Glycyrrhiza glabra L. (Fabaceae), one of the oldest medicinal plants of the world, is a ligneous perennial shrub growing in Mediterranean region and Asia. Because of the expectorant, anti-spasmodic and anti-inflammatory effects extracts from roots are used therapeutically against bronchitis and gastric ulcer. In order to investigate new modes of action we investigated the influence of isolated polysaccharides from Liquorice roots with regard to their capacity to reduce bacterial binding to host cells. In the present study an in-situ adhesion model with Helicobacter pylori and Porphyromonas gingivalis on sections of human gastric mucosa resp. rat esophagus mucosa was used as screening model for anti-adhesive activity. Preincubation of Helicobacter-suspensions with a solution of the raw polysaccharide resulted in a significant decrease in the bacterial adhesion to gastric mucosa of 40% compared with the non-treated control. Fractionation of the raw polysaccharide via anion ion-exchange chromatography (AEX) yielded 5 subfractions. The strongest reduction of adhesion exhibited the 0.25 molar fraction (60% inhibition) while the other fractions were inactive. The AEX-fractions were further separated by gel permeation chromatography. Respective polysaccharide structures were elucidated. Considerable anti-adhesive effects of liquorice root polysaccharides were also observed after pre-treatment of P. gingivalis. Furthermore the agar diffusion-test revealed absence of any cytotoxicity of the raw polysaccharides against H.pylori and P.gingivalis. Thus, data show that polysaccharides from Glycyrrhiza glabra L. are a potent agent against bacterial adhesion and are able to block the initial step of an infection.
