Ethyl maltol-d 5 is the deuterium labeled Ethyl maltol. Ethyl maltol (2-Ethyl-3-hydroxy-4H-pyran-4-one) is an orally active and important food additive and flavor enhancer. Ethyl maltol is less toxic to rats and dogs. Ethyl maltol can enhance copper-mediated cytotoxicity and induce apoptosis in lung epithelial cells.