Abietic acid

Abietic acid (also known as abietinic acid or sylvic acid) is a mild organic acid found in coniferous trees.

It is a commercially important component of paints, soaps, foods, and soldering flux, and is the primary component of resin acid.

Characteristics
Abietic acid is found in pine trees, including:
 * Pinus insularis (Khasi Pine)
 * Pinus kesiya Royle
 * Pinus strobus (Eastern White Pine)
 * Pinus sylvestris (Scots Pine).

Pure abietic acid is a colorless solid, but commercial samples are usually a glassy or partly crystalline yellowish solid that melts at temperatures as low as 85 C.

Abietic acid is soluble in alcohols, acetone, and ethers. Its ester or salt is called an abietate.

Abietic acid belongs to the abietane diterpene group of organic compounds derived from four isoprene units.

Preparation
Abietic acid is extracted from tree rosin (via isomerization) and is the most abundant of several closely related organic acids that constitute most of rosin, the solid portion of the oleoresin of coniferous trees.

Resin acids are converted into ester gum by reaction with controlled amounts of glycerol or other polyhydric alcohols.

Uses
Abietic acid has drying properties, and as ester gum is used in paints, varnishes, and lacquers.

It is also used in soaps, for the analysis of resins, and the preparation of metal resinates.

As rosin
Rosin, of which abietic acid is the principal component:
 * Has been used for centuries as a flux for soldering. (Abietic acid in the flux removes oxidation from the surfaces of metals, increasing their ability to bond with the liquified solder.)
 * Is rubbed on the hair of a violin bow to increase friction.
 * Has been used for centuries for caulking ships.
 * Is approved by the US FDA as a miscellaneous food additive.

Safety

 * As the chief component of rosin, 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 wood and resin. 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.