Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group. [1] Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides. [2]
Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group. [1] Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides. [2]
CPAs are derived from unsaturated fatty acids by cyclopropanation. The methylene donor is a methyl group on S-adenosylmethionine (SAM). The conversion is catalyzed by cyclopropane-fatty-acyl-phospholipid synthase. [3] The mechanism is proposed to involve transfer of a CH3+ group from SAM to the alkene, followed by deprotonation of the newly attached methyl group and ring closure. [4]
Cyclopropene fatty acids are even rarer molecules. The best-known examples are malvalic acid and sterculic acid. A triglyceride made of 3 sterculic acid molecules esterified with glycerol is present in Sterculia foetida seed oil (in amounts greater than 60%) and at low levels in the seed oil of other species of Malvaceae [a] (~12%), cottonseed oil (~1%). The cyclopropene ring is destroyed during refining and hydrogenation of the oils. They have attracted interest because they reduce levels of the enzyme stearoyl-CoA 9-desaturase (SCD), which catalyzes the biodesaturation of stearic acid to oleic acid. [7]
At least one review indicates that these compounds are carcinogenic. [8]