Absorption, Distribution and Excretion
In rabbits, the percentage of levonorgestrel excreted after binding with glucuronic acid depends on the dose; the higher the dose, the lower the binding rate. Metabolism/Metabolites Levomenthol readily binds with glucuronic acid in rabbits to form levonorgestrel-β-D-glucuronide. Approximately half of the levonorgestrel administered to rabbits is excreted as a glucuronide conjugate; the fate of the other half is unclear, but cyclic cleavage may occur, leading to significant degradation of the menthol molecule. In dogs, menthol undergoes extensive oxidation, with only about 5% of the dose being recovered in urine as glucuronide. /Menthol/ Levomenthol is rapidly but incompletely glucuroninated. Except for one subject, all subjects who pre-administered cimetidine (1 g/day for 1 week, an oxidative drug metabolism inhibitor) and all subjects who pre-administered the drug-metabolizing enzyme inducer phenobarbital (60 mg once nightly for 10 days) showed increased production of levmenthyl glucuronide. Corynebacterium RWM1 strain was able to grow using (-)-menthol, (-)-menthone, and other acyclic monoterpenes as the sole carbon source. Growth on menthol was very slow, with a doubling time exceeding 24 hours; growth on (-)-menthone was also slow (doubling time 12 hours). Growth was inhibited at carbon source concentrations exceeding 0.025%. Cells cultured in (-)-menthone medium transiently accumulate 3,7-dimethyl-6-hydroxyoctanoate during growth, while cells cultured in (-)-menthol medium oxidize (-)-menthol, (-)-menthone, 3,7-dimethyl-6-octanolactone, and 3,7-dimethyl-6-hydroxyoctanoate. Although menthol oxidase or menthol dehydrogenase was not detected in cell extracts from either (-)-menthol or (-)-menthone medium, an inducible NADPH-coupled monooxygenase active to (-)-menthone was readily detected. In the crude cell extract, only 3,7-dimethyl-6-hydroxyoctanoate was detected as a reaction product. When (-)-menthone monooxygenase was separated from the induced 3,7-dimethyl-6-octanolactone hydrolase by hydroxyapatite chromatography, the 3,7-dimethyl-6-octanolactone was found to be an oxidation product.
The known metabolites of (-)-menthol include (2S,3S,4S,5R)-3,4,5-trihydroxy-6-[(1R,2S,5R)-5-methyl-2-propyl-2-cyclohexyl]oxaoxane-2-carboxylic acid and p-menthane-3,8-diol.
L-menthol rapidly binds to glucuronic acid to form L-methyl-β-glucuronide. Approximately half of the absorbed menthol is excreted as glucuronic acid (A661).

[1]. Menthol Induces Surgical Anesthesia and Rapid Movement in Fishes. The Open Neuroscience. 2014 Feb; 8(1):1-8.

D,l-Menthol is a white crystalline solid with a minty odor and taste. (NTP, 1992)
(-)-Menthol is a p-menthane-3-ol with a (1R,2S,5R) stereochemical configuration. It is the most common naturally occurring enantiomer. It is used as an antipruritic, antitussive, and antispasmodic. It is the enantiomer of (+)-menthol.
Menthol is a covalent organic compound that can be synthesized or extracted from peppermint or other peppermint oils. Menthol is usually solid at room temperature, forming transparent or white waxy crystals. (-)-Menthol is the main naturally occurring form of menthol with a (1R,2S,5R) configuration. Menthol has local anesthetic and antiirritant effects and is therefore widely used to relieve mild throat irritation.
L-menthol has been reported in citrus (Citrus reticulata), pomegranate (Punica granatum), and several other organisms with relevant data. Levomenthol, the levorotatory isomer of menthol, is an organic compound that can be synthesized or extracted from peppermint or peppermint oil. It has flavoring and local anesthetic effects. When added to pharmaceuticals and foods, menthol enhances the peppermint flavor. It also has a counter-irritant effect on the skin and mucous membranes, thus producing local analgesic or anesthetic effects. Menthol is an alcohol made from peppermint oil or prepared synthetically. Menthol is a covalent organic compound that can be synthesized or extracted from peppermint or other peppermint oils. It is a waxy crystalline substance, transparent or white, solid at room temperature and melting slightly above room temperature. The main form of menthol found in nature is (-)-menthol, with the molecular formula (1R,2S,5R). Menthol has local anesthetic and counter-irritant effects and is widely used to relieve mild throat irritation. See also: Menthol (note moved here).

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Drug Indications
For the treatment of occasional mild irritation, pain, oral ulcers, sore throat, and cough caused by colds or inhaled irritants.

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Mechanism of Action
Menthol primarily activates the cold-sensitive TRPM8 receptor in the skin. Upon topical application, menthol stimulates the "cold" receptors by inhibiting Ca++ currents on neuronal membranes, thereby producing a cooling sensation. It may also exert its analgesic effect by activating κ-opioid receptors.

C10H20O

156.2652

156.151

89-78-1

16666

White to off-white solid powder

0.9±0.1 g/cm3

215.4±8.0 °C at 760 mmHg

34-36 °C(lit.)

93.3±0.0 °C

0.0±0.9 mmHg at 25°C

1.457

3.2

1

1

1

11

120

3

C[C@@H]1CC[C@H]([C@@H](C1)O)C(C)C

NOOLISFMXDJSKH-KXUCPTDWSA-N

InChI=1S/C10H20O/c1-7(2)9-5-4-8(3)6-10(9)11/h7-11H,4-6H2,1-3H3/t8-,9+,10-/m1/s1

(1R,2S,5R)-5-methyl-2-propan-2-ylcyclohexan-1-ol

2934.99.9001

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 : ~100 mg/mL (~639.92 mM)
H2O : ~1 mg/mL (~6.40 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (16.00 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.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (16.00 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.

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