Stearic acid amide is used in the manufacture of candles, cosmetics, shaving soaps, lubricants and pharmaceuticals. In nature stearic acid is a mixture of about equal proportions of stearic and palmitic acids and small amounts of oleic acid. It is more abundant in animal fats than in vegetable fats; lard and tallow often contain up to 30% of stearic acid.
Metabolism of dietary stearic acid
After digestion, stearic acid is oxidized in the beta-oxidation pathway to produce acetyl-CoA which enters the citric acid cycle. In the citric acid cycle, ATP is produced through a process of oxidative phosphorylation. Alternatively, acetyl-CoA can also enter the anabolic pathway, which is responsible for the endogenous synthesis of fats.
Fatty acid amide hydrolase (FAAH): FAAH-1 and FAAH-2 are the enzymes that catalyse the hydroxylation of fatty acid amides like stearic acid to their metabolites. These two enzymes are widely expressed in placental mammals, and exhibit tissue distributions and substrate selectivity that are overlapping but distinct.
The expression of these enzymes is largely controlled by tissue-specific cellular mechanisms which are known to regulate absorption, metabolism and excretion of chemicals in the human body. Among the tissues, FAAH-1 is expressed in brain, small intestine and testis, while FAAH-2 is only present in heart.
Biodegradation of stearic acid amide:
The OECD Guideline 301 B states that stearic acid amide is likely to be biodegradable under certain environmental conditions and has low environmental persistence. Based on CO2 evolution tests in activated sludge, stearic acid amide reached 62% degradation after 28 days(6,7).