Vinyldithiins, more precisely named 3-vinyl-4''H''-1,2-dithiin and 2-vinyl-4''H''-1,3-dithiin, are

organosulfur Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur der ...

phytochemicals Phytochemicals are naturally-occurring chemicals present in or extract, extracted from plants. Some phytochemicals are nutrients for the plant, while others are metabolites produced to enhance plant survivability and reproduction. The field ...

formed in the breakdown of

allicin Allicin is an organosulfur compound obtained from garlic and leeks. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma of fresh garlic. Allicin is unstable and quickl ...

from crushed

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...

(''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 Garlic oil is the volatile oil derived from garlic. It is usually prepared using steam distillation, and can also be produced via distillation using ether. It is used in cooking and as a seasoning, a nutritional supplement, and also as an insecti ...

macerates that are made by incubation of crushed garlic in oil. __TOC__

Structure and occurrence

When a garlic clove is crushed, the

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

alliinase In enzymology, an alliin lyase () is an enzyme that catalyzes the chemical reaction :an ''S''-alkyl-L-cysteine ''S''-oxide \rightleftharpoons an alkyl sulfenate + 2-aminoacrylate Hence, this enzyme has one substrate, ''S''-alkyl-L-cysteine ...

is released forming allicin from the cysteine sulfoxide

alliin Alliin is a sulfoxide that is a natural constituent of fresh garlic. It is a derivative of the amino acid cysteine. When fresh garlic is chopped or crushed, the enzyme alliinase converts alliin into allicin, which is responsible for the aroma o ...

. Allicin breaks down into additional organosulfur compounds. In the presence of oil or organic solvents, among the compounds formed are the

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

ic vinyldithiins and

ajoene Ajoene is an organosulfur compound found in garlic (''Allium sativum'') extracts. It is a colorless liquid that contains sulfoxide and disulfide functional groups. The name (and pronunciation) is derived from "ajo", the Spanish word for garlic. ...

. 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-4''H''-1,2-dithiin (4) and 2-vinyl-4''H''-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.

Potential health benefits

Vinyldithiins have been investigated as a preventative for

cardiovascular disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina, heart attack), heart failure, hypertensive heart disease, rheumati ...

and as

antioxidant Antioxidants are Chemical compound, compounds that inhibit Redox, oxidation, a chemical reaction that can produce Radical (chemistry), free radicals. Autoxidation leads to degradation of organic compounds, including living matter. Antioxidants ...

s. In the early 1980s, it was noted that people in the

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

had lower risk of cardiovascular disease. Since garlic is used extensively in the Mediterranean, it is hypothesized that the chemicals in garlic might have cardiovascular effects. Studies have been done measuring the use of garlic for controlling serum

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

levels. Analysis of these studies show that vinyldithiins in garlic have little to no effect on serum

lipids Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins Vitamin A, A, Vitamin D, D, Vitamin E, E and Vitamin K, K), monoglycerides, diglycerides, phospholipids, and others. The fu ...

. Vinyldithiins in garlic have been shown to significantly lower the incidence of

platelet aggregation Platelets or thrombocytes () are a part of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a blood clot. Platelets have no cell nucleus; they are fragments of cytop ...

. Reduction of platelet aggregation may result in reduction of

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when Ischemia, blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction (tissue death) to the heart muscle. The most common symptom ...

ischemic stroke Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop ...

. It is now known that

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

has cardioprotective effects in cases of ischemia related to its effects as an endogenous messenger molecule, primarily via its reduction of the rate of cellular metabolism. The masked dithioacetal functionality of the geminal vinyldithiin isomer can release small but biologically relevant amounts of hydrogen sulfide through a hydrolytic process. Furthermore, divalent organosulfur compounds themselves, such as vinyldithiins are known to reduce oxidative stress via a radical process, which would be relevant to the protection of the cardiovascular system. Ingestion of foods containing vinyldithiins and other organosulfur compounds may decrease the risk of gastric and colon

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

. 2-Vinyl-4''H''-1,2-dithiin was found to exhibit inhibitory activity against

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

hydroperoxide Hydroperoxides or peroxols are Chemical compound, compounds of the form ROOH, where R stands for any group, typically Organic compound, organic, which contain the hydroperoxy functional group (). Hydroperoxide also refers to the hydroperoxide anio ...

(LOOH) formation in human

low-density lipoprotein Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall density ...

(LDL). A

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

of 2-vinyl-4''H''-1,2-dithiin and ''N''-vinylpyrrolidone has been patented as a biocompatible polymer with antithrombogenic (

antithrombotic An antithrombotic agent is a drug that reduces the formation of blood clots ( thrombi).http://cancerweb.ncl.ac.uk/cgi-bin/omd?antithrombotic Antithrombotics can be used therapeutically for prevention ( primary prevention, secondary prevention) or ...

) and

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

properties.Hermes RE. Antithrombogenic and antibiotic composition and methods of preparation thereof. US 4917921, January 1, 1990. http://www.osti.gov/bridge/product.biblio.jsp?osti_id=867345

References

{{reflist, 2 Dithiins Phytochemicals Vinyl compounds Anti-inflammatory agents Dietary antioxidants Pungent flavors Garlic Antifungals