Homogentisic Acid

Homogentisic Acid (CAS No.: 451-13-8) is a phenolic acid belonging to the class of 2-(hydroxyphenyl)acetic acids and serves as a key intermediate in the metabolic degradation of aromatic amino acids, including phenylalanine and tyrosine. Biologically, it is formed endogenously and is notably accumulated in the metabolic disorder alkaptonuria, where its progressive deposition in connective tissues leads to ochronosis and associated degenerative changes. Functionally, homogentisic acid is recognized as an amyloidogenic and pigment-forming molecule that can cross the blood-brain barrier and modulate barrier integrity by downregulating tight junction proteins such as claudin-5, occludin, and ZO-1. Mechanistically, both homogentisic acid and its oxidation derivatives promote aggregation and fibrillogenesis of multiple amyloid-prone proteins, including amyloid-β, α-synuclein, serum amyloid A, transthyretin, and atrial natriuretic peptide, while simultaneously inducing oxidative stress, disrupting Wnt/β-catenin signaling, and contributing to neurotoxicity and synaptic dysfunction. These properties position it as a valuable tool compound for studying protein misfolding disorders, secondary amyloidosis, neurodegenerative diseases, and pigment-related pathologies. In vitro, its biological effects are typically observed across micromolar concentration ranges, with context-dependent cytotoxic or protective outcomes, including reports of low toxicity toward peripheral blood lymphocytes and modulation of genotoxic stress responses. In experimental settings, homogentisic acid is widely applied in cellular and animal models to investigate disease mechanisms, barrier function, and amyloid aggregation processes, with dosing regimens varying according to specific study designs and endpoints in biomedical and drug discovery research.