Evaluation of an aqueous-ethanolic extract from Pelargonium sidoides (EPs super([registered]) 7630) for its activity against group A-streptococci adhesion to human HEp-2 epithelial cells

• Published in: Journal of ethnopharmacology 2011-01, Vol.133 (1), p.147-152
• Main Authors: Janecki, Aneta, Conrad, Andreas, Engels, Inge, Frank, Uwe, Kolodziej, Herbert
• Format: Article
• Language: English
• Subjects: Data processing; Epithelial cells; Flow cytometry; Geraniaceae; Herbal medicines; Immune system; Infection; Microorganisms; Pathogens; Pelargonium; Powder; proanthocyanidins; pyrogallol; Respiratory tract diseases; Roots; Skin; Streptococcus pyogenes
• ISSN: 0378-8741
• DOI: 10.1016/j.jep.2010.09.018

Aim of the study: The root extract of Pelargonium sidoides DC (Geraniaceae), EPs super([registered]) 7630, is currently used to treat respiratory tract infections. The therapeutic benefits are largely related to the modulation of the non-specific immune system. The present study was designed to investigate the anti-adhesive activity of this herbal medicine with Streptococcus pyogenes as model microorganism and to identify the underlying biologically active principle. Materials and methods: Adherence of fluorescent-labelled group A-streptococci (GAS) to human epithelial (HEp-2) cells was assessed by flow cytometry. Anti-adhesive properties of the parent extract as well as a methanol-soluble (MSF) and a methanol-insoluble fraction (MIF) derived thereof were examined. Treatment with skin powder produced polyphenol-free samples which were included for comparison. Anti-adherence studies were extended to a series of highly purified proanthocyanidins including homogenous epicatechin- and catechin-based polyflavans, a 'mixed' procyanidin sample, an A-type proanthocyanidin mixture as well as a prodelphinidin test substance. Results: After pre-treatment of GAS with EPs super([registered]) 7630 or its subfractions MIF and MSF at concentrations of 30 mu g/ml, adhesion of the pathogen to HEp-2 cells was inhibited by ca. 45%, ca. 35% and ca. 30%, respectively. However, following preincubation of cells with the extract and the fractions no effect was observed. This finding indicates that the anti-adhesive effects are due to interactions with binding factors on the bacterial surface. Since polyphenol-free samples proved to be inactive, proanthocyanidins appear to represent the anti-adhesive principle. Comparative studies with chemically defined proanthocyanidins revealed that the prodelphinidin nature, i.e. the pyrogallol B-ring elements of constituent flavanyl units, represented an important structural feature of the anti-adhesive potential of this herbal medicine. Conclusions: The current data provide strong evidence for a potent anti-adhesion principle of the Pelargonium sidoides root extract related to specific proanthocyanidins. This finding suggests an interaction with bacterial binding sites in a specific rather than non-specific manner. However, the blocked adhesion molecules remain to be identified. The anti-adhesive mechanism may well contribute to the anti-infective activity of EPs super([registered]) 7630 at an early time point of a bacterial infection.