Preventative anti-inflammatory effect of pectic galacturonans after oral administration

Pectic substances are well known to be the major structural components of plant cell walls and to possess anti-inflammatory activity. The segments of alfa-1,4-D-galacturonan are well known to make up the obligatory backbone of all pectins and to inhibit leukocyte adhesion in vitro. The aim of the study is to elucidate an anti-inflammatory effect of pectic galacturonans after oral administration.

Galacturonans deprived of side sugar chains were obtained by partial acidic hydrolysis (2M TFA, 100°C, 5h) of pectins from marsh cinquefoil Comarum palustre (comaruman), siberian tea Bergenia crassifolia (bergenan), duckweed Lemna minor (lemnan), seagrass Zostera marina (zosteran) and commercial citrus pectin. The glycuronic acid content was determined using interaction with 3,5-dimethyl phenol in the presence of conc. sulphuric acid (calibration curve was obtained for D-galacturonic acid). The mol. weights of polysaccharides were analyzed by HPLC. The fractions with Mw >300, 100–300 and 50–100 kDa were obtained from galacturonans using membrane ultrafiltration. Anti-inflammatory capacity of galacturonans obtained was assessed in the carrageenan paw edema test in mice. Positive control and reference groups received indomethacin and apple pectin, respectively.

The resulting galacturonans consist of residues of galacturonic acid (approximately 98%) and rhamnose (traces, ˜0.5%); the protein impurities are absent. Galacturonans were determined to present about one third of the macromolecule, [alfa]_D ²⁰ of galacturonans (+226– +278) were higher compared with those of the parent pectins (+113– +198). The parent pectins, except comaruman, failed to possess an anti-inflammatory effect. All galacturonans with Mw >300 were found to reduce inflammatory reaction. The maximal effect of galacturonans was observed at 1h after carrageenan injection (ca. 60% reduction of footpad swelling) and was comparable with that of indomethacin. The delayed edema (5h) was less affected by the pre-administration of galacturonans (ca. 33% reduction). Galacturonans with Mw less than 300 kDa failed to exhibit anti-inflammatory activity.

Thus, the galacturonans with Mw >300 kDa were shown to possess an anti-inflammatory activity after oral administration. An elimination of side sugar chains of the pectic macromolecule appeared to be useful in development of an anti-inflammatory remedy.