Endogenous Metabolite; Microbial Metabolite

Well-known for its anti-inflammatory and antioxidant properties, allantoin is a common ingredient in cosmetic products [1]. In a dose-dependent manner, allantoin improved the viability of β-cells generated by STZ while attenuating cytotoxicity and apoptosis. Allantoin enhances the expression of phosphorylated B-cell lymphoma 2 (Bcl-2) and decreases caspase-3. Imidazoline 3 (I3) receptors have been demonstrated to be activated by allantoin [2].

Subchronic treatment of allantoin (1, 3 or 10 mg/kg for 7 days) significantly increased scopolamine-induced cholinergic blockade and latency evaluated in a passive avoidance task in normal young rats. Allantoin therapy (3 or 10 mg/kg for 7 days) also elevated phosphorylated phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (Akt), and phosphorylated glycogen synthase kinase 3β ( GSK-3β) expression levels. Allantoin dramatically enhances neuronal cell proliferation in immature neurons in the dentate gyrus area of the hippocampus [1]. Daily injection of allantoin for 8 days in STZ-treated rats dramatically lowered plasma glucose and boosted plasma insulin levels [2]. Allantoin decreases SHR blood pressure at 30 minutes, which is the most effective time. Furthermore, SHR treated with allantoin displayed an antihypertensive impact in a dose-dependent manner. Furthermore, in sedated rats, allantoin reduces cardiac contractility and heart rate. In addition, allantoin can considerably improve peripheral blood flow [3].

ApoTox-Glo triplex assay [2]
The β-cells were seeded into 96-well plates at a total density of 1 × 104 cells per well. Each well contained 200 µl RPMI 1640 medium and the test compound where appropriate. ApoTox-Glo Triplex Assay was used according to the manufacturer’s instructions to measure the β-cells’ viability, cytotoxicity, and apoptosis. After 24 h the Viability/Cytotoxicity reagent, containing both the GF-AFC substrate and the bis-AAF-R110 substrate, was added to all wells and incubated for 30 min. Caspase-Glo 3/7 was added to the wells and mixed briefly for 30 s, then incubated for 30 min at room temperature. Fluorescence was measured at 380EX/510EM to assess viability, 485EX/520EM to assess cytotoxicity, and luminescence was mesured to assess apoptosis.

The primary cultured cells were devided into 6-well plates. The medium was removed, and the cells were washed once with phosphate-buffered saline (PBS). RPMI 1640 medium containing 25 mM glucose was added to each well with 5 mM STZ and incubated for 6 h to induce cell apoptosis. To know the role of allantoin in the protection of pancreatic β-cells against STZ, allantoin pretreatment at various doses was provided before 30 min prior to the addition of 5 mM STZ and incubated for 6 h. To identify the signaling pathway of allantoin in β-cells, 1 µM KU14R: an I3 binding site antagonist, or 1 µM U73122: the phospholipase C (PLC) inhibitor were provided before 30 min prior to the addition of allantoin as previously described before. All the medium was removed, and the cells were washed three times with PBS prior to processing for the evaluation of morphology[2].

Mice: For memory ameliorating study, mice are administered vehicle solution, allantoin (1, 3 or 10 mg/kg, p.o.) or donepezil (5 mg/kg, p.o.) at the same time (10:00-12:00 a.m) and same place for 7 days. For memory enhancing study, mice are administered vehicle solution, allantoin (1, 3 or 10 mg/kg, p.o.) or piracetam (200 mg/kg, i.p.). The final administration of allantoin, donepezil or piracetam is performed 1 h before an acquisition trial in the passive avoidance task[1]

---

Glucose and insulin levels in STZ-treated rats: The induction of pancreatic cell damage was accomplished by injecting 45 mg/kg STZ dissolved in 10 mM Na-citrated buffer intraperitoneally. STZ-treated rats with blood glucose above 200 mg/dl at 7 days post-injection were included in the group. Total of 24 rats were divided into three groups as follows: Control (STZ) (n = 8), STZ + allantoin (n = 8), STZ + KU14R + allantoin (n = 8). The third group was treated with an intravenous injection of 8 mg/kg/day KU14R; the first and second groups were treated with the same volume of vehicle injected intravenously. After 30 min of KU14R injection, the second and third groups received 10 mg/kg/day of allantoin intravenously. The first group was injected the same volume of vehicle intravenously. The experiments were performed for 8 days. The blood samples were obtained from tail vein everyday. The plasma glucose levels were measured everyday, and the plasma insulin levels were measured on day 0, 4, 6, 8 [2].

---

Rats: Animals are randomly divided into four groups: (I) the control group treated with the vehicle, saline; (II) the allantoin group treated by intravenous injection of allantoin at 0.5 mg/kg; (III) the allantoin+efaroxan group treated with allantoin at the most effective dose (0.5 mg/kg, i.v.) and efaroxan at effective dose (1.5 mg/kg, i.v.) 30 minutes before injection of allantoin; and (IV) the allantoin treated SHRs group treated by intravenous injection of allantoin at various dose for desired time. After treatment of allantoin, the rats are placed into a holder for the determination of the mean blood pressure[3].

Absorption, Distribution and Excretion
In studies on human subjects, a recovery of 19% and 34% of allantoin in the urine was observed but only in two individuals and only after the administration of massive doses of allantoin. After intravenous administration, recovery in the urine was practically quantitative with doses of 75 to 600 mgm in the human model. After 240 mgm, excretion continued for 72 hours in human subjects and the results were similar in regards to subcutaneous injection.
Urinary clearance is the predominant excretion route.
Some studies suggest that the average renal clearance of allantoin in normal, healthy human subjects is approximately 123 cc per minute. It is generally agreed upon that exogenously administered allantoin is rapidly excreted.
Allantoin administered to dogs orally as solid or solution was excreted in the urine to an extent of between 35 and 92 per cent within 24 hours. No allantoin was recovered either in urine or feces when given to rabbits orally. In man the recovery was 19 and 34 per cent in two individuals after massive doses. After intravenous administration recovery in the urine was practically quantitative with doses of 75 to 600 mgm. in the dog and in man. After 240 mgm. in man excretion continued for 72 hours. The results were similar after subcutaneous injection. Uric acid injected intravenously into a dog was converted into allantoin within two hours.

---

Metabolism / Metabolites
Uricase is the enzyme that possesses the functionality to convert uric acid to allantoin. Considering humans do not possess any endogenous uricase, uric acid is the only final breakdown product in the purine degradation of unwanted waste product purine nucleotides. The presence of allantoin in human urine is subsequently the result of non-enzymatic processes on uric acid with reactive oxygen species. Such non-enzymatic processes are consequently potentially suitable biomarkers for measuring oxidative stress in chronic illnesses and aging. Furthermore, as allantoin is found endogenously and is part of basic, natural metabolic pathways, no accumulation is expected of it. Additionally, allantoin is not believed to be metabolized to a measurable extent in humans and animals.
In humans, uric acid is the final breakdown product of unwanted purine nucleotides. Uric acid is the last stage in purine degradation, because humans lack the enzyme uricase which converts uric acid into allantoin.
Allantoin in the presence of calcium ions has been implicated as a potential toxic agent in Reye's syndrome. An investigation of possible alternative sources of allantoin in humans, which lack the enzyme uricase, has been initiated. Urate is a strong reducing agent which can reduce cytochrome c nonenzymatically, with the concomitant production of CO2 and H+. The stoichiometries measured for the various reactants and products were 1 urate:2 cytochrome c:1 H+:1 CO2. The initial reaction rate depended on the concentrations of both urate and cytochrome c, with reaction kinetics that were first order with respect to urate and second order with respect to cytochrome c. The participation of molecular oxygen in this reaction could not be detected. The pH and ionic strength optima for this reaction were determined to be 9.5-10.5 and 10(-5) M, respectively. Based on the results reported here, the following balanced equation can be written: urate-2 + 2 cytochrome c+3 + 2 H2O----allantoin + 2 cytochrome c+2 + H+ + HCO3-. /The authors/ propose that allantoin can be generated from the oxidation of urate by cytochrome c+3, and that this is a potential source of allantoin in human tissues.
Uric acid is the main nitrogenous waste product in birds but it is also known to be a potent antioxidant. Hominoid primates and birds lack the enzyme urate oxidase, which oxidizes uric acid to allantoin. Consequently, the presence of allantoin in their plasma results from non-enzymatic oxidation.
In most mammals purine degradation ultimately leads to the formation of allantoin. Humans lack the enzyme uricase, which catalyzes the conversion of uric acid to allantoin.
For more Metabolism/Metabolites (Complete) data for ALLANTOIN (11 total), please visit the HSDB record page.

---

Biological Half-Life
When studied in cattle, sheep, and horses, the half-life of allantoin is in the range of 1 to 2.5 hours.

Interactions
Feed containing 0.2% allantoin ... with or without 0.2% sodium nitrite, was given ad lib. to groups of 20 or 24 male and 20 or 24 female F344 rats for 106 wk. ... Control rats were given untreated feed ... and nitrite-treated controls were given sodium nitrite at a concentration of 0.2% in feed or drinking-water. At the end of the treatment period the rats were given untreated feed ...and observed until death. There was little or no life-shortening effect in any treatment group. /Allantoin / administered alone /and in combination with sodium nitrite did not induce/ an increase in the incidence of any tumor in comparison with the untreated control groups ...

[1]. Effects of allantoin on cognitive function and hippocampal neurogenesis. Food Chem Toxicol. 2014 Feb;64:210-6.

[2]. Allantoin ameliorates chemically-induced pancreatic β-cell damage through activation of the imidazoline I3 receptors. PeerJ. 2015 Aug 6;3:e1105.

[3]. Antihypertensive action of allantoin in animals. Biomed Res Int. 2014;2014:690135.

Therapeutic Uses
A urea hydantoin that is found in URINE and PLANTS and is used in dermatological preparations.
Allantoin, a component in Comfrey, stimulates tissue repair and wound healing through cell proliferation. Allantoin has also had significant effect on cellular multiplication in degenerating and regenerating peripheral nerves.
In humans, the allantoin to uric acid ratio in plasma increases during oxidative stress, thus this ratio has been suggested to be an in vivo marker for oxidative stress in humans.
Diagnostic marker for oxidative stress during antituberculous (anti-TB) therapy.
For more Therapeutic Uses (Complete) data for ALLANTOIN (8 total), please visit the HSDB record page.

---

Drug Warnings
Skin: For external use only. Ocular: Avoid contact with eyes. Sensitization: Mederma is contraindicated in individuals who have shown hypersensitivity to any of its components /Mederma/

---

Pharmacodynamics
There is no well controlled and appropriate data that can formally substantiate the pharmacodynamic properties of allantoin. Nevertheless, ongoing studies suggest that allantoin possesses moisturizing and keratolytic effects, as well as abilities to increase the water content of the extracellular matrix and enhance the desquamation of upper layers of dead skin cells, all of which are activities that can promote cell proliferation and facilitate wound healing.

C4H6N4O3

158.1154

158.043

C, 30.39; H, 3.83; N, 35.43; O, 30.36

97-59-6

Allantoin-13C2,15N4;1219402-51-3; 97-59-6 (racemic); 7303-80-2 (R-isomer); 3844-67-5 (S-isomer)

204

White to off-white solid

1.7±0.1 g/cm3

478ºC

230 °C (dec.)(lit.)

230-234°C

1.616

Microbe

-2.89

4

3

1

11

225

0

O=C(NC1C(=O)NC(=O)N1)N

POJWUDADGALRAB-UHFFFAOYSA-N

InChI=1S/C4H6N4O3/c5-3(10)6-1-2(9)8-4(11)7-1/h1H,(H3,5,6,10)(H2,7,8,9,11)

1-(2,5-dioxoimidazolidin-4-yl)urea

5-Ureidohydantoin; SD 101; Allantion; Sebical; Septalan; Allantol; Cordianine; NSC 7606; DL-Allantoin; Glyoxyldiureid; Glyoxyldiureide; Glyoxylic diureide; Psoralon;

2933.21.0000

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

DMSO : ~50 mg/mL (~316.22 mM)
H2O : ~3.85 mg/mL (~24.35 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (15.81 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume 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: ≥ 2.5 mg/mL (15.81 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.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

---

View More

Solubility in Formulation 3: ≥ 2.5 mg/mL (15.81 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 is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

Solubility in Formulation 4: 2 mg/mL (12.65 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

---

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