Allicin is an organosulfur compound obtained from garlic, a species in the family Alliaceae. It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic. The allicin generated is very unstable and quickly changes into a series of other sulfur containing compounds such as diallyl disulfide. It exhibits antibacterial, antifungal, antiviral, and antiprotozoal activity. Allicin is garlic's defense mechanism against attacks by pests.