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PubMed1991

Fructan chemical structure and sensitivity to an exohydrolase.

A fructan exohydrolase selective for (2----1)-linked terminal fructosyl linkages, isolated from barley (Hordeum vulgare L. cv. Morex) stems and leaf sheaths, was used to elucidate the chemical structures of several oligomeric fructans extracted from liliaceous and graminaceous species. Products released by enzymic and mild acid hydrolysis were separated by reversed-phase high-performance liquid chromatography. Gas-liquid chromatography-mass spectrometry of partially methylated alditol acetates permitted unequivocal deduction of many linkage sequences, first of the hydrolysis products and then of the original oligomers. We found that bifurcose, a tetrasaccharide formed by addition of a fructosyl unit to O-6 of the central fructose residue of 1-kestose, was a central molecule in the generation of the branched, oligomeric fructans of wheat (Triticum aestivum L. cv. Fidel). These arise by the extension of both (2----1)- and (2----6)-linked chains from the bifurcose branch-point residue. Some of the (2----6)-linked units that slowly accumulate in oligomers may arise in vivo from selective hydrolysis, by fructan exohydrolases, of (2----1)-linked terminal units at branch point residues rather than by the action of (2----6)-specific synthases. Limited hydrolysis by specific exohydrolases in vitro coupled with separation of the oligomeric products constitutes an effective approach to the sequence analysis of complex oligosaccharides.

Carbohydrate Conformation↗

PubMed2005

Molecular monitoring and characterization of the faecal microbiota of healthy dogs during fructan supplementation.

The large intestine of dogs contains a complex microbial ecosystem with predominance of streptococci, bifidobacteria, lactobacilli, Bacteroides and Clostridium. Generally, this predominant microbiota in dogs is relatively stable in time but much less is known about its taxonomic composition. Moreover, almost no studies have been conducted to investigate this stability of the faecal microbial population in dogs upon prebiotic administration. The objective of the present study was to monitor possible changes in faecal microbiota of seven healthy adult dogs related to the administration of two fructans, oligofructose and inulin. For this purpose, population fingerprints generated by denaturing gradient gel electrophoresis (DGGE) analysis of universal V3 16 S rRNA gene PCR amplicons were compared between control (baseline) samples and samples collected after prebiotic feeding. From these DGGE gels, marked changes were observed in the faecal microbiota between subjects and before and after fructan administration. One DGGE band that appeared or intensified after fructan intake was further analyzed. Sequence analysis could attribute this band to a member of the Streptococcus bovis-equinus group. Following cultivation on MRS medium, a set of faecal isolates that most likely represent the stimulated streptococci were allocated to the species Streptococcus lutetiensis by (GTG)(5)-PCR fingerprinting and partial 16 S rRNA and sodA gene sequencing. The data provided in this study demonstrate the ability of fructans to influence the bacterial composition of the gut microbiota in healthy dogs. More work is needed to unravel the relevance of S. lutetiensis or other autochthonous organisms of the dog gut as target groups for prebiotic supplementation.

Animals↗

PubMed2006

Developing fructan-synthesizing capability in a plant invertase via mutations in the sucrose-binding box.

Fructans are fructose polymers that are synthesized from sucrose by fructosyltransferases. Fructosyltransferases are present in unrelated plant families suggesting a polyphyletic origin for their transglycosylation activity. Based on sequence comparisons and enzymatic properties, fructosyltransferases are proposed to have evolved from vacuolar invertases. Between 1% and 5% of the total activity of vacuolar invertase is transglycosylating activity. We investigated the nature of the changes that can convert a hydrolysing invertase into a transglycosylating enzyme. Remarkably, replacing 33 amino acids (amino acids 143-175) corresponding to the N-terminus of the mature onion vacuolar invertase with the corresponding region of onion fructan:fructan 6G-fructosyltransferase (6G-FFT) led to a shift in activity from hydrolysis of sucrose towards transglycosylation between two sucrose molecules. The substituted N-terminal region contains the sucrose-binding box that harbours the nucleophile involved in sucrose hydrolysis (Asp164). Subsequent research into the individual amino acids responsible for the enhanced transglycosylation activity revealed that mutations in amino acids Trp161 and Asn166, can give rise to a shift towards polymerase activity. Changing the amino acid at either of these positions in the sucrose-binding box increases the transglycosylation capacity of invertases two- to threefold compared to wild type. Combining the two mutations had an additive effect on transglycosylation ability, resulting in an approximately fourfold enhancement. The mutations generated correspond with natural variation present in the sucrose-binding boxes of vacuolar invertases and fructosyltransferases. These relatively small changes that increase the transglycosylation capacity of invertases might explain the polyphyletic origin of the fructan accumulation trait.

Amino Acid Sequence↗

PubMed2005

Fructan synthesis is inhibited by phosphate in warm-grown, but not in cold-treated, excised barley leaves.

The inhibition of fructan accumulation by phosphate was investigated in warm-grown and cold-treated barley (Hordeum vulgare) plants. Detached leaves were incubated in water or phosphate for 24 h under lighting or in darkness. Fructosyltransferase, sucrose phosphate synthase (SPS) and cytosolic fructose-1,6-bisphosphatase (FBPase) activities were subsequently analysed, as well as the content of carbohydrates, hexose-phosphates, phosphate, amino acids and protein. In warm-grown leaves, phosphate decreased fructan accumulation and total carbon in carbohydrates and did not affect protein content. Phosphate increased hexose-phosphates, phosphate and amino acids. Fructosyltransferase and FBPase activities were not affected by phosphate feeding, while SPS activity was inhibited by phosphate in incubations in both light and darkness. In cold-treated leaves, which before incubation had higher SPS activities than warm-grown leaves, phosphate had no inhibitory effect on fructan accumulation, carbohydrate content or total C in carbohydrates. The activities of SPS and FBPase were unaffected by phosphate. The results indicate that phosphate decreases fructan accumulation through an inhibition of SPS whenever this activity is not high before a rise in phosphate content.

Amino Acids↗

PubMed1998

Dietary fructans.

Fructan is a general term used for any carbohydrate in which one or more fructosyl-fructose link constitutes the majority of osidic bonds. This review focuses on the fate of inulin-type fructans (namely native chicory inulin, oligofructose produced by the partial enzymatic hydrolysis of chicory inulin, and synthetic fructans produced by enzymatic synthesis from sucrose) in the gastrointestinal tract, as well as on their systemic physiological effects on mineral absorption, carbohydrate and lipid metabolism, hormone balance, and nitrogen homeostasis. The scientific evidence for the functional claims of inulin-type fructans is discussed, as well as their potential application in risk reduction of disease, namely constipation, infectious diarrhea, cancer, osteoporosis, atherosclerotic cardiovascular disease, obesity, and non-insulin dependent diabetes.

Animals↗

PubMed1999

Synthesis of fructans by fructosyltransferase from the tuberous roots of Viguiera discolor (Asteraceae).

Sucrose:sucrose fructosyltransferase (SST) and fructan:fructan fructosyl-transferase (FFT) activities from crude extracts of tuberous roots of Viguiera discolor growing in a preserved area of cerrado were analyzed in 1995-1996. SST activity was characterized by the synthesis of 1-kestose from sucrose and FFT activity by the production of nystose from 1-kestose. The highest fructan-synthesizing activity was observed during early dormancy (autumn), when both (SST and FFT) activities were high. The increase in synthetic activity seemed to start during the fruiting phase in the summer, when SST activity was higher than in spring. During winter and at the beginning of sprouting, both activities declined. The in vitro synthesis of high molecular mass fructans from sucrose by enzymatic preparations from tuberous roots collected in summer showed that long incubations of up to 288 h produced consistently longer polymers which resembled those found in vivo with respect to chromatographic profiles.

Asteraceae↗

PubMed2001

Stimulation of apoptosis by two prebiotic chicory fructans in the rat colon.

Prebiotics, in particular the chicory derived beta(2-1) fructans, have been shown to exert cancer protective effects in animal models. The present study was carried out to determine the effects of two chicory fructans--oligofructose (RaftiloseP95; average degree of polymerization DP = 4) and long chain inulin (RaftilineHP; average DP = 25), on apoptosis and bacterial metabolism associated with carcinogenesis. Eighteen rats were fed a stock diet for one week. Three groups of six animals were then fed one of three diets: basal, basal with oligofructose (5%w/w) or basal with long chain inulin (5%w/w), for a three week period. All animals were then dosed with 1,2-dimethylhydrazine and killed 24 h later. The mean number of apoptotic cells per crypt was significantly higher in the colon of rats fed oligofructose (P = 0.049) and long chain inulin (P = 0.017) as compared to those fed the basal diet alone. This suggests that oligofructose as well as the long chain inulin exert protective effects at an early stage in the onset of cancer, as the supplements were effective soon after the carcinogen insult. Comparison of the apoptotic indices between the two oligosaccharide diets showed no significant difference even though the mean apoptotic index was higher in animals fed long chain inulin. For all animals, apoptosis was significantly higher in the distal colon as compared to the proximal colon (P = 0.0002) however no significant site specific effect of diet occurred. There were no significant dietary effects on bacterial enzyme activities or ammonia concentration despite a trend towards increased colonic beta-glucosidase and reduced ammonia concentration during the oligosaccharide diets. This is the first time that a significant effect of chicory fructans on apoptosis has been shown and the results contribute to the growing evidence that chicory fructans may have cancer preventing properties.

Ammonia↗

PubMed2005

Molecular genetics of fructan metabolism in perennial ryegrass.

Fructans are the main storage carbohydrates of temperate grasses, sustaining regrowth immediately after defoliation, as well as contributing to the nutritive value of feed. Fructan metabolism is based on the substrate sucrose and involves fructosyltransferases (FTs) for biosynthesis and fructan exohydrolases (FEHs) for degradation. Sucrose is also utilized by invertases (INVs), which hydrolyse it into its constituent monosaccharides for use in metabolism. The isolation, molecular characterization, functional analysis, and phylogenetic relationships of genes encoding FTs, FEHs, and INVs from temperate grasses are reviewed, with an emphasis on perennial ryegrass (Lolium perenne L.). The roles these enzymes play in fructan accumulation and remobilization, and future biotechnological applications in molecular plant breeding are discussed.

Journal Article↗

PubMed1972

Use of specifically labeled sucrose for comparison of extracellular glucan and fructan metabolism by oral streptococci.

Sucrose labeled in the fructosyl ((3)H) and glucosyl ((14)C) moieties was used to quantitate extracellular polysaccharide production and degradation by cariogenic and noncariogenic oral streptococci. All of the strains produced glucan and fructan. Streptococcus salivarius produced primarily fructan, whereas S. mutans and S. sanguis produced more glucan than fructan. The cariogenic streptococci could degrade the fructan produced by noncariogenic strains. Although the soluble glucans from all of the strains were sensitive to dextranase, the insoluble glucan from S. mutans could be distinguished from the S. sanguis insoluble glucan by its greater resistance to this enzyme.

Carbon Isotopes↗

PubMed1997

Analysis of fructans from higher plants by matrix-assisted laser desorption/ionization mass spectrometry.

In this communication both matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and high-performance anion-exchange chromatography (HPAEC) have been applied to analyze fructans from higher plants. Size distribution of a commercially available fructan preparation from Dahlia variabilis L. was determined by MALDI-MS. Molecular masses ranged from 2,000 up to 6,000 Da with a peak value of distribution at 2,635 Da. Essentially the same pattern was obtained using HPAEC. Low-molecular-weight fructans from onion bulbs (Allium cepa L.) were studied in more detail. Tissue extracts were analyzed by MALDI-MS without any analyte purification. Mass-spectra of both proteins and oligosaccharides were obtained. For identification, metastable ion scanning was performed. Neither deproteinization nor deionization of the samples affected the oligosaccharide pattern. Using HPAEC, a more complex oligosaccharide pattern was obtained because isomeric glycans were differentiated. However, the overall size distribution was similar to that obtained by MALDI-MS. In further experiments epidermal or parenchyma cell layers of the onion bulb were placed into matrix solution and were then subjected to MALDI-MS and metastable ion scanning as well. By taking this approach, analyte desorption was achieved immediately from plant tissue. Oligosaccharide mass spectra were essentially the same as those of the extracts. To our knowledge, this is the first time that MALDI-MS has been applied as a microprobe to plant tissue. Finally MALDI-MS analysis was performed using single-cell extracts from onion tissues without any purification of the analyte.

Allium↗

PubMed1994

Conformation of (2-->1)-beta-D-fructan in aqueous solution.

The conformation and dilute solution properties of (2-->1)-beta-D-fructan in aqueous solution were studied by gel permeation chromatography, low-angle laser light-scattering photometry, viscometry, small-angle X-ray scattering and electron microscopy. Fractions covering a broad range of weight-average molecular weights (Mw) from 1.49 x 10(4) to 5.29 x 10(6) were obtained from a native sample by ultrasonic degradation and fractional precipitation. For Mw < 4 x 10(4), the intrinsic viscosity [eta] varies with Mw0.71, indicating that the fructan chain behaves as a random coil expanded by an excluded-volume effect in this molecular weight region. For Mw > 10(5), [eta] exhibits an unusually weak dependence on Mw and finally becomes almost independent of molecular weight. This behaviour is interpreted in terms of a globular conformation of the high-molecular-weight fructan molecules. Small-angle X-ray-scattering measurements and electron microscopic observations support this interpretation of the values of [eta] observed.

Aspergillus↗

PubMed1980

binding constants of levans and D-fructo-oligosaccharides to BALB/c and NZB D-fructan-specific, myeloma proteins, determined by affinity electrophoresis.

The association constants for the interaction of BALB/c (UPC 10, Y5476, W3082, and UPC 61) and NZB (PC 3660) myeloma anti-D-fructans in pure form, or in ascitic fluids, with high-molecular-weight levans (Ka) and with such low-molecular-weight compounds as rye-grass levan, inulin, sucrose, and D-fructo-oligosaccharides (Kia) were determined by affinity electrophoresis, measuring the extent of retardation of the D-fructan-specific band by levan and its restoration by the low-molecular-weight compounds and oligosaccharide haptens. With different levans,Ka values ranged from 1.14 X 10(5) TO 1.52 X 10(6) ML/g for PC 3660, 1.35 X 10(5) TO 6.45 X 10(5) mL/g for UPC 10, 1.0 X 10(4) to 7.9 X 10(4) mL/g for Y5476, 7.63 X 10(3) to 6.38 X 10(4) mL/g for W 3082, and 3.35 X 10(3) to 1.54 X 10(4) mL/g for UPC 61. The retarded, D-fructan-specific bands of W3082 and UPC 61 were restored by inulin, having beta-D-(2 leads to)-linkages, and rye-grass levan, having beta-D-(2 leads to 6)-linkages, and those of PC 3660, UPC 10, and Y5476 by rye-grass levan. The Kia values of inulin with W3082 and UPC 61 were 10 times those of rye-grass levan. The Kia values of inulin (3.65 X 10(5) M-1 for W3082, and 4.44 X 10(5) M-1 for UPC 61) were very similar to those of [beta-D-Fruf-(2 leads to 1)]2-beta-D-Fruf-(2 leads to 6)-D-Glc (3) (3.95 X 10(5) M-1 for W3082, and 4.5 X 10(5) M-1 for UPC 61). With sucrose and the D-fructo-oligosaccharides, the order of Kia values of W3082 and UPC 61 was 3 greater than beta-D-Fruf-(2 leads to 1)-beta-D-Fruf-(2 leads to 6)-D-Glc greater than sucrose greater than beta-D-Fruf-(2 leads to 6)-D-Glc. With rye-grass levan, Kia values were 4.25 X 10(5) M-1 for PC 3660, 2.7 X 10(5) M-1 for UPC 10, and 8.77 X 10(4) M-1 for Y5476. These results confirm earlier findings that W3082 and UPC 61 have dual specificity for beta-(2 leads to 1) and beta-(2 leads to 6) D-fructofuranosyl linkages, that PC 3660, Y5476, and UPC 1U have specificity for beta-(2 leads to 6) D-fructofuranosyl linkages, and that the combining sites of W3082 and UPC 61 are most complementary to the tetrasaccharide 3. That W3082 and Y5476 share the same, cross-reacting idiotype, although their combining sites differ in specificity, provides further evidence that these two properties do not run parallel.

Animals↗

PubMed2003

Structural elucidation and antitumor activity of a fructan from Cyathula officinalis Kuan.

A fructan named CoPS3 was isolated from Cyathula officinalis Kuan. The structure of CoPS3 was determined by methylation, by the reductive-cleavage method combined with GC-MS analysis, and both 1D and 2D 1H and 13C NMR spectroscopy. These results show that CoPS3 is a graminans-type fructan that is comprised of a beta-D-fructofuranosyl backbone having residues linked (2-->1)- and (2-->6) with branches and an alpha-D-glucopyranose residue on the nonreducing end of the fructan chain. Each branch is terminated by a beta-D-Fruf residue. Bioassay showed that it could inhibit growth of Lewis pulmonary carcinoma implanted in mice.

Amaranthaceae↗

PubMed2002

Preparative continuous annular chromatography (P-CAC) enables the large-scale fractionation of fructans.

Fructans (fructo-oligosaccharides and inulin) are of increasing physiological and nutritional interest due to their health-promoting effects. Fructans originally extracted from chicory roots were separated by continuous annular and fixed-bed conventional gel chromatography. Both columns were packed with Toyopearl HW 40 (S) and eluted with deionized water. A multicomponent fractionation was established to obtain single oligosaccharides in a low molecular weight range up to a chain length of five and fractions containing an overall size distribution in the high molecular weight range up to a chain length of 90 monosaccharide units. The productivity and resolution of the continuous annular size exclusion chromatograph (40 cm bed height) were investigated and compared with those of the fixed-bed counterpart (2 x 100 cm bed height). The eluting fractions were analyzed by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The productivity of the annular system was found to be 25-fold higher than the conventional system. Thus, annular chromatography exemplified for the fractionation of fructans is a powerful method for the large-scale and continuous fractionation of oligomeric and polymeric carbohydrates.

Chemical Fractionation↗

PubMed2003

Fructans in the diet cause alterations of intestinal mucosal architecture, released mucins and mucosa-associated bifidobacteria in gnotobiotic rats.

The effects of fructans in the diet on the mucosal morphometry (height of villi, depth of the crypts, number of goblet cells), the thickness of the epithelial mucus layer and the histochemical composition of intestinal mucosubstances in the distal jejunum and the distal colon were investigated by comparing germ-free (GF) rats, rats harbouring Bacteroides vulgatus and Bifidobacterium longum (diassociated (DA) rats), and rats with a human faecal flora (HFA). The rats were fed either a commercial standard diet (ST) or ST + (50 g oligofructose (OF)-long-chain inulin (lcIN))/kg. Changes in total bacteria, bifidobacteria and Bacteroides-Prevotella in response to feeding these diets were investigated by fluorescent in situ hybridization with 16S rRNA-targeted probes both in intestinal contents (lumen bacteria) and tissue sections (mucosa-associated bacteria). The OF-lcIN-containing diet resulted in higher villi and deeper crypts in bacteria-associated, but not in GF rats. In DA and HFA rats, the colonic epithelial mucus layer was thicker and the numbers of the goblet cells were greater than in GF rats. These effects were enhanced by the OF-lcIN-containing diet. In both dietary groups, bacterial colonization of GF rats caused an increase in neutral mucins in the distal jejunum and colon. Bacteria-associated rats had more acidic mucins in the colon than GF rats, and the OF-lcIN-containing diet stimulated sulfomucins as the predominant type of acidic mucins, while sialomucins dominated in the ST-fed groups. The number of mucosa-associated bifidobacteria detected in the colon of DA and HFA rats was greater with OF-lcIN than ST (4.9 and 5.4 v. 3.5 and 4.0 log10/mm2 mucosal surface respectively), whereas the number of luminal bifidobacteria was only affected by fructans in DA rats. Bacteroides did not differ between the groups. The stabilisation of the gut mucosal barrier, either by changes in the mucosal architecture itself, in released mucins or by stimulation of mucosal bifidobacteria with fructans, could become an important topic in the treatment and prophylaxis of gastrointestinal disorders and health maintenance.

Analysis of Variance↗

PubMed2001

Effects of fructans-type prebiotics on lipid metabolism.

Several nondigestible but fermentable dietary carbohydrates are able to regulate lipemia and triglyceridemia in both humans and animals. The mechanism of their serum lipid-lowering effect remains to be elucidated. Oligofructose, which is a mixture of nondigestible and fermentable fructans, can decrease triacylglycerol in VLDL when given to rats. The triacylglycerol-lowering action of oligofructose is due to a reduction of de novo fatty acid synthesis in the liver through inhibition of all lipogenic enzymes, namely acetyl-CoA carboxylase (EC 6.4.1.2), fatty acid synthase, malic enzyme (EC 1.1.1.40), ATP citrate lyase (EC 4.1.3.8), and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). Our results suggest that oligofructose decreases lipogenic enzyme gene expression. Postprandial insulin and glucose concentrations are low in the serum of oligofructose-fed animals and this could explain, at least partially, the metabolic effect of oligofructose. Moreover, some events occurring in the gastrointestinal tract after oligofructose feeding could be involved in the antilipogenic effect of this fructan: the production of propionate through fermentation, a modulation of the intestinal production of incretins (namely glucose-dependent insulinotropic peptide and glucagon-like peptide-1), or the modification of the availability of digestible carbohydrates. Recent studies showed that the hypotriglyceridemic effect of fructans also occurs in humans.

Animals↗

PubMed2000

Dietary fructans modulate polyamine concentration in the cecum of rats.

Nondigestible but fermentable dietary fructans such as oligofructose exert many effects on gut physiology through their fermentation end products such as short-chain fatty acids. Could other metabolites be produced in the gut and contribute to the physiologic effects of dietary fructans? The aim of the study was to evaluate the influence of oligofructose on putrescine, spermidine and spermine concentrations in the cecum, the portal vein and the liver of rats and to assess their involvement in cecal enlargement and the modulation of hepatic lipid metabolism. Putrescine, spermidine and spermine were quantified by HPLC in samples obtained from male Wistar rats fed a nonpurified standard diet (controls) or the same diet enriched with 10 g/100 g oligofructose (OFS) for 4 wk. OFS-fed rats had significantly greater cecal content and tissue weights. OFS almost doubled the concentration of putrescine in the cecal contents. The concentration of all three polyamines in the cecal tissue was significantly greater than in controls. The concentration of spermidine in portal plasma was lower in rats fed OFS, whereas the treatment did not affect the polyamine concentrations in the liver. The fermentation of dietary fructans contributed to an increase in the concentration of putrescine in the gut without modifying putrescine concentration in either the portal blood or liver. Moreover, the greater levels of polyamines in cecal tissue may be related to the cell proliferation resulting from OFS fermentation in the gut.

Animals↗

PubMed1975

Structural differences in fructans elaborated by streptococcus mutans and Strep. salivarius.

D-Fructans synthesized from sucrose by cell-free systems of strains of Streptococcus mutans and Strep. salivarius have been shown by methylation and enzymatic studies to have different glycosidic linkages. The cold water-insoluble D-fructans from Strep. mutans strain BHT and JC-1 have inulin-type structures consisting beta-(2 leads to 1)-D-fructofuranosidic linkages, with average repeating units of 8 and 27 sugar residues, respectively, whereas the water-soluble fructan from Strep. salivarius strain HHT has a levan-type branched structure consisting beta-(2 leads to 6)-D-fructofuranosidic linkages with an average repeating unit of 9 sugar residues. The solubility properties of these fructants are discussed on the basis of the structural differences.

Fructans↗