Vinyldithiin facts for kids
Vinyldithiins, more precisely named 3-vinyl-4H-1,2-dithiin and 2-vinyl-4H-1,3-dithiin, are organosulfur phytochemicals formed in the breakdown of allicin from crushed garlic (Allium sativum). Vinyldithiins are Diels-Alder dimers of thioacrolein, H2C=CHCH=S, formed in turn by decomposition of allicin. In garlic supplements, vinyldithiins are only found in garlic oil macerates that are made by incubation of crushed garlic in oil.
Structure and occurrence
When a garlic clove is crushed, the enzyme alliinase is released forming allicin from the cysteine sulfoxide alliin. Allicin breaks down into additional organosulfur compounds. In the presence of oil or organic solvents, among the compounds formed are the isomeric vinyldithiins and ajoene. As shown in the Scheme, allicin (1) decomposes into 2-propenesulfenic acid (2) and thioacrolein (3). Compound 2 reforms allicin while 3 gives Diels-Alder dimers 3-vinyl-4H-1,2-dithiin (4) and 2-vinyl-4H-1,3-dithiin (5). Garlic cloves yield about 2.5-4.5 mg of allicin per gram when crushed. One fresh garlic clove weighs 2-4 g.
At temperatures above 400 °C, both vinyldithiins undergo retro-Diels-Alder reactions and regenerate the thioacrolein 3.
