{"id":17795,"date":"2025-10-22T16:06:06","date_gmt":"2025-10-22T09:06:06","guid":{"rendered":"https:\/\/nhathuocngocanh.com\/bp\/?p=17795"},"modified":"2025-10-22T16:06:06","modified_gmt":"2025-10-22T09:06:06","slug":"levomenthol","status":"publish","type":"post","link":"https:\/\/nhathuocngocanh.com\/bp\/levomenthol\/","title":{"rendered":"Levomenthol"},"content":{"rendered":"<p><em>(Ph. Eur. monograph 0619)<\/em><\/p>\n<p>C<sub>10<\/sub>H<sub>20<\/sub>O 156.3 2216-51-5<\/p>\n<p><strong>Action and use<\/strong><\/p>\n<p>Decongestant.<\/p>\n<p><strong>Preparations<\/strong><\/p>\n<p>Levomenthol Cream<\/p>\n<p>Menthol and Benzoin Inhalation<\/p>\n<h2>DEFINITION<\/h2>\n<p>(1R,2S,5R)-5-Methyl-2-(1-methylethyl)cyclohexanol.<\/p>\n<h2>CHARACTERS<\/h2>\n<h3>Appearance<\/h3>\n<p>Prismatic or acicular, colourless, shiny crystals.<\/p>\n<h3>Solubility<\/h3>\n<p>Practically insoluble in water, very soluble in ethanol (96 per cent) and in light petroleum, freely soluble in fatty oils and in liquid paraffin, very slightly soluble in glycerol.<\/p>\n<h3>mp<\/h3>\n<p>About 43 \u00b0C.<\/p>\n<h2>IDENTIFICATION<\/h2>\n<p>First identification: A, C.<\/p>\n<p>Second identification: B, D.<\/p>\n<p>A. Specific optical rotation (see Tests).<\/p>\n<p>B. Thin-layer chromatography (2.2.27).<\/p>\n<p>Test solution: Dissolve 25 mg of the substance to be examined in methanol R and dilute to 5 mL with the same solvent.<\/p>\n<p>Reference solution: Dissolve 25 mg of menthol CRS in methanol R and dilute to 5 mL with the same solvent.<\/p>\n<p>Plate: TLC silica gel G plate R.<\/p>\n<p>Mobile phase: ethyl acetate R, toluene R (5:95 V\/V).<\/p>\n<p>Application: 2 \u03bcL.<\/p>\n<p>Development: Over a path of 15 cm.<\/p>\n<p>Drying: In air, until the solvents have evaporated.<\/p>\n<p>Detection: Spray with anisaldehyde solution R and heat at 100-105 \u00b0C for 5-10 min.<\/p>\n<p>Results: The principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with the reference solution.<\/p>\n<p>C. Examine the chromatograms obtained in the test for related substances.<\/p>\n<p>Results: The principal peak in the chromatogram obtained with test solution (b) is similar in position and approximate dimensions to the principal peak in the chromatogram obtained with reference solution (c).<\/p>\n<p>D. Dissolve 0.20 g in 0.5 mL of anhydrous pyridine R. Add 3 mL of a 150 g\/L solution of dinitrobenzoyl chloride R in anhydrous pyridine R. Heat on a water-bath for 10 min. Add 7.0 mL of water R in small quantities with stirring and allow to stand in iced water for 30 min. A precipitate is formed. Allow to stand and decant the supernatant. Wash the precipitate with 2 quantities, each of 5 mL, of iced water R, recrystallise from 10 mL of acetone R, wash with iced acetone R and dry at 75 \u00b0C at a pressure not exceeding 2.7 kPa for 30 min. The crystals melt (2.2.14) at 154 \u00b0C to 157 \u00b0C.<\/p>\n<h2>TESTS<\/h2>\n<h3>Solution S<\/h3>\n<p>Dissolve 2.50 g in 10 mL of ethanol (96 per cent) R and dilute to 25.0 mL with the same solvent.<\/p>\n<h3>Appearance of solution<\/h3>\n<p>Solution S is clear (2.2.1) and colourless (2.2.2, Method II).<\/p>\n<h3>Acidity or alkalinity<\/h3>\n<p>Dissolve 1.0 g in ethanol (96 per cent) R and dilute to 10 mL with the same solvent. Add 0.1 mL of phenolphthalein solution R. The solution is colourless. Not more than 0.5 mL of 0.01 M sodium hydroxide is required to change the colour of the indicator to pink.<\/p>\n<h3>Specific optical rotation (2.2.7)<\/h3>\n<p>-48 to -51, determined on solution S.<\/p>\n<h3>Related substances<\/h3>\n<p>Gas chromatography (2.2.28).<\/p>\n<p>Test solution (a): Dissolve 0.20 g of the substance to be examined in methylene chloride R and dilute to 50.0 mL with the same solvent.<\/p>\n<p>Test solution (b): Dilute 1.0 mL of test solution (a) to 10.0 mL with methylene chloride R.<\/p>\n<p>Reference solution (a): Dissolve 40.0 mg of the substance to be examined and 40.0 mg of isomenthol R in methylene chloride R and dilute to 100.0 mL with the same solvent.<\/p>\n<p>Reference solution (b): Dilute 0.10 mL of test solution (a) to 100.0 mL with methylene chloride R.<\/p>\n<p>Reference solution (c): Dissolve 40.0 mg of menthol CRS in methylene chloride R and dilute to 100.0 mL with the same solvent.<\/p>\n<p>Column:<\/p>\n<p>\u2014 material: glass;<\/p>\n<p>\u2014 size: l = 2.0 m, \u00d8 = 2 mm;<\/p>\n<p>\u2014 stationary phase: diatomaceous earth for gas chromatography R impregnated with 15 per cent m\/m of macrogol 1500 R.<\/p>\n<p>Carrier: gas nitrogen for chromatography R.<\/p>\n<p>Flow rate: 30 mL\/min.<\/p>\n<p>Temperature:<\/p>\n<p>\u2014 column: 120 \u00b0C;<\/p>\n<p>\u2014 injection port: 150 \u00b0C;<\/p>\n<p>\u2014 detector: 200 \u00b0C.<\/p>\n<p>Detection: Flame ionisation.<\/p>\n<p>Injection: 1 \u03bcL.<\/p>\n<p>Run time: Twice the retention time of menthol.<\/p>\n<p>System suitability:<\/p>\n<p>\u2014 resolution: minimum 1.4 between the peaks due to menthol and isomenthol in the chromatogram obtained with reference solution (a);<\/p>\n<p>\u2014 signal-to-noise ratio: minimum 5 for the principal peak in the chromatogram obtained with reference solution (b).<\/p>\n<p>Limits: Test solution (a):<\/p>\n<p>\u2014 total: not more than 1 per cent of the area of the principal peak;<\/p>\n<p>\u2014 disregard limit: 0.05 per cent of the area of the principal peak.<\/p>\n<h3>Residue on evaporation<\/h3>\n<p>Maximum 0.05 per cent.<\/p>\n<p>Evaporate 2.00 g on a water-bath and heat in an oven at 100-105 \u00b0C for 1 h. The residue weighs not more than 1.0 mg.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>(Ph. Eur. monograph 0619) C10H20O 156.3 2216-51-5 Action and use Decongestant. Preparations Levomenthol Cream Menthol and Benzoin Inhalation DEFINITION (1R,2S,5R)-5-Methyl-2-(1-methylethyl)cyclohexanol. CHARACTERS Appearance Prismatic or acicular, colourless, shiny crystals. Solubility Practically insoluble in water, very soluble in ethanol (96 per cent) and in light petroleum, freely soluble in fatty oils and in liquid paraffin, very slightly&#8230;<\/p>\n","protected":false},"author":4,"featured_media":17823,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[174],"tags":[],"class_list":["post-17795","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicinal-substances"],"acf":[],"_links":{"self":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17795","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/comments?post=17795"}],"version-history":[{"count":2,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17795\/revisions"}],"predecessor-version":[{"id":17825,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17795\/revisions\/17825"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media\/17823"}],"wp:attachment":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media?parent=17795"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/categories?post=17795"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/tags?post=17795"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}