked structures in the original polysaccharide. These could be present as block-type structures.

The polysaccharides formed on hot alkaline extraction of the ascomycetous lichen Teloschistes flavicans were fractionated to give two glucans, which were characterised by methylation analysis and 1D and 2D NMR spectroscopy. One was a branched beta-glucan containing (1-->3) and (1-->6) linkages, a structure which is more typical of basidiomycetes rather than ascomycetes, which have linear glucans. The other was an alpha-glucan with alternating (1-->4) and (1-->6) linkages, found for the first time in Nature. This structure can be classified as a pullulan, which has been isolated from the fungi Aureobasidium pullulans, Tremella mesenterica, and Cyttaria harioti, but has different ratios of the component glycosidic linkages. The significance of the presence of the isolated alpha- and beta-glucans is discussed.

An alpha-glucan from the lichen Ramalina celastri has previously been demonstrated to have cytotoxic effects against HeLa cells. This polysaccharide was studied using Sarcoma-180 cells as tumoral model, and its effects on peritoneal exudate cells, namely, hydrogen peroxide production, phagocytic activity and cell eliciting activity are evaluated. Tumors developing in animals treated with the glucan at a dose of 200 mg kg(-1), had a tumor size approximately 80% smaller than that of the control group, showing an impairment of tumor establishment. The polysaccharide was injected into mice not bearing a tumor and after 7, 15 and 30 days the cells were collected from the peritonea. The number of peritoneal cells increased approximately 130% 7 days after inoculation, and then gradually decreased. Hydrogen peroxide production was 75% greater 7 and 15 days after inoculation, on in vitro phorbol myristate acetate (PMA) triggering. Without PMA, the difference in hydrogen peroxide production was not significant. Phagocytic assays using fluorescent beads showed that the uptake increased 7 and 15 days after inoculation, when compared with the control. These results thus suggest a possible role of the R. celastri glucan as a biological response modifier (BRM).

Extraction of Dictyonema glabratum with hot 2% (w/v) aqueous KOH at 100 degrees C, followed by neutralisation and freeze-thawing, gave an insoluble glucan. The residue was further extracted by a similar process, but with hot 10% (w/v) aqueous KOH, furnishing a mixture of glucan, mannan and xylan. The mannan and xylan were obtained via precipitation of its copper complex with Fehling's solution, leaving the glucan in the supernatant. The insoluble complex was finally purified through gel permeation chromatography. Methylation analysis, one- and two-dimensional nuclear magnetic resonance examination showed the polysaccharides to be a (1-->3)-linked alpha-glucan (pseudonigeran) and a (1-->4)-linked beta-xylan, both not previously encountered in lichens, and a newly discovered (1-->6)-linked beta-mannan.

Beta-D-glucans of the laminaran type were prepared from 15 Cladonia spp., Cladonia bellidiflora, Cladonia boryi, Cladonia clathrata, Cladonia connexa, Cladonia crispatula, Cladonia furcata, Cladonia gracilis, Cladonia ibitipocae, Cladonia imperialis, Cladonia miniata, Cladonia penicillata, Cladonia salmonea, Cladonia signata, Cladonia substellata and Cladonia uncialis. They were extracted with 10% aqueous KOH at 100 degrees C, giving polysaccharides with varying yields and proportions of mannose, galactose and glucose. Their aqueous solutions were freeze-thawed giving precipitates of mixed alpha-glucan (nigeran) and beta-glucans, which were isolated and suspended in aqueous 0.5% KOH at 50 degrees C, which preferentially dissolved the beta-glucan. In the case of the C. uncialis product, it was subjected to methylation analysis, which gave rise to 2,4,6-tri-O-methylglucitol acetate only, corresponding to (1-->3)-linkages. Its specific rotation (+4 degrees ) and one- and two-dimensional nuclear magnetic resonance (NMR) spectra were consistent with beta-linkages. 13C and (1)H-1 signals were observed, respectively, at delta 102.8 (C-1), 86.0 (C-3), 76.2 (C-5), 72.6 (C-2), 68.3 (C-4) and 60.7 (C-6), and 4.55 (H-1), 3.31 (H-2), 3.49 (H-3), 3.27 (H-4), 3.27 (H-5), 3.48 (H-6) and 3.72 (H-6'). Similar (13)C-NMR spectra were obtained from the glucans from the other 14 Cladonia spp. The beta-D-glucans of the laminaran type seems to be present in all Cladonia spp. being significant for chemotyping since it was observed in every species studied.

The chemical structures of the glucans, galactoglucomannans and galactomannoglucans of two species of the Cladonia, section Cocciferae, Cladonia miniata and Cladonia salmonea, were determined and compared. alpha-D-Glucans of the nigeran type were isolated from both species, in common with all Cladonia spp., along with galactoglucomannans containing (1-->6)-linked main-chains of alpha-D-Manp units substituted by structurally different and typical side-chains. Isolated were previously unreported galactomannoglucans, with (1-->3)-linked main-chains of beta-D-Glcp units, substituted at O-2,6 by side-chains. These consisted of beta-D-Galf, 6-O-substituted beta-D-Galf and 2-O-, 4-O-, 6-O- and 2, 3-di-O-substituted alpha-D-Manp units. According to (13)C NMR spectroscopy, a similar galactomannoglucan was isolated from the Cladonia spp. Cladonia signata, Cladonia crispatula, Cladonia penicillata, Cladonia imperialis, Cladonia clathrata, Cladonia connexa, Cladonia substellata and Cladonia ibitipocae. Its presence could also contribute to the classic taxonomy of lichenized fungi.

The galactoglucomannans of two species of the lichen genus Cladonia, C. substellata and C. ibitipocae, were compared. They were homogeneous on gel-filtration chromatography and structurally related, having (1-->6)-linked alpha-D-mannopyranosyl main-chains, but were substituted in different patterns by alpha- and beta-D-galacto-, beta-D-gluco- and alpha-D-mannopyranosyl groups. The C-1 portions of their 13C-NMR spectra are typical of the lichen species and indicate differences between the two polysaccharides. Partial acetolysis of the galactoglucomannan from C. substellata gave rise to oligosaccharides and three were identified, namely alpha-D-Manp-(1-->3)-alpha beta-D-Galp, alpha-D-Manp-(1-->2)-alpha beta-D-Manp and alpha-D-Manp-(1-->2)-[beta-D-Glcp-(1-->4)]-alpha beta-D-Manp, whereas only the latter two were obtained from that of C ibitipocae. Methylation and Smith degradation data confirmed these results. Whereas the mannobiose represents a common structure in lichen heteropolysaccharides, it is the first time that the other oligosaccharides have been isolated from those of lichens.

Three glycolipids (1-3) were isolated from the basidiolichen Dictyonema glabratum. Their carbohydrate and lipid components were structurally characterized using 1D 1H and 13C and 2D NMR spectroscopy, complemented by mass spectrometry, as were the carbohydrate moieties formed on saponification. These were O-alpha-D-Galp-(1''-->6')-O-beta-D-Galp-(1'<-->1)-2, 3-diacyl-D-glycerol (2) and two others not previously found in lichens, O-beta-D-Galp-(1'<-->1)-2,3-diacyl-D-glycerol (1) and O-alpha-D-Galp-(1'''-->6'')-O-alpha-D-Galp-(1' '-->6')-O-beta-D-Galp-(1'<-->1)-2,3-diacyl-D-glycerol (3). Each was saponified to give the free carbohydrates and its fatty acid methyl esters. The most abundant fatty acid esters in 1-3 was palmitic C16:0, but there was a wide variation of ester composition. Others present were C8:0 and C14:0 in 1, C14:0, C15:0, C17:0, C18:0, C18:1 (oleic), C18:2 (linoleic), C22:0, and C24:0 in 2, and C8:0, C14:0, C18:0, C18:1 (oleic), C18:2 (linoleic), and C18:3 (linolenic) in 3. As in ascolichens, the glycolipids appear to arise from the phycobiont.

The most active polysaccharides which show anti-tumoral activity are (1-->3)-beta-D-glucans, branched or not at O-6. Since these structures are sometimes poorly soluble in aqueous media, alpha-D-glucans and their chemical derivatives, which are more soluble, were also studied. The present object is to observe morphological alterations in HeLa cells caused by two different polysaccharides obtained from the lichen Ramalina celastri, which are (1-->3),(1-->4)-linked alpha-D-glucan and its sulphated derivative. The cells were incubated in Eagle's medium in the absence or presence of each polysaccharide and routinely processed and analysed by light and electron microscopy. Even though the alpha-D-glucan altered the cellular volume, cytoplasmic densities, and mitosis, the resulting monolayer was similar to the control. TEM analysis showed cytoplasmic blebbing and the presence of an amorphous electron-dense material free in the cytoplasm and interior membranes. The enhanced injury caused by the sulphated derivative was apparent, altering cell adhesion and causing cell aggregation. Nuclear modifications such as fragmentation and condensation of chromatin under the nuclear envelope, which showed to be convoluted, suggested the occurrence of cell death by apoptosis.

Extraction of Evernia prunastri with hot aqueous alkali solubilized heteropolysaccharide-containing material which was purified via Fehling precipitation. Further workup of this polysaccharide with Cetavlon gave two fractions having related but different structures. Each structure consisted of a 1-->6-linked alpha-D-Man p main chain partially monosubstituted at O-2 with side chains of alpha-D-Gal p and partially disubstituted at O-2 and O-4 with alpha-D-Gal p and beta-D-Gal p, respectively. The fractions differed in that one contained much more uronic acid than the other, with corresponding predominance of side chains containing alpha-D-Glc pA-(1-->3)-D-Glc p, alpha-D-Gal p-(1-->2)-D-Glc p, and beta-D-Gal f units.

We report for the first time the detection of glycolipids in a lichen. Three glycolipids were extracted from Ramalina celastri and their carbohydrates were determined. The main component was O-alpha-D-galactopyranosyl-(1-->6)-O-beta-D-galactopyranosyl-(1-->1)-D- glyceritol, esterified with long-chain fatty acids, some of which were unsaturated.

The lichen Parmotrema cetratum contains traces of the unusual threitol and unexpected volemitol, along with galactose (2%). Present is a complex containing a lightly branched beta-glucan containing (1-->3) and (1-->4)-linkages in a 25:47 molar ratio chemically linked to a galactomannan with structural features common in other lichens. A glucogalactomannan with a small proportion of Glc rho side chains was also characterized.

Three aldoses, six alditols, eight oligosaccharides, three polysaccharides and a glycopeptide were found in a Sticta sp. The most interesting of these were gentiobiose, -triose and -tetraose, O-alpha-D-Galp-(1-->6)-O-beta-D-Galp-(1-->1)-D-glyceritol released on alkaline treatment, and a polysaccharide with predominant (1-->4)-linked beta-D-Xylp units. Present were a galactoglucomannan, a polysaccharide, possibly a mixture, containing beta-D-Galf, and alpha-L-Araf units and a glycopeptide with alpha- and beta-D-Galf, Galp, Glcp and Manp units, having a core with successive (1-->2)-linked alpha-D-Manp residues substituted at O-3 with those of alpha-D-Galf. After four years storage of the lichen, the contents of the principal polyols, ribitol (0.86%), arabinitol (0.99%) and mannitol (2.50%) fell to practically zero, with the appearance of threitol (0.03%), xylitol (0.01%) and myo-inositol (0.03%). Also, the protein content fell from 34 to 18%. The most abundant amino acids were valine (10.5% of total) in fresh lichen and threonine (14.6%) in stored lichen.

Mannose-containing polysaccharides of 18 lichen species were prepared via successive alkaline extraction, precipitation with Fehling solution and fractional precipitation with Cetavlon. Products from Fehling and Cetavlon precipitation, the latter at pH 8.5 in the presence of borax, were structurally similar, except with those of Usnea sp., U. meridionalis, Parmotrema araucaria and Evernia prunastri, which were mixtures and initially provided precipitates at pH 7 due to the presence of carboxyl groups. With one exception, glucosyl units were detected in all preparations, but possibly arose from glucan contaminants of the galactomannans. Tornabenia intricata, however, did not contain galactose, and a glucomannan was isolated. It consisted of two components with M(r)s of ca 0.85 x 10(5) and ca 1.1 x 10(5) and whose 13C NMR spectra were identical. The overall preparation contained a (1-->6)-linked alpha-D-Manp main-chain substituted at 0-2 mainly with side chains of alpha-D-Manp with smaller amounts of alpha-D-Glcp, alpha-D-Glcp-(1-->2)-[alpha-D-Manp-(1-->4)]-alpha-D-Manp, and possibly alpha-D-Manp-(1-->2)-[alpha-D-Manp-(1-->4)]-alpha-D-Manp+ ++.

Abstract: The three main polysaccharides from the lichenized fungus Umbilicaria mammulata were isolated and characterized. Their structures were determined using GC-MS of derived alditol acetates, GC-MS-methylation analysis and 13C NMR spectroscopy. Two of them were (1→3)-and (1→6)-linked β-glucans, namely laminaran and pustulan, respectively. The other was a galactofuranomannan, which was analyzed as well as a galactose-free polysaccharide formed on partial hydrolysis. The former consisted of a main chain of (1→6)-linked α-mannopyranosyl residues, part of them being substituted at O-2, O-4, and O-2,4 by complex, branched side chains containing α-mannopyranosyl and β-galactofuranosyl units. This heteropolysaccharide is related to those of other Umbilicariaceae, and its chemical characterization presents a useful tool for the systematics of lichenized fungi. [Copyright &y& Elsevier]

A galactomannan was isolated from the cyanolichen Leptogium azureum via successive alkaline extraction and precipitation with Fehling solution. The structure of the polysaccharide was investigated using NMR spectroscopy, methylation analysis, Smith degradation, and HPSEC-MALLS. As galactomannans from other lichens species, the polymer obtained presents a (1→6)-linked main chain of α-mannopyranose, substituted preferentially at O-2 by α-Manp or β-Galp non-reducing ends. As observed in previous investigations, the C-1 region of the 13C-NMR of these heteropolysaccharides are typical of some lichens species, and can be used as fingerprints in chemotaxonomy. However, in despite of the general structure in common, the substitution level of this structure and their content of mannose is higher than of the others galactomannans obtained of lichenized fungi contained the green alga of the genus Trebouxia. [Copyright &y& Elsevier]