4-Hydroxynonenal-d3 is the deuterated form of 4-Hydroxynonenal (4-HNE), an α,β-unsaturated hydroxyalkenal and a biomarker of oxidative/nitrosative stress. This compound acts as both a substrate and inhibitor of ALDH2. It modulates numerous signaling pathways primarily through covalent adduct formation with nucleophilic functional groups in proteins, nucleic acids, and membrane lipids. Additionally, 4-Hydroxynonenalal plays a significant role in cancer through mitochondrial interactions.