Alliin

One of the organic sulphur compounds contributing to the flavour-precursor fraction in garlic and other Allium vegetables — the odourless cysteine sulfoxide stockpiled in intact cloves. The moment cells are crushed, alliinase enzymes convert it into pungent allicin, the plant’s chemical defence against pests and microbes. Alliin content varies with variety, growing conditions and storage, and supplement makers standardise garlic extracts on their potential to generate allicin. It is the quiet precursor behind garlic’s bite: harmless in the intact clove, formidable once released.