Evidence for bioadhesive effects of polysaccharides and polysaccharide-containing herbs in an ex vivo bioadhesion assay on buccal membranes

Aqueous extracts of polysacchride-containing plants are widely used in therapy for irritated mucus membranes in the pharynx region. In order to prove the existence of mucilaginous effects of polysaccharide hydrocolloids on epithelia an ex vivo system based on porcine buccal membranes was established. The tissue culture was stable and there was no indication of cytolytic processes during the 5 hour incubation period. This was confirmed through histological studies and the respective LDH values as toxicity marker. The test system was shown to discriminate the adhesive effects of different raw polysaccharides, obtained from a variety of medicinal plants. While polysaccharides from Altheae officinalis, Plantago lanceolata, Malva moschata, or Tilia cordata showed only moderate bioadhesion to epithelial tissue, strong adhesive processes were observed with polysaccharides from Fucus vesiculosus and Calendula officinalis. The adhesive effects were concentration-dependent. Histological studies of membranes, incubated with a fluorescence-labelled rhamnogalacturonan, indicated the presence of distinct polysaccharide layers on the apical membrane surface. With these results, adsorption effects of certain polysaccharides on mucus membranes were shown for the first time. Such effects suggest that this may account, at least in part, for the therapeutic effects of mucilage-containing plants in the treatment of irritated buccal membranes.