High molecular weight polysaccharides from black currant seeds inhibit adhesion of Helicobacter pylori to human gastric mucosa

Several crude and purified polysaccharides from black currant seeds (Ribes nigrum L.) have been isolated, analysed and examined on their effects against Helicobacter pylori in in situ adhesion studies on sections of human gastric mucosa. After pretreatment of Helicobacter pylori with 0.01 to 0.1% solutions of the isolated raw polysaccharide (RPS), the epithelial binding of the bacteria was considerably reduced in a concentration-dependent manner, as compared with a non-treated control suspension. Preincubation of the mucosal sections with 0.1% solutions did not result in a reduced binding of non-treated bacteria. An anion-exchange fraction of RPS eluted with 0.1 M phosphate buffer exhibited a comparable, concentration-dependent reduction of adhesion, whereas the water-eluted fraction was ineffective at the respective concentrations. Both subfractions consisted of similar 1,3-linked galactans, decorated with side chains posses-sing 1,4-galacturonic acid, galactose and arabinose residues. Molecular weight profiling by GPC revealed that the antiadhesive activity of the buffer eluate correlated with high molecular weight components ranging from about 1000 Da to 340 kDa, whereas the ones of the inactive water eluate had molecular weights of about 100 and 25 kDa, respectively. None of the active fractions revealed inhibitory effects on bacterial growth in vitro. We conclude that acidic, high molecular weight galactans are responsible for the antiadhesive qualities of black currant seed extracts and that these polymers are able to block Helicobacter surface receptors, thus inhibiting their interaction with specific binding factors located on human gastric epithelia.