Comparative study on the mechanisms of citrus pectin and polygalacturonic acid in alleviating food allergies

Pectin has a complex structure, and different structures lead to different biological functions. Citrus pectin (PC) has been widely proven to possess immunomodulatory activity. This study compared and analyzed the anti-allergic activities of PC and polygalacturonic acid (PGA) based on intestinal microbiota, metabolomics, and molecular docking. The results showed that dietary interventions with PC and PGA significantly relieved allergic symptoms, intestinal damage, and the contents of specific antibodies IgE and IgG1. Among them, PGA exhibited a significant suppressive effect on histamine and alleviated the Th1/Th2 imbalance caused by food allergies. Furthermore, after fermentation by intestinal flora, the metabolites of both PC and PGA activated the NOTCH/NF-κB pathway through the gut-spleen axis to mitigate food allergies. Interestingly, the linear main chain of PGA was more easily degraded by the intestinal flora, thereby promoting histamine metabolism. In contrast, the complex side chains of PC facilitated the production of co-metabolites by the host microbiota, allowing them to participate in immune regulation. This study investigated the structure-activity relationship of pectin substances, providing a theoretical basis for the high-value utilization of citrus processing byproducts and the development of targeted nutritional intervention strategies.