Anacardic acid

General structure of anacardic acids. R is an alkyl chain of variable length, which may be saturated or unsaturated.

Anacardic acids are chemical compounds found in the shell of the cashew nut (Anacardium occidentale). As they are closely related to urushiol, they also cause an allergic skin rash on contact,^[1] known as urushiol-induced contact dermatitis. Anacardic acid is a yellow liquid. It is miscible partially in alcohol and ether, but nearly immiscible in water. Chemically, anacardic acid is a mixture of several closely related organic compounds. Each consists of a salicylic acid substituted with an alkyl 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.^[2] of which the 15 carbon unsaturated side chain found in the cashew plant is very lethal to Gram positive bacteria.

Primarily used for tooth abscesses, it is also active against acne, some insects, tuberculosis, and MRSA. It is primarily found in foods such as cashew nuts, cashew apples, and cashew nutshell oil, but also in mangos and Pelargonium geraniums.^[3]

Experimental antibacterial properties

Anacardic acid (C15:3, all-Z, major component)
IUPAC name 2-hydroxy-6-[(8Z,11Z)-pentadeca-8,11,14-trienyl]benzoic acid
Identifiers
CAS number	11034-77-8 Y
PubChem	9875131
MeSH	anacardic+acid
ChEMBL	CHEMBL455368 N
Jmol-3D images	Image 1
SMILES C=CCC=CCC=CCCCCCCCC1=C(C(=CC=C1)O)C(=O)O
Properties
Molecular formula	C22H30O3
Molar mass	342.4718 g/mol
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

The side chain with three unsaturated bonds was the most active against Streptococcus mutans, the tooth decay bacterium, in test tube experiments. The number of unsaturated bonds was not material against Propionibacterium acnes, the acne bacterium.^[4] Eichbaum claims that one part to 200,000 to as high as 2,000,000 parts of solution of anacardic acid is lethal to Gram positive bacteria in 15 minutes in vitro. Somewhat higher ratios killed tubercle bacteria of tuberculosis in 30 minutes.^[5] Heating these anacardic acids converts them to the alcohols (cardanols), but does not destroy their activity^[6] unless high heat is used, which decarboxylates (??? makes no sense) them.^[7] It is said that the people of the Gold Coast use cashew leaves and bark for a toothache.^[8]

Industrial uses

Anacardic acid is the main component of cashew nutshell liquid (CNSL), and finds use in the chemical industry for the production of cardanol, 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.^[9]

History

The first chemical analysis of the oil of the cashew nut shell from the Anacardium occidentale was published in 1847.^[10] 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 from the seed of anise (Umbelliferae) and linalool from green tea in vitro [Muroi & Kubo, p1782]. The totarol in the bark of Podocarpus trees is synergistic with anacardic acid in its bactericidal effects.^[11]

Other and potential uses

There is also a suspicion that anacardic acids inhibit the growth of cancer tumors such as breast cancer. [Kubo et al., 1993]

Anacardic acid (2-hydroxy-6-alkylbenzoic acid) provides resistance to small pest insects (aphids and spider mites).^[12]

Anacardic acid kills methicillin-resistant Staphylococcus aureus (MRSA) cells more rapidly than totarol.^[13]

See also

• List of phytochemicals and foods in which they are prominent

References