Page 80 - phytochemistry I - PharmD Clinical
P. 80
Oxidation O Menthone
Dichromate soln
OH
Dehydration Dehydrogenation
ZnCl2
Menthol P- menthene P- cymene
Color tests:
- Few crystals of menthol are dissolved in few drops of conc. H2SO4 and
few drops of vanillin/H2SO4 are added → orange yellow color is developed
which changes to violet on the addition of few drops of water.
- Few crystals of menthol are dissolved in glacial acetic acid then 3 drops
of conc. H2SO4 and one drop of conc. HNO3 are added, no green color is
produced (c.f. thymol which gives a green color).
Uses:
- Menthol is a local antipruritic. It has been used on the skin or mucous
membranes as a counterirritant and antiseptic.
- Menthol is chiefly used to relieve symptoms of bronchitis, sinusitis as it
is a good decongestant and expectorant.
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