antioxidant, antiviral and antimicrobial properties. There is no known
toxicity or contraindications for this compound.
O
O
O
H
OH
O
H
O
H
O
OMe
O
O
O
O
H
O
H
Oleuropein, a bioactive secoiridoid glycoside
6.5 Terpenoids
Terpenoids are compounds derived from a combination of two or more
isoprene units. Isoprene is a five carbon unit, chemically known as
2-methyl-1,3-butadiene. According to the isoprene rule proposed by Leopold Ruzicka, terpenoids arise from head-to-tail joining of isoprene units.
Carbon 1 is called the ‘head’ and carbon 4 is the ‘tail’. For example,
myrcene is a simple 10-carbon-containing terpenoid formed from the headto-tail union of two isoprene units as follows.
1
2 3
4
Isoprene unit
Tail
1
2 3
4
Isoprene unit
Head
Myrcene
Terpenoids are found in all parts of higher plants and occur in mosses,
liverworts, algae and lichens. Terpenoids of insect and microbial origins
have also been found.
6.5.1 Classification
Terpenoids are classified according to the number of isoprene units involved
in the formation of these compounds.
Number of carbon
Number of isoprene
Type of terpenoids
atoms
units
Example
Monoterpene
10
2
Limonene
Sesquiterpene
15
3
Artemisinin
Diterpene
20
4
Forskolin
Triterpene
30
6
a-amyrin
Tetraterpene
40
8
b-carotene
Polymeric terpenoid
Several
Several
Rubber
6.5 TERPENOIDS
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