Pectic polysaccharides from Biophytum petersianum Klotzsch, and their activation of macrophages and dendritic cells

The Malian medicinal plant Biophytum petersianum Klotzsch (Oxalidaceae) is used as a treatment against various types of illnesses related to the immune system, such as joint pains, inflammations, fever, malaria, and wounds. A pectic polysaccharide obtained from a hot water extract of the aerial parts of B. petersianum has previously been reported to consist of arabinogalactans types I and II (AG-I and AG-II), probably linked to a rhamnogalacturonan backbone. We describe here further structural characteristics of the main polysaccharide fraction (BP1002) and fractions obtained by enzymatic degradations using endo-alpha-d-(1-->4)-polygalacturonase (BP1002-I to IV). The results indicate that in addition to previously reported structures, rhamnogalacturan type II and xylogalacturonan areas appear to be present in the pectic polymer isolated from the plant. Atomic force microscopy confirmed the presence of branched structures, as well as a polydisperse nature. We further tested whether the BP1002 main fraction or the enzymatically degraded products could induce immunomodulating activity through stimulation of subsets of leukocytes. We found that macrophages and dendritic cells were activated by BP1002 fractions, while there was little response of T cells, B cells, and NK cells. The enzymatic treatment of the BP1002 main fraction gave important information on the structure-activity relations. It seems that the presence of rhamnogalacturonan type I is important for the bioactivity, as the bioactivity decreases with the decreased amounts of rhamnose, galactose, and arabinose. The demonstration of bioactivity by the plant extracts might indicate the mechanisms behind the traditional medical use of the plant.     

Bioactive polysaccharides from the stems of the Thai medicinal plant Acanthus ebracteatus: their chemical and physical features

Crude water-soluble polysaccharides were isolated from Acanthus ebracteatus by hot water extraction followed by ethanol precipitation after pre-treatment with 80% ethanol. The crude polysaccharides were separated into neutral and acidic polysaccharides by anion-exchange chromatography. The neutral polysaccharide (A1001) was rich in galactose, 3-O-methylgalactose and arabinose, whereas the acidic polysaccharide (A1002) consisted mainly of galacturonic acid along with rhamnose, arabinose and galactose as minor components indicating a pectin-type polysaccharide with rhamnogalacturonan type I (RG-1) backbone. 3-O-Methylgalactose is also present in the acidic fraction. Both neutral and acidic fractions showed potent effects on the complement system using pectic polysaccharide PM II from Plantago major as a positive control. A small amount of 3-O-methylgalactose present in the pectin seemed to be of importance for activity enhancement in addition to the amount of neutral sugar side chains attached to RG-1. The relationship between chemical structure and effect on the complement system of the isolated polysaccharides is considered in the light of these data. The presence of the rare monosaccharide 3-O-methylgalactose may indicate that this can be used as a chemotaxonomic marker. The traditional way of using this plant as a medical remedy appears to have a scientific basis.     

Purification and partial characterization of an acidic polysaccharide with complement fixing ability from the stems of Avicennia marina

An acidic polysaccharide fraction that had high anticomplementary activity was isolated from the stems of Grey Mangrove in 0.15% yield. The final fractions was designated HAM-3-IIb-II. The polysaccharide fraction appeared to be homogenous by high performance size exclusion chromatography with an estimated molecular weight of 105 kDa. The isolated polysaccharide is more effective than polysaccharide K (PSK) in its anticomplementary activity at 58 microg/ml of PSK and 23 microg/ml of HAM-3-IIb-II that inhibit 50% of complement activity in the complement fixation assay. Structural studies indicated that HAM-3-IIb-II was rich in galacturonic acid along with arabinose, galactose and rhamnose, characterizing a pectin-type polysaccharide, which was also confirmed by FT-IR spectrum. The presence of rich neutral sugar side chains of arabinogalactans may have contributed to the expression of high activity. Traditionally, this mangrove plant is used for medicinal purposes and it appears to have some scientific applications.     

Isolation and structural study of polysaccharides from campion Silene vulgaris

Silenan SV, a pectic polysaccharide, was isolated from the aerial part of Silene vulgaris (Moench) Garke (Oberna behen (L.) Ikonn.), widespread through the European North of Russia. The polysaccharide was found to contain residues of galacturonic acid (63%), arabinose, galactose, and rhamnose as the main constituents. The results of a partial acidic hydrolysis, pectinase digestion, and NMR studies of silenan SV indicated that its molecule contains a linear alpha-1,4-D-galacturonan backbone and ramified regions. The core of the ramified regions is composed of residues of alpha-1,4-D-galacturonic acid along with 2-substituted alpha-rhamnopyranose residues. The NMR data showed that the silenan SV side chains are composed of the blocks built from the terminal alpha-1,5-linked arabinofuranose and beta-1,4-linked galactopyranose residues; these most likely are the side chains of rhamnogalacturonan, characteristic of other pectic polysaccharides. The nonreducing ends of these side chains contain alpha-arabinofuranose residues.     

Purification, structure and immunobiological activity of an arabinan-rich pectic polysaccharide from the cell walls of Prunus dulcis seeds

The structure and bioactivity of a polysaccharide extracted and purified from a 4M KOH + H3BO3 solution from Prunus dulcis seed cell wall material was studied. Anion-exchange chromatography of the crude extract yielded two sugar-rich fractions: one neutral (A), the other acidic (E). These fractions contain a very similar monosaccharide composition: 5:2:1 for arabinose, uronic acids and xylose, respectively, rhamnose and galactose being present in smaller amounts. As estimated by size-exclusion chromatography, the acidic fraction had an apparent molecular mass of 762 kDa. Methylation analysis (from the crude and fractions A and E), suggests that the polysaccharide is an arabinan-rich pectin. In all cases, the polysaccharides bear the same type of structural Ara moieties with highly branched arabinan-rich pectic polysaccharides. The average relative proportions of the arabinosyl linkages is 3:2:1:1 for T-Araf:(1-->5)-Araf:(1-->3,5)-Araf:(1-->2,3,5)-Araf. The crude polysaccharide extract and fractions A and E induced a murine lymphocyte stimulatory effect, as evaluated by the in vitro and in vivo expression of lymphocyte activation markers and spleen mononuclear cells culture proliferation. The lymphocyte stimulatory effect was stronger on B- than on T-cells. No evidence of cytotoxic effects induced by the polysaccharide fractions was found.     

Cell wall localization of the natural substrate of a β-galactosidase, the main enzyme responsible for the autolytic process of Cicer arietinum epicotyl cell walls

The Hw pectic fraction, extracted with hot water, is the major component of 4 days old epicotyl cell walls of Cicer arietinum L. cv. Castellana and is formed of arabinose and galactose, with smaller amounts of rhamnose, xylose, glucose and mannose. The cell wall 2βIII enzymatic fraction, with β-galactosidase activity (EC 3.2.1.23) and the main enzyme responsible for the autolytic process, essentially acts on the Hw fraction, and is able to hydrolyze 560 μg of this fraction per g of epicotyls, releasing mainly galactose as monosaccharide.
The 2βIII fraction acts very weakly on the other polysaccharide fractions of the cell wall, both pectic and hemicellulosic, releasing 80, 60 and 14 μg per g of epicotyls from the fractions extracted with oxalate (Ox), KOH 10% (KI) and KOH 24% (KII), respectively. It can be concluded that the natural substrate of this enzyme is the Hw pectic fraction, probably an arabinogalactan that is found in the cell wall in isolated form or as side chains of the rhamnogalacturonan I.     

Structural analysis of a pectic polysaccharide from the leaves of Diospyros kaki

A pectic polysaccharide DL-2A with a molar mass of 8.5 x 10(5), was obtained from the boiling water extract of Diospyros kaki leaves. It had [alpha]20D -21.8 degrees (c 0.22, H2O) and consisted of rhamnose, arabinose, galactose, xylose and galacturonic acid units in the molar ratio of 0.4:3.4:2.4:1.0:0.8, along with traces of glucuronic acid. About 16.7% of galacturonic acid existed as the methyl ester. A combination of linkage analyses, periodate oxidation, partial acid hydrolysis, selective lithium-degraded reaction, ESIMS, 1H- and 13C- NMR spectral analyses revealed its structural features. It was found that DL-2A possessed an alpha-(1-->4)-galacturonan backbone with some insertions of alpha-1,2-Rhap residues. The side-chains of arabino-3,6-galactan were attached to the backbone via O-4 of Rhap residues and O-3 of GalAp residues, while 4-linked xylose residues (forming short linear chains) were directly linked to O-4 of rhamnose residues, not as part of the xylogalacturonan. These novel structural features enlarge the knowledge on the fine structure of pectic substances in the plant kingdom.     

Fractionation and characterization of polysaccharides from abaca fibre

Abaca fibre polysaccharides were fractionated into water soluble, pectic, 1% NaOH soluble, hemicellulosic and cellulose fractions by extraction with hot water, dilute hydrochloric acid (pH 1.6), aqueous 1% NaOH and 17.5% NaOH, respectively. Cellulose (60.4–63.6%) and hemicelluloses (20.8%) were the major polysaccharides in abaca fibres. The hot water soluble polysaccharides contained noticeable amounts of pectic substances and a large proportion of neutral polysaccharides. The pectic polysaccharide preparation was enriched in both galacturonic acid and neutral sugars, including xylose, glucose, galactose, arabinose, and rhamnose. Extraction of the fibre with aqueous 1% NaOH produced the hemicellulose–lignin complex, which was enriched in xylose and, to a lesser extent, glucose-, arabinose- and galactose-containing polysaccharides, together with 7.6% associated lignin. Further extraction of the delignified fibre residue with aqueous 17.5%. NaOH removed the hemicellulose fractions, which were strongly enriched in xylose-containing polysaccharides. Besides ferulic and p-coumaric acids, six other phenolic monomers were also detected in the mixtures of alkaline nitrobenzene oxidation of associated lignin in all the polysaccharide fractions. The content of bound lignin in water soluble, pectic, and 1% NaOH soluble polysaccharides (Fractions 1, 2, and 3), isolated directly from the lignified fibres, was 12 times that of the hemicellulosic preparations (Fractions 4 and 5) isolated from the delignified fibre residues.     

STRUCTURE OF EXTRACELLULAR POLYSACCHARIDES PRODUCED BY A SOIL CRYPTOMONAS SP. (CRYPTOPHYCEAE)1

The Hindak strain of a Cryptomonas species (Cryptophyceae) produces extracellular polysaccharides. Because there is no information on the structure of these compounds in the Cryptophyceae we conducted structural studies. Gas–liquid chromatographic analyses showed that the polysaccharide is composed of fucose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid, and traces of 3-O-methyl galactose. The polysaccharide was separated into two subtractions by ion-exchange chromatography. Fraction A consisted mainly of 1,3-linked galactose units and 1,4-linked galacturonic acid. Unlike fraction B, fraction A did not have xylose, 3-O-methyl galactose, or glucuronic acid. Also, its degree of branching was low compared to that of fraction B. Only traces of sulfate were present infraction A, but fraction B was 10–15% sulfated. Protein was approximately 1% in both fractions. These polysaccharides appear to be a novel type of polymer in algae.     

Structural elucidation of a new arabinogalactan from the leaves of Nerium indicum

A polysaccharide fraction, NIB-2, was obtained from the 3% aqueous sodium carbonate extract of Nerium indicum leaves using anion-exchange chromatography and gel-permeation chromatography. It was found to be composed of rhamnose, arabinose, galactose, in the ratios of 1.0:10.4:4.4, along with 4% of galacturonic acid. The results of methylation analysis, periodate oxidation, partial acid hydrolysis, pectinase treatment, and 13C and 1H NMR spectroscopy indicate that it is mainly an arabinogalactan having a backbone of 1,6-linked beta-Galp, with branches at O-3, consisting of terminal, 1,5-, and 1,3,5-linked arabinofuranosyl residues, and a small proportion of galactosyl residues at the termini. Rhamnose and galacturonic acid arose from a contaminating rhamnogalacturonan.     

An immunomodulating pectic polymer from Glinus oppositifolius

An immunomodulating pectic polymer, GOA1, obtained from the aerial parts of the Malian medicinal plant Glinus oppositifolius (L.) Aug. DC. (Aizoaceae) has previously been reported to consist of arabinogalactans type I and II, probably linked to a rhamnogalacturonan backbone. To further elucidate the structure of the polymer GOA1, enzymatic degradation studies and weak acid hydrolysis were performed. Five different glycosidases were used, endo-alpha-D-(1-->4)-polygalacturonase, exo-alpha-L-arabinofuranosidase, endo-alpha-L-(1-->5)-arabinanase, endo-beta-D-(1-->4)-galactanase and exo-beta-D-galactosidase. It appears that GOA1 may contain a structural moiety consisting of a 1,3-linked galactopyranosyl (Galp) main chain with 1,6-linked Galp side chains attached to position 6 of the main chain. The 1,6-linked Galp side chain may be branched in position 3 with arabinofuranosyl (Araf) side chains. A 1,4-linked Galp backbone which might carry side chains or glycosyl units attached to position 3 is also a structural element in the polymer. We further show that GOA1 induce proliferation of B cells and the secretion of IL-1beta by macrophages, in addition to a marked increase of mRNA for IFN-gamma in NK-cells. To elucidate structure-activity relations the native polymer and the digested fractions were tested for complement fixing activity and intestinal immune stimulating activity. The partial removal of Araf residues after enzymatic degradations did not affect the bioactivities, while the acid hydrolysed fraction showed reduced complement fixing activity. A decrease in Araf units, 1,3,6-linked Galp units and a partial hydrolysed rhamnogalacturonan backbone, in addition to a reduction in molecular weight are factors that might have contributed to reduced bioactivity.     

Characterisation of cell wall polysaccharides from okra (Abelmoschus esculentus (L.) Moench)

Okra pods are commonly used in Asia as a vegetable, food ingredient, as well as a traditional medicine for many different purposes; for example, as diuretic agent, for treatment of dental diseases and to reduce/prevent gastric irritations. The healthy properties are suggested to originate from the high polysaccharide content of okra pods, resulting in a highly viscous solution with a slimy appearance when okra is extracted with water. In this study, we present a structural characterisation of all major cell wall polysaccharides originating from okra pods. The sequential extraction of okra cell wall material yielded fractions of soluble solids extractable using hot buffer (HBSS), chelating agent (CHSS), dilute alkaline (DASS) and concentrated alkaline (CASS). The HBSS fraction was shown to be rich in galactose, rhamnose and galacturonic acid in the ratio 1.3:1:1.3. The degree of acetylation is relatively high (DA = 58) while the degree of methyl esterification is relatively low (DM = 24). The CHSS fraction contained much higher levels of methyl esterified galacturonic acid residues (63% galacturonic acid; DM = 48) in addition to minor amounts of rhamnose and galactose. The ratio of galactose to rhamnose to galacturonic acid was 1.3:1.0:1.3 and 4.5:1.0:1.2 for HBSS and CHSS, respectively. These results indicated that the HBSS and CHSS fractions contain rhamnogalacturonan type I next to homogalacturonan, while the latter is more prevailing in CHSS. Also the DASS fraction is characterised by high amounts of rhamnose, galactose, galacturonic acid and some arabinose, indicating that rhamnogalacturonan I elements with longer arabinose- and galactose-rich side chains were part of this fraction. Partial digestion of HBSS and CHSS by pectin methyl esterase and polygalacturonase resulted in a fraction with a lower Mw and lower viscosity in solution. These samples were subjected to NMR analysis, which indicated that, in contrast to known RG I structure, the acetyl groups in HBSS are not located on the galacturonic acid residues, while for CHSS only part of the acetyl groups are located on the RG I galacturonic acid residues. The CASS fraction consisted of XXXG-type xyloglucan and 4-methylglucuronoxylan as shown by their sugar (linkage) composition and enzymatic digestion.     

Inositol Metabolism in Plants. III. Conversion of Myo-inositol-2-H to Cell Wall Polysaccharides in Sycamore (Acer pseudoplatanus L.) Cell Culture

Prolonged growth of cell cultures of sycamore (Acer pseudoplatanus L.) on agar medium containing myo-inositol-2-(3)H resulted in incorporation of label predominately into uronosyl and pentosyl units of cell wall polysaccharides. Procedures normally used to distinguish between pectic substance and hemicellulose yielded carbohydrate-rich fractions with solubility characteristics ranging from pectic substance to hemicellulose yet the uronic acid and pentose composition of these fractions was decidedly pectic. Galacturonic acid was the only uronic acid present in each fraction. Subfractionation of alkali-soluble (hemicellulosic) polysaccharide by neutralization followed by ethanol precipitation gave 3 fractions, a water-insoluble, an ethanol-insoluble, and an ethanol-soluble fraction, each progressively poorer in galacturonic acid units and progressively richer in arabinose units; all relatively poor in xylose units.Apparently, processes involved in biosynthesis of primary cell wall continued to produce pectic substance during cell enlargement while processes leading to biosynthesis of typically secondary cell wall polysaccharide such as 4-0-methyl glucuronoxylan were not activated.     

Structural analysis of the capsular polysaccharide from Sinorhizobium fredii HWG35

We have determined the structure of a capsular polysaccharide from Sinorhizobium fredii HWG35. This polysaccharide was isolated following the standard protocols applied for lipopolysaccharide isolation. On the basis of monosaccharide analysis, methylation analysis, mass spectrometric analysis, one-dimensional (1)H and (13)C NMR, and two-dimensional NMR experiments, the structure was shown to consist of a polymer having the following disaccharide repeating unit: -->6)-2,4-di-O-methyl-alpha-d-Galp-(1-->4)-beta-d-GlcpA-(1-->. Strain HWG35 produces a capsular polysaccharide that does not show the structural motif (sugar-Kdx) observed in those S. fredii strains that, while effective with Asiatic soybean cultivars, are unable to form nitrogen-fixing nodules with American soybean cultivars. Instead, the structure of the capsular polysaccharide of S. fredii HWG35 is in line with those produced by strains HH303 (rhamnose and galacturonic acid) and B33 (4-O-methylglucose-3-O-methylglucuronic acid), two S. fredii strains that form nitrogen-fixing nodules with both groups of soybean cultivars. Hence, in these three strains that effectively nodulate American soybean cultivars, the repeating unit of the capsular polysaccharide is composed of two hexoses, one neutral (methylgalactose, rhamnose, or methylglucose) and the other acidic (glucuronic, galacturonic, or methylglucuronic acid).     

Beta-D-(1→4)-galactan-containing side chains in RG-I regions of pectic polysaccharides from Biophytum petersianum Klotzsch. contribute to expression of immunomodulating activity against intestinal Peyer's patch cells and macrophages

The aerial parts of the medicinal plant Biophytum petersianum have a long tradition for being used in Mali and other West-African countries against various ailments such as wound healing and malaria. Previous studies on polysaccharides from water extracts of the aerial parts showed the presence of pectic like polymers with an effect on the human complement system as well as the ability to activate macrophages and dendritic cells.The present study shows that pectic polysaccharide fragments (BPII.1 and BPII.2) as well as the original pectic polysaccharide (BPII) expressed immunomodulating activity against Peyer’s patch immunocompetent cells. Exo-β-d-(1 → 3)-galactanase digestion succeeded to decrease IL-6 production enhancing activity against Peyer’s patch cells of BPII.2, but the activity of BPII.1 did not decrease. Endo-β-d-(1 → 4)-galactanase digestion reduced the activities of both BPII.1 and BPII.2. BPII.1 and BPII.2 also stimulated IL-6 production enhancing activity against macrophages, and the activities of both pectic fragments were significantly decreased by either enzymic digestion with exo-β-d-(1 → 3)-galactanase or endo-β-d-(1 → 4)-galactanase. Trimming of terminal GlcA by exo-β-d-glucuronidase digestion did not affect IL-6 production enhancing activity against macrophages of both pectic fragments. Methylation analyses of endo-β-d-(1 → 4)-galactanase digestion products showed the characteristic decrement of 4-linked Gal residues in the pectic fragments. These results suggest that β-d-(1 → 4)-galactan-containing side chains in BPII.1 and BPII.2 play an important role for expression of immunomodulating activity against both Peyer’s patch immunocompetent cells and macrophages in addition to β-d-(1 → 3,6)-galactan chains.     

Isolation and characterization of polysaccharides from Tansy

Using extraction with 0.75% aqueous ammonium oxalate, the following polysaccharide fractions were isolated: tanacetans TVF, TVS, and TVR from floscules, sprouts, and roots, respectively, of Tanacetum vulgare L., spread throughout the European North of Russia. The sugar chain of tanacetan TVF consists of D-galacturonic acid (61.4%), arabinose (14.7%), galactose (10.2%), and rhamnose (3.7%) as the main constituents as well as xylose, glucose, mannose, apiose, and 2-O-methylxylose in trace amounts. Tanacetans TVS and TVR were shown to differ in the sugar quantitative composition. They contain 67 and 28% galacturonic acid, respectively. A partial acid hydrolysis of the tanacetan TVF gave a polysaccharide fragment TVF1, alpha-1,4-D-galacturonan (GalA 98.2%). Digestion with pectinase (alpha-1,4-D-polygalacturonase) resulted in fragment TVF3, containing residues of arabinose (27.1%) and galactose (17.3%). NMR spectroscopy allowed detection of the terminal residues of alpha-Araf and beta-Galp as well as of the residues of alpha-Araf substituted in 3,5- and 5-positions. Thus, tanacetan TVF was proved to be a pectic polysaccharide.     

Inositol Metabolism in Plants. III. Conversion of Myo-inositol-2-3H to Cell Wall Polysaccharides in Sycamore (Acer pseudoplatanus L.) Cell Culture

Prolonged growth of cell cultures of sycamore (Acer pseudoplatanus L.) on agar medium containing myo-inositol-2-³H resulted in incorporation of label predominately into uronosyl and pentosyl units of cell wall polysaccharides. Procedures normally used to distinguish between pectic substance and hemicellulose yielded carbohydrate-rich fractions with solubility characteristics ranging from pectic substance to hemicellulose yet the uronic acid and pentose composition of these fractions was decidedly pectic. Galacturonic acid was the only uronic acid present in each fraction. Subfractionation of alkali-soluble (hemicellulosic) polysaccharide by neutralization followed by ethanol precipitation gave 3 fractions, a water-insoluble, an ethanol-insoluble, and an ethanol-soluble fraction, each progressively poorer in galacturonic acid units and progressively richer in arabinose units; all relatively poor in xylose units.     

Enzymatic extraction and linkage analysis of pectic polysaccharides from onion

Pectin lyase was superior to polygalacturonase for the extraction of onion cell wall pectic polysaccharides. Exhaustive treatment of onion tissue with pectin lyase solubilized 89% of the total uronides of the tissue. The galacturonides released from the tissue were separated into three fractions (10.7, 5.3 and 84%, in order of MW) by gel filtration on Sephadex G-100. The low MW fraction was a mixture of oligogalacturonides. High and intermediate MW fractions were purified by DEAE-Sephadex column chromatography. The intermediate MW fraction was a rhamnogalacturonan II type component which contained 3- and 3,4-linked rhamnose. Methylation analysis showed that the pectic polysaccharides of onion resembled those of potato tuber.     

Water-soluble polysaccharides from Angelica sinensis (Oliv.) Diels: Preparation, characterization and bioactivity

Crude water-soluble polysaccharides (ASP) were separated from Angelica sinensis (Oliv.) Diels by hot water extraction. They were fractionated into neutral and acidic polysaccharides by anion-exchange chromatography. The neutral polysaccharide (ASP1) was rich in glucose, galactose, and arabinose suggesting a mixture of glucan and arabinogalactan. The acidic polysaccharide (ASP2, ASP3) consisted mainly of galacturonic acid along with rhamnose, arabinose, and galactose indicating a pectic polysaccharide. The degree of esterification of ASP and ASP3 were 54.06% and 47.14% for the crude and purified sample, respectively. ASP3, with a molecular weight of 3.4 × 10⁴ Da determined by high-performance size-exclusion chromatography (HPSEC), was the major constituent for the crude extracts. The radioprotective effect of the pectic polysaccharide ASP3 was studied in murine models. ASP3 pretreated mice exhibited a significant decrease of apoptosis (P < 0.05, dosage of 200 mg/kg d body weight) in peripheral lymphocytes compared to the irradiated control. The results showed that ASP3 can protect leucocytes and lymphocytes of mice against radiation induced damage, which has potential radioprotective effect on acute radiation injured mice.     

Extraction, purification and chemical characterisation of xylogalacturonans from pea hulls

Pea hulls contained 925 mg/g sugar including 659 mg/g cellulosic glucose and 90 mg/g uronic acid. They were de-esterified by NaOH (pH>13 at 4°C, 2 h) and treated with HCl (0.1 mol/l, 80°C, 24 h). The HCl-soluble fraction represented 95 mg/g initial pea hulls. It was rich in galacturonic acid (259 mg/g), xylose (93 mg/g) and rhamnose (91 mg/g), which co-eluted in anion-exchange chromatography. The HCl-soluble fraction was degraded by a rhamnogalacturonan-hydrolase and the reaction products were fractionated by size-exclusion chromatography. Two fractions, representing together 18 mg/g initial pea hulls, were composed almost exclusively of galacturonic acid and xylose and could be defined as xylogalacturonans. The first fraction exhibited a high molar mass, a molar ratio Xyl/GalA of 1 and contained almost 5% of rhamnose. The molar mass of the second fraction was much lower and the molar ratio Xyl/GalA was 0.6. Methylation analysis showed the presence in both fractions of a (1→4) galacturonan backbone highly substituted on O-3 either by terminal xylosyl residues or by short side-chains of (1→2) linked xylosyl residues.