Abstract
Recently a new homologous series of secondary products, N-phenylpropenoyl-L-amino acids (NPAs), isolated and structurally elucidated from cocoa seeds, were reported [1]. Hensel et al. demonstrated N-(E)-caffeic acid L-aspartic acid amide as a strong antiadhesive substance with properties against the adhesion of Helicobacter pylori (HP) to gastric tissue sections [2]. Using a new flow cytometric method, 35 different NPAs were analysed for a better understanding of the structural requirements needed for the antiadhesive effect against HP. Within the family of the NPAs, the N-(E)-caffeic acid L-dihydroxyphenylalanine amide and N-(E)-p-coumaric acid L-dihydroxyphenylalanine amide showed the best antiadhesive properties, inhibiting significantly the adhesion of HP to gastric epithelial cells (AGS) by almost 20%. This was shown to be a similar range as the positive control 3'sialyllactose, which interacts specifically with the HP neuraminyl-lactose-binding hemagglutinin (NLBH). Quantitative structure-activity relations of the NPA homologous serie revealed that the best activity seems to be enhanced by the presence of two vicinal hydroxyl groups within the phenylpropenoyl or amino acid part of the molecule. In addition, the presence of a carboxylic group in the amidic linkage derived from the amino acid also influences positively the activity, as demonstrated with the corresponding compounds N-(E)-caffeic acid L-phenylalanine and N-(E)-caffeic acid L-phenylethylalanine. Higher acidity of the amino acid part increased strongly the inhibitory activity. The described structural properties of NPAs are suggested to be responsible for the antiadhesive effect.
Published Version
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