AICAR, or 5-aminoimidazole-4-carboxamide ribonucleoside, is a cell-permeable adenosine analogue used in the laboratory as an activator of AMP-activated protein kinase (AMPK), the cellular energy sensor. Once inside a cell it is phosphorylated to a compound that mimics adenosine monophosphate, which allows researchers to switch on AMPK signalling without disturbing the cell’s actual energy balance. AICAR is a small molecule and not a peptide, so its quality control differs from that of the research peptides it is often sold alongside. This article summarises its structure, mechanism, published research areas and the analytical and storage standards needed for reproducible work. It is written for laboratory researchers and offers no guidance on human use.
What is AICAR?
AICAR is classified as a nucleoside analogue and a purine biosynthesis intermediate derivative. It is also known as AICA riboside and, in its pharmaceutical development, as acadesine. The molecule consists of the heterocyclic base 5-aminoimidazole-4-carboxamide attached to a ribose sugar. Its molecular formula is C9H14N4O5 and its molecular weight is approximately 258.2 Da, which places it among the smallest research compounds commonly supplied alongside peptides.
The biochemistry behind the name is useful. In the cell, the de novo synthesis of purines proceeds through a series of ribonucleotide intermediates, and one of them is 5-aminoimidazole-4-carboxamide ribonucleotide, abbreviated ZMP or AICA ribotide. AICAR is the corresponding riboside, which lacks the phosphate group. Because charged nucleotides cross membranes poorly, the uncharged riboside is the form that can be applied to cells, and it is converted to ZMP once inside.
The compound was characterised in the 1980s as a purine metabolism intermediate and was studied in clinical development under the name acadesine in settings involving reduced blood flow to tissue. In the early 1990s, work by David Carling, Grahame Hardie and colleagues established that ZMP could substitute for AMP in activating AMPK, and a 1995 paper by Corton and colleagues described the riboside as a method for activating AMPK in intact cells. This is the basis of its use in research.
Regulatory context matters for any UK buyer. To the author’s understanding, AICAR is not authorised as a medicine in the United Kingdom, and it appears on the World Anti-Doping Agency prohibited list, though the current list should be checked directly because it is revised annually. The Medicines and Healthcare products Regulatory Agency (MHRA) has issued warnings about unlicensed products marketed for human use. The material is relevant here only as a laboratory research reagent.
Mechanism of action
AICAR does not act on a cell-surface receptor. Its mechanism is intracellular and depends on metabolic conversion. The riboside enters cells through nucleoside transporters, the same family that carries adenosine, and is phosphorylated by adenosine kinase to ZMP. ZMP accumulates because it is cleared slowly.
ZMP is an analogue of adenosine monophosphate (AMP). AMPK is a heterotrimeric kinase, made of a catalytic alpha subunit and regulatory beta and gamma subunits, and it senses the cell’s energy state through the ratio of AMP and ADP to ATP. The gamma subunit contains binding sites for these nucleotides. When AMP binds, AMPK is activated through allosteric effects and by promoting phosphorylation of a threonine residue (Thr172) on the alpha subunit by upstream kinases such as LKB1, and by protecting that site from dephosphorylation. ZMP binds the same gamma-subunit sites and mimics these effects, so AMPK is activated even though the cell’s ATP level has not fallen.
Active AMPK phosphorylates many targets. It inhibits energy-consuming anabolic processes, such as fatty acid and cholesterol synthesis through acetyl-CoA carboxylase, and it stimulates energy-producing catabolic processes, including glucose uptake and fatty acid oxidation. It also regulates gene expression through coactivators and transcription factors.
A point of experimental caution follows from the mechanism. ZMP is not a perfectly selective AMPK activator. It can affect other AMP-sensitive enzymes, including fructose-1,6-bisphosphatase and glycogen phosphorylase, and AICAR can influence purine metabolism and adenosine signalling in ways that do not depend on AMPK. Experiments should therefore include genetic controls, such as AMPK-deficient cells, or pharmacological controls, such as an AMPK inhibitor, to establish that an observed effect depends on the kinase.
In cell-based work, “dosage” means molar concentration in the medium. AICAR is usually applied at concentrations in the high micromolar to millimolar range in cell culture, and the effective concentration depends strongly on the cell type and on transporter and adenosine kinase expression, so values should be taken from primary papers for the model in use.
What the research shows
The literature on AICAR is large and mostly concerns AMPK biology. Four areas are summarised below in general terms. Readers should consult the primary papers for methods, concentrations and statistics, because commercial summaries often overstate findings.
The first area is the establishment of AICAR as an AMPK activator. Work in the early 1990s showed that the riboside could activate AMPK in isolated cells through accumulation of ZMP, and Corton and colleagues described the approach and its limitations in 1995. This body of work gave researchers a way to activate the kinase pharmacologically and shaped how AMPK signalling has been studied since. The relevant papers can be located through a PubMed search on AICA riboside as a method for activating AMPK in intact cells.
The second area is skeletal muscle and metabolism in rodents. Studies in rats and mice administered AICAR and examined glucose uptake and fatty acid oxidation in muscle, in line with known AMPK targets. These experiments were carried out under ethical approval, with exposures expressed per kilogram of body weight, and the values differ with species and route, so they should be taken from the primary papers.
The third area is a 2008 paper by Narkar and colleagues in Cell, which reported that AICAR treatment of sedentary mice altered the expression of genes involved in oxidative metabolism in skeletal muscle, with involvement of AMPK and the nuclear receptor PPAR-delta. The paper is widely cited, and it is described here only as a rodent study of gene regulation. It carries no implication for use in people, and nothing in this article suggests any application outside the laboratory. The work can be explored through a PubMed search on AMPK and PPAR-delta agonists in mouse skeletal muscle.
The fourth area is clinical development of acadesine. The compound was investigated in clinical programmes under regulatory oversight, including studies in patients undergoing cardiac surgery and, later, in certain haematological malignancies. These are mentioned here only for completeness. They were conducted under medical supervision with a manufactured pharmaceutical formulation, they say nothing about research-grade material, and nothing in this article describes a use outside such a setting.
A recurring limitation runs through the field. AICAR is not a specific AMPK activator, concentrations used in cell culture are high, and some of its effects occur independently of the kinase. Interpretation depends on appropriate controls and on knowing exactly what material was used.
Research applications
In the laboratory, AICAR is used in several contexts. The most common is cell-based studies of AMPK signalling, where it serves as a pharmacological activator in cell lines such as myotubes, hepatocytes and adipocytes, and in primary cells, to examine phosphorylation of AMPK targets, glucose uptake, lipid synthesis and autophagy.
A second context is cancer and cell-growth research. AMPK restrains the mTOR pathway and cell proliferation, so AICAR is used to examine how energy-sensing pathways affect growth and survival in cultured tumour cell lines. Interpretation requires care because of the compound’s AMPK-independent effects.
A third context is metabolic research in animal models, which requires institutional ethical review and, in the United Kingdom, authorisation under the Animals (Scientific Procedures) Act 1986. Study design should include vehicle controls, blinded assessment and analytical confirmation of the material administered.
A fourth context is analytical and anti-doping science. Because AICAR appears on the World Anti-Doping Agency prohibited list, reference material of defined identity and purity is used to develop detection methods, which are complicated by the fact that AICAR is also an endogenous metabolite. Distinguishing exogenous from endogenous compound relies on quantitative and isotopic methods, so a well-characterised reference is essential.
Purity, storage and handling
Quality control for AICAR follows small-molecule practice, which differs from peptide practice in several ways. There is no net peptide content, no amino acid analysis and no sequence to verify. Instead, identity is confirmed by mass spectrometry and, ideally, by nuclear magnetic resonance spectroscopy, and purity is assessed by high-performance liquid chromatography (HPLC) with UV detection. The imidazole carboxamide chromophore absorbs strongly near 267 nm, so detection at 254 to 270 nm is more informative than the 214 nm region used for peptides. A main peak of at least 98 per cent is commonly expected.
AICAR is very polar, and it may be poorly retained on a standard C18 column, so a method may need an aqueous start, an ion-pairing agent or hydrophilic interaction chromatography to separate it from related impurities. Likely impurities include related nucleosides, residual starting materials from synthesis and the free base. A stated purity is meaningful only if the method and chromatogram are available.
HPLC should be paired with mass spectrometry. The expected protonated ion is at about m/z 259.1. A batch-specific certificate of analysis should carry a lot number matching the vial, the method and result for purity, the mass found, the test date and, ideally, NMR confirmation and residual solvent and water content. Because the substance is a defined small molecule, the weighed mass is close to the mass of compound, but water and residual solvent can still contribute, and the certificate should say how they were measured.
Because the compound’s biological activity depends on its conversion to ZMP in cells, identity errors have direct consequences. A related nucleoside would not activate AMPK in the same way, and a batch with substantial impurities of other nucleosides could affect purine metabolism and adenosine signalling in ways that confound results, so batch-level verification matters as much here as for any peptide. UK laboratories sourcing Aicar should expect a batch-specific certificate of analysis that states the purity method, the mass found and the identity confirmation, with storage at -20°C, and the same documentation standard applies when weighing any best peptides supplier uk claim, since a supplier’s analytical record rather than its search ranking shows whether the vial matches its stated specification.
AICAR is typically supplied as a crystalline solid and is stable for long periods when stored at -20°C in a sealed container protected from moisture. Vials should reach room temperature before opening so that condensation does not form on the cold solid. It dissolves in water and in dimethyl sulfoxide, and aqueous solutions are generally less stable than the solid, so many suppliers advise preparing fresh solutions and not storing dilute aqueous solutions for more than a short time. Where a stock must be kept, it should be divided into single-use aliquots, frozen and tested for stability in the intended assay and not assumed to be stable. Dimethyl sulfoxide stocks carry their own hazards, since it can carry dissolved compounds through skin, and they should be handled with appropriate gloves.
Light sensitivity is a minor concern for this compound, though amber vials or dark storage remain good practice. Laboratory safety follows ordinary chemical hygiene. The safety data sheet should be read before use, gloves, a laboratory coat and eye protection are standard, powder should be weighed in a ventilated enclosure, and institutional COSHH assessments should cover the material and procedure.
Labelling is a final indicator of quality. Clear naming that gives the chemical name, CAS number, molecular weight, lot number and an unambiguous research-only statement suggests a supplier that understands its market. Wording that implies use in humans is a warning sign and raises regulatory concerns in the United Kingdom.
Frequently asked questions
What is AICAR used for in laboratory research?
It is used as a cell-permeable activator of AMP-activated protein kinase in studies of energy sensing, glucose and lipid metabolism, autophagy and cell growth, and as a reference material in anti-doping analytical methods. It is a research reagent and not an authorised medicine in the United Kingdom.
Is AICAR a peptide?
No. AICAR is a nucleoside analogue with a molecular weight of about 258 Da, made of an imidazole base attached to ribose. It is often sold alongside peptides, but its quality control uses small-molecule methods such as HPLC, mass spectrometry and NMR, not peptide-specific tests.
How does AICAR activate AMPK?
AICAR enters cells through nucleoside transporters and is phosphorylated to ZMP, which mimics adenosine monophosphate and binds the regulatory subunit of AMPK. This activates the kinase without a fall in cellular ATP. ZMP can also affect other enzymes, so AMPK-deficient controls are recommended.
How should AICAR be stored for research?
Store the solid at -20°C in a sealed, dry container and allow it to reach room temperature before opening. Prepare aqueous solutions fresh where possible, because they are less stable than the solid, and validate the stability of any stored aliquots for the assay.
AICAR is supplied for in-vitro laboratory research only and is not intended for human or veterinary use.
