Propyl Gallate, Gallic Acid, and Pyrogallol: A Comprehensive Review of Their Chemistry, Metabolism, Bioactivity, and Applications

This comprehensive review examines propyl gallate (PG), gallic acid (GA), and pyrogallol (PY), structurally related phenolic compounds bridging synthetic additives and natural metabolites. While PG is a widely used antioxidant, its safety profile is complicated by its intricate metabolic fate. This study delineates their properties and synthesis, contrasting traditional methods with modern biocatalysis and metabolic engineering. A central focus is the critical metabolic cascade where ingested PG is rapidly hydrolyzed in the liver to GA, subsequently decarboxylated by gut microbiota to the reactive and potentially toxic metabolite, PY. This transformation is pivotal for interpreting divergent toxicological profiles, reclassifying PG as a metabolic "pro-drug" and elucidating PY's potent pro-oxidant effects. Specifically, PY's "oxidative assault" mechanism, characterized by a ROS burst and glutathione depletion, is analyzed as a dual driver for both anticancer efficacy and systemic toxicity. Furthermore, the analysis explores structure-activity relationships like the "cut-off effect" governing alkyl gallates, and PG's emerging role in active packaging and antibiotic resistance reversal. By investigating advanced applications in mussel-inspired biomaterials and nanocarrier-based delivery, this synthesis underscores the intricate link between chemical structure, metabolic fate, and biological function.