Structural Features of (Glucurono)Arabinoxylans Extracted from Wheat Bran by Barium Hydroxide

A (glucurono)arabinoxylan extract obtained from water-unextractable cell wall material of industrial wheat bran was fractionated by means of anion-exchange chromatography and graded ethanol precipitation. Methylation analysis and enzymic degradability of various fractions were used to elucidate their structures. Approximately one third of the extracted (glucurono)arabinoxylan was very lowly substituted (Ara/Xyl≈0·2). Substitution occurred predominantly by arabinose at theO-3 position of xylose residues. Enzymic degradation showed a random distribution of the substituents, which are probably interrupted by stretches of 6 or more contiguous unsubstituted xylose residues. More than half the extracted (glucurono)arabinoxylan was highly substituted (Ara/Xyl≥1). The complexity of the structure was shown by poor enzymic degradability and the presence of considerable amounts of branched arabinose and terminal xylose. Substitution of xylose occurred not only throughO-3 mono-,O-2 andO-3 disubstitution by terminal arabinose andO-2 monosubstitution by (4-O-methyl)glucuronic acid, but also through dimeric arabinose, xylose and possibly galactose containing branches as well as through 2,3-linked arabinose. The remainder of the extracted (glucurono)arabinoxylan (15%) was either intermediately substituted (Ara/Xyl≈0·5) or very highly substituted (Ara-Xyl≈1·2) and associated with protein and lignin.     

Triterpenoid saponins from corms of Crocus sativus: Localization, extraction and characterization

A mixture of highly glycosilated triterpenoid saponins (CS5) isolated from the corm of Crocus sativus or saffron showed cytotoxic activity against HeLa tumoral cells. The main reverse phase HPLC fraction of this mixture (CS5-1) contains two new oleanane-type saponins, denominated Azafrine 1 (1) and Azafrine 2 (2). The bidesmosidic saponins were respectively characterized as (1) 3-O-β-d-glucopyranosiduronic acid echinocystic acid 28-O-β-D-galactopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 4)]-α-d-rhamnopyranosyl-(1 → 2)-[4-O-di-α-L-rhamnopyranosyl-3,16-dihydroxy-10-oxo-hexadecanoyl]-α-D-fucopyranoside and (2) 3-O-β-D-galactopyranosiduronic acid echinocystic acid 28-O-β-D-galactopyranosyl-(1 → 2)-α-L-arabinopyranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 4)]-α-L-rhamnopyranosyl-(1 → 2)-[4-O-di-α-L-rhamnopyranosyl-3,16-dihydroxy-10-oxo-hexadecanoyl]-β-D-fucopyranoside. The surfactant properties of saponins, probably involved in the cytotoxic activity of CS5 and their exclusive localization in the external part or the corm, indicate their possible role as phytoprotectans. The similarity of their structural compositions to that of other triterpenoid saponins which are of special use in the pharmaceutical industry suggest a new application for C. sativus crops through the exploitation of corm for saponin extraction.     

Pretreatment of partially delignified hybrid poplar for biofuels production: Characterization of organosolv hemicelluloses

In this study, extraction of hemicelluloses from the carbohydrate-enriched residues was successfully carried out with organic solvent and the residue was used for bio-based energy production. The chemical composition and physico-chemical properties of six hemicelluloses released were elucidated by a combination of sugar analysis, molecular determination, Fourier transform infrared, and ¹H, ¹³C and 2D-HSQC NMR spectroscopy. The results showed that the successful treatments resulted in a fractionation of the native hemicelluloses. The sugar analysis indicated that xylose (47.14-56.91%) was found to be the major sugar components and small amounts of glucose (14.1-19.06%) and mannose (12.41-18.09%) were also observed in these hemicellulosic fractions. Further studies by NMR spectroscopy exhibited that the acetylated hemicellulosic fraction had a main structure of (1 → 4)-linked β-d-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid as a side chain and a minor structure of linear β-(1 → 4)-linked glucomannans. Furthermore, these hemicelluloses possessed a low substituted degree which was beneficial for enzymatic saccharification.     

Amino Acid-Coupled Bromophenols and a Sulfated Dimethylsulfonium Lanosol from the Red Alga Vertebrata lanosa

Vertebrata lanosa is a red alga that can commonly be found along the shores of Europe and North America. Its composition of bromophenols has been studied intensely. The aim of the current study was therefore to further investigate the phytochemistry of this alga, focusing more on the polar components. In total, 23 substances were isolated, including lanosol-4,7-disulfate (4) and the new compounds 3,5-dibromotyrosine (12), 3-bromo-5-sulfodihydroxyphenylalanine (13), 3-bromo-6-lanosyl dihydroxyphenylalanine (14), 3-(6′-lanosyl lanosyl) tyrosine (15) and 5-sulfovertebratol (16). In addition, 4-sulfo-7-dimethylsulfonium lanosol (7) was identified. While, in general, the dimethylsulfonium moiety is widespread in algae, its appearance in bromophenol is unique. Moreover, the major glycerogalactolipids, including the new ((5Z,8Z,11Z,14Z,17Z)-eicosapentaenoic acid 3′-[(6′’-O-α-galactopyranosyl-β-D-galactopyranosyl)]-1-glycerol ester (23), and mycosporine-like amino acids, porphyra-334 (17), aplysiapalythine A (18) and palythine (19), were identified.     

Isolation and Structure Elucidation of GM4-Type Gangliosides from the Okinawan Starfish Protoreaster nodosus

Three new ganglioside molecular species, termed PNG-1, PNG-2A, and PNG-2B were isolated from pyloric caeca of the starfish Protoreaster nodosus. Their structures were elucidated using a combination of spectroscopic and chemical methods, and characterized as 1-O-[8-O-methyl-N-acetyl-α-neuraminosyl-(2→3)-β-galactopyranosyl]-ceramide for PNG-1, 1-O-[β-galactofuranosyl-(1→3)-α-galactopyranosyl-(1→4)-8-O-methyl-N-acetyl-α-neuraminosyl-(2→3)-β-galactopyranosyl]-ceramide for PNG-2A, and 1-O-[β-galactofuranosyl-(1→3)-α-galactopyranosyl-(1→9)-N-acetyl-α-neuraminosyl-(2→3)-β-galactopyranosyl]-ceramide for PNG-2B. PNG-2A and PNG-2B represent the first GM4 elongation products in nature.     

1-O-Alkylglycerol Ethers from the Marine Sponge Guitarra abbotti and Their Cytotoxic Activity

The cytotoxicity-bioassay-guided fractionation of the ethanol extract from the marine sponge Guitarra abbotti, whose 1-O-alkyl-sn-glycerol ethers (AGEs) have not been investigated so far, led to the isolation of a complex lipid fraction containing, along with previously known compounds, six new lipids of the AGE type. The composition of the AGE fraction as well as the structures of 6 new and 22 previously known compounds were established using ¹H and ¹³C NMR, GC/MS, and chemical conversion methods. The new AGEs were identified as: 1-O-(Z-docos-15-enyl)-sn-glycerol (1), 1-O-(Z-docos-17-enyl)-sn-glycerol (2), 1-O-(Z-tricos-15-enyl)-sn-glycerol (3), 1-O-(Z-tricos-16-enyl)-sn-glycerol (4), 1-O-(Z-tricos-17-enyl)-sn-glycerol (5), and 1-O-(Z-tetracos-15-enyl)-sn-glycerol (6). The isolated AGEs show weak cytotoxic activity in THP-1, HL-60, HeLa, DLD-1, SNU C4, SK-MEL-28, and MDA-MB-231 human cancer cells. A further cytotoxicity analysis in JB6 P⁺ Cl41 cells bearing mutated MAP kinase genes revealed that ERK2 and JNK1 play a cytoprotective role in the cellular response to the AGE-induced cytotoxic effects.     

Structural Characteristics and Anticancer Activity of Fucoidan from the Brown Alga Sargassum mcclurei

Three different fucoidan fractions were isolated and purified from the brown alga, Sargassum mcclurei. The SmF1 and SmF2 fucoidans are sulfated heteropolysaccharides that contain fucose, galactose, mannose, xylose and glucose. The SmF3 fucoidan is highly sulfated (35%) galactofucan, and the main chain of the polysaccharide contains a →3)-α-l-Fucp(2,4SO₃⁻)-(1→3)-α-l-Fucp(2,4SO₃⁻)-(1→ motif with 1,4-linked 3-sulfated α-l-Fucp inserts and 6-linked galactose on reducing end. Possible branching points include the 1,2,6- or 1,3,6-linked galactose and/or 1,3,4-linked fucose residues that could be glycosylated with terminal β-d-Galp residues or chains of alternating sulfated 1,3-linked α-l-Fucp and 1,4-linked β-d-Galp residues, which have been identified in galactofucans for the first time. Both α-l-Fucp and β-d-Galp residues are sulfated at C-2 and/or C-4 (and some C-6 of β-d-Galp) and potentially the C-3 of terminal β-d-Galp, 1,4-linked β-d-Galp and 1,4-linked α-l-Fucp residues. All fucoidans fractions were less cytotoxic and displayed colony formation inhibition in colon cancer DLD-1 cells. Therefore, these fucoidan fractions are potential antitumor agents.     

Fractionation and characterisation of arabinoxylans from brewers' spent grain and wheat bran

Two agro-industrial co-products, brewers' spent grain and wheat bran, were fractionated by sequentially extracting with alkali of increasing strength. Over 60% of the brewers' grain biomass was solubilised by these treatments, compared with only 25% for wheat bran. The carbohydrate and phenolic composition of the solubilised fractions were determined, highlighting two compositionally different sets of fractions. In both co-products arabinoxylan was the main polysaccharide released. The degree of arabinose substitution of the extracted arabinoxylan diminished as the alkali strength increased. Insoluble residues contained both cellulose and non-cellulosic polysaccharides. In spent grain, the composition of the arabinoxylan in the residue was similar to that of the starting material. In wheat bran, the residual xylan was very highly substituted with arabinose. Both ferulic acid and three forms of diferulic acid (5,5′, 8-O-4′ and 8,5′) were present in the solubilised material, even after treatment with 4 M KOH. Esterified acetate was also present on polymers solubilised with KOH at concentrations up to 1 M. The more soluble fractions of spent grain represented a heterogeneous aggregation of feruloylated arabinoxylans with a broad molecular mass range, but the fractions extracted with stronger base were separated into low molecular weight moieties, presumably due to cleavage of covalent cross-links. Potential food and non-food uses for the isolated fractions from the cereal co-products are discussed.     

Secondary Metabolites of a Mangrove Endophytic Fungus Aspergillus terreus (No. GX7-3B) from the South China Sea

The mangrove endophytic fungus Aspergillus terreus (No. GX7-3B) was cultivated in potato dextrose liquid medium, and one rare thiophene compound (1), together with anhydrojavanicin (2), 8-O-methylbostrycoidin (3), 8-O-methyljavanicin (4), botryosphaerone D (5), 6-ethyl-5-hydroxy-3,7-dimethoxynaphthoquinone (6), 3β,5α-dihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (7), 3β,5α,14α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (8), NGA0187 (9) and beauvericin (10), were isolated. Their structures were elucidated by analysis of spectroscopic data. This is the first report of a natural origin for compound 6. Moreover, compounds 3, 4, 5, 7, 8 and 10 were obtained from marine microorganism for the first time. In the bioactive assays in vitro, compounds 2, 3, 9 and 10 displayed remarkable inhibiting actions against α-acetylcholinesterase (AChE) with IC₅₀ values 2.01, 6.71, 1.89, and 3.09 μM, respectively. Furthermore, in the cytotoxicity assays, compounds 7 and 10 exhibited strong or moderate cytotoxic activities against MCF-7, A549, Hela and KB cell lines with IC₅₀ values 4.98 and 2.02 (MCF-7), 1.95 and 0.82 (A549), 0.68 and 1.14 (Hela), and 1.50 and 1.10 μM (KB), respectively; compound 8 had weak inhibitory activities against these tumor cell lines; compounds 1, 2, 3, 4, 5, 6 and 9 exhibited no inhibitory activities against them.     

Barley (1→3; 1→4)-β-glucan and arabinoxylan content are related to kernel hardness and water uptake

Harder kernels in barley are thought to be a factor affecting the modification of the endosperm during malting by restricting water and enzyme movement within the endosperm. The objective of this study was to investigate the relationship between kernel hardness, water uptake and the endosperm composition in barley. A range of barley samples from 2003 and 2004 crops were analyzed for kernel hardness by the Single Kernel Characterization System, water uptake during steeping and chemical composition of the endosperm including (1→3; 1→4)-β-glucan, arabinoxylan and total protein. Both (1→3; 1→4)-β-glucan and arabinoxylan content of the endosperm were correlated significantly with kernel hardness in barley samples from both 2003 (r=0.873 and 0.601, respectively, p<0.01) and 2004 seasons (r=0.764 and 0.501, respectively, p<0.01). Hardness of the kernel was highly correlated with its water uptake in both 2003 and 2004 samples (r=−0.853 and −0.752, respectively, p<0.01). β-Glucan content of the endosperm was also correlated significantly with the kernel water uptake for both years (2003: r=−0.752, p<0.01; 2004: r=−0.551, p<0.01). Arabinoxylan content of the endosperm was correlated significantly with the kernel water uptake for the 2003 barley but not for 2004 barley (2003: r=−0.523, p<0.01; 2004: r=−0.151, p>0.01). Protein content of the endosperm was not correlated with the kernel hardness in either year. These results demonstrate that endosperm cell wall components may have significant impact on kernel hardness as well as water uptake of barley.     

1-O-Sulfatobastadins-1 and -2 from Ianthella basta (Pallas). Antagonists of the RyR1-FKBP12 Ca2+ Channel

Two new sulfate monoesters of hemibastadins-1 and -2 were isolated from the marine sponge Ianthella basta (Pallas) from Guam. A third new compound was tentatively assigned the structure 34-O-sulfatobastadin-9. The 1-O-sulfatohemibastadins-1 and –2 were antagonists of the RyR1-FKBP12 Ca²⁺ channel under conditions where the known compound bastadin-5 exhibits potent agonism (EC₅₀ 2 μM).     

Three New Asperentin Derivatives from the Algicolous Fungus Aspergillus sp. F00785

Three new asperentin-type compounds, 6-O-α-d-ribosylasperentin (1) and 6-O-α-d-ribosyl-8-O-methylasperentin (2) and 5-hydroxyl-6-O-methylasperentin (3), along with asperentin (4) and its known analogues (5–9), were isolated from a halotolerant Aspergillus sp. strain {"type":"entrez-nucleotide","attrs":{"text":"F00785","term_id":"707638","term_text":"F00785"}}F00785, an endotrophic fungus from marine alga. Their structures were determined using extensive NMR and HRESIMS spectroscopic analysis, including the X-ray crystallographic data for the assignment of the absolute configurations of compound 9. Compound 4 exhibited highly potent inhibitory activity against crop pathogens, Colletotrichum gleosporioides Penz. and Colletotrichum gleosporioides (Penz.) Sacc.     

Structural characterization and isolation of lignin and hemicelluloses from barley straw

Structural characterization and isolation of lignin and hemicelluloses from crops are very important for industrial utilization. In this paper, the sequential treatments of barley straw using 90% dioxane, 80% acidic dioxane, 100% dimethyl sulfoxide, and 8% NaOH released total 93% of original lignin and 87% of original hemicelluloses. The extractions with acidic dioxane and dimethyl sulfoxide produced the original hemicelluloses and high-condensed lignin mainly from the middle lamella. FT-IR and NMR analyses show that the hemicelluloses of barley straw contain acidic arabinxylans as the major polysaccharides, which are substituted by α-l-arabinofuranose, 4-O-methyl-glucuronic acid, acetyl group (DS = 0.13), and xylose at O-3 and/or O-2 of xylan, and lignin contains β-O-4′ as a predominant interunit linkage with high amounts of β-5′ and β-1′. The guaiacyl and syringyl units are more etherified, and the proportion of erythro-β-O-4′ is slightly higher than that of threo-β-O-4′ in the lignin of barley straw.     

Effects of Lissoclibadins and Lissoclinotoxins,Isolated from a Tropical Ascidian Lissoclinum cf. badium,on IL-8 production in a PMA-stimulated Promyelocytic Leukemia Cell Line

The effects of seven compounds 1–7, isolated from a tropical ascidian Lissoclinum cf. badium, on IL-8 production in PMA-stimulated HL-60 cells were examined. Lissoclibadins 2 (2) and 3 (3) and lissoclinotoxin F (5) increased the IL-8 production in a dose-dependent manner. Compounds 2 and 5 are structural isomers possessing dimeric structures of trans and cis-orientations, respectively, and showed a very similar activity on the induction of IL-8 levels. Compound 3 and lissoclinotoxin E (4) are also structural isomers having dimeric trans and cis-structures, respectively, but 4 did not induce the IL-8 production. Lissoclibadin 1 (1, trimeric compound) and two monomeric compounds (6 and 7) did not increase the IL-8 level. Therefore, the differences in their structures remarkably affected the IL-8 production activity, the inhibition of cell proliferation, and the survival of HL-60 cells. Lissoclibadin 2 was the most interesting compound of the seven metabolites tested in this study.     

Secondary metabolites from an algicolous Aspergillus versicolor strain

Two new compounds, asperversin A (1) and 9ξ-O-2(2,3-dimethylbut-3-enyl)brevianamide Q (2), and nine known compounds, brevianamide K (3), brevianamide M (4), aversin (5), 6,8-di-O-methylnidurufin (6), 6,8-di-O-methylaverufin (7), 6-O-methylaverufin (8), 5α,8α-epidioxyergosta-6,22-dien-3β-ol (9), ergosta-7,22-diene-3β,5α,6β-triol (10), and 6β-methoxyergosta-7,22-diene-3β,5α-diol (11), were obtained from the culture of Aspergillus versicolor, an endophytic fungus isolated from the marine brown alga Sargassum thunbergii. The structures of these compounds were established by spectroscopic techniques. Compounds 4, 7 and 8 exhibited antibacterial activities against Escherichia coli and Staphyloccocus aureus, and 7 also showed lethality against brine shrimp (Artemia salina) with an LC₅₀ value of 0.5 μg/mL.     

Fucose-Rich Sulfated Polysaccharides from Two Vietnamese Sea Cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera: Structures and Anticoagulant Activity

Fucosylated chondroitin sulfates (FCSs) FCS-BA and FCS-HS, as well as fucan sulfates (FSs) FS-BA-AT and FS-HS-AT were isolated from the sea cucumbers Bohadschia argus and Holothuria (Theelothuria) spinifera, respectively. Purification of the polysaccharides was carried out by anion-exchange chromatography on DEAE-Sephacel column. Structural characterization of polysaccharides was performed in terms of monosaccharide and sulfate content, as well as using a series of non-destructive NMR spectroscopic methods. Both FCSs were shown to contain a chondroitin core [→3)-β-d-GalNAc-(1→4)-β-d-GlcA-(1→]_n bearing sulfated fucosyl branches at O-3 of every GlcA residue in the chain. These fucosyl residues were different in pattern of sulfation: FCS-BA contained Fuc2S4S, Fuc3S4S and Fuc4S at a ratio of 1:8:2, while FCS-HS contained these residues at a ratio of 2:2:1. Polysaccharides differed also in content of GalNAc4S6S and GalNAc4S units, the ratios being 14:1 for FCS-BA and 4:1 for FCS-HS. Both FCSs demonstrated significant anticoagulant activity in clotting time assay and potentiated inhibition of thrombin, but not of factor Xa. FS-BA-AT was shown to be a regular linear polymer of 4-linked α-L-fucopyranose 3-sulfate, the structure being confirmed by NMR spectra of desulfated polysaccharide. In spite of considerable sulfate content, FS-BA-AT was practically devoid of anticoagulant activity. FS-HS-AT cannot be purified completely from contamination of some FCS. Its structure was tentatively represented as a mixture of chains identical with FS-BA-AT and other chains built up of randomly sulfated alternating 4- and 3-linked α-L-fucopyranose residues.     

Ferulic Acid Dehydrodimers in Rye(Secale cereale L.)

Four ferulic acid dehydrodimers were isolated from rye bran and purified by preparative HPLC after alkaline hydrolysis. The identity of the compounds were confirmed by UV,¹H and¹³C-NMR and mass spectroscopy. The content of the four identified dimers corresponded to a total dimer concentration of 307 μg/g (dry matter) of the whole grain. The concentrations in the bran fraction were 10–20 times higher than in the starchy endosperm. The four dimers were in decreasing amounts: ((Z)- β -{4-[(E)-2-carboxyvinyl]-2-methoxyphenoxy}-4-hydroxy-3-methoxy-cinnamic acid (8-O-4′-DiFA);trans -5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxy-phenyl)-7-methoxy-2,3-dihydrobenzofuran-3-carboxylic acid (8-5′-DiFA benzofuran form), (E,E)-4,4′-dihydroxy-5,5′-dimethoxy-3,3′-bicinnamic acid (5-5′-DiFA) and (E,E)-4,4′-dihydroxy-3,5′-dimethoxy-β,3′-bicinnamic acid (8-5′-DiFA). The ferulic acid dehydrodimers were also synthesised by a simple procedure from ethyl ferulate using peroxidase and hydrogen peroxide.     

Chemistry and Tumor Cell Growth Inhibitory Activity of 11,20-Epoxy-3Z,5(6)E-diene Briaranes from the South China Sea Gorgonian Dichotella gemmacea

Eighteen new 11,20-epoxy-3Z,5E-dien briaranes, gemmacolides AA–AR (1–18), were isolated together with three known analogs, dichotellides F (19) and I (20), and juncenolide C (21), from the South China Sea gorgonian Dichotella gemmacea. The structures of the compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configuration was determined based on the ECD experiment. In the in vitro bioassay, compounds 1–3, 5, 6, 8–12, and 14–19 exhibited different levels of growth inhibition activity against A549 and MG63 cell lines. Preliminary structure-activity analysis suggests that 12-O-isovalerate may increase the activity whereas 13- or 14-O-isovalerate may decrease the activity. Contribution of substitutions at C-2 and C-16 remains uncertain.     

Unusual Structures and Cytotoxicities of Chitonoidosides A,A1, B,C, D,and E,Six Triterpene Glycosides from the Far Eastern Sea Cucumber Psolus chitonoides

Six new triterpene tetra-, penta- and hexaosides, chitonoidosides A (1), A₁ (2), B (3), C (4), D (5), and E (6), containing one or two sulfate groups, have been isolated from the Far-Eastern sea cucumber Psolus chitonoides, collected near Bering Island (Commander Islands) from the depth of 100–150 m. Three of the isolated compounds (1, 3 and 6) are characterized by the unusual aglycone of new type having 18(20)-ether bond and lacking a lactone in contrast with wide spread holostane derivatives. Another unexpected finding is 3-O-methylxylose residue as a terminal unit in the carbohydrate chains of chitonoidosides B (3), C (4), and E (6), which has never been found before in the glycosides from holothurians belonging to the Psolidae family. Moreover, this monosaccharide is sulfated in the compound 4 into unprecedented 3-O-methylxylose 4-O-sulfate residue. Chitonoidoside C (4) is characterized by tetrasaccharide moiety lacking a part of the bottom semi-chain, but having disaccharide fragment attached to C-4 of Xyl1. Such architecture is not common in sea cucumber glycosides. Cytotoxic activities of the compounds 1–5 against mouse and human erythrocytes and human cancer cell lines: adenocarcinoma HeLa, colorectal adenocarcinoma DLD-1, and leukemia promyeloblast HL-60 cells were studied. The cytotoxic effect of chitonoidoside d (5) was the most significant in this series due to the presence of pentasaccharide disulfated sugar chain in combination with holostane aglycone. Surprisingly, the glycosides 1 and 3, comprising the new aglycone without γ-lactone, demonstrated similar activity to the known compounds with holostane aglycones. Chitonoidoside C (4) was less cytotoxic due to the different architecture of the carbohydrate chain compared to the other glycosides and probably due to the presence of a sulfate group at C-4 in 3-O-MeXyl4.     

Influence of Non-Starch Polysaccharides Structure on the Metabolisable Energy of U.K. Wheat Fed to Poultry

With the inclusion of wheat in European poultry diets at 600 g/kg, or more, there is increasing concern that its apparent metabolisable energy (AME) is more variable than would be predicted by conventional analysis. Twelve samples of wheat with a range of AME values (8·34–13·74 MJ/kg dry matter when fed to broiler chicks aged 11–14 d at 750 g/kg diet) were used to investigate the causes of this variability. AME was not correlated with the amount of total water-soluble non-starch polysaccharide (sNSP), soluble arabinoxylan (the major polysaccharide contributing to NSP) or (1→3, 1→4)-β-glucan released from the grain or with the viscosity of aqueous extracts. Surprisingly,in vitroviscosity was negatively related to soluble (r²=0·61) and total (r²=0·82) arabinoxylan. This was thought to be due to the slow, but cumulative, action of endogenous hydrolases in the stored grain. Soluble NSP from each wheat was characterised by measurement of molecular weight distribution and the structural features of arabinoxylan determined from the amount and nature of the oligosaccharides released following treatment with an endo-xylanase. Oligomer molecular weight was determined by matrix-assisted laser desorption/ionisation time of flight mass spectrometry and structure by NMR. Multivariate analysis of the 32 variables measured provided a three-term model able to explain approximately 0·80 of the variation between wheat samples: AME=8·07+11·16(XRAX)+30·67(AX-6)−0·355(sNSP) Two terms (XRAX, the proportion of arabinoxylan resistant to hydrolysis by xylanase and AX-6, the properties of branched six-sugar present in hydrolysates) reflected the degree of branching of arabinoxylan and were positively associated with AME while the third term, the amount of sNSP present, was negatively related.