Antiadhesive glycoconjugates from immature Okra fruits against Helicobacter pylori

Helicobacter pylori is a gram negative bacterium which colonizes the human stomach. It is responsible for several gastrointestinal diseases such as gastritis, ulcers, and gastric cancer. The WHO has classified H. pylori as a class I carcinogen. Due to increasing resistance to antibiotics the treatment of H. pylori infection is faced with severe problems. The adhesion of H. pylori to the gastric mucosa can be seen as the first and most important step of the development of its pathogenicity. Thus, the prevention of adhesion by natural compounds can be seen as a new cytoprotective strategy against H. pylori. Previous studies indicated that several bacterial adhesins such as BabA and SabA are responsible for the specific attachment to the host cells. Recently it has been shown that an aqueous extract from Okra fruits (Abelmoschus esculentus), traditionally used in Asia and Africa for gastritits, inhibits the adhesion of H. pylori to human gastric mucosa. This antiadhesive effect is supposed to be related to glycosylated proteins and polysaccharides with a pectin-like rhamnogalacturonan structure (1).

The antiadhesive effect of a dialyzed water extract of immature okra fruits against H. pylori was proven in an in vitro flow cytometric assay by using fluorescence activated cell sorting. The antiadhesive effect was concentration-dependent in the range of 0.2 to 2,7 mg/mL. A concentration of 2,7 mg/mL results in 70% inhibition of adhesion. Protein depletion from this extract by both heat and acid decreases the antiadhesive effect about 20%. This indicates a cumulative effect of both polysaccharides and proteins. Sequential extraction of different polysaccharide classes (pectins, hemicelluloses, etc.) from okra fruits indicated galactoxyloglucan to exert highest antiadhesive effects against bacterial attachment of H. pylori (inhibition of 95% for 1,5 mg/mL galactoxyloglycan).

Reference:

[1] Lengsfeld C, Titgemeyer F, Faller G, Hensel A. (2004)J. Agricul. Food Chem. 52, 1495 – 1503