The guardian that guides: cinnamic acid enhances oral bioavailability of diverse TCM components by reinforcing rather than disrupting intestinal barrier integrity

This study established a Caco-2/HT29 co-culture intestinal epithelial model to systematically investigate the intestinal absorption and transport mechanisms of cinnamic acid (CA). The results indicate that CA enhances intestinal barrier integrity by regulating the expression of tight junction proteins and promoting the secretion of neutral mucus, and significantly increases the intestinal absorption rates of alkaloids (sinomenine hydrochloride, SH), monoterpenes (paeoniflorin, PF), saponins (glycyrrhizic acid, GA), and flavonoids (liquiritin, LQ). These findings provide experimental evidence supporting the use of CA as a natural permeation enhancer to improve oral bioavailability.