DL-Menthol Racemic Mixture: Forms Eutectic Crystals at Low Temperatures for Crystallization Control in Oral Sprays

Menthol is a chemical compound extracted from the leaves and stems of mint plants. It appears as white crystals with the molecular formula C₁₀H₂₀O and serves as the primary component in peppermint and spearmint essential oils. Globally, China and Brazil are the leading producers of natural mint, each yielding 2,000–3,000 tons of mint oil annually. Both menthol and racemic menthol can be used as flavorings in toothpaste, perfumes, beverages, and confectionery. In medicine, it serves as a topical irritant applied to the skin.

(1) Medicine and Healthcare: Due to its cooling and local anesthetic effects, it is widely used in medications for sore throats and oral irritation (such as cough drops and mouthwashes), topical preparations for relieving minor pain and sprains, and nasal decongestants. It is also a common ingredient in anti-itch creams and ointments to alleviate itching and hives. In Japan's over-the-counter drug classification, it falls under dermatological analgesics, antipruritics, astringents, and anti-inflammatory agents.

(2) Oral and Personal Care: As a key flavoring and cooling agent, it is extensively used in oral hygiene products like toothpaste and mouthwash to combat bad breath and provide freshness.

(3) Food and Tobacco Industry: It imparts mint flavor to foods like ice cream and chewing gum. Since the 1920s-1930s, it has been added to cigarettes for flavoring and reducing throat irritation.

(4) Cosmetics and Fragrance Industry: In perfume manufacturing, it provides diffusion, uplifting effects, and freshness. It is also used in products like shampoos and tonics.

(5) Scientific Research: Serves as a green solvent in developing hydrophobic low-melting-point solvents for extracting capsaicinoids and carotenoids.

(1) Cooling and Itch Relief: By activating cold receptors (TRPM8) in the skin or mucous membranes, it produces a subjective cooling sensation that distracts from itching, thereby providing relief.

(2) Local Anesthesia: When applied topically, it delivers mild local anesthetic effects, helping alleviate muscle soreness, sprains, and joint discomfort.

(3)Anti-inflammatory and Anti-allergic: Topically applied, it dilates skin blood vessels, first inducing a cooling sensation followed by analgesic effects, useful for alleviating symptoms of dermatitis and hives.

(4) Cough Suppression and Antispasmodic: Exhibits cough-suppressing and antispasmodic properties, aiding in relief of respiratory discomfort such as bronchitis and sinusitis. When ingested, it also functions as a carminative.