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10
cucumber. These substances have been bred out from commercially available varieties, as
they taste very bitter and are toxic.
In Digitalis sp. (foxgloves, Plantaginaceae) stigmasterol can be converted into pregnenolone and further to cardenolides such as progesterone, which can be converted in
several steps into digoxigenin and further to digitoxin and lanatoside by adding sugar
moieties. These are also called cardiac glycosides because they control the heart rhythm
IPP + DMAPP
2,3-Oxidosqualene
FPP
Squalene
Protosteryl cation
Dammarenyl cation
Lanosterol
Cucurbitadienol
Cycloartenol
Lupeol
α-Amyrin
β-Amyrin
Sterols
Triterpene
β-Sitosterol
Cholesterol
Stigmasterol
Brassinosteroid
Betulinic acid
Ursolic acid
Oleanic acid
Avenacin
Glycyrrhizin
2x
O
Digoxygenin
Euphol
H
H
H
H
H
H
H
H
H
HO
HO
HO
H
H
H
HO
HO
H
H
H
HO
H
H
H
HO
. Fig. 10.6 Schematic overview of the biosynthetic and representative members of sterols and triterpene subfamilies. Abbreviations: IPP isopentenyl diphosphate, DMAPP dimethylallyl diphosphate, FPP
farnesyl pyrophosphate
Chapter 10 · Terpenes and Terpenoids