A Comprehensive Review of Pyrogallol: From Fundamental Chemistry to Advanced Applications and Toxicological Insights

Pyrogallol (benzene-1,2,3-triol) is a simple polyphenol whose vicinal trihydroxyl structure imparts a potent, dualistic redox chemistry, forming the basis for both significant biotechnological promise and considerable toxicological hazard. This review moves beyond a general overview to provide a critical, data-driven, and comprehensive analysis of pyrogallol's molecular mechanisms and applications. A key focus is its biotechnological potential, examining its production via metabolic engineering (e.g., E. coli platforms achieving > 1 g/L titers) and its role as a foundational building block for advanced biomaterials. The high reactivity of its hydroxyl groups is leveraged in mussel-inspired bioadhesives, self-healing hydrogels for tissue engineering, and multifunctional nanoparticles for targeted drug delivery. The quantitative performance of these materials is critically analyzed, such as specific adhesion strengths and drug release kinetics. Concurrently, an in-depth, quantitative assessment is presented of its therapeutic activities, detailing the IC₅₀ values and dose-response relationships in various cancer and microbial models and linking them to specific pathway disruptions (e.g., PI3K/AKT, Nrf2). This therapeutic potential is contrasted by a rigorous, expanded analysis of its toxicological profile. Specific LD₅₀/LC₅₀ data are synthesized, and mechanistic toxicology is explored, including its biotransformation via cytochrome P450 enzymes and its role in glutathione (GSH) depletion, which underpins its well-documented hepatotoxicity, nephrotoxicity, and broader ecotoxicity. This review synthesizes these conflicting "promise and peril" aspects, concluding that the future of pyrogallol in biotechnology hinges on strategies-namely nanocarrier-based targeted delivery and covalent immobilization within polymer matrices-designed to mitigate its systemic toxicity while harnessing its powerful localized reactivity.