A review on the metabolism and anti-allergic effects of ellagitannins.

Allergic diseases, such as allergic rhinitis, asthma, and atopic dermatitis, are IgE-mediated conditions closely linked to Th2 cells. Their increasing prevalence has posed significant global health and economic challenges. Conventional anti-allergic drugs, though effective, often lead to side effects like sedation and dependency, driving the search for safer, plant-derived alternatives. Ellagitannins, a class of phenolic compounds abundant in many plants, and their metabolites (e.g., ellagic acid, gallic acid) have demonstrated promising anti-allergic and anti-inflammatory properties. However, the impact of their structural variability on bioavailability and biological activity remains unclear. To date, no comprehensive review has been conducted on the effects of different ellagitannin structures and their metabolism on anti-allergic biological activities. This study proposes a novel classification method for ellagitannins based on their in vivo digestion and absorption, provides a comprehensive review of their metabolic pathways and influencing factors, and, for the first time, explores the anti-allergic activities and mechanisms of ellagitannins and their metabolites. These findings lay a foundation for future research into the structural characteristics and anti-allergic functional activities of ellagitannins.