Menthol, also known as menthol, is a terpenoid organic compound with the chemical formula C 10 H 20 O。 Menthol is extracted from the leaves and stems of peppermint. It is a white crystal. It is the main component of peppermint and peppermint essential oils. There are generally two isomers of menthol (D-type and L-type), and the natural menthol is mainly left-handed isomer（ L-menthol ）Menthol here generally refers to racemic menthol（ DL menthol ）. Menthol can be used as a flavoring agent for toothpaste, perfume, beverage and candy. It is used as an irritant in medicine. It acts on the skin or mucous membrane and has a cooling and antipruritic effect. It can be used as an antipyretic for headache, rhinopharynx and laryngitis. Its ester can also be used in perfume and medicine.
Physical and chemical properties
Peppermint oil, also known as menthol, is a cyclic monoterpene. Medium, fully flammable. It is colorless acicular or prismatic crystal or white crystalline powder; It has a special aroma of mint, which is hot at the beginning and cool after taste; Ethanol solution showed neutral reaction. This product is very easy to dissolve in ethanol, chloroform, ether, liquid paraffin or volatile oil, but very slightly dissolved in water.
Calculate chemical data
1. Reference value of hydrophobic parameter calculation (xlogp): 3
2. Number of hydrogen bond donors: 1
3. Number of hydrogen bond receptors: 1
4. Number of rotatable chemical bonds: 1
5. Number of tautomers: 0
6. Topological molecular polar surface area (TPSA): 20.2
7. Number of heavy atoms: 11
8. Surface charge: 0
9. Complexity: 120
10. Number of isotope atoms: 0
11. Determination of the number of atomic conformation centers: 3
12. Number of indeterminate atomic stereocenters: 0
13. Determine the number of chemical bond conformation centers: 0
14. Number of uncertain chemical bond conformation centers: 0
15. Number of covalent bond units: 1
Customs Code: 2906110000
Dangerous goods transport code: UN 1888 6.1/pg 3
Wgk germany:2
Hazard category code: R36 / 37 / 38
Safety instructions: S36 / 37 / 39-s24 / 25-s26
RTECS No.: ot0350000
Dangerous goods mark: Xi
Properties and stability
It is a kind of l-colorless needle like crystal. Soluble in ethanol, miscible with oil. It has cool, fresh and pleasant Mint characteristic aroma, with sweet and pungent breath. It gives people a cold feeling, and the fragrance is transparent, but it is not long-lasting. The taste is also fresh, sweet and cool.
2. It exists in flue-cured tobacco, oriental tobacco and mainstream smoke.
3. It is naturally found in peppermint oil and Japanese mint oil, and a small amount in essential oil such as Geranium oil.
4. There are trace liquid oil and non-volatile matter on the surface of ordinary crystal, and the synthesized menthol is a mixture of various isomers.
5. It has certain toxicity, irritation and allergic reaction.
Main uses
1. Menthol and racemic menthol are both used as flavoring agents for toothpaste, perfume, beverage and candy. In medicine, it is used as a stimulant, acting on the skin or mucous membrane, with cooling and antipruritic effect; It can be used as an antipyretic for headache, rhinopharynx and laryngitis. Its ester is used in perfume and medicine. In the world, China and Brazil are the main natural mint production parks, with the annual output of mint oil reaching 2000-3000t.
2. Widely used in daily flavor, edible flavor and tobacco flavor. Generally, it is 1100mg / kg in gum; 400mg/kg in candy; 130 mg / kg in baked food; Ice cream 68mg/kg; 35mg/kg in soft drinks.
3. It has the function of sterilization and antisepsis.
4. As a special additive for therapeutic cosmetics. For toilet water, etc. It can also be used as a perfumer for toothpaste, perfume, beverage and candy. It can be used in confectionery and beverage.
Preparation
In industry, menthol and menthol are extracted from peppermint by steam distillation and organic solvent extraction. The former has low extraction efficiency, while the latter has the toxicity of residual organic solvents. Menthol (Menthol) extracted from Mentha haplocalyx by supercritical carbon dioxide can eliminate the disadvantages of the above two methods. Its yield is about 5 times higher than that of steam distillation and 3 times higher than that of organic solvent method. The product maintains pure natural characteristics, good quality, high purity, no solvent residual toxicity, easy to meet the export requirements, has better competitiveness and can occupy the market. Menthol can be purified from natural peppermint crude oil or synthesized. The essential oil from the above ground parts (stems, branches, leaves and inflorescences) of Mentha haplocalyx L. was distilled by steam. The yield of essential oil was 0.5-0.6. There are many ways to synthesize gracile.
Made from citronellal
utilize Citronellal Cyclization Isohu menthol The properties of d-citronellal were studied acid catalyst (such as silica gel) cyclized into l-isohu-menthol, separated into l-isohu-menthol, hydrogenated to produce l-menthol. Its stereoisomers can be partially converted into d-citronellal by thermal cracking and recycled.
Made from thymol
In the presence of m-cresol aluminum, m-cresol was synthesized by alkylation reaction Thymol . All four pairs of stereoisomers of menthol (racemic menthol; racemic neomenthol; racemic isomenthol and racemic neoisomenthol) were obtained by catalytic hydrogenation. It was distilled, the menthol fraction was eliminated, and the ester was produced and recrystallized repeatedly for isomer separation and optical resolution. The separated l-menthol ester is saponified to obtain menthol.
Racemic menthol can be separated from the other three pairs of isomers by distillation. The remaining isomer mixture can be balanced into racemic menthol, racemic neomenthol and racemic isomenthol in the ratio of 6:3:1. The content of new isomenthol is negligible. Racemic menthol can be separated from the above mixture. Racemic menthol meridian Benzoate ester The solution or the mixture is inoculated with the pure l-menthol ester, and then separated by l-helix; D-menthol and other isomers can be converted into racemic menthol in equilibrium according to hydrogenation conditions.
pharmacological action
The product and Glucuronic acid The conjugates are excreted in urine and bile, and various isomers combine with glucuronic acid in different amounts. Molecular degradation reactions were observed in dogs and rats. It can Menthone Metabolites exist in the form of.
character
The product is produced in ethanol, ethanol and chloroform 、 Liquid paraffin Or volatile oil is very easy to dissolve, very slightly dissolved in water.
Add 1 ml of alcohol into the sample according to the law, and determine the precision by adding 1 ml of alcohol.
Indications
External use for local pain relief, itching, headache, dizziness, mosquito bites; Nasal drip is used for cold and nasal congestion, inhalation or spray is used for pharyngitis; Oral administration can strengthen the stomach.
Drug interactions
It is often combined with camphor to enhance the antipruritic effect.
usage and dosage
Apply it to the itchy area of the skin. It can be used many times a day. 0.02-0.1g, more tablets. Or into the ointment, ointment, external application of the affected area.
Preparation and specification
Menthol powder, ointment and tincture: 1% - 2%.
Adverse reactions
Occasional local irritation.
Contraindications
It is forbidden for infants and young children.
Storage
Seal and store in a cool place.
First aid for poisoning
Since menthol has irritating effect on skin and eyes and certain toxicity, gloves and safety glasses must be worn when using it in large quantities.
1. Inhalation: transfer the poisoned person to a ventilated place and take general first aid measures.
2. Eye contact: Rinse eyes according to general procedures. Consult a physician if necessary.
3. Skin contact: wash with water and soap.
4. Others: consult a physician
Made from peppermint oil
The menthol oil was crystallized after freezing, centrifuged and recrystallized with low boiling solvent to obtain pure l-menthol. After removing the crystallization, the mother liquor still contains 40% - 50% menthol and a large amount of menthone, which is converted into a mixture of L-menthol and d-neomenthol by hydrogenation. More l-menthol can be obtained by saponification of the ester, crystallization, distillation or boric acid ester, and then separating the other parts of peppermint oil.
