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Phytochemistry, Pharmacology, and Applications of Phytoecdysteroids
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Figure 5.1: The multiplicity of C27-phytoecdysteroids inside the same structural entity.
Source: https://www.researchgate.net/publication/226759652_Phytoecdysteroids_Diversity_Biosynthesis_and_Distribution.
Wang et al. (2003) separated 5 novel phytoecdysteroid glycosides
from an entire plant Froelichia oridana. They were then tested against
the human deoxyribonucleic acid topoisomerase but did not display the
inhibitory activity. Kumpun et al. (2007) currently studied their existence
in Chenopodium quinoa, an antique Andean crop having a high value of
nutrition. In addition to large amounts of 20-hydroxyecdysone, lower
amounts of 24-epi-makisterone A, makisterone A, polypodine B, and
24(28)-dehydromakisterone were also found. They also recognized 3 novel
natural compounds, more predominantly 25,27-dehydroinokosterone,
5b-hydroxy-24(28)dehydromakisterone A, and 24,25-dehydroinokosterone.
Ecdysteroids were focused on the ber of Chenopodium quinoa (Brandt,
2003; Destrez et al., 2008). Tan et al. (2011) recognized the less usual
phytoecdysteroid having the skeleton of 5a-cholestane in Cyanotis
arachnoidea. Novel phytoecdysteroids were found in the Achyranthes
bidentata roots. These steroids comprise the furan ring on the acetonide moiety
and are labeled niuxixinsterone A, B, and C. Brainesterosides A to E were
separated as the phytoecdysteroid glycosides from rhizomes of the Brainea
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Natural Compounds: An Introduction
insignis, as well as 3 known phytoecdysteroids (20-hydroxyecdysone,
ponasteroside A, and ponasterone A). In Serrulata wole, an extensive variety
of structurally diverse ecdysteroids were discovered: compounds having an
additional double-bound at the position 20(22) (20,22-didehydrotaxisterone
and 1-hydroxy-20,21-didehydrotaxisterone), with the furan ring in a side
chain (serfurosterone A and B) or with the intramolecular ether function in
a side chain (shidasterone derivatives). In a Serrulata wolfi, Vanyolos et al.
(2012) recognized still novel ecdysteroids having the group of a-hydroxyl,
structures that are comparatively infrequently seen among the category of
ecdysteroids (3-epi-22-deoxy-20-hydroxyecdysone and 3-epi-shidasterone),
along with ponasterone-22-apioside.
All of the investigations validate the phytoecdysteroids’ position as
vital secondary metabolites in the plants. The same Hungarian group
of researchers discovered three novel ecdysones in the Polypodium
vulgare: 20-deoxyshidasterone, polypodine B 2-b-D-glucoside, and
5-hydroxyecdysone. Phytoecdysteroids possess common structural features
like C24–29C atoms, various hydroxyl substituents, the D
7
-6-keto grouping
in a B ring, the cis junction of A/B rings, and the side chain normally containing
the (R)-C22-OH group. In most cases, phytoecdysteroids are separated in a
free state, even though several derivatives like esters, glycosides, and ethers
have been separated as well.
Most usually, 1–3 major ecdysteroids will signify about 95% of the
entire ecdysteroid in 1 plant species. As exhibited in tables, the secondary
ecdysteroids form the combination of ecdysteroid structural analogs.
Instances of C27-phytoecdysteroids with the other functional groups
(Figures 5.2–5.9) (Albanese et al., 2000; Lafont and Dinan, 2003).
Figure 5.2: Structure of Ajugasterone D.
Source: https://link.springer.com/referenceworkentry/10.1007%
2F978-3-642-22144-6_173.
Phytochemistry, Pharmacology, and Applications of Phytoecdysteroids
Figure 5.3: Structure of Vitexirone.
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Source: https://pubchem.ncbi.nlm.nih.gov/compound/Vitexirone.
141
Figure 5.4: The structural formula of the 26-OH-polypodine.
Source: https://link.springer.com/referenceworkentry/10.1007%
2F978-3-642-22144-6_173.
Figure 5.5: The structural formula of the 22-deoxy-20,26-diOH-ecdysone.
Source: https://www.sciencedirect.com/science/article/pii/
B9780125644853500142.
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Figure 5.6: Structure of Inokosterone.
Source: https://pubchem.ncbi.nlm.nih.gov/compound/5458789.
Natural Compounds: An Introduction
Figure 5.7: Structural formulas of (a) Calonysterone; (b) Calonysterone; (c)
Calonysterone; and (d) Pinnatasterone 24-(pyrrol-2-carboxylate).
Source: https://link.springer.com/article/10.1023/A:1026662505403.
Phytochemistry, Pharmacology, and Applications of Phytoecdysteroids
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Figure 5.8: Structural formulas of (a) Podecdysone C; (b) Polypodosaponin; (c) Stachysterone D; (d) Ecdysterone 2,3-acetonide; and (e) Ecdysterone
20,22-acetonide.
Source: https://link.springer.com/article/10.1023/A:1026662505403.
Figure 5.9: Instances of C-29 phytoecdysteroids: (a) Makisterone C; and (b)
Makisterone D.
Source: https://www.sciencedirect.com/science/article/pii/
B9780444634733000058.
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Natural Compounds: An Introduction
Toth and Bathori (2008) dened a comparatively simple separation
process for phytoecdysteroids from the Silene viridiora. By the purication
process in 4 steps, the phytoecdysteroids were made accessible in sufcient
amounts (Figure 5.10).
Figure 5.10: Ecdysterone biosynthesis in Ajuga reptans and polypodium vulgare: Recommended early steps.
Source: https://pubmed.ncbi.nlm.nih.gov/7470069/.
5.4. BIOSYNTHESES OF PHYTOECDYSTEROIDS
Currently, the path for biosynthesis in the plants might vary from that
in the animals. A large number of the ecdysteroids discovered in plants
makes it improbable that the single pathway is dealt with. In a Polypodium
vulgare, the cholesterol is transformed to a-ecdysone, 5-b-OH-ecdysterone,
and ecdysterone. It is accepted that the A/B-cis junction and the D
keto grouping ascend at the 1
st
stages of biosynthesis of the cholesterol,
hydroxylation in position 14-a happening next. It is recommended that in
some ecdysteroids having trans-A/B junctions, the isomerization of chiral
center 5 has taken place. The order of consequent introduction of the
hydroxyl groups into the side chain and steroidal moiety, along with the
side-chain alkylation, does not appear to be determined strictly and varied
from one family of a plant to another.
7
-6-
Phytochemistry, Pharmacology, and Applications of Phytoecdysteroids
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The Ajuga genus is exceptional for the great diversity of phytoecdysteroids,
having a wide spectrum of pharmacological and biological actions. They
gather in several plant organs like stems, owers, leaves, fruits, and roots,
usually existent in smaller quantities of order 0.01 to 0.1% of the dry weight
of the plant. The key phytoecdysteroid is 20-hydroxyecdysone and is the
energetic molting hormone of insects (Figure 5.11).
Figure 5.11: Biosynthesis of spinach ecdysteroids: The endogenously biosynthesized ecdysone-3-phosphate and ecdysone are transformed to 20-hydroxyecdysone.
Source: https://link.springer.com/article/10.1007/BF02537830.
In this biosynthetic approach, both lathosterol and cholesterol are
involved and yield the ecdysterone moiety through 7-dehydro-cholesterol.
The midway 5,6-epoxide would be the plausible description for the creation
of the 6-keto group. Current evidence recommends that the conjugates of
phosphate are signicant in the targeting or processing of ecdysteroids and
sterols in the biosynthesis in spinach. In plants, phosphorylated ecdysteroids
seem to be indulged in the biosynthetic path. In animals, the ecdysteroids
are phosphorylated for elimination for parent ecdysteroids from the gut of
an animal (Marion-Poll and Descoins, 2002).
Devarenne et al. (1995) nurtured radiolabeled [22,23having Zea mays leaves. Post-incubation, among 57 and 75%, of the radiolabeled material recuperated was existent as unmetabolized [
3
H]ecdysone
3
H]ecdysone.
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Natural Compounds: An Introduction
The lasting radioactivity was recuperated as [3H]ecdysone phosphate,
3
polyphosphorylated ecdysone, and [
H]ecdysone diphosphate. The same
authors discovered lathosterol and not cholesterol as a favored forerunner
to ecdysteroids in spinach and theorized it is a similar circumstance in Zea
mays, since it took substantially more time to transform cholesterol into the
ecdysteroids. Ecdysteroid polyphosphates normally have a downregulatory
effect on the biosynthesis of the ecdysteroids. This might lead to the
conscation of lathosterol into the steryl ester pool and consequently the slow
discharge of the lathosteryl ester for extra biosynthesis of the ecdysteroid
polyphosphates (Figures 5.12 and 5.13).
Figure 5.12: Detoxication mechanisms for the phytoecdysteroids in insects.
Source: https://www.researchgate.net/publication/226759652_Phytoecdysteroids_Diversity_Biosynthesis_and_Distribution.
Phytochemistry, Pharmacology, and Applications of Phytoecdysteroids
Figure 5.13: Main metabolic paths of 20-hydroxyecdysone in the mice.
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147
Source: https://www.springer.com/gp/book/9781402091117.
5.5. FUNCTIONS OF PHYTOECDYSTEROIDS
Various recommendations have normally been put forward, but the theory
that phytoecdysteroids behave as anti-feeding agents and potent deterrents
against insects received possibly the greatest support.
As minor plant metabolites, phytoecdysteroids motivate protein synthesis
in the plants, possibly behave as the plant growth regulators, and activate
cell mitosis. Ecdysteroids impact signal transduction paths, correspondingly
to anabolic steroids. They should not bind to the cytosolic steroid receptors
but perform by membrane-bound receptors.
They also defend plants against the phytophagous insects by endocrine
disruption or feeding deterrence upon ingestion, which causes death. As
an example, an Indian snack moth Plodia interpunctella can generally be
taken. The concentration of 200 parts per million of phytoecdysteroids in
the diet revealed signs of poisonousness as a reduction in larval weight, an
upsurge in mortality, and induction of cannibalism, along with the disruption
of development. Negligible structural differences considerably affected the
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Natural Compounds: An Introduction
poisonousness of phytoecdysteroids, makisterone A. Silkworm or Bombyx
mori is an instance in which the phytoecdysteroids have harmful effects
such as hindrance of growth and death without or with promoted prothetely
and molting. Weirdly enough, when the silkworms are open to low amounts
of 20-hydroxyecdysone at specic times during the development, enhanced
synchrony of cocoon creation and higher silk produce could be observed.
Also, in the honeybees’ fertility of wax is enhanced by a similar effect. Still,
the method of action is unidentied. It is postulated that the low levels of
phytoecdysteroids might improve the confrontation against stress (Rharrabe
et al., 2007).
Conversely, some species of insect remain undisturbed by
phytoecdysteroids existent in the food even at the concentrations of around
400 parts per million and more (e.g., the tobacco budworm or Heliothis
virescens, the cotton bollworm or Heliothis armigera, the migratory locust or
Locusta migratoria, the tobacco hornworm or Manduca sexta, the Egyptian/
African cotton leafworm or Spodoptera littoralis, a moth known as brightline brown-eye or Lacanobia oleracea, a moth known as death’s-head
hawk or Acherontia atropos). The following inactivation and detoxication
mechanisms, correspondingly in mice and insects, have been dened to
detoxify phytoecdysteroids (Marion-Poll et al., 2004):
• Conjugation to the fatty acids, thus hindering the C-22 hydroxyl
group. The mechanism depends on the quantity of the fatty acids
in the environment. In the circumstance of low concentration,
the insects will be fatigued earlier by spending their energetic
capacity.
• Instead of the fatty acids, phosphorylation (C-2 or C-22),
glycosidation (C-22, C-25), 3-oxo/3-epi derivatization, and
acetylation (C-3) can take place.
• The cleavage of the side-chain is done amongst C-20 and C-22.
• Evacuating unmetabolized hydroxyecdysone is seen.
The phytophagous conduct of insects plays a vital role. The insect’s lenient
to phytoecdysteroids will not vary their phagous behavior. The polyphagous
insects can avert plants comprising higher levels of the phytoecdysteroids,
while insect monophagous for the ecdysteroid-comprising plants will
be quite sensitive. The insects can guard themselves by emerging taste
receptors, which simplify averting ecdysteroid-comprising plants in the diet
(Dinan, 1998; Soriano et al., 2004).
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