Distinct fractions of Pelargonium sidoides-extract (EPs® 7630) inhibit adhesion of group A streptococci to epithelial cells

EPs® 7630, a special aqueous-ethanolic extract of the roots of Pelargonium sidoides, showed in vitro antibacterial, antiviral and immunomodulatory properties in several studies [1]. However, the direct antibacterial activities proved to be only weak under therapeutic conditions and speculation about an anti-infective defence mechanism by which EPs® 7630 might exert antibacterial activity was recently guided by consideration of anti-adhesive effects [2]. The demonstrated significant reduction of adhesion of group A streptococci (GAS) to intact epithelial cells prompted the present study to provide a chemical rationale for this particular biological activity. Flow cytometric investigations of GAS adherence to human HEp-2 epithelial cells revealed that a methanol-insoluble (MIF) and a methanol-soluble fraction (MSF) as well as an enriched fraction of proanthocyanidin dimers revealed similar antiadhesive potentials compared to EPs® 7630. Adhesion was diminished by ca. 30% in a sample concentration of 30µg/ml. Interestingly, treatment of the samples with skin powder producing polyphenol free materials resulted in complete loss of this inhibitory activity, suggesting that proanthocyanidins play a major role in the bacterial interaction with epithelial cells. To gain insight into possible structural features, a range of proanthocyanidin mixtures with distinct molecular elements was included in this study but failed to exhibit antiadhesive effects. This finding provides convincing evidence for a unique molecular structure of the proanthocyanidins present in EPs® 7630.

References: [1] Kolodziej H, Kiderlen AF. Phytomedicine 2007; 14 (Suppl. VI): 18–26

[2] Conrad A et al. Phytomedicine 2007; 14 (Suppl. VI): 52–59