Abietic acid (also known as ''abietinic acid'' or ''sylvic acid'') is a

diterpenoid Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primar ...

found in coniferous trees. It is supposed to exist to defend the host plant from insect attack or various wounds. Chemically, it is a complicated molecule featuring two alkene groups and a carboxylic acid within a chiral tricyclic framework. As the major component of

rosin Rosin (), also known as colophony or Greek pitch (), is a resinous material obtained from pine trees and other plants, mostly conifers. The primary components of rosin are diterpenoids, i.e., C20 carboxylic acids. Rosin consists mainly of r ...

, it is commercially important. Historically speaking, it was a major component of

naval stores Naval stores refers to the industry that produces various chemicals collected from conifers. The term was originally applied to the compounds used in building and maintaining wooden sailing ships. Presently, the naval stores industry are used to ...

. It is the most common of the resin acids. Another common resin acid is pimaric acid, which converts to abietic acid upon heating.

Characteristics and occurrence

Abietic acid is found in rosin obtained from pine trees. Pure abietic acid is a colorless solid, but commercial samples are usually a glassy or partly

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

yellowish solid that melts at temperatures as low as . Abietic acid is soluble in

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

, and

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

s. Its

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s and

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

s are called an abietates, e.g. ethyl abietate and sodium abietate.Lars-Hugo Norlin "Tall Oil" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. The ancient presence of abietic acid (and other resin acids), being abundant and resilient, can inferred by analysis of rocks and archeological samples. Through the process of

diagenesis Diagenesis () is the process of physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sedi ...

, abietic acid changes into a collection of simpler compounds called abietanes.

Biosynthesis

Abietic acid is derived from the

diterpene Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primary ...

abietadiene, which in turn is made from copalyl pyrophosphate (CPP), which is derived from

geranylgeranyl pyrophosphate Geranylgeranyl pyrophosphate is an intermediate in the biosynthesis of diterpenes and diterpenoids. It is also the precursor to carotenoids, gibberellins, tocopherols, and chlorophylls. It is also a precursor to geranylgeranylated proteins, whic ...

( GGPP), the precursor to many diterpenoids. In air and in the presence of certain

cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...

enzymes, abietadiene is oxidized to abietic acid. An entire family of so-called resin acids form similarly. Together with abietic acid, these resin acids are a major portion of rosin, the solid portion of the

oleoresin Oleoresins are semi-solid extracts composed of resin and essential or fatty oil, obtained by evaporation of the solvents used for their production. The oleoresin of conifers is known as crude turpentine or gum turpentine, which consists of oil o ...

of coniferous trees. Geranylgeranyl diphosphate to copalyl diphosphate mechanism from Peters 2010

The conformation of the GGPP molecule dictates the

stereochemistry Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which are defined ...

of the CPP intermediate after cyclization. The

of the typical abietane skeleton suggests a GGPP precursor with its fused cyclohexyl rings in a

chair A chair is a type of seat, typically designed for one person and consisting of one or more legs, a flat or slightly angled seat and a back-rest. It may be made of wood, metal, or synthetic materials, and may be padded or upholstered in vario ...

-chair ("normal") conformation, although some abietanes with alternative

may be cyclized from CCP isomers containing alternative combinations of

boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size or capacity, its shape, or its ability to carry boats. Small boats are typically used on inland waterways s ...

and chair cyclohexane conformers. After the initial cyclization to CPP, which forms rings A and B in the abietane skeleton, the C ring is formed with the help of a class I diterpene synthase enzyme. Subsequent methyl migration and dehydrogenation steps yield the abietene isomers.

Preparation

Abietic acid is extracted from tree

. Laboratory procedures illustrate the nature of the extraction, which is the basis of a substantial industry, formerly known as naval stores.

Uses

As a component of

and one of the principal resin acids, abietic acid has many uses, e.g. in some paints, soaps, foods, soldering

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

Safety

* As the chief component of

, abietic acid is approved by the US FDA as a miscellaneous food additive. * Abietic acid is considered a "nonhazardous natural substance" in tall oil ("liquid rosin"). * In the U.S., abietic acid is listed in the inventory of the Toxic Substances Control Act. * Abietic acid is the primary irritant in

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

wood and

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

. As a contact allergen it is the cause of abietic acid dermatitis. (However, compounds resulting from its oxidation by air elicit stronger responses.) * 50% ethanol extracts from ''Resina pini'' of Pinus sp. (Pinaceae) showed inhibitory activity against testosterone 5α-reductase prepared from rat prostate. The fraction responsible for this activity was purified, and the active constituent was isolated and identified as abietic acid, which exhibited potent inhibitory activity against testosterone 5α-reductase ''

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 ...

''.

References

External links

Abietic acid MS Spectrum

Wolfram Alpha Page
{{Authority control Carboxylic acids Diterpenes Phenanthrenes Wood extracts