Isol. from garlic (Allium sativum). Nutriceutical Allicin is an organic compound obtained from garlic. It is also obtainable from onions, and other species in the family Alliaceae. It was first isolated and studied in the laboratory by Chester J. Cavallito in 1944. This colourless liquid has a distinctively pungent smell. This compound exhibits antibacterial and anti-fungal properties. Allicin is garlic's defence mechanism against attacks by pests.