The effect of provenance and species on the chemical composition of <i>Epilobium</i> herbal tea

BACKGROUND: herb are widely consumed in Europe for prostate-related and anti-inflammatory effects. However, they are often sold under generic names without clear species differentiation or quality specifications, raising concerns about chemical consistency and therapeutic equivalence. OBJECTIVE: products and refine the framework for quality marker selection by integrating pharmacological relevance with structural assessment. MATERIALS AND METHODS: Pan-Assay Interference Compounds (PAINS) structural filters. RESULTS: < 0.05). Flavonol glycosides (e.g., hyperoside, isoquercitrin) also varied substantially. Although species identity influenced phenolic profiles, overlapping concentration ranges indicated a lack of chemical equivalence among products. Geographic origin contributed additional but secondary variability. DISCUSSION: Oenothein B, hyperoside, and isoquercitrin were identified as priority quality markers based on abundance and analytical suitability. Structural reassessment demonstrated that pharmacological ranking alone may be misleading for polyphenol-rich matrices due to redox-related interference. CONCLUSION: teas differ chemically and are not interchangeable. A structure-informed approach is essential for reliable quality assessment and for aligning commercial products with pharmacopeial standards.