Allixin is a

phytoalexin Phytoalexins are antimicrobial substances, some of which are antioxidative as well. They are defined, not by their having any particular chemical structure or character, but by the fact that they are defensively synthesized ''de novo'' by plants t ...

found in

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...

(''Allium sativum'') bulbs. It was first isolated and characterized in 1989. When garlic is stored for long periods of time, it can form visible accumulations of crystalline allixin on its surface, particularly in areas where tissue has become

necrotic Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

. After 2 years of storage, the amount of allixin accumulated can approach 1% of the dry weight of the cloves. Since allixin has weak

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

activity, these high concentrations are thought to be produced by the garlic bulb to protect itself from further damage from microorganisms. Since allixin is found in high concentrations in garlic, there has been scientific interest in determining if it is responsible for any of the known health benefits of garlic. As a result of ongoing research, a variety of biological activities have been attributed to allixin. Pharmaceutical

drug discovery In the fields of medicine, biotechnology and pharmacology, drug discovery is the process by which new candidate medications are discovered. Historically, drugs were discovered by identifying the active ingredient from traditional remedies or by ...

research based on derivatives of allixin has followed.

Laboratory synthesis

Two laboratory syntheses of allixin have been developed. In the first method, reported in 1997, allixin was synthesized in 22 steps starting from D-mannose. A shorter synthesis was developed in 1998 which involved only 5 steps, starting from 5-methylfurfural.

Biological activities

In ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...

'' studies, allixin demonstrates

neurotrophic Neurotrophic factors (NTFs) are a family of biomolecules – nearly all of which are peptides or small proteins – that support the growth, survival, and differentiation of both developing and mature neurons. Most NTFs exert their trop ...

activity, but at high concentrations it has

cytotoxic Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa''). Cell physiology Treating cells ...

effects. Simple chemical analogs of allixin were found to have more potent neurotrophic activity, but without the cytotoxic effects. Allixin may therefore be a useful starting point for the development of pharmaceutical drugs for the treatment of neurodegenerative disorders or for neuronal regeneration in the brain. Pharmacological studies have demonstrated that allixin exerts an anti-promoting activity against skin tumors induced by the chemical 12-''O''-tetradecanoylphorbol-13-acetate (TPA) and an inhibitory effect on

aflatoxin B1 Aflatoxin B1 is an aflatoxin produced by ''Aspergillus flavus'' and '' A. parasiticus''. It is a very potent carcinogen with a TD50 3.2 μg/kg/day in rats. This carcinogenic potency varies across species with some, such as rats and monkeys, seem ...

-induced

mutagenesis Mutagenesis () is a process by which the genetic information of an organism is changed by the production of a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens. It can also be achieved experimentally using la ...

. Allixin may therefore be responsible, at least in part, for the tumor-preventative effects of garlic extract. Allixin has also been shown to have a

radical Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...

scavenging Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding be ...

effect.

Metal complexes

Metal complexes with allixin have been shown to have beneficial pharmacological effects in animal models of diabetes. A complex with

vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...

, bis(allixinato)oxovanadium(IV), is a potent anti-diabetic agent. In studies in

streptozotocin Streptozotocin or streptozocin (INN, USP) (STZ) is a naturally occurring alkylating antineoplastic agent that is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. It is used in medicine for treating certain canc ...

-induced diabetic mice, this vanadium complex was shown to be an insulin mimetic with hypoglycemic effects. Similarly, a

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

-allixin complex, bis(allixinato)zinc(II), shows the same insulin mimetic effects. The

mechanism of action In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targe ...

by which these complexes regulate insulin signaling pathways is unclear. File: VO(alx)2.svg, Bis(allixinato)oxovanadium(IV) File:Zn(alx)2.svg, Bis(allixinato)zinc(II)

References

{{reflist 4-Pyrones Phytoalexins