organic substance. Although carbohydrates are primary metabolites, they become
part of the huge number of secondary metabolites through glycosidation linkages.
Glycosides consist of a sugar part known as glycone. The glycone sugars are mainly
glucose, galactose, rhamnose, mannose, digitoxose, cymose, etc. Mucilages and
gums are the polymeric product of simple sugars and uronic acids (Asif et al. 2011).
Carbohydrates can be defined as carbon, hydrogen, and oxygen-containing
polyhydroxy aldehydes or ketones that on hydrolysis produce simple sugars. They
are classified into monosaccharides, disaccharides, oligosaccharides (trisaccharides,
tetrasaccharides, etc.), and polysaccharides. Carbohydrates are classified based on
their presence of saccharide units as follows:
Acetyl CoA (C 2 )
Acetoacetyl CoA (C 4 )
HMG CoA (C 6 )
Mevalonic acid (C 6 )
IPP (C 5 )
DMAPP (C 5 )
GPP (C 10 )
FPP (C 15 )
GGPP (C 20 )
GFPP (C 25 )
Monoterpenoids (C 10 )
Sesquiterpenes (C 15 )
C 30 PP
Squalene (C 30 )
Steroids
Diterpenoids (C 20 )
Carotenoids (C 40 )
Polyterpenoids (C > 40 )
Sesterterpenoids (C 25 )
HMG CoA Hydroxy methyl glutaryl CoA IPP
Isopentenylpyrophosphate GPP Geranyl pyrophosphate
DMAPP Dmethylallyl pyrophosphate
FPP Farnesyl pyrophosphate GGPP Geranylgeranyl pyrophosphate
GFPP Geranylfarsenyl pyrophosphate
Isopentenyl pyrophosphate
Isopentenyl pyrophosphate
Isopentenyl pyrophosphate
Fig. 10.25 Flow chart of the biosynthetic pathway of terpenes (Kokate et al. 2005; Lalonde 2005)
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C. C. Kandar