Anacardic acids are

phenolic lipid Phenolic lipids are a class of natural products composed of long aliphatic chains and phenolic rings. Phenolic lipids occur in plants, fungi and bacteria. Types * Alkylcatechols * Alkylphenols (nonylphenol, cardanol) * Alkylresorcinols * Anaca ...

s, chemical compounds found in the shell of the cashew nut (''

Anacardium occidentale Cashew is the common name of a tropical evergreen tree ''Anacardium occidentale'', in the family Anacardiaceae. It is native to South America and is the source of the cashew nut and the cashew apple, an accessory fruit. The tree can grow as tal ...

''). An acid form of

urushiol Urushiol is an oily mixture of organic compounds with Allergic contact dermatitis, allergenic properties found in plants of the Family (biology), family Anacardiaceae, especially ''Toxicodendron'' ''spp.'' (e.g., poison oak, Toxicodendron vernic ...

, they also cause an allergic

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

rash on contact, known as

urushiol-induced contact dermatitis Urushiol-induced contact dermatitis (also called Toxicodendron dermatitis or Rhus dermatitis) is a type of allergic contact dermatitis caused by the oil urushiol found in various plants, most notably sumac family species of the genus ''Toxicodendr ...

. Anacardic acid is a yellow liquid. It is partially miscible with ethanol and ether, but nearly immiscible with water. Chemically, anacardic acid is a mixture of several closely related

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s. Each consists of a

salicylic acid Salicylic acid is an organic compound with the formula HOC6H4COOH. A colorless (or white), bitter-tasting solid, it is a precursor to and a active metabolite, metabolite of acetylsalicylic acid (aspirin). It is a plant hormone, and has been lis ...

substituted with an

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...

chain that has 15 or 17 carbon atoms. The alkyl group may be saturated or unsaturated; anacardic acid is a mixture of saturated and unsaturated molecules. The exact mixture depends on the species of the plant. The 15-carbon unsaturated side chain compound found in the cashew plant is lethal to

Gram-positive bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain ...

. Folk use for tooth abscesses, it is also active against

acne Acne ( ), also known as ''acne vulgaris'', is a long-term Cutaneous condition, skin condition that occurs when Keratinocyte, dead skin cells and Sebum, oil from the skin clog hair follicles. Typical features of the condition include comedo, ...

, some insects,

tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

, and

MRSA Methicillin-resistant ''Staphylococcus aureus'' (MRSA) is a group of gram-positive bacteria that are genetically distinct from other strains of ''Staphylococcus aureus''. MRSA is responsible for several difficult-to-treat infections in humans. ...

. It is primarily found in foods such as

cashew Cashew is the common name of a tropical evergreen tree ''Anacardium occidentale'', in the family Anacardiaceae. It is native to South America and is the source of the cashew nut and the cashew apple, an accessory fruit. The tree can grow as t ...

nuts, cashew apples, and cashew nutshell oil, but also in

mango A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...

s and ''

Pelargonium ''Pelargonium'' () is a genus of flowering plants that includes about 280 species of perennial plant, perennials, succulent plant, succulents, and shrubs, common name, commonly called geraniums, pelargoniums, or storksbills. ''Geranium'' is also ...

'' geraniums.

Experimental antibacterial properties

The side chain with three unsaturated bonds was the most active against ''

Streptococcus mutans ''Streptococcus mutans'' is a Facultative anaerobic organism, facultatively anaerobic, gram-positive coccus (round bacteria, bacterium) commonly found in the human oral cavity and is a significant contributor to dental caries, tooth decay. The m ...

'', the tooth decay bacterium, in test tube experiments. The number of unsaturated bonds was not material against ''

Cutibacterium acnes ''Cutibacterium acnes'' (''Propionibacterium acnes'') is the relatively slow-growing, typically aerotolerant anaerobic, gram-positive bacterium (rod) linked to the skin condition of acne; it can also cause chronic blepharitis and endophthalmitis ...

'', the acne bacterium. Eichbaum claims that a solution of one part anacardic acid to 200,000 parts water to as low as one part in 2,000,000 is lethal to Gram-positive bacteria in 15 minutes ''in vitro''. Somewhat higher ratios killed tubercle bacteria of

in 30 minutes. Heating these anacardic acids converts them to the alcohols (

cardanol Cardanol is a phenolic lipid obtained from anacardic acid, the main component of cashew nutshell liquid (CNSL), a byproduct of cashew nut processing. Cardanol finds use in the chemical industry in resins, coatings, frictional materials, and su ...

s) with reduced activity compared to the acids. Decarboxylation, such as through heating done in most commercial oil processing, results in compounds with significantly reduced activity. It is said that the people of the Gold Coast (now Ghana) use cashew leaves and bark for a toothache.

Industrial uses

Anacardic acid is the main component of

cashew nutshell liquid Cashew is the common name of a tropical evergreen tree ''Anacardium occidentale'', in the family Anacardiaceae. It is native to South America and is the source of the cashew nut and the cashew apple, an accessory fruit. The tree can grow as tal ...

(CNSL), and finds use in the chemical industry for the production of

, which is used for resins, coatings, and frictional materials. Cardanol is used to make phenalkamines, which are used as curing agents for the durable epoxy coatings used on concrete floors.

History

The first chemical analysis of the oil of the cashew nut shell from the ''Anacardium occidentale'' was published in 1847. It was later found to be a mixture rather than one chemical, sometimes the plural anacardic acids is used.

Synergies

Anacardic acid is synergistic with

anethole Anethole (also known as anise camphor) is an organic compound that is widely used as a flavoring substance. It is a derivative of the aromatic compound allylbenzene and occurs widely in the essential oils of plants. It is in the class of phenylpr ...

from the seed of

anise Anise (; '), also called aniseed or rarely anix, is a flowering plant in the family Apiaceae native to the eastern Mediterranean region and Southwest Asia. The flavor and aroma of its seeds have similarities with some other spices and herbs, ...

(

Umbelliferae Apiaceae () or Umbelliferae is a family of mostly aromatic flowering plants named after the type genus '' Apium,'' and commonly known as the celery, carrot, or parsley family, or simply as umbellifers. It is the 16th-largest family of flowering ...

) and

linalool Linalool () refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Together with geraniol, nerol, and citronellol, linalool is one of the rose alcohols. Linalool has multiple commercial app ...

from green tea ''

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

'' uroi & Kubo, p1782 The

totarol Totarol is a naturally produced diterpene that is bioactive. It was first isolated by McDowell and Easterfield from the heartwood of ''Podocarpus totara'', an endemic conifer species found in New Zealand. ''Podocarpus totara'' was investigated f ...

in the bark of ''

Podocarpus ''Podocarpus'' () is a genus of conifers, the most numerous and widely distributed of the podocarp family, the Podocarpaceae. ''Podocarpus'' species are evergreen shrubs or trees, usually from tall, known to reach at times. The cones have ...

'' trees is synergistic with anacardic acid in its bactericidal effects.

Other and potential uses

There is also a suspicion that inhibiting anacardic acids may arrest the growth of cancer tumors such as

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

. ubo et al., 1993Inhibition of lysine acetyltransferase by anacardic acid was shown to make cancer cells using alternative lengthening of telomeres more sensitive to

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

. Anacardic acid (2-hydroxy-6-alkylbenzoic acid) provides resistance to small pest insects (

aphids Aphids are small sap-sucking insects in the Taxonomic rank, family Aphididae. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Eriosomatinae, woolly ...

and

spider mites Spider mites are members of the family Tetranychidae, which includes about 1,200 species. They are part of the subclass Acari (mites). Spider mites generally live on the undersides of leaves of plants, where they may spin protective silk webs, a ...

). Anacardic acid kills methicillin-resistant ''Staphylococcus aureus'' (MRSA) cells more rapidly than

List of anacardic acids

* 6-pentadecyl salicylic acid (6-PDSA), a potent HAT inhibitor from

cashew nut Cashew is the common name of a tropical evergreen tree ''Anacardium occidentale'', in the family Anacardiaceae. It is native to South America and is the source of the cashew nut and the cashew apple, an accessory fruit. The tree can grow as tal ...

shell liquid, and sensitizer of cancer cells to

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

References

{{reflist, 30em Antiseptics Phenolic lipids Salicylic acids Histone Acetyltransferase Inhibitor Plant toxins