Levopimaric acid is an abietane-type of diterpene resin acid. It is a major constituent of pine oleoresin with the chemical formula of C20H30O2. In general, the abietene types of diterpene resin acid have various biological activities, such as antibacterial, cardiovascular and antioxidant. About 18 to 25% of levopimaric acid is found in pine oleoresin. The production of oleoresin by conifer species is an important component of the defense response against insect attack and fungal pathogen infection.

Resin acid is the general name for all kinds of acids that share the same basic skeleton, a three-fused ring and the empirical formula C20H30O2. The resin acids may be classified into two types, abietic and pimaric. The abietic-type group include levopimaric, l-abietic and neoabietic. The structure of these compounds differ only in the position of the conjugated double bond system. This feature influences their chemical reactivity. The pimaric-type acids are dextropimaric and isodextropimaric.

Synthesis of Levopimaric acid

Levopimaric acid can be extracted by dissolving Longleaf pine oleoresin in acetone and then adding 2-amino-2-methyl-1-propanol.

Biosynthesis of Levopimaric acid

The abietane skeleton of levopimaric acid is formed by the cyclization of a diterpenoid precursor, substrate (a), all-trans-geranyl-geranyl diphophate (Reaction 1). All diterpenes are considered to be derived from the C20 isoprenoid intermediate geranylgeranyl pyrophosphate. The intermediate which is formed in Reaction (1), (+)-copalyl diphosphate, goes through the oxidation and rearrangement to give the intermediate (c), levopimaradiene, and diphosphate molecule. Then, the levopimaradiene goes through several more steps of oxidation processes, using oxygen molecules as the oxidizing agent, and NADPH as the proton donor.LaFever, R. E., Vogel, B. S., Croteau, R. Diterpenoid resin acid biosynthesis in conifers: enzymatic cyclization of geranylgeranyl pyrophosphate to abietadiene, the precursor of abietic acid, Arch Biochem Biophys,.1994, 313 (1) , 139-149

Role in Biology

Oleoresin in pines is defined as pine gum, which is the nonaqueous secretion of resin acids dissolved in a terpene hydrocarbon oil, which is produced in or exuded from the intercellular resin ducts of a living tree. The viscous oleoresin secretion is composed of a complex mixture of terpenoids, consisting of roughly equal parts of volatile turpentine and rosin (also known as diterpene resin acids). Accumulated resin is released upon tissue injury and/or pro- duced locally at the site of infestation, with the consequence that the beetle and associated fungal pathogens are killed, encased in resin, and expelled from the bore hole point of entry. This process is called pitching out, and it results in not only killing the attackers and flushing the wound site but also moving the oleoresin to the trunk surface where the turpentine evaporates to permit the resin acids to form a formidable physical barrier that seals the wound.
Diterpene resin acids (DRA) play important roles in confer defense against insects and microbial pathogens. Levopimaric acid, an abietane-type DRA, is one of the principal resin acids.