Alliin (S-allyl-L-cysteine-S-oxide) is a phytochemical compound sulfoxide,. a derivative of the amino acid cysteine, belonging to the class of sulfur compounds, found abundantly in fresh garlic and onion. Health Benefits 1. Antioxidant properties In the investigation of the antioxidant properties of garlic compounds representing the four main chemical classes, alliin, allyl cysteine, allyl disulfide, and …