Pure menthol crystals, also known as menthol, is a terpenoid organic compound, CAS 89-78-1, The chemical formula is C10H20O. Menthol is extracted from the leaves and stems of peppermint, with white crystals, and is the main component of peppermint and peppermint essential oils. Burning, fully burned, with no smoke during combustion. Colorless needle shaped or prismatic crystals or white crystalline powder; There is a special aroma of mint, which is initially hot and then cool; Ethanol solution exhibits neutral reaction. This product is highly soluble in ethanol, chloroform, ether, liquid paraffin or volatile oil, and only slightly soluble in water. There are generally two isomers (D-type and L-type), and the natural substance is mainly the left-handed isomer (L-menthol), where menthol generally refers to racemic menthol (DL menthol). Menthol can be used as an aroma enhancer for toothpaste, perfume, drinks and candies. Used as a stimulant in medicine, it acts on the skin or mucous membranes and has a cooling and itching relieving effect. Oral administration can be used as a wind dispelling medicine for headaches, as well as for symptoms such as nasal, pharyngeal, and pharyngitis. Its esters can also be used in fragrances and medicines.
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Chemical Formula |
C10H20O |
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Exact Mass |
156 |
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Molecular Weight |
156 |
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m/z |
156 (100.0%), 157 (10.8%) |
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Elemental Analysis |
C, 76.86; H, 12.90; O, 10.24 |
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Melting point 34-36 ° C (lit.), Boiling point 216 ° C (lit.), Density 0.89 g / ml at 25 ° C (lit.), Vapor pressure 0.8 mm Hg (20 ° C), Refractive index 1.4615, FEMA 2665 | MENTHOL RACEMIC, Flash point 200 ° f, Storage conditions 2-8 ° C, Practically soluble in water, very soluble in ethanol (96 per cent) and in light petroleum, free soluble in fat oils and in liquid paraffin, very slowly soluble in glucose.
As a natural active ingredient, Pure menthol crystals has shown extensive application value in fields such as medicine, food, daily chemical, and industry. Its unique pharmacological mechanism and multi-target effects give it unique advantages in pain management, respiratory regulation, digestion promotion, and other areas. With the development of modern formulation technology, the clinical application of menthol will be further expanded, especially in the fields of neurodegenerative diseases and tumor adjuvant therapy, showing potential.
Pharmacological effects and biological mechanisms
1. Neural receptor regulation
Cold sensation receptor activation: Menthol stimulates TRPM8 receptors (cold sensation receptors) in the skin and mucous membranes directly, producing a cool sensation, reflexively causing vasoconstriction, and reducing local temperature.
Increased pain threshold: activates the kappa opioid receptors in the spinal dorsal horn, inhibits pain signal transduction, and is effective for acute pain such as headache and muscle pain.
Inhibition of anti-inflammatory pathway: Blocking the NF - κ B signaling pathway, reducing the release of pro-inflammatory factors such as TNF - α and IL-6, and alleviating skin and respiratory inflammation.
2. Respiratory system regulation
Mucosal vasoconstriction: After nasal administration, menthol stimulates the alpha receptors of nasal mucosal blood vessels, constricts blood vessels, and improves nasal congestion symptoms.
Enhanced ciliary movement: promotes respiratory ciliary oscillation frequency, accelerates mucus clearance, and assists in the treatment of bronchitis.
3. Effects on the digestive system
Gastrointestinal motility promotion: activates the vagus nerve, increases the secretion of motilin, and improves functional dyspepsia.
Bile secretion stimulation: Promotes bile flow and assists fat digestion through TGR5 receptors (bile acid receptors).
4. Central nervous system effects
Awakening enhancement: By activating the locus coeruleus of the hypothalamus, increasing the activity of dopaminergic neurons, it produces a refreshing effect.
Emotion regulation: Sniffing menthol can enhance the activity of the prefrontal cortex, alleviate mild anxiety and cognitive fatigue.
Application in the field of medicine
1. Treatment of skin diseases
Pruritus:
Mechanism: Inhibits degranulation of mast cells and reduces histamine release.
Preparation: Hearthstone lotion containing 2% menthol, used for urticaria and mosquito bites.
Eczema/dermatitis:
Function: Anti inflammatory, anti itch, repairing skin barrier.
Formula: Compound menthol ointment (containing camphor and salicylic acid) is used for contact dermatitis.
2. Pain management
Headache: Menthol caffeine compound preparations (such as certain cooling oils) improve migraine by dilating cerebral blood vessels.
Joint pain: External patches (containing menthol and capsaicin) alleviate osteoarthritis pain through a dual mechanism.
Postoperative analgesia: Menthol vapor inhalation is used as an auxiliary analgesic method to reduce the dosage of opioid drugs.
4. Indications for digestive system
Functional dyspepsia: Mentha Caps, a enteric coated capsule of menthol, improves postprandial fullness.
Irritable bowel syndrome (IBS): Local effects reduce intestinal spasms and alleviate abdominal pain.
3. Respiratory system diseases
Rhinitis/Sinusitis:
Nasal spray: The preparation containing 0.1% menthol can quickly relieve nasal congestion.
Combination therapy: Combined with budesonide to enhance anti-inflammatory effects.
Chronic obstructive pulmonary disease (COPD): Menthol inhalers assist in expectoration, reducing the risk of acute exacerbation.
5. Assistance for neurodegenerative diseases
Alzheimer's disease: Menthol nasal preparations improve cognitive function by activating the olfactory pathway (clinical trial phase).
Parkinson's disease: Preliminary studies suggest it may alleviate bradykinesia, further validation is needed.
Food industry applications
1. Fragrance and seasoning
Candy and chewing gum:
Dosage standard: EU regulations allow the addition of menthol in candies to be ≤ 400mg/kg.
Technical challenge: Need to balance the threshold of coolness and bitterness.
Beverages and cold drinks:
Microencapsulation technology: protects the volatility of menthol and prolongs the duration of coolness.
Typical products: Mint flavored carbonated beverages, ice cream.
2. Development of functional foods
Digestive aid: Sugar free peppermint candies containing menthol promote saliva secretion and alleviate dry mouth.
Sports nutrition: Menthol+electrolyte drinks to improve heat dissipation efficiency during exercise.
3. Food safety considerations
Allergy risk: Menthol has low allergenicity, but in rare cases, cross reactivity should be monitored.
Children's food: It should be avoided to add it to food for children under 3 years old to prevent the risk of accidental ingestion.
Cosmetics and Personal Care
1. Skin care
Sunscreen products: Menthol enhances skin heat dissipation and improves post sun repair effectiveness.
Acne removing gel: 0.5% menthol+2% salicylic acid formula, anti-inflammatory and bacteriostatic.
Sensitive muscle care: Avoid high concentration preparations to prevent irritation reactions.
4. Special cosmetics
Men's skincare: Menthol+tea tree oil formula, aimed at calming after shaving.
Sports skin care: Mint+Mint essential oil spray can cool down quickly after sports.
2. Hair care
Shampoo: The cooling effect of pure menthol crystals stimulates scalp blood circulation and promotes hair growth.
Hair growth solution: Combination with minoxidil may enhance therapeutic efficacy (clinical validation required).
3. Oral care
Toothpaste: formulated with menthol and fluoride, it has dual effects of preventing decay and refreshing breath.
Mouthwash: 0.05% menthol solution inhibits oral bacteria and assists in the treatment of gingivitis.
Industrial and other uses
1. essence industry
Basic spice: Menthol is a key raw material for synthesizing menthone and menthol acetate.
Fragrance application: Mix with fennel, citral, etc. to create a refreshing fragrance.
2. Agricultural applications
Insecticide enhancer: Menthol enhances the activity of pyrethroid insecticides.
Feed additives: Add 50-100mg/kg to poultry feed to increase feed intake.
3. Materials Science
Thermal sensitive material: Menthol is used as a phase change material for temperature regulation in smart textiles.
Biosensors: Developing drug screening models by utilizing the binding properties of menthol to specific proteins.
4. Environmental Engineering
Air freshener: a combination of menthol and lavender essential oil to improve indoor air quality.
Wastewater treatment: Menthol inhibits anaerobic bacteria from producing gas and reduces the odor of wastewater treatment plants.
In industry, the extraction of peppermint oil and menthol from peppermint is carried out using steam distillation and organic solvent extraction methods. The former has low extraction efficiency, while the latter has the toxicity of residual organic solvents. The use of supercritical carbon dioxide to extract menthol from peppermint can eliminate the drawbacks of the two methods mentioned above. Its yield is about 5 times higher than that of steam distillation method and about 3 times higher than that of organic solvent method. The product maintains pure natural characteristics, with good quality, high purity, no solvent residue toxicity, easy to meet export requirements, and has better competitiveness, which can occupy the market. Menthol can be purified from natural peppermint crude oil or synthesized. The essential oil obtained by steam distillation of the aboveground parts (stems, branches, leaves, and inflorescences) of the mint plant in the family Lamiaceae is called peppermint crude oil, with an oil yield of 0.5-0.6. There are various methods for synthesizing thin brain tissue.
Method 1: Manufacturing from citral
By utilizing the property of easy cyclization of citral to isomenthol, right-handed citral is cyclized to left-handed isomenthol using an acid catalyst (such as silica gel), resulting in the separation of left-handed isomenthol and hydrogenation to produce left-handed peppermint. Its stereoisomers can be partially converted into dextrocitral through thermal cracking and recycled.
Method 2: Manufacturing from Thymol
In the presence of meta cresol aluminum, meta cresol undergoes alkylation reaction to produce thymol. All four pairs of menthol stereoisomers (i.e. racemic menthol; racemic neomenthol; racemic isomenthol and racemic neoisomenthol) were obtained through catalytic hydrogenation. Distillation is carried out to remove the spin menthol fraction, and the ester is repeatedly recrystallized for isomer separation and optical separation. The separated left-handed menthol ester is saponified to obtain menthol.
Racemic menthol can be separated from the other three pairs of isomers by distillation, and the remaining mixture of isomers can be balanced into racemic menthol, racemic new menthol, and racemic isomenthol under thymol hydrogenation conditions, with a ratio of 6:3:1. The content of new isomenthol is very small and can be ignored. From the above mixture, racemic menthol can be further separated. Racemic menthol is crystallized by inoculating it with a saturated solution of benzoate or its ultracold mixture as a levo ester, and then separated and saponified to obtain pure levo menthol; Unwanted right-handed menthol and other isomers can be converted to racemic menthol under hydrogenation conditions.
Method 3: Manufacturing from peppermint oil
After freezing peppermint oil, pure menthol crystals were precipitated, and the crystals obtained by centrifugation were recrystallized using a low boiling solvent to obtain pure left-handed menthol. After crystallization, the mother liquor still contains 40% to 50% menthol and a large amount of menthone, which is converted into a mixture of left-handed menthol and right-handed new menthol through hydrogenation. Partial saponification of the ester, followed by crystallization, distillation, or preparation of its boronic acid ester, and separation of other parts from peppermint oil, can yield more left-handed menthol.
Frequently Asked Questions
What is DL menthol?
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DL-Menthol is a racemic mixture of D- and L-menthol. Menthol is a covalent organic compound made synthetically or obtained from peppermint or other mint oils.
What is the difference between menthol and DL menthol?
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Menthol has two typical chiral forms, d- and l-, which exhibit different behaviours. l-Menthol is known for its physiological effect on sensitivity (i.e., a cooling effect), whereas d-menthol causes skin irritation. Menthol molecules may affect not only the thermoreceptors on biomembranes, but also the membrane itself.
What are DL menthol crystals used for?
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Used in aromatherapy, Menthol Crystals promote easier breathing, temporarily relieve nasal congestion, soothe sore throats, alleviate fever symptoms, coughs, headaches, and sinus discomforts, support immunity, and stabilize the emotions.
Can I swallow menthol crystals?
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There are calcium and sodium channels in cell membranes throughout our bodies, and that is why we can see systemic toxicity after swallowing or inhaling concentrated amounts of menthol. Serious effects include seizures, coma, and death. Menthol can cause eye and skin irritation.
What are the side effects of menthol crystals?
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In conclusion, while menthol is generally safe when used as directed, it is not without its side effects. Skin irritation, respiratory issues, gastrointestinal distress, allergic reactions, potential drug interactions, and its numbing effect are all possible adverse outcomes.
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