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| Targets |
Inosine-13C5 does not target biological receptors or enzymes as a labeled internal standard. However, unlabeled Inosine (the parent compound) targets multiple biological systems. Inosine acts as an endogenous purine nucleoside with anti-inflammatory, immunomodulatory, anti-nociceptive, and neuroprotective effects. It binds to adenosine receptors (A1, A2A, A2B, A3) with lower affinity than adenosine and is also an agonist of the uridine-adenosine receptor. Inosine activates intracellular signaling pathways including PKA, PKC, and MAPK cascades. The 13C5-labeled version is chemically identical to unlabeled Inosine and retains the same molecular structure and properties, but with a +5 Da mass shift for analytical detection.
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| ln Vitro |
Stable heavy isotopes of hydrogen, carbon, and other elements have been incorporated into drug molecules, largely as tracers for quantitation during the drug development process. Studies involving the human use of drugs with labeled deuterium suggest that these compounds may offer some advantages when compared with their nondeuterated counterparts. Deuteration has gained attention because of its potential to affect the pharmacokinetic and metabolic profiles of drugs. Deutetrabenazine is the first deuterated drug to receive Food and Drug Administration approval. This deuterated form of the drug tetrabenazine is indicated for the treatment of chorea associated with Huntington's disease as well as tardive dyskinesia. Ongoing clinical trials suggest that a number of other deuterated compounds are being evaluated for the treatment of human diseases and not merely as research tools. [1]
In vitro, unlabeled Inosine has been shown to exert neuroprotective effects in primary neuronal cultures, reduce glutamate excitotoxicity, and promote neurite outgrowth. Inosine also exhibits anti-inflammatory activity by suppressing pro-inflammatory cytokine production (TNF-alpha, IL-1beta, IL-6) in activated microglia and macrophages. The 13C5-labeled Inosine has identical in vitro properties to unlabeled Inosine, but these properties are not utilized when the compound is used as an internal standard, as it is typically added at very low tracer concentrations (ng/mL to microg/mL range). No dedicated in vitro activity studies have been conducted using Inosine-13C5 as the test article. |
| ln Vivo |
Deuterated compounds may, in some cases, offer advantages over nondeuterated forms, often through alterations in clearance. Deuteration may also redirect metabolic pathways in directions that reduce toxicities. The approval of additional deuterated compounds may soon follow. Clinicians will need to be familiar with the dosing, efficacy, potential side effects, and unique metabolic profiles of these new entities.
In vivo, unlabeled Inosine has been studied in animal models of spinal cord injury, stroke, Parkinson‘s disease, and epilepsy, where it promotes axonal regeneration, reduces inflammation, and provides neuroprotection. Inosine also exhibits anti-inflammatory and immunomodulatory effects in models of sepsis and autoimmune disease. The 13C5-labeled version has the same pharmacological properties as unlabeled Inosine, but it is not used for efficacy studies; rather, it is used as an internal standard for quantifying endogenous Inosine levels in biological samples. If administered exogenously, Inosine-13C5 would be metabolized and distributed similarly to unlabeled Inosine. No published in vivo efficacy studies specifically using Inosine-13C5 exist. |
| Enzyme Assay |
No dedicated cell-free receptor binding protocols exist for Inosine-13C5, as it is not used for binding studies. For unlabeled Inosine in adenosine receptor binding assays: Incubate membrane preparations from cells expressing human adenosine receptors (e.g., CHO cells stably transfected with A1, A2A, A2B, or A3 receptors) with [3H]-DPCPX (A1-selective) or other radioligands (0.5-5 nM) in assay buffer (50 mM Tris-HCl, pH 7.4, 10 mM MgCl2, 1 mM EDTA, 0.1% BSA). Add Inosine at varying concentrations (1 nM to 1 mM) in the presence or absence of 100 microM GTPgammaS. Incubate for 60-90 minutes at 25degC or 37degC. Terminate by rapid filtration through GF/B filters. Wash 3-5 times with ice-cold buffer, dry filters, and count bound radioactivity in scintillation counter. Calculate IC50 and Ki values. For Inosine-13C5, when used as internal standard in receptor binding studies, it would be spiked into samples prior to LC-MS analysis of bound/free inosine.
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| Cell Assay |
No cell-based assay protocols are established for Inosine-13C5 as a test article. For cell-based studies of unlabeled Inosine: Culture neuronal cell lines (e.g., PC12, SH-SY5Y) or primary neurons in appropriate medium. Treat with Inosine (1-1000 microM) for 24-72 hours. Assess viability by MTT assay, neurite outgrowth by microscopy, and apoptosis by flow cytometry (Annexin V/PI staining). Measure intracellular cAMP levels by ELISA to assess adenosine receptor activation. For anti-inflammatory studies: Treat microglial cell lines (e.g., BV-2, HMC3) or primary microglia with Inosine (10-500 microM) for 1 hour prior to LPS stimulation (100 ng/mL, 24 hours). Collect culture supernatants for cytokine measurement (TNF-alpha, IL-1beta, IL-6) by ELISA. Inosine-13C5 is not used in these protocols as the test compound.
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| Animal Protocol |
No animal protocols are established for Inosine-13C5 as a test article. For unlabeled Inosine studies in spinal cord injury mouse model: Adult female C57BL/6 mice undergo laminectomy at T9-10 and moderate spinal cord contusion injury. Inosine (50-100 mg/kg) or vehicle (PBS) is administered intraperitoneally daily for 4 weeks. Assess locomotor recovery using Basso Mouse Scale (BMS) weekly. Collect spinal cord tissues for histological analysis (axon counts, GFAP staining) and mRNA analysis (qPCR for inflammatory markers). For stroke model: Adult male Sprague-Dawley rats undergo middle cerebral artery occlusion (MCAO) for 60-90 minutes. Inosine (50-150 mg/kg) is administered IP at 1, 6, and 24 hours post-occlusion. Measure infarct volume by TTC staining at 72 hours. For quantification of endogenous Inosine in animal samples using Inosine-13C5 as IS: Collect plasma, brain tissue, or CSF samples. Add fixed concentration (10-100 ng/mL) of Inosine-13C5 as internal standard. Extract with acetonitrile or methanol, analyze by LC-MS/MS, and calculate Inosine concentrations using isotope dilution method.
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| ADME/Pharmacokinetics |
Pharmacokinetic data for Inosine-13C5 have not been reported separately. PK properties of unlabeled Inosine: Inosine is endogenously present in plasma (0.5-2 microM in humans). Exogenously administered Inosine (oral or IV) has a short plasma half-life (t½ = 0.5-2 hours in rodents) due to rapid degradation by purine nucleoside phosphorylase (PNP) to hypoxanthine and ribose-1-phosphate. Oral bioavailability is low (<20%) due to first-pass metabolism. Volume of distribution is moderate (~0.5-1 L/kg). Clearance is primarily renal and hepatic. Inosine-13C5 is chemically identical to unlabeled Inosine and would have identical PK properties. When used as internal standard, it is typically spiked into ex vivo samples and not dosed in vivo. The isotopic enrichment is ≥99 atom% 13C with chemical purity ≥98%.
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| Toxicity/Toxicokinetics |
No dedicated toxicity data for Inosine-13C5 exist. Unlabeled Inosine is considered safe and is generally recognized as safe (GRAS) for use as a dietary supplement. Acute toxicity: Oral LD50 in rats >5000 mg/kg. No significant adverse effects at doses up to 1000 mg/kg/day in animal studies. In humans, Inosine has been studied in clinical trials for multiple sclerosis and Parkinson's disease with a favorable safety profile. Mild gastrointestinal discomfort (nausea, diarrhea) may occur at high doses. Inosine can increase uric acid levels, which may precipitate gout in susceptible individuals. No carcinogenicity, genotoxicity, or reproductive toxicity concerns have been identified. Inosine-13C5 is for research use only, not for human consumption.
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| References | |
| Additional Infomation |
Inosine-13C5 is a research-use only stable isotope-labeled compound, not approved for diagnostic or therapeutic use. It has not been evaluated in clinical trials. Its primary application is as an internal standard (IS) for LC-MS/MS quantification of endogenous Inosine levels in biological samples (plasma, urine, tissues, cell lysates) for metabolomics, biomarker discovery, and pharmacokinetic studies. Inosine (parent compound) is an endogenous purine nucleoside produced from adenosine by adenosine deaminase (ADA). Inosine has anti-inflammatory, immunomodulatory, anti-nociceptive, and neuroprotective effects. Inosine is being investigated for spinal cord injury, stroke, Parkinson's disease, and multiple sclerosis. The 13C5-labeling provides a +5 Da mass shift for precise quantitation.
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| Molecular Formula |
C513C5H12N4O5
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| Molecular Weight |
273.19
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| Appearance |
Solid powder
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
DMSO : 10 mg/mL (36.60 mM; with sonication)
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| Solubility (In Vivo) |
Solubility in Formulation 1: ≥ 1 mg/mL (3.66 mM)(saturation unknown) in 10% DMSO 40% PEG300 5% Tween-80 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution This solution produces a clear solution of ≥ 1 mg/mL (saturation unknown).
For example, if 1 mL of working solution, add 100 μL of 10.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix well; then add 50 μL Tween-80 to the above system and mix well; then add 450 μL saline to make up to 1 mL. *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 1 mg/mL (3.66 mM)(saturation unknown) in 10% DMSO 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution This protocol will produce a clear solution of ≥ 1 mg/mL (saturation unknown). . For example, if 1 mL of working solution, add 100 μL of 10.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD in saline and mix. *Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Solubility in Formulation 3: ≥ 1 mg/mL (3.66 mM)(Saturation unknown) in 10% DMSO 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution, add 100 μL of 10.0 mg/mL clear DMSO stock solution to 900 μL corn oil and mix well. (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 3.6605 mL | 18.3023 mL | 36.6046 mL | |
| 5 mM | 0.7321 mL | 3.6605 mL | 7.3209 mL | |
| 10 mM | 0.3660 mL | 1.8302 mL | 3.6605 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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