Pharmacognosy - medicinal plants (herbs)
Pharmacognosy - medicinal plants (herbs)

Theme IX: Essential oils

Monocyclic terpenes. Menthol - Limonene - thymol

Monocyclic terpenes. Characteristics. Menthol, limonene, thymol, cymene, menthone, terpineol.

Monocyclic terpenes are related to menthane, which is not found in nature but can be obtained from cymene whose structural formula is:

cymene

Limonene

Limonene

 

The limonene is a monocyclic terpene, which has double bonds at carbons 1-2 and 8-9. The C4 Carbon Fixation is asymmetrical allowing the existence of optical isomers and the racemate named dipentene.

 

Limonene is the most abundant terpene present in citrus essences of lemon, orange, lime and also found in celery, mint and pine fir.

Menthol - thymol - menthone - terpinol

Among these terpenes are also menthol (3-p-Menthanol) and the menthone or 3-menthanone present in the mint oil, which has eight optical isomers due to three asymmetric carbons within its chain.

 

A racemic mixture of menthol may be obtained by catalytic hydrogenation of thymol, a monovalent phenol with the hydroxyl group adjacent to the methyl radical.

 

Terpineol is 8 - menthanol with a double bond between carbons 1-2. Is responsible for the scent of lilacs in many essences

Thymol menthone menthol terpineol

See also

Write a comment

Comments: 0

Monocyclic terpenes. Characteristics. Menthol, limonene, thymol, cymene, menthone, terpineol.