A method of producing polysulfides comprising the step of adding elemental sulphur to an allicin-containing plant extract. In preferred embodiments, the plant extract is mechanically treated members of the genus Allium, especially garlic. In further preferred aspects of the invention, the plant extract and sulphur mixture is heated, and the pH is controlled to allow manipulation of the polysulfide chain length. The addition of organic bases, containing nitrogen lone pairs, allows further control of polysulfide chain length.