CAS: 541-15-1 · MW: 161.20 Da · Purity: ≥99% by reverse-phase HPLC · Format: 600 mg powder · Identity: ESI-MS confirmed · Optical rotation: [α]D²⁰ = -29.5° to -32.0°

L-Carnitine is a quaternary ammonium compound with the molecular formula C₇H₁₅NO₃ and the IUPAC name (3R)-3-hydroxy-4-(trimethylazaniumyl)butanoate, presented as an internal zwitterion in its free form. This research-grade L-carnitine is supplied as a 600 mg crystalline powder at ≥99% purity by reverse-phase HPLC, with third-party analytical verification of identity, purity, and optical rotation for every manufactured lot.

For laboratory research use only. Not for human consumption, veterinary use, food, or therapeutic use. Not a drug, supplement, or cosmetic. Sold exclusively to qualified research professionals and institutions.

Structure & Identity

L-Carnitine has been characterized in the biochemical literature as the biologically active stereoisomer of the carnitine zwitterion pair, with the (R)-configuration at the C-3 hydroxyl center [1]. The molecule is endogenously biosynthesized from L-lysine and L-methionine in mammalian liver and kidney tissue, and serves as the obligate cofactor for the carnitine palmitoyltransferase (CPT) shuttle system that transports long-chain fatty acyl groups across the inner mitochondrial membrane [1,2]. The molecular weight is 161.20 Da. L-Carnitine exists as a stable internal zwitterion at physiological pH, with the quaternary trimethylammonium cation balanced by the carboxylate anion. The D-enantiomer is biologically inactive and is not present in this material.

Research Background

L-Carnitine is one of the most extensively characterized cofactors in mitochondrial bioenergetics and serves as a standard reference reagent across multiple research domains. Published research contexts include:

• Mitochondrial fatty acid β-oxidation research. Referenced as the substrate for the carnitine palmitoyltransferase I (CPT1) and II (CPT2) enzymes, which catalyze the rate-limiting step of long-chain fatty acid import into the mitochondrial matrix for β-oxidation. Used as a defined reagent in isolated mitochondrial preparations and permeabilized cell systems to study acyl-carnitine flux [1,2].
• Acyl-carnitine profiling and metabolomics research. Used as the analytical reference standard for tandem mass spectrometry (MS/MS) acyl-carnitine profiling assays, including the methodologies underlying newborn screening research and inborn-error-of-metabolism research [3].
• Carnitine biosynthesis pathway research. Referenced as the end product of the four-enzyme biosynthetic pathway from trimethyllysine, in research characterizing γ-butyrobetaine hydroxylase (BBOX1) and other pathway enzymes in animal-model systems [4].
• Cultured cell metabolic research. Used as a defined supplement in serum-free and chemically defined media formulations for studies of cellular fatty acid metabolism, particularly in hepatocyte, cardiomyocyte, and skeletal muscle cell line research [2].

These references describe findings in non-human in vitro, animal-model, or chemistry research contexts. They do not constitute claims about effects in humans and are not intended to characterize the molecule’s approved therapeutic indications.

Specifications

Storage & Handling

L-Carnitine is hygroscopic and must be protected from atmospheric moisture during storage and handling. Crystalline material is stable at 2–8°C for 24 months in tightly closed containers under desiccant; long-term storage at -20°C under inert atmosphere is preferred for analytical reference use. Once dissolved in aqueous laboratory buffer, solutions should be aliquoted into low-binding tubes and stored at -20°C; the zwitterion is chemically stable in solution at neutral pH but can undergo lactonization under acidic conditions. Handle under standard laboratory aseptic technique with PPE per institutional biosafety guidelines.

Quality Assurance

Every manufactured lot is accompanied by batch-specific analytical documentation including: third-party reverse-phase HPLC chromatogram, ESI-MS deconvoluted mass spectrum, chiral HPLC confirming ≥99.5% enantiomeric excess of the (R)-isomer, polarimetric specific rotation measurement, residual moisture (loss on drying), residue on ignition, and heavy-metals quantification. Reference standards are maintained at -20°C and cross-validated against pharmacopeial reference preparations. Manufacturing occurs in ISO 9001-certified facilities under documented quality-management procedures.

This material is supplied exclusively to qualified research professionals, academic laboratories, contract research organizations, and institutional purchasing departments. Proof of institutional affiliation may be required.

For laboratory research use only. Not for human consumption, veterinary use, food, or therapeutic use. Not a drug, supplement, or cosmetic.

Frequently Asked Questions

What is L-carnitine?

L-Carnitine is a quaternary ammonium zwitterion with the chemical name (3R)-3-hydroxy-4-(trimethylazaniumyl)butanoate. CAS 541-15-1. Molecular weight 161.20 Da. It is the biologically active (R)-stereoisomer of the carnitine pair, endogenously biosynthesized in mammals from L-lysine and L-methionine.

What is the difference between L-carnitine and D-carnitine?

The two are stereoisomers differing in configuration at the C-3 hydroxyl center. L-Carnitine (the R-isomer) is the biologically active form recognized by the carnitine palmitoyltransferase shuttle system. D-Carnitine (the S-isomer) is biologically inactive and is not present in this material (≥99.5% enantiomeric excess confirmed by chiral HPLC).

What is the molecular weight of L-carnitine?

161.20 Da. Molecular formula C₇H₁₅NO₃.

What is the CAS number for L-carnitine?

541-15-1.

What purity is L-carnitine supplied at?

≥99% by reverse-phase HPLC, with ≥99.5% enantiomeric excess of the (R)-isomer confirmed by chiral HPLC. Each manufactured lot is third-party analyzed with documentation of HPLC purity, ESI-MS identity, chiral purity, optical rotation, residual moisture, and heavy metals.

How should L-carnitine be stored?

L-Carnitine is hygroscopic and must be protected from atmospheric moisture. Crystalline material is stable at 2–8°C for 24 months in tightly closed containers under desiccant. For analytical reference use, long-term storage at -20°C under inert atmosphere is preferred. Once dissolved in laboratory buffer, aliquot and store at -20°C.

How is L-carnitine reconstituted for laboratory work?

L-Carnitine is highly water-soluble (>250 mg/mL at 20°C) and also dissolves readily in methanol and ethanol. Researchers typically reconstitute in sterile water, PBS, or assay buffer for in vitro experimental work, following standard aseptic technique. Avoid prolonged exposure to acidic conditions to prevent lactonization.

What is L-carnitine used for in research?

L-Carnitine has been referenced in the peer-reviewed literature as a defined substrate in mitochondrial β-oxidation research, as an analytical reference standard for acyl-carnitine MS/MS profiling, as the end product in carnitine biosynthesis pathway studies, and as a defined media supplement in cellular metabolism research. All published characterizations referenced here are in non-human in vitro or animal systems.

Who can purchase L-carnitine?

This material is supplied exclusively to qualified research professionals, academic laboratories, contract research organizations, and institutional purchasing departments. Proof of institutional affiliation may be required.

References

1. Bremer J. Carnitine—metabolism and functions. Physiol Rev. 1983;63(4):1420-80. PMID: 6361812
2. McGarry JD, Brown NF. The mitochondrial carnitine palmitoyltransferase system. From concept to molecular analysis. Eur J Biochem. 1997;244(1):1-14. PMID: 9063439
3. Chace DH, Kalas TA, Naylor EW. Use of tandem mass spectrometry for multianalyte screening of dried blood specimens from newborns. Clin Chem. 2003;49(11):1797-817. PMID: 14578311
4. Vaz FM, Wanders RJ. Carnitine biosynthesis in mammals. Biochem J. 2002;361(Pt 3):417-29. PMID: 11802770