Ajoene is an organosulfur compound found in garlic (''Allium sativum'') extracts. It is a colorless liquid that contains sulfoxide and

disulfide In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

functional groups. The name (and pronunciation) is derived from "ajo", the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

word for garlic. It is found as a mixture of up to four

stereoisomers In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms ...

, which differ in terms of the stereochemistry of the central alkene (''E''- vs ''Z''-) and the chirality of the sulfoxide sulfur (''R''- vs ''S''-).

History and syntheses

The structure of ajoene was determined and it was synthesized based on biosynthetic considerations in 1984, correcting an incorrect structure published in 1983. A short, scalable total synthesis of ajoene was reported in 2018 by Wirth and coworkers while a biosynthetically modeled synthesis of trifluoroajoene from difluoroallicin was published in 2017. Syntheses of various ajoene analogues have also been reported. The chemistry of ajoene has been extensively investigated. When a garlic clove is crushed or finely chopped, allicin is released, with subsequent formation of ajoene when the material is dissolved in various solvents including

edible oil Cooking oil is plant, animal, or synthetic liquid fat used in frying, baking, and other types of cooking. It is also used in food preparation and flavoring not involving heat, such as salad dressings and bread dips, and may be called edible oil ...

s. Ajoene is also found in garlic extract. Ajoene is most stable and most abundant in macerate of garlic (chopped garlic in edible oil). The reaction sequence that forms ajoene (2 in the diagram) involves two molecules of allicin. First, one allicin molecule (1 in the diagram) fragments to form 2-propenesulfenic acid and thio acrolein. These two react in separate stages with another allicin molecule by way of a conjugated thiocationic intermediate.

Medicinal properties

Ajoene has multiple medicinal uses. It functions as an antioxidant by inhibiting the release of

superoxide In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...

. Ajoene also has antithrombotic (anti-clotting) properties, which helps prevent

platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...

s in the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

from forming

blood clot A thrombus (plural thrombi), colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of ...

s, potentially reducing the risk of heart disease and stroke in humans. Ajoene has shown potential virucidal properties against a number of viruses including vesicular stomatitis, vaccinia, human rhinovirus parainfluenza, and herpes simplex. In the infected cell system of a human immunodeficiency virus (HIV), it is shown to block the

integrin Integrins are transmembrane receptors that facilitate cell-cell and cell-extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle ...

-dependent processes. Ajoene has broad-spectrum antimicrobial (antibacterial and antifungal) properties. For example, Ajoene has been shown to have activity against the human dermatophyte ''Trichophyton rubrum'', the most common cause of tinea pedis, commonly known as Athlete's Foot. The specific mechanism of action is unclear, but is thought to be related to the inhibition of phosphatidylcholine biosynthesis in human dermatophytes. In a randomized study by Ledezma et al. (2000), 70 soldiers from the Venezuelan Armed Forces with KOH or culture proven tinea pedis interdigitalis were randomly distributed into 3 treatment groups: 0.6% ajoene, 1% ajoene, and 1% terbinafine (commercially available as Lamisil AT®) applied twice daily for 1 week. At the 60 day follow up, 72%, 100%, and 94% of the patients treated with 0.6% and 1% ajoene, and 1% terbinafine, respectively, had maintained culture-proven mycologic cure suggesting that short-term topical treatment with ajoene is at least as effective as topical terbinafine for treating tinea pedis. Ajoene has been investigated as a chemotherapeutic agent for treatment of

cancer stem cells Cancer stem cells (CSCs) are cancer cells (found within tumors or hematological cancers) that possess characteristics associated with normal stem cells, specifically the ability to give rise to all cell types found in a particular cancer sampl ...

glioblastoma multiforme Glioblastoma, previously known as glioblastoma multiforme (GBM), is one of the most aggressive types of cancer that begin within the brain. Initially, signs and symptoms of glioblastoma are nonspecific. They may include headaches, personality cha ...

, of lung adenocarcinoma and as an anti-leukemia agent for

acute myeloid leukemia Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may inclu ...

therapy. Ajoene has been found to decrease

basal-cell carcinoma Basal-cell carcinoma (BCC), also known as basal-cell cancer, is the most common type of skin cancer. It often appears as a painless raised area of skin, which may be shiny with small blood vessels running over it. It may also present as a raise ...

tumor size by inducing apoptosis while it has also been shown effective in inhibiting

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

growth by targeting the microtubule cytoskeleton of such cells and by other mechanisms. Ajoene inhibits genes controlled by

quorum sensing In biology, quorum sensing or quorum signalling (QS) is the ability to detect and respond to cell population density by gene regulation. As one example, QS enables bacteria to restrict the expression of specific genes to the high cell densities at ...

References

External links

{{commons category inline, Ajoene Organic disulfides