Structural characterization of a polysaccharide and a beta-glucan isolated from the edible mushroom Flammulina velutipes

Two polysaccharides were isolated from the basidiomycete Flammulina velutipes, via successive hot extraction with water, 2% and 25% aq. KOH, and then submitted to freeze-drying. The precipitate formed by repeated freeze-thawing from the 2% aq. KOH extraction PK2 was analyzed by determination of its monosaccharide composition, as well as by methylation analyses using GC-MS, mono- ((13)C, (1)H NMR) and bidimensional ((1)H (obs.), (13)C HMQC) spectroscopy, and controlled Smith degradations. It was established to be a branched beta-glucan, with a main chain of (1-->3)-linked-Glcp residues, substituted at O-6 by single-unit beta-Glcp side chains. The precipitate formed by repeated freeze-thawing from the 25% KOH extraction PK25 contained Xyl, Man, and Glc and was heterogeneous by HSPEC and extraction with DMSO gave a soluble xylomannan (XM). It was homogeneous with a molar mass 30.8 x 10(4)g/mol (dn/dc=0.186). Using the above chemical analyses, it was a xylomannan with Man and Xyl in a 3:2 molar ratio. Its main chain consisted of (1-->3)-linked alpha-Manp units, mainly substituted at O-4 by beta-Xylp units or with some beta-Xylp-(1-->3)-beta-Xylp groups.     

A fungus-type beta-galactofuranan in the cultivated Trebouxia photobiont of the lichen Ramalina gracilis

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.     

Comparative studies of the polysaccharides isolated from lichenized fungi of the genus Cladonia: significance as chemotypes

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.     

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.     

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.     

A gel-forming beta-glucan isolated from the fruit bodies of the edible mushroom Pleurotus florida

Glucans of basidiomycetes are considered to be an important class of polysaccharides, as they can act as biological response modifiers. We now isolate a gel-forming, water-soluble beta-glucan, with a molecular mass of 1.2 x 10(6)g/mol (HPSEC), from the fruit bodies of the edible mushroom Pleurotus florida, via alkaline extraction, followed by fractionation by freeze-thawing. Structural assignments were carried out using mono- and bi-dimensional nuclear magnetic resonance spectroscopy, monosaccharide composition, methylation analyses, and a controlled Smith degradation. It was a branched beta-glucan, with a main chain of (1-->3)-linked-Glcp residues, substituted at O-6 by single-unit Glcp side chains, on average to every fourth residue of the backbone.     

Structural characterization of the cell wall D-glucans isolated from the mycelium of Botryosphaeria rhodina MAMB-05

Three D-glucans were isolated from the mycelium of the fungus Botryosphaeria rhodina MAMB-05 by sequential extraction with hot-water and hot aqueous KOH (2% w/v) followed by ethanol precipitation. Following their purification by gel permeation chromatography on Sepharose CL-4B, the structural characteristics of the D-glucans were determined by FT-IR and 13C NMR spectroscopy and, after methylation, by GC-MS. The hot-water extract produced a fraction designated Q1A that was a beta-(1-->6)-D-glucan with the following structure: [Formula: see text] The alkaline extract, when subjected to repeated freeze-thawing, yielded two fractions: K1P (insoluble) that comprised a beta-(1-->3)-D-glucan with beta-D-glucose branches at C-6 with the structure: [Formula: see text] and K1SA (soluble) consisting of a backbone chain of alpha-(1-->4)-linked D-glucopyranosyl residues substituted at O-6 with alpha-D-glucopyranosyl residues: [Formula: see text]     

The structure of the rough-type lipopolysaccharide from Shewanella oneidensis MR-1, containing 8-amino-8-deoxy-Kdo and an open-chain form of 2-acetamido-2-deoxy-D-galactose

The LPS from Shewanella oneidensis strain MR-1 was analysed by chemical methods and by NMR spectroscopy and mass spectrometry. The LPS contained no polysaccharide O-chain, and its carbohydrate backbone had the following structure: (1S)-GalNAco-(1-->4,6)-alpha-Gal-(1-->6)-alpha-Gal-(1-->3)-alpha-Gal-(1-P-3)-alpha-DDHep-(1-->5)-alpha-8-aminoKdo4R-(2-->6)-beta-GlcN4P-(1-->6)-alpha-GlcN1P, where R is P or EtNPP. There are several novel aspects to this LPS. It contains a novel linking unit between the core polysaccharide and lipid A moieties, namely 8-amino-3,8-dideoxy-D-manno-octulosonic acid (8-aminoKdo) and a residue of 2-acetamido-2-deoxy-D-galactose (N-acetylgalactosamine, GalNAco) in an open-chain form, linked as cyclic acetal to O-4 and O-6 of D-galactopyranose. The structure contains a phosphodiester linkage between the alpha-D-galactopyranose and D-glycero-D-manno-heptose (DDHep) residues.     

Structure of a highly substituted beta-xylan of the gum exudate of the palm Livistona chinensis (Chinese fan)

Structural features of the acidic, highly substituted glycanoxylan (LCP; 87% yield) from the gum exudate of the palm, Livistona chinensis, family Arecaceae, were determined. It had [alpha]D -30 degrees, Mw 1.9x10(5) and a polydispersity ratio Mw/Mn of approximately 1.0. Acid hydrolysis gave rise to Rha, Fuc, Ara, Xyl, and Gal, in a 1:6:46:44:3 molar ratio, and 12% of uronic acid was present. LCP had a highly branched structure with side-chains containing nonreducing end-units (% values are approximate) of Araf (15%), Fucp (4%), Xylp (7%), GlcpA, and 4-Me-GlcpA, and internal 2-O- (5%) and 3-O-substituted Araf (8%), and 2-O-substituted Xylp (14%) units. The (1-->4)-linked beta-Xylp main-chain units of LCP were substituted at O-3 (4%), O-2 (17%), and O-2,3 (16%). Partial acid hydrolysis gave 4-Me-alpha-GlcpA-(1-->2)-[beta-Xylp-(1-->4)](0-2)-Xyl, identified by showing that the uronic acids were single-unit side-chain substituents on O-2. Milder hydrolysis conditions removed from O-3 other side-chains containing Fucp and Araf nonreducing end-units and internal Arap, and 2-O- and 3-O-substituted Araf units. Carboxyl-reduced LCP contained 4-O-methylglucose and glucose in a 3.2:1 molar ratio, arising from GlcpA and 4-OMe-GlcpA nonreducing end-units, respectively. The gum contained small amounts of free alpha-Fucp-(1-->2)-Ara, which corresponds to structures in the polysaccharide. Free myo- and D- or L-chiro-inositol were present in a 9:1 ratio.     

Cassia grandis Linn. f. seed galactomannan: structural and crystallographical studies

Cassia grandis is a small or medium sized tree, found in abundance throughout India. The seeds contain about 50% endosperm gum and possess the characteristics of becoming a potential source of seed gum. The purified polysaccharide has been characterized as a pure galactomannan having a mannose-galactose ratio of 3.15; molecular weight (Mw) 80,200; polydispersity (Mw/Mn), 1.35 and intrinsic viscosity [eta], 848 mL/g. Methylation, periodate oxidation, Smith degradation and 13C NMR studies confirm that the polysaccharide has the basic structure of legume galactomannans consisting of a beta-(1-->4)-linked main mannan backbone to which galactose units are attached at O-6. The orthorhombic lattice constants of the hydrated gum are as follows: a=9.00, b=24.81, c=10.30 A. The crystallographic data establish that the probable space group symmetry of the unit cell is P2(1)2(1)2. The results are in contradiction to earlier reports (Indian J. Chem. 16B (1978) 966; J. Indian Chem. Soc. 55 (1978) 1216) in which a non-galactomannan polysaccharide structure has been assigned having a main chain of (1-->4)-linked galactose and mannose units in the molar ratio 6:3, where 50% of the galactose units branched with two galactose and one mannose through 1-->3 linkage.     

Phase-variation of the truncated lipo-oligosaccharide of Neisseria meningitidis NMB phosphoglucomutase isogenic mutant NMB-R6

The detection of antibodies specific to meningococcal lipo-oligosaccharides (LOSs; outer-core-->inner-core-->lipid A) in sera of patients convalescent from meningococcal infection suggests the potential use of LOS as a vaccine to combat pathogenic Neisseria spp. Removal of the outer-core region, which expresses glycans homologous to human blood-group antigens, is a required first-step in order to avoid undesirable immunological reactions following vaccination. To this end, we describe here the structural makeup of the LOS produced by serogroup B N. meningitidis NMB isogenic phosphoglucomutase (Pgm) mutant (NMB-R6). The dominant LOS types produced by NMB-R6 expressed a deep-truncated inner-core region, GlcNAc-(1-->2)-LDHepII-(1-->3)-LDHepI-(1-->5)-[Kdo-2-->4]-Kdo-->lipid A, with one PEA unit attached at either O-6 or O-7 of LDHepII, or with two simultaneously PEA moieties attached at O-3 and O-6 or O-3 and O-7 of the same unit. Unexpectedly, this mutation did not completely deactivate the production of Glc, as some LOS molecules were observed to carry Glc at O-4 of LDHepI and at O-3 of LDHepII. A glycoconjugate vaccine comprised of NMB-R6 LOSs is currently being evaluated in our laboratory.     

Isolation and characterization of a mannoglucan from edible Cordyceps sinensis mycelium

Cordyceps sinensis is a well known tonic food or invigorant with broad-spectrum medicinal properties that is widely used in the People's Republic of China. A neutral mannoglucan 1 with a molar mass of approximately 7.7x10(3) Da was obtained from the 0.05 M acetate buffer extract of C. sinensis mycelium. It had [alpha](D)(20)+126 (c 0.2, H(2)O) and consisted of Man and Glc units in the molar ratio of 1:9. A combination of chemical analysis and NMR and IR spectroscopy together with digestion with alpha-D-amylase showed 1 to have a alpha-D-glucan backbone with (1-->4)- and (1-->3)-linkages, and the side chains of alpha-D-(1-->6)-Manp were attached to the backbone via O-6 of alpha-(1-->3)-Glcp residues. Compound 1 showed weak cytotoxicity activity against SPC-I (IC(50)=63 microg/mL) cancer line, and no obvious cytotoxicity activities against BCAP37 (IC(50)>100 microg/mL) and SW480 (IC(50)>100 microg/mL) cancer lines.     

Structural features of a pectic arabinogalactan with immunological activity from the leaves of Diospyros kaki

A water-soluble acidic heteroglycan, DL-3Bb, isolated from the leaves of Diospyros kaki, had [alpha](D)(20) -19.9 degrees (c 0.30, water), and contained rhamnose, arabinose, xylose, galactose and galacturonic acid in the molar ratio of 1.0:4.5:0.7:1.5:1.0. About 44% of the galacturonic acid existed as its methyl ester, and O-acetyl groups (approx 5.7%) were also identified. Its molecular weight was determined to be 9.0x10(5) Da by high-performance gel-permeation chromatography. Its structural features were elucidated by a combination of methylation analysis, periodate oxidation, two steps of partial acid hydrolysis, and 1H and 13C NMR spectroscopy and ESI mass spectrometry. The data obtained indicated that DL-3Bb possessed a backbone of a disaccharide of [-->4)-alpha-GalAp-(1-->2)-alpha-Rhap-(1-->], with approx 58.7% substitution at O-4 of the rhamnopyranosyl residues by beta-(1-->4)-linked xylopyranosyl residues, and by beta-(1-->3) and beta-(1-->6)-linked galactopyranosyl (galactan) residues. The side chains were further substituted by arabinofuranosyl residues at O-2 by beta-(1-->4)-linked xylopyranosyl residues and at O-3 by beta-(1-->6)-linked galactopyranosyl residues. Preliminary tests in vitro revealed that it could stimulate LPS-induced B lymphocyte proliferation, but not for ConA-induced T lymphocyte proliferation. It was proposed that the acid-labile arabinofuranosyl residues in the side chains would not be needed for the expression of the enhancement of the immunological activity, and that the presence of GalAp in the backbone has an important, but not crucial effect on the expression of the activity.     

Structural investigation of lipopolysaccharides from nontypeable Haemophilus influenzae: investigation of inner-core phosphoethanolamine addition in NTHi strain 981

LPS of NTHi comprises a conserved tri-l-glycero-D-manno-heptosyl inner-core moiety (l-alpha-D-Hepp-(1-->2)-[PEtn-->6]-l-alpha-D-Hepp-(1-->3)-[beta-D-Glcp-(1-->4)]-l-alpha-D-Hepp-(1-->5)-alpha-Kdop) in which addition of PEtn to the central heptose (HepII) in strain Rd is controlled by the gene lpt6. It was recently shown that NTHi strain 981 contains an additional PEtn linked to O-3 of the terminal heptose of the inner-core moiety (HepIII). In order to establish whether lpt6 is also involved in adding PEtn to HepIII, lpt6 in strain 981 was inactivated. The structure of the LPS of the resulting mutant strain 98llpt6 was investigated by MS and NMR techniques by which it was confirmed that the lpt6 gene product is responsible for addition of PEtn to O-6 of HepII in strain 981. However, it is not responsible for adding PEtn to O-3 of HepIII since the 981lpt6 mutant still had full substitution with PEtn at HepIII.     

The structure of the carbohydrate backbone of the rough type lipopolysaccharides from Proteus penneri strains 12, 13, 37 and 44

The following structure of the lipid A-core backbone of the rough type lipopolysaccharides (LPS) from Proteus penneri strains 12, 13, 37, and 44 was determined using NMR and mass spectroscopy and chemical analysis of the oligosaccharides obtained by mild-acid hydrolysis, alkaline O,N-deacylation, O-deacylation with hydrazine, and deamination of the LPSs:where K=H, R=PEtN, R(1)=alpha-Hep-(1-->2)-alpha-DDHep, and R(2)=alpha-GalN (strains 12 and 13) or beta-GlcNAc-(1-->4)-alpha-GlcN (strains 37 and 44). LPS from each strain contained several structural variants. LPS from strain 12 contained a variant with R(1)=alpha-DDHep, whereas LPS from strains 13, 37, and 44 contained structures with K=amide of beta-GalA with putrescine or spermidine. The phosphate group at O-1 of the alpha-GlcN residue in the lipid part was partially substituted with Ara4N.     

Furostanol saponins and quercetin glycosides from the leaves of Helleborus viridis L

Phytochemical analysis of the polar extracts of the leaves of Helleborus viridis (Ranunculaceae) resulted in the isolation of two new furostanol saponins (25R)-26-[(alpha-L-rhamnopyranosyl)oxy]-22alpha-methoxyfurost-5-en-3beta-yl O-beta-D-glucopyranosyl-(1-->3)-O-[6-acetyl-beta-D-glucopyranosyl-(1-->3)]-O-beta-D-glucopyranoside (1) and (25R)-26-[(alpha-L-rhamnopyranosyl)oxy]-22alpha-methoxyfurost-5-en-3beta-yl O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranoside (2) and three new quercetin glycosides, quercetin 3-O-(2-E-caffeoyl)-alpha-L-arabinopyranosyl-(1-->2)-beta-D-galactopyranoside-7-O-beta-d-glucopyranoside (3), quercetin 3-O-(2-E-caffeoyl)-alpha-L-arabinopyranosyl-(1-->2)-beta-D-galactopyranoside (4), and quercetin 3-O-alpha-L-arabinopyranosyl-(1-->2)-beta-D-galactopyranoside (5). The structures of the new compounds were determined by spectroscopic analysis, including 2D NMR data and mass spectrometry.     

Structural determination of the O-antigenic polysaccharide from the Shiga toxin-producing Escherichia coli O171

The structure of the O-antigenic part of the lipopolysaccharide (LPS) obtained from the verotoxin-producing Escherichia coli O171 has been determined. (1)H and (13)C NMR spectroscopy techniques in combination with component analysis were used to elucidate the O-antigen structure of O-deacylated LPS. Subsequent NMR analysis of the native LPS revealed acetylation at O-7/O-9 of the sialic acid residue. The sequence of sugars was determined by inter-residue correlations in (1)H,(1)H-NOESY and (1)H,(13)C-heteronuclear multiple-bond correlation spectra. The O-antigen is composed of pentasaccharide repeating units with one equivalent of O-acetyl groups distributed over two positions: -->4)-alpha-Neu5Ac7,9Ac-(2-->6)-beta-D-Galp-(1-->6)-beta-DGlcp-->(1-->3)-beta-D-Galp-(1-->3)-beta-D-GalpNAc-(1--> Based on biosynthetic considerations, this should also be the biological repeating unit.     

Linear beta-mannose-containing polysaccharide,beta-xylan,and amylose from the cultured photobiont Trebouxia sp. of the ascolichen Ramalina celastri

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.     

Characterization of an acetylated heteroxylan from Eucalyptus globulus Labill

A heteroxylan was isolated from Eucalyptus globulus wood by extraction of peracetic acid delignified holocellulose with dimethyl sulfoxide. Besides (1-->4)-linked beta-D-xylopyranosyl units of the backbone and short side chains of terminal (1-->2)-linked 4-O-methyl-alpha-D-glucuronosyl residues (MeGlcA) in a 1:10 molar ratio, this hemicellulose contained galactosyl and glucosyl units attached at O-2 of MeGlcA originating from rhamnoarabinogalactan and glucan backbones, respectively. About 30% of MeGlcA units were branched at O-2. The O-acetyl-(4-O-methylglucurono)xylan showed an acetylation degree of 0.61, as determined by 1H NMR spectroscopy, and a weight-average molecular weight (M(w)) of about 36 kDa (P=1.05) as revealed from size-exclusion chromatography (SEC) analysis. About half of the beta-D-xylopyranosyl units of the backbone were found as acetylated moieties at O-3 (34 mol%), O-2 (15 mol%) or O-2,3 (6 mol%). Practically, all beta-D-xylopyranosyl units linked at O-2 with MeGlcA residues were 3-O-acetylated (10 mol%).     

Structural features of pectic polysaccharides from the skin of Opuntia ficus-indica prickly pear fruits

After removal of the mucilage with water at room temperature, pectic polysaccharides were solubilized from Opuntia ficus-indica fruit skin, by sequential extraction with water at 60 degrees C (WSP) and EDTA solution at 60 degrees C (CSP). Polysaccharides with neutral sugar content of 0.48 and 0.36 mol/mol galacturonic acid residue were obtained, respectively, in the WSP and CSP extracts. These pectic polysaccharides were de-esterified and fractionated by anion-exchange chromatography, yielding for each extract five fractions, which were thereafter purified by size-exclusion chromatography. Two of these purified fractions were characterized by sugar analysis combined with methylation and reduction-methylation analysis. The study was then supported by (1)H and (13)C NMR spectroscopy. The results showed that the water-soluble fraction WSP3 and the EDTA soluble fraction CSP3, consisted of a disaccharide repeating unit -->2)-alpha-l-Rhap-(1-->4)-alpha-d-GalpA-(1--> backbone, with side chains attached to O-4 of the rhamnosyl residues. The side chains contained highly branched alpha-(1-->5)-linked arabinan and short linear beta-(1-->4)-linked galactan.