Carnitine

Carnitine, with the chemical formula \(C_7H_{15}NO_3\), is a quaternary ammonium compound that plays a crucial role in the metabolism of most mammals, plants, and some bacteria[3]. It is involved in the transport of long-chain fatty acids from the cytosol into the mitochondria, where they are oxidized to produce energy. Carnitine also helps in removing metabolic byproducts from cells[3].

Chemically, carnitine is an amino-acid betaine, which is a butanoate molecule substituted with a hydroxy group at the C-3 position and a trimethylammonium group at the C-4 position[1]. It exists as two enantiomers: d-carnitine (S-(+)-) and l-carnitine (R-(−)-), with only the l-carnitine form being biologically active and naturally occurring in animals. The d-carnitine form is toxic as it inhibits the activity of the l-form[3].

Carnitine is a whiteish powder at room temperature and is a water-soluble zwitterion with relatively low toxicity[3]. It has a molar mass of 161.201 g/mol[3]. The compound is also known for its low bioavailability, which is less than 10%, and it is not bound to proteins in the plasma. It is metabolized slightly in the body and is excreted primarily in the urine[3].

In terms of its solubility and partitioning properties, carnitine has a high water solubility, estimated to be 1e+006 mg/L at 25 degrees Celsius, and a very low log octanol-water partition coefficient (Log Kow) of -5.48, indicating that it is not lipophilic[4]. The Henry's Law Constant for carnitine is very low, suggesting that it has a negligible tendency to volatilize from aqueous solutions into the atmosphere[4].

Carnitine is also considered to be readily biodegradable, with a high probability of rapid biodegradation in the environment[4]. This is supported by various biodegradation models, including the Linear Model (Biowin1) and the Non-Linear Model (Biowin2), which predict a rapid biodegradation[4].

Levocarnitine, a specific form of carnitine, has additional roles as an antilipemic drug, a water-soluble vitamin, a nutraceutical, a nootropic agent, and a metabolite in Saccharomyces cerevisiae[2]. It was approved by the U.S. Food and Drug Administration under the brand name Carnitor on December 27, 1985[3].

Despite its critical metabolic functions and use as a dietary supplement, excessive intake of carnitine can lead to side effects such as nausea, vomiting, abdominal cramps, diarrhea, and body odor that smells like fish[3]. Certain medications, like antibiotics and anticonvulsants, can affect carnitine levels in the body, either by increasing its excretion or reducing its blood levels[3].

Citations:

[1] https://pubchem.ncbi.nlm.nih.gov/compound/Carnitine

[2] https://pubchem.ncbi.nlm.nih.gov/compound/Levocarnitine

[3] https://en.wikipedia.org/wiki/Carnitine

[4] http://www.chemspider.com/Chemical-Structure.10455.html

[5] https://www.sciencedirect.com/science/article/pii/S0021961418300284

[6] https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI%3A17126

[7] https://www.nature.com/articles/4000805

[8] https://www.sciencedirect.com/science/article/abs/pii/S0021961418300284