Effect on cell surface hydrophobicity and susceptibility of Helicobacter pylori to medicinal plant extracts

Effects of aqueous extracts of medicinal plants on ten Helicobacter pylori strains were studied by the salt aggregation test to determine the possibil ity to modulate their cell surface hydrophobicity and by an agar diffusion assay for detection of antimicrobial activity. It was established that aque ous extracts of bearberry and cowberry leaves enhance cell aggregation of a ll H. pylori strains tested by the salt aggregation test, and the extract o f bearberry possessed a remarkable bacteriostatic activity. Pure tannic aci d showed a result similar to that of bearberry and cowberry extracts which contained a large amount of tannins. In contrast, extracts of wild camomile and pineapple-weed, which blocked aggregation of H. pylori, contained smal l amounts of tannins and did not reveal any antimicrobial activity. Tannic acid seems to be the component of bearberry and cowberry aqueous extracts w ith the highest activity to decrease cell surface hydrophobicity as well as in antibacterial activity against H. pylori. (C) 1999 Federation of Europe an Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.