A Comprehensive Review on the Bioactivities, Mechanism, and Translational Potential of Platycodin D

Platycodin D (PD) as the main triterpene saponins in <em>Platycodon grandiflorum</em> (Jacq.) A. DC. (PG), has both food and medicinal value, and has shown broad application prospects in functional food and health products. This article systematically reviews the pharmacological activities, mechanisms of action and pharmacokinetic characteristics of PD. Some studies have shown that PD has various biological activities such as anti-cancer, anti-inflammatory, anti-oxidation, metabolic regulation and organ protection by regulating phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR), nuclear factor-κB (NF-κB) and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathways. For example, it can induce tumor cell apoptosis, arrest cell cycle, alleviate airway inflammation through inhibiting toll-like receptor 4 (TLR4)/NF-κB pathway, and improve metabolic syndrome by activating AMP-activated protein kinase (AMPK) pathway. In terms of preparation, enzymatic conversion methods (such as β-glucosidase catalysis) and response surface method can significantly improve the extraction process of PD. Dehydroxylation and deglycosylation are the primary metabolic pathways of PD <em>in vivo</em>. However, its oral bioavailability in rats is relatively low (absolute bioavailability 1.89%), necessitating the use of nanodelivery systems or other technologies to enhance absorption. Safety evaluation showed that PD has low toxicity at therapeutic doses, but its hemolytic activity and concentration-dependent cytotoxicity still need attention. Future research should concentrate on the development of novel delivery systems, analysis of multi-target action networks and clinical translation to promote the application of PD in functional foods and innovative drugs.