Galacturonan / Pectin

Structural description

Pectic polysaccharides are a major part of the plant cell wall. They form a network independent from the hemicellulose/cellulose network and influence cell wall properties such as porosity or tensile strength. Pectins consist of three major structural elements: galacturonan, which is a linear chain of α(1-4)-linked D-galacturonic acids, rhamnogalacturonan I, which consists of a back bone of altering α-1,4-linked galacturonic acid and α(1-2)-linked rhamnose units and the complex rhamnogalacturonan II (RG II). RG II is a well-defined structural element of pectin. It is of low molecular weight. Its 12 different sugars are connected via 20 different linkages. Attached to a backbone of 8–10 galacturonic acid residues rhamnogalacturonan II contains four side chains with rare and therefore diagnostic sugars: 2-O-methyl fucose, 2-O-methyl xylose, apiose, 3-C-carboxy-5-deoxy-L-xylose (aceric acid), 3-deoxy-D-lyxo-2-heptulosaric acid (DHA), and 3-deoxy-D-manno-2-octulosonic acid (KDO).

Apiogalacturonans are present in the walls of some aquatic monocots including Lemna minor and Zostera marina. The backbone is mainly made of α(1-4) linked D-galacturonic acid substituted with single β-D-Apiose and β-D-Apiose-(1-5)-β-D-Apiose side chains at C2/C3 position. In the ramified region of the macromolecule, arabinose, galactose, xylose and O-Me-Xylose are possible minor components of side chains.

Activities and Uses

The main use for galacturonan (pectin) is as a gelling agent, thickening agent and stabilizer in food. They have shown prebiotic activities as dietary fibers, anti-angiogenic and immunomodulatory activities.

Oligogalacturonides (OGA) prepared by homogalacturonan hydrolysis (either by chemical or enzymatic):

  • Induce reponse involved in plant defenses (B.L. Ridley et al., 2001. Phytochem., 57; 929–967)
  • Have bifidogenic, prebiotic properties, inhibit the adherence of bacteria to epithelial cells, the initial and crucial stage of infection. (DP2-DP7)
  • Stimulate the apoptosis of colon cancer cells
  • Might implicate an additional mechanism of immunologic protection provided by human milk of the infants (Vos, A. P., Stahl, B., et al. 2007, Pediatric Allergy and Immuno., 18, 304-312)

Apiogalacturonan are used as ingredient intended for skin care.

Rhamnogalacturonan

Rhamnogalacturonan polysaccharide from gombo (Okra) - 10 mg

Rhamnogalacturonan polysaccharide from gombo (Okra) - 10 mg
trait
GAT300

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Acetylated and galactose branched Rhamnogalaturonate polysaccharide extracted and purified from Gombo or Okra (Abelmoschus esculentus).