 2-Propenesulfenic acid, formed from allicin, is thought to be responsible for garlic’s potent antioxidant activity.Mass spectrometry with a DART ion source were used to identify 2-propenesulfenic formed when garlic is cut or crushed and to demonstrate that this sulfenic acid has a lifetime of less than one second.The pharmacological activity of certain drugs, such as omeprazole, esomeprazole, ticlopidine, clopidogrel, and prasugrel is proposed to involve sulfenic acid intermediates.