a) Acyclic monoterpenes:
CH 3
CHO
C
H 3
CH 3
CH 3
CH 2 OH
C
H 3
CH 3
Citral
Geraniol
CH 3
CHO
C
H 3
CH 3
Citronellal
CH 3
C
H 3
CH 3
OH
CH 2
Linalool
b) Monocyclic monoterpenes
CH 3
C
H 3
CH 3
OH
Menthol
CH 3
C
H 3
CH 3
O
CH 3
C
H 3
CH 2
O
CH 3
C
H 3
CH 2
Menthone
Carvone
Limonene
c) Bicyclic monoterpenes
i) Class –I type:
CH 3
C
H 3
CH 3
alpha-Thjene
CH 2
C
H 3
CH 3
( ) - Sabinene
CH 3
C
H 3
CH 3
CH 3
C
H 3
CH 3
O
Car-2-ene
Carone
ii) Class –II type:
CH 3
CH 2
Ch 2 OH
CH 2
O
alpha - Pinene beta - Pinene
Myrtenol
Pinocarvone
iii) Class –III type:
CH 3
O
CH 3
CH 3
OH
CH 3
O
Camphor
Camphene
Borneol
Fenchone
Fig. 10.22 The structures of different classes of monoterpenes of plant sources
10 Secondary Metabolites from Plant Sources
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