Beyond Preservation: Propyl Gallate's Evolving Story as a Metabolic Precursor and Bioactive Compound

Propyl gallate (PG), a long-standing synthetic antioxidant, is integral to the food, cosmetic and pharmaceutical industries for its established effectiveness in inhibiting lipid peroxidation. This review synthesizes the evolving scientific narrative of PG, reframing it from a simple preservative to a multifaceted bioactive compound and metabolic precursor. It details PG's physicochemical properties, chain-breaking antioxidant mechanism and applications in advanced active packaging. A central focus is its metabolic fate: PG is rapidly and extensively hydrolyzed to gallic acid (GA) upon ingestion. This transformation is critical, as the systemic biological activities and toxicological profile are largely attributable to its metabolites, positioning PG as a pro-drug. This metabolic context clarifies the historical discrepancy between in vitro genotoxicity, driven by reactive oxygen species (ROS) generation, and its general lack of in vivo genotoxicity. The review examines PG's dual bioactivity, where its pro-oxidant potential underlies promising anti-cancer effects via the induction of apoptosis in various cancer cell lines and restores antibiotic efficacy against resistant bacteria. By summarizing current toxicological data, including its role as a contact allergen, this work highlights the urgent need for future research designed to precisely differentiate the in vivo activities of PG from GA, enabling a more nuanced understanding of its complex and often paradoxical biological role.