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) * Alkylresorcinol Alkylre ...

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

Anacardium occidentale The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ''Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cult ...

''). An acid form of

urushiol Urushiol is an oily mixture of organic compounds with allergenic properties found in plants of the family Anacardiaceae, especially ''Toxicodendron'' ''spp.'' (e.g., poison oak, Chinese lacquer tree, poison ivy, poison sumac), ''Comocladia sp ...

, 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 cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

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 species of the genus ''Toxicodendron'': poison ...

. 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 In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

s. Each consists of a

salicylic acid Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substance ...

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 is derived from a cycloalk ...

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. Gram-positive bact ...

. Folk use for

tooth abscess A dental abscess is a localized collection of pus associated with a tooth. The most common type of dental abscess is a periapical abscess, and the second most common is a periodontal abscess. In a periapical abscess, usually the origin is a bac ...

es, 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, black ...

, some insects,

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

, 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 The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ''Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cult ...

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 is believed to have originated in the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South a ...

s and ''

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

'' geraniums.

Experimental antibacterial properties

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

Streptococcus mutans ''Streptococcus mutans'' is a facultatively anaerobic, gram-positive coccus (round bacterium) commonly found in the human oral cavity and is a significant contributor to tooth decay. It is part of the " streptococci" (plural, non-italic lowercase ...

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

Cutibacterium acnes ''Cutibacterium acnes'' (formerly ''Propionibacterium acnes'') is the relatively slow-growing, typically aerotolerant Anaerobic organism, anaerobic, gram-positive bacterium (rod) linked to the skin condition of acne vulgaris, acne; it can also ca ...

'', 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 Gold Coast may refer to: Places Africa * Gold Coast (region), in West Africa, which was made up of the following colonies, before being established as the independent nation of Ghana: ** Portuguese Gold Coast (Portuguese, 1482–1642) ** Dutch G ...

(now Ghana) use cashew leaves and bark for a toothache.

Industrial uses

Anacardic acid is the main component of

cashew nutshell liquid The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ''Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cult ...

(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 phenylpropene, a type of aromatic compound that occurs widely in nature, in essential oils. It is in the class of p ...

from the seed of

anise Anise (; '), also called aniseed or rarely anix is a flowering plant in the family Apiaceae native to Eurasia. The flavor and aroma of its seeds have similarities with some other spices and herbs, such as star anise, fennel, licorice, and ta ...

(

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 plants ...

) and

linalool Linalool () refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of ...

from green tea ''

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 ...

'' uroi & Kubo, p1782 The

totarol Totarol is a naturally produced diterpene that is bioactive as totarol. It was first isolated by McDowell and Esterfield from the heartwood of ''Podocarpus totara'', a conifer tree found in New Zealand.Short, W. F.; Stromberg, H. ''J. Chem. Soc.'' ...

in the bark of ''

Podocarpus ''Podocarpus'' () is a genus of conifers, the most numerous and widely distributed of the podocarp family, the Podocarpaceae. The name comes from Greek πούς (poús, “foot”) + καρπός (karpós, “fruit”). ''Podocarpus'' species ...

'' 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 cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a re ...

. 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 through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

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

aphids Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

and

spider mites Spider mites are members of the Tetranychidae family, 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 The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus ''Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cult ...

shell liquid, and sensitizer of cancer cells to

ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

References

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