Agmatine sulfate targets an exceptionally wide range of molecules, earning it the nickname "molecular shotgun," and exerts its functions by simultaneously modulating multiple receptor and enzyme systems. Its targets include: (1) Neurotransmitter receptor systems: It acts as an endogenous agonist at imidazoline receptors and binds to α₂A-, α₂B-, and α₂c-adrenergic receptors with Ki values of 46.98 μM, 164.4 μM, and 26.3 μM, respectively; it also functions as an antagonist at NMDA receptors, 5-HT3 receptors (IC₅₀=141 μM), and nicotinic acetylcholine receptors; (2) Nitric oxide synthase (NOS): It competitively inhibits all NOS isoforms, with Ki values of 660, 220, 7,500, and 260 μM for neuronal (nNOS), macrophage (iNOS), endothelial (eNOS), and inducible NOS, respectively; (3) Ion channels and transporters: It blocks ATP-sensitive potassium channels (K_ATP); (4) Polyamine metabolism: It participates in the regulation of polyamine metabolic pathways.

Agmatine stimulates the release of catecholamines from adrenal chromaffin cells via binding to imidazoline and α2-adrenergic receptors. There is arginine decarboxylase, its biosynthetic enzyme, in the brain. Agmatine, which is generated topically, functions as a neurotransmitter and is an endogenous agonist of imidazoline receptors as well as a non-catecholamine ligand for α2-adrenergic receptors [1]. The brain produces gabapentin, which is then stored in synaptic vesicles of neurons that are selectively localized, accumulated by uptake, released upon depolarization, and rendered inactive by the gabapentin enzyme. Agmatine causes the release of some peptide hormones and inhibits nitric oxide synthase [2]. Agmatine, or 4-(aminobutyl)guanidine, is created when arginine decarboxylase breaks down L-arginine. Agmatine is not a precursor of NO; rather, it is a competitive inhibitor of all NOS isoenzymes. Ki values for NOS I, NOS II, and NOS III are roughly 660 µM, 220 µM, and 7.5 mM, respectively [3]. Agmatine causes three times as much nitrite to be produced by endothelial cells as they do at rest. Agmatine has been seen to cause cytosolic calcium transients in endothelial cells and to displace [3H]-imidazoxane on the endothelial cell membrane. Agmatine downregulates transients when exposed repeatedly; transients are unaffected by norepinephrine pretreatment [4].

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Agmatine sulfate exhibits differential regulatory effects on various cell types in vitro. On one hand, it promotes the proliferation of thymocytes, lymphocytes, and neural stem cells; on the other hand, it exerts anti-proliferative effects on smooth muscle cells, macrophages, fibroblasts, astrocytes, and various cancer cells, with cell proliferation effects being dependent on cell type and differentiation stage. Importantly, although agmatine sulfate is cytotactic for specific cell types, it is not cytotoxic. At the molecular level, this compound is released from and taken up by synaptosomes, demonstrating neurotransmitter-like activity. Furthermore, it concentration-dependently blocks ATP-sensitive potassium channels in mouse pancreatic β-cells and antagonizes 5-HT3 receptors (IC₅₀=141 μM) in mouse N1E-115 neuroblastoma cells.

Agmatine has antidepressant-like effects when tested in mice using the forced swim test and tail suspension test (dose range: 0.01–50 mg/kg, intraperitoneally), but it does not affect the mice's ability to walk in the open [5]. Agmatine preserves the blood-brain barrier during ischemic stroke; this can be observed in vivo by measuring permeability with dynamic contrast-enhanced magnetic resonance imaging [6]. Agmatine notably increased MK-801's antidepressant-like effects, supporting the theory that it modifies NMDA receptor activity [7].

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Agmatine sulfate exhibits broad biological activities in various in vivo models. In the nervous system, intraperitoneal administration at 0.01-50 mg/kg produces antidepressant-like effects in mice (assessed by forced swimming test and tail suspension test) without altering spontaneous locomotion in the open field test. In aged rat models, 8 weeks of oral agmatine sulfate treatment (40 mg/kg, twice daily) improves age-related cognitive dysfunction (assessed by passive avoidance test and Morris water maze test), restores endothelial function, and upregulates eNOS and BDNF protein expression. For analgesia, agmatine sulfate reduces the ED₅₀ of morphine by 5.2-fold and that of [D-Pen²,D-Pen⁵]enkephalin (DPDPE) by 4.7-fold in the mouse tail flick assay. In cerebral ischemia, agmatine sulfate protects blood-brain barrier integrity.

Inhibitory activity of agmatine sulfate against nitric oxide synthase (NOS) isoforms is assessed using radioactive enzyme activity assays. For nNOS determination, the test compound is incubated with recombinant nNOS and the substrate L-[³H]arginine in buffer containing Ca²⁺ and calmodulin. The product L-[³H]citrulline is separated by cation exchange chromatography and quantified by scintillation counting. For receptor binding assays, radioligand competitive binding methods are employed: membrane preparations expressing specific receptors are incubated with fixed concentrations of radiolabeled ligands (e.g., [³H]-clonidine or [³H]-idazoxan) and increasing concentrations of agmatine sulfate (typically 1 nM-10 mM). Following incubation, membrane-bound fractions are rapidly collected by filtration, radioactivity is measured using a scintillation counter, and IC₅₀ and Ki values are calculated. This method is used to determine affinities for α₂-adrenergic receptors (Ki values of 46.98, 164.4, and 26.3 μM) and imidazoline receptors (Ki=74.4 μM).

The effect of agmatine sulfate on cell proliferation is typically evaluated using various cell lines. The experimental procedure is as follows: logarithmically growing cells (such as neural stem cells, lymphocytes, or cancer cell lines) are seeded in 96-well plates (5×10³-1×10⁴ cells per well) and allowed to adhere overnight in medium containing 10% fetal bovine serum at 37°C, 5% CO₂. Increasing concentrations of agmatine sulfate (typically 0-1000 µM) are added, and after 48-72 hours of treatment, cell viability is measured by MTT or CCK-8 assays to calculate IC₅₀ values. To assess proliferative effects, BrdU incorporation assays or EdU staining can be performed in parallel to detect cell proliferation markers. Additionally, apoptosis can be evaluated by Annexin V/PI double staining flow cytometry to confirm the non-cytotoxic nature of agmatine sulfate. Studies have shown that agmatine sulfate at concentrations of 1-10 µM promotes neural stem cell proliferation, while higher concentrations (>100 µM) exhibit inhibitory effects on cancer cells.

In vivo efficacy study protocols for agmatine sulfate vary depending on the experimental objective. In mouse behavioral studies (e.g., antidepressant-like effect assessment), agmatine sulfate is administered intraperitoneally at doses of 0.01-50 mg/kg, typically as a single dose 30 minutes prior to behavioral testing, which includes the forced swimming test and tail suspension test. In sub-chronic toxicity studies, mice receive oral gavage of agmatine sulfate at 300-900 mg/kg/day for periods ranging from 7 to 95 days to assess safety. In aged rat cognitive function studies, rats receive oral agmatine sulfate (40 mg/kg, twice daily for 8 weeks), and cognitive function is evaluated using the passive avoidance test and Morris water maze test. In vascular dementia models, aged rats of various ages (4, 18, and 24 months) receive oral agmatine sulfate at 40 mg/kg twice daily for 8 weeks, with evaluation parameters including systolic blood pressure, endothelium-dependent vasorelaxation responses in the thoracic aorta, passive avoidance latency, and spatial learning and memory performance.

The pharmacokinetic profile of agmatine sulfate has been preliminarily characterized in humans. Following oral administration, the compound is rapidly absorbed in the gastrointestinal tract and distributed throughout the body, including the brain, within minutes. In humans, ingested agmatine sulfate is readily absorbed and eliminated unmetabolized by the kidneys, with an apparent plasma elimination half-life of approximately 2 hours. In animal studies, oral administration similarly demonstrates rapid distribution characteristics. Agmatine sulfate is primarily eliminated through two metabolic pathways: first, via arginase and agmatinase to urea and putrescine (the latter being a precursor for polyamine and GABA biosynthesis), and second, via an oxidative pathway to agmatine aldehyde, which is subsequently secreted by the kidneys. A high-throughput screening study showed that, among 119 screened targets (including CYP3A4), agmatine sulfate only exhibited binding activity at the multidrug resistance transporter, suggesting that it is unlikely to cause significant drug interactions.

Agmatine sulfate demonstrates a favorable safety profile in various animal models and clinical studies. Regarding genotoxicity, the most recent studies evaluated agmatine sulfate using the Ames test (bacterial reverse mutation assay), in vitro chromosomal aberration test, and in vivo mouse micronucleus test, all showing that the compound lacks mutagenic, clastogenic, and genotoxic effects. In sub-chronic toxicity studies, rats receiving high-dose oral agmatine sulfate for 95 days (829.85 mg/kg/day for females, 568.51 mg/kg/day for males) exhibited no adverse effects; mice receiving 300 mg/kg/day for 95 days showed no pathological alterations upon gross necropsy and histological examination. In clinical studies, healthy volunteers tolerated up to 3.560 g/day oral agmatine sulfate for 3 weeks; a case report showed no measurable adverse effects following 5 years of continuous intake at 2.67 g/day. The compound is non-cytotoxic to various cell types in vitro. According to the Globally Harmonized System (GHS) of classification and labeling of chemicals, the hazard labels include: H315 (skin irritation), H319 (eye irritation), and H335 (respiratory tract irritation).

[1]. Agmatine: an endogenous clonidine-displacing substance in the brain. Science. 1994 Feb 18;263(5149):966-9.

[2]. Is agmatine a novel neurotransmitter in brain? Trends Pharmacol Sci. 2000 May;21(5):187-93.

[3]. Inhibition of mammalian nitric oxide synthases by agmatine, an endogenouspolyamine formed by decarboxylation of arginine. Biochem J. 1996 May 15;316 ( Pt 1):247-9.

[4]. Agmatine activation of nitric oxide synthase in endothelial cells. Proc Assoc Am Physicians. 1997 Jan;109(1):51-7.

[5]. Agmatine produces antidepressant-like effects in two models of depression in mice. Neuroreport. 2002 Mar 25;13(4):387-91.

[6]. Effects of agmatine on blood-brain barrier stabilization assessed by permeability MRI in a rat model of transient cerebral ischemia. AJNR Am J Neuroradiol. 2015 Feb;36(2):283-8.

[7]. Agmatine enhances antidepressant potency of MK-801 and conventional antidepressants in mice. Pharmacol Biochem Behav. 2015 Mar;130:9-14.

Agmatine is a primary amino compound belonging to the Agmatine family. It is a metabolite of E. coli and mice and is the conjugate base of the Agmatine ion (2+). Agmatine is a natural metabolite of the amino acid arginine. It is produced by the decarboxylation of arginine catalyzed by arginine decarboxylase and is naturally found in ragweed pollen, ergot, octopus muscle, herring sperm, sponges, and mammalian brain tissue. Agmatine is currently in the experimental and research stage. As an investigational drug, a non-blinded prospective case study in the United States is evaluating it in patients aged 18 to 75 years diagnosed with small fiber peripheral neuropathy. As of July 2013, the results of this study have not been published. As an experimental drug, arginine is being investigated for the treatment of various diseases, such as cardioprotection, diabetes, decreased renal function, neuroprotection (stroke, severe central nervous system injury, epilepsy, glaucoma, and neuropathic pain), and mental illnesses (depression, anxiety, schizophrenia, and cognitive impairment). The exact mechanism of action of arginine is still under investigation to evaluate all its potential indications. Arginine is a metabolite found in or produced by Escherichia coli (K12, MG1655 strains). It has also been reported to be present in soybeans, scallops, and other organisms with relevant data. Arginine is decarboxylated arginine and can be isolated from various plant and animal sources, such as pollen, ergot, herring sperm, and octopus muscle. Drug Indications Experimental studies are currently underway to evaluate the application of arginine in various indications, such as cardioprotection, diabetes, renal impairment, neuroprotection (stroke, severe central nervous system injury, epilepsy, glaucoma, and neuropathic pain), and mental illnesses (depression, anxiety, schizophrenia, and cognitive impairment). As an investigational drug, Agmatine is undergoing a non-blinded prospective case study in the United States in patients diagnosed with small fiber peripheral neuropathy. Mechanism of Action The exact mechanism of action for all potential indications of Agmatine is still under investigation. Several biochemical mechanisms have been identified that are related to the indications of Agmatine in diabetes, neuroprotection, and mental illness. In diabetes, Agmatine increases cellular glucose uptake by increasing insulin release from pancreatic islet cells and by increasing adrenal endorphin release, thus producing a hypoglycemic effect. In neuroprotection, the effects of Agmatine are thought to involve the regulation of receptors (NMDA, α2, and imidazoline receptors) and ion channels (ATP-sensitive potassium channels and voltage-gated calcium channels), as well as blocking nitric oxide synthesis. Arginine blocks nitric oxide synthesis by reducing the protein levels of nitric oxide synthase-2 (NOS-2) in astrocytes and macrophages. Regarding the therapeutic effects of arginine in mental illness, studies suggest that its mechanism involves the regulation of neurotransmitter receptors, including NMDA receptors, α2 receptors, serotonin receptors, opioid receptors, and imidazoline receptors. Specifically, when arginine binds to imidazoline and α2 receptors, it acts as a neurotransmitter, prompting the adrenal glands to release catecholamines.

C5H16N4O4S

228.2699

228.089

C, 26.31; H, 7.07; N, 24.54; O, 28.04; S, 14.04

2482-00-0

306-60-5 ( free base);2482-00-0 (sulfate);

2794990

White to off-white solid powder

281.4ºC at 760 mmHg

234-238 °C(lit.)

124ºC

0.00357mmHg at 25°C

1.527

5

6

4

14

166

0

C(CCN=C(N)N)CN.OS(=O)(=O)O

PTAYFGHRDOMJGC-UHFFFAOYSA-N

InChI=1S/C5H14N4.H2O4S/c6-3-1-2-4-9-5(7)8;1-5(2,3)4/h1-4,6H2,(H4,7,8,9);(H2,1,2,3,4)

2-(4-aminobutyl)guanidine;sulfuric acid

Agmatine sulfate; 2482-00-0; Guanidine, N-(4-aminobutyl)-, sulfate (1:1); Guanidine, (4-aminobutyl)-, sulfate (1:1); UNII-RU0176QL8I;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ≥ 100 mg/mL (~438.08 mM)
DMSO : ~1 mg/mL (~4.38 mM)

Solubility in Formulation 1: 25 mg/mL (109.52 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with heating and sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)