Abstract
BackgroundTraditional Asian and African medicine use immature okra fruits (Abelmoschus esculentus) as mucilaginous food to combat gastritis. Its effectiveness is due to polysaccharides that inhibit the adhesion of Helicobacter pylori to stomach tissue. The present study investigates the antiadhesive effect in mechanistic detail.MethodologyA standardized aqueous fresh extract (Okra FE) from immature okra fruits was used for a quantitative in vitro adhesion assay with FITC-labled H. pylori J99, 2 clinical isolates, AGS cells, and fluorescence-activated cell sorting. Bacterial adhesins affected by FE were pinpointed using a dot-blot overlay assay with immobilized Lewisb, sialyl-Lewisa, H-1, laminin, and fibronectin. 125I-radiolabeled Okra FE polymer served for binding studies to different H. pylori strains and interaction experiments with BabA and SabA. Iron nanoparticles with different coatings were used to investigate the influence of the charge-dependence of an interaction on the H. pylori surface.Principal findingsOkra FE dose-dependently (0.2 to 2 mg/mL) inhibited H. pylori binding to AGS cells. FE inhibited the adhesive binding of membrane proteins BabA, SabA, and HpA to its specific ligands. Radiolabeled compounds from FE bound non-specifically to different strains of H. pylori, as well as to BabA/SabA deficient mutants, indicating an interaction with a still-unknown membrane structure in the vicinity of the adhesins. The binding depended on the charge of the inhibitors. Okra FE did not lead to subsequent feedback regulation or increased expression of adhesins or virulence factors.ConclusionNon-specific interactions between high molecular compounds from okra fruits and the H. pylori surface lead to strong antiadhesive effects.
Highlights
The immature fruits of Abelmoschus esculentus (L.) Moench, Malvaceae, known as okra or lady’s finger, are widely used as a food vegetable in Asia, Africa, and South-America
Non-specific interactions between high molecular compounds from okra fruits and the H. pylori surface lead to strong antiadhesive effects
The antiadhesive effects are caused by an interaction with the bacteria, while pretreatment of human stomach tissue with the plant polysaccharides prior to the addition of H. pylori does not lead to reduced bacterial adhesion [3]
Summary
The immature fruits of Abelmoschus esculentus (L.) Moench, Malvaceae, known as okra or lady’s finger, are widely used as a food vegetable in Asia, Africa, and South-America. The structural elements of mucilage have recently been characterized as pectinlike rhamnogalacturonans [1,3] with unusual structural features [2]. These okra rhamnogalacturonan polysaccharides reportedly possess antiadhesive properties that interrupt the adhesion of Helicobacter pylori to human stomach tissue [3]. The antiadhesive effects are caused by an interaction with the bacteria, while pretreatment of human stomach tissue with the plant polysaccharides prior to the addition of H. pylori does not lead to reduced bacterial adhesion [3]. Traditional Asian and African medicine use immature okra fruits (Abelmoschus esculentus) as mucilaginous food to combat gastritis. The present study investigates the antiadhesive effect in mechanistic detail
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