Complex Standard Formulation as an Example for Synergism and Improved Antibacterial Activity Against Uropathogenic Escherichia coli for Urinary Tract Infections

For the treatment of urinary tract infections, mixtures of different herbal materials are frequently used within traditional clinical practice. A complex formulation, widely used in Germany for the preparation of aqueous extracts with <i>Betula</i> sp., <i>Agropyron repens, Solidago gigantea</i>, and <i>Ononis spinosa</i>, was infused as a mixture from all four components (combined extract). In addition, the four herbs were extracted separately, and the extracts were mixed subsequently (separate extract). None of the extracts influenced the proliferation of UPEC-UTI89 and the cell viability of T24 bladder cells. The combined extract significantly reduced the activity of type-1 fimbriae of UPEC CFT073. This effect was not observed for the mixture of the separately extracted herbs. Systematic investigation of the combined extract and binary mixtures by LC-MS and bioassays indicated that a series of malonylated dammarane triterpenes from <i>Betula</i> spp. leaves was extracted in the presence of <i>Solidago</i> sp. These dammaranes are responsible for the antiadhesive effect. The combined extract of <i>Betula</i> sp. and <i>Solidago gigantea</i> BSC, as well as a dammarane-enhanced fraction (DEF), showed significant antiadhesive effects in a 2D-adhesion assay, as well as in three-dimensional RT4- bladder cell spheroids. RT-qPCR of UTI89 incubated with DEF indicated downregulation of <i>fimC, fimD</i>, and <i>fimH</i> with impact on the chaperone-usher system and correct pili formation. Increased expression of the motility gene <i>fliC</i> indicates a switch from a static to a motile lifestyle. The S-fimbrial gene <i>sfaG</i> was significantly downregulated, but this did not result in phenotypic changes. Based on an improved extraction of birch leaf constituents, the data rationalize the importance of combinations of herbal drugs.