Phytoecdysteroids and Related Sterols Isolated from Mexican Cacti: their Potential Use as Natural Insecticides - Natural Antioxidants and Biocides from Wild Medicinal Plants - page 169

capable of making the dealkylation, they
can synthesize C 28 or C 29 ecdysteroids
(Shaaya, 2008; Lafont & Koolman, 2009).
Although the ecdysteroids are structur-
ally diverse, they are expected to have a set
of minimum structural requirements to
carry out their biological activity. The struc-
tural requirements for most biologically
active ecdysteroids include: (i) a cis A/B
ring junction (5b-H); (ii) a 7-en-6-one group;
(iii) a complete sterol side chain with a 22R
oxygen function; (iv) an oxygen function
generally in the form of a 3b-OH group; and
(v) additional OH groups at C-14a and C-2b,
and, in many cases, also at C-20 and C-25
(Dinan, 2001). Despite these structural char-
acteristics, there are several examples of
biologically active substances but with

some changes in the patterns of hydroxyla-
tion and configurations in ring junctions,
including the A/B ring junction.
Interestingly, almost on par with the
discovery of ecdysone from silk worms,
similar molecules were isolated from plants.
Some of the first ecdysone-like compounds
isolated from plants (Fig. 11.3) reported in
the literature were viperidinone ( 11 ), viperi-
done ( 12 ) and deoxyviperidone ( 13 ), all
from Wilcoxia viperina (Djerassi et al ., 1964;
Knight et al ., 1966), a plant from Mexico
belonging to Cactaceae, now named
Peniocereus viperinus (Arias et al ., 2005).
Moreover, the first truly ecdysteroid
molecules were isolated from two species of
Podocarpus : 20-hydroxyecdysone ( 2 ) from the
Australian brown pine, Podocarpus elatus

(a)

H

H

HO

HO

Stigmasterol ( 8 )

β -Sitosterol ( 7 )

(b)

H H

HO HO

Ergosterol ( 10 )

Campesterol ( 9 )

Fig. 11.2. Most common (a) plant and (b) fungal sterols. Some phytophagous arthropods and non-
arthropod vertebrates have to consume these sterols in their diets, being able to synthesize ecdysteroids
from this source.

H

HO OH HO

H

HO HO HO

H H H

O O O

Viperidone ( 12 )

Viperidinone ( 11 ) Deoxyviperidone ( 13 )

Fig. 11.3. Structures of ecdysteroid-like compounds isolated from Cactaceae.