Evaluating birch leaf tea as a functional herbal beverage: Beneficial impact on the urinary tract, and metabolism in human organism

Herbal teas are considered as a potential constituent of novel functional beverages consumed daily. One of the commonly used herbal teas is silver birch ( Betula pendula Roth) leaf infusion, traditionally used in urinary tract diseases. In this study, the potential of birch leaf infusion as a functional beverage, emphasizing its active ingredients ' bioavailability, anti-inflammatory, and antiadhesive properties concerning urinary tract health, was investigated. A complex approach was proposed, which included phytochemical screening, bioavailability, gut microbiota biotransformation, and an in vivo test for urine metabolomics assessment. The bioassays confirmed significant anti-inflammatory (interleukins IL -6 and IL -8 secretion) and anti -adhesive (Uropathogenic Escherichia coli and T24 bladder cells) activities. The high -resolution mass spectrometry metabolomics studies linked gut microbiota metabolites and the metabolites present in the urine. Several metabolites connected with phenolics ' consumption were detected in the urine, e.g., glucuronides and sulfates of caffeic acid and dihydroxyphenyl gamma-valerolactones. Based on the presented results, the birch leaf should be considered useful in designing functional beverages, especially targeted to the groups at high risk of urinary diseases.