With the increasing amount of evidence linking certain disorders of the human body to a disturbed gut microbiota, there is a growing interest for compounds that positively influence its composition and activity through diet. Besides the consumption of probiotics to stimulate favorable bacterial communities in the human gastrointestinal tract, prebiotics such as inulin-type fructans (ITF) and arabinoxylan-oligosaccharides (AXOS) can be consumed to increase the number of bifidobacteria in the colon. Several functions have been attributed to bifidobacteria, encompassing degradation of non-digestible carbohydrates, protection against pathogens, production of vitamin B, antioxidants, and conjugated linoleic acids, and stimulation of the immune system. During life, the numbers of bifidobacteria decrease from up to 90% of the total colon microbiota in vaginally delivered breast-fed infants to <5% in the colon of adults and they decrease even more in that of elderly as well as in patients with certain disorders such as antibiotic-associated diarrhea, inflammatory bowel disease, irritable bowel syndrome, obesity, allergies, and regressive autism. It has been suggested that the bifidogenic effects of ITF and AXOS are the result of strain-specific yet complementary carbohydrate degradation mechanisms within cooperating bifidobacterial consortia. Except for a bifidogenic effect, ITF and AXOS also have shown to cause a butyrogenic effect in the human colon, i.e., an enhancement of colon butyrate production. Butyrate is an essential metabolite in the human colon, as it is the preferred energy source for the colon epithelial cells, contributes to the maintenance of the gut barrier functions, and has immunomodulatory and anti-inflammatory properties. It has been shown that the butyrogenic effects of ITF and AXOS are the result of cross-feeding interactions between bifidobacteria and butyrate-producing colon bacteria, such as Faecalibacterium prausnitzii (clostridial cluster IV) and Anaerostipes, Eubacterium, and Roseburia species (clostridial cluster XIVa). These kinds of interactions possibly favor the co-existence of bifidobacterial strains with other bifidobacteria and with butyrate-producing colon bacteria in the human colon.

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Bifidobacteria and butyrate-producing colon bacteria: Importance and strategies for their stimulation in the human gut

The classic definitions of inulin and oligofructose are constructively criticized. It is observed that inulin cannot unequivocally be described as a polydisperse 1-kestose-based (GFn) beta (2-->1) linear fructan chain, but that inulin always contains small amounts of Fm and branched molecules. This review article describes the presence of inulin and oligofructose in common foodstuffs. Historical data on human consumption add an extra dimension. Modern analytical techniques (HPLC, LGC, HPAEC-PAD) are used to check the variety of data mentioned in the literature throughout the past century. Methods to determine inulin and oligofructose in natural foodstuffs (cereals, fruit, and vegetables) are optimized and used to determine the loss of inulin during storage and during preparation of the food. These findings allow quantification of the amount of inulin and oligofructose in the average daily western diet. The daily per capita intake is estimated to range from 1 to 10 g, depending on geographic, demographic, and other related parameters (age, sex, season, etc.). Inulin and oligofructose are not measured by classic methods of dietary fiber analysis and consequently are often not mentioned in food tables. Their significant contribution (1 to 10 g/d/per capita) to the dietary fiber fraction (recommended at 25 g/d/per capita) is not taken into account in any nutritional recommendations. In view of this, inulin and oligofructose deserve more attention, both in food composition tables and in diet or nutrition studies.

On the presence of inulin and oligofructose as natural ingredients in the western diet.

Garlic (Allium sativum) and onion (Allium cepa) are two food ingredients widely used in our gastronomy. Moreover, garlic and onion extracts have been recently reported to be effective in cardiovascular disease, because of their hypocholesterolemic, hypolipidemic, anti-hypertensive, anti-diabetic, antithrombotic and anti-hyperhomocysteinemia effects, and to possess many other biological activities including antimicrobial, antioxidant, anticarcinogenic, antimutagenic, antiasthmatic, immunomodulatory and prebiotic activities. Given the importance of these vegetables and derived supplements as much in feeding as in therapeutic, in the present work, their main biological activities have been reviewed, indicating the compounds responsible for each one of them. In addition, the influence of the processing on the bioactivity and the adverse effects and interactions with different medications have also been considered.

Biological properties of onions and garlic

Members of the genus Bifidobacterium can be found as components of the gastrointestinal microbiota, and are believed to play an important role in maintaining and promoting human health by eliciting a number of beneficial properties. Bifidobacteria can utilize a diverse range of dietary carbohydrates that escape degradation in the upper parts of the intestine, many of which are plant-derived oligo- and polysaccharides. The gene content of a bifidobacterial genome reflects this apparent metabolic adaptation to a complex carbohydrate-rich gastrointestinal tract environment as it encodes a large number of predicted carbohydrate-modifying enzymes. Different bifidobacterial strains may possess different carbohydrate utilizing abilities, as established by a number of studies reviewed here. Carbohydrate-degrading activities described for bifidobacteria and their relevance to the deliberate enhancement of number and/or activity of bifidobacteria in the gut are also discussed in this review.

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Carbohydrate metabolism in Bifidobacteria.

Most plants store starch or Suc as reserve carbohydrates, but about 15% of all flowering plant species store fructans, which are linear and branched polymers of Fru. Among the plants that store fructans are many of significant economic importance, such as cereals (e.g. barley, wheat, and oat),

Fructan: More Than a Reserve Carbohydrate?

Properties of Fructosyltransferases Involved in the Synthesis of Fructan in Liliaceous Plants

(1991). Separation of Fructooligosaccharide Isomers by Anion-exchange Chromatography. Agricultural and Biological Chemistry: Vol. 55, No. 5, pp. 1427-1428.

Separation of Fructooligosaccharide Isomers by Anion-exchange Chromatography

The accumulation of fructo-oligosaccharides and the activities of fructosyltransferase (sucrose:sucrose 1 F -fructosyltransferase (SST), 1 F -fructosyltransferase (1 F -FT) and 6 G -fructosyltransferase (6 G -FT)) in the bulbs of three onion cultivars were investigated from June to September 1993. The total fructo-oligosaccharide content increased from June until August, then decreased in September, except in one cultivar. The levels of neokestose and its related tetrasaccharides(1 F ,6 G -di-β-D-fructofuranosyl sucrose and 6 G (1-β-D-fructofuranosyl)2sucrose) were higher than those of 1-kestose and nystose throughout growth. The activities of 6 G -FT, 1 g -FT and SST were high in June and July, then decreased; SST activity was very low in September. The activity ratios of 6 G -FT to 1 F -FT varied between 1.86 and 2.65 over the growth period. Two trisaccharides, three tetrasaccharides and four pentasaccharides were identified, together with a mixture of hexa- and heptasaccharides, all of which were synthesized in vitro from 0.1 M sucrose by an enzyme preparation of onion bulbs harvested in August. Octa- and nonasaccharides other than the saccharides formed from sucrose were also synthesized from 0.1 M 1-kestose or 0.1 M neokestose. All the saccharides produced from sucrose, 1-kestose or neokestose by the crude enzyme prepared from onion bulbs were identical to the saccharides occurring naturally in onion bulbs.

Fructo‐oligosaccharide content and fructosyltransferase activity during growth of onion bulbs

SUMMARY
Fructopolysaccharide (asparagosin, fructan) was prepared from an extract of asparagus roots by chromatography on carbon-Celite, paper and Toyopearl HW-40S (gel permeation). The asparagus fructopolysaccharide was a mixture of saccharides ranging from DP (degree of polymerization) 12 to 22 approximately. It yielded fructose and glucose by hydrolyzing with acid or yeast β-fructofuranosidase. The ratio of fructose to glucose in the enzyme hydrolysate was 13:1 by HPLC analysis. Structural determinations were made by 13C-NMR spectroscopy. Strong signals corresponding to carbon-1 (C-l), C-2, C-3, C-4, C-6 and C-5 of fructose residues in the fructopolysaccharide were observed at δ61.08–61.77, 103.64–104.26, 77.42–78.08, 74.43–75.09, 62.71–63.00 and 81.74 respectively. These chemical shifts were similar to those of inulin. Moreover, weaker signals were also detected at δ92.85, 71.80, 73.13, 69.79 and 72.23 due to C-l, C-2, C-3, C-4 and C-5 of the glucose residue. The chemical shifts are almost identical to those of glucose carbons in raffinose, neokestose, 6G(l-β-D-fructofuranosyl)2sucrose and lF,6G-di-β-D-fructofuranosyl sucrose. These findings were confirmed by analysis of methanolysate from permethylated fructopolysaccharide by using gas-liquid chromatography. The fructopolysaccharide from asparagus roots was composed of saccharides possessing approximately 11–21 fructose residues linked by β-2,l bonds and a non-terminal glucose residue bound with fructose residues at positions C-l and C-6.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1993.tb03734.x

Structure of fructopolysaccharide (asparagosin) from roots of asparagus (Asparagus officinalis L.)

Summary The eects of c-irradiation, maleic hydrazide (MH) and carbamate isopropyl, N-phenyl (CIP) on the carbohydrate content, respiration rate (RR) sprouting and rotting of red onion bulbs (Allium cepa L.) c.v. Rouge Amposta stored at 4, 10 and 20 ∞C were investigated. Between 6 and 8 weeks soluble sugars increased in concentration and varied between 6.0 and 6.5% fresh weight both at 10 and 20 ∞C. However, this peak did not exceed 6.0% fresh weight at 4 ∞C. The basal amount of soluble sugars was about 3% fresh weight. The content appeared to be influenced by temperature, with greater accumulation at 10 and 20 ∞C than at 4 ∞C. The RR increased when the bulbs sprouted, whereas it was reduced by the following treatments: irradiation, MH and CIP, the respiration of irradiated bulbs decreased during the final stage of storage because of the death of the sprouts. The chemical treatment used were eective in controlling sprouting of the bulbs during storage, although not as eective as irradiation and chilling.

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Storage technology of onion bulbs c.v. Rouge Amposta: effects of irradiation, maleic hydrazide and carbamate isopropyl, N‐phenyl (CIP) on respiration rate and carbohydrates

Norio Shiomi

Papers

Properties of Fructosyltransferases Involved in the Synthesis of Fructan in Liliaceous Plants

Separation of Fructooligosaccharide Isomers by Anion-exchange Chromatography

Fructo‐oligosaccharide content and fructosyltransferase activity during growth of onion bulbs

Structure of fructopolysaccharide (asparagosin) from roots of asparagus (Asparagus officinalis L.)

Storage technology of onion bulbs c.v. Rouge Amposta: effects of irradiation, maleic hydrazide and carbamate isopropyl, N‐phenyl (CIP) on respiration rate and carbohydrates