The plant whose bulb contains allicin, a sulfur compound with antibiotic properties, is garlic.
Garlic is Allium sativum, a bulb-forming plant related to onions, shallots, leeks, and chives. Its bulb is made up of individual cloves enclosed by papery protective layers. Garlic has been cultivated and used as both food and traditional medicine for thousands of years, especially across Central Asia, the Mediterranean, and Asia.
Allicin is not stored in large quantities in an intact clove. It forms when garlic cells are damaged by cutting, crushing, chewing, or chopping. An enzyme called alliinase then converts alliin into allicin and other sulfur compounds responsible for garlic’s sharp aroma and hot flavor. Laboratory research has demonstrated antimicrobial activity, although that does not mean eating garlic replaces clinically proven antibiotics.
Cooking changes the chemistry: heat reduces allicin and softens garlic’s pungency. A frequent mix-up is onion, which is a close relative and also contains sulfur compounds, but garlic is the standard answer when allicin is the defining clue.