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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6035_Библиотеки_им_академика_М_И_Перельмана.pdf
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Prior research has documented that chrysophanol functions as an inhibitor of the
epidermal growth factor receptor/mammalian target of rapamycin pathway, displaying
anticancer and anti-inammatory properties (Lee et al., 2011).
FIGURE 14.16 Polyketides penicitrinol G (41), penicitrinol H (42), chrysophanol (43), and (2,11-dihydroxy-
1-methoxycarbonyl-9-carboxylxanthone (44) isolated from fungus Penicillium citrinum.
⏎
14.3.4 NPS FROM PLANTS AS CATHEPSIN INHIBITORS
Several natural compounds isolated from various plants have demonstrated many interesting inhibitory activities against cathepsins. The first inhibitor was a member of the
cystatin superfamily (Brzin et al., 1998). They were phytocystatin isolated from extract
of red kidney bean (Phaseolus vulgaris L.). Phytocystatins are potent inhibitors of CPs
produced by plants, forming strong and stable complexes with them. Phytocystatin was
found to be a potent inhibitor of human Caths B, H, and L, with Ki values 3.6, 2.8, and
0.02 nM, respectively.
In their study , W isutsitthiwong et al. (201 1) explored the potential of 7-oxo-7-deacetoxygedunin (7-OG), a limonoid of the gedunin type (Figure 14.17) derived from the seeds of
the mangrove Xylocarpus moluccensis, as a potent inhibitor of osteoclastogenesis. Notably ,
7-OG exhibited robust anti-osteoclastogenic activity with minimal cytotoxicity toward the
monocyte/macrophage progenitor cell line, displaying an IC50 of 4.14 μM. Treatment with
7-OG led to the complete suppression of Cath K mRNA expression. In-vitro experiments
demonstrated that 7-OG effectively inhibited RANKL-induced osteoclast differentiation.
These suppressive effects on osteoclast formation can be attributed, at least in part, to 7-OG’ s
ability to inhibit the NF-κB and MAPK pathways. Furthermore, the anti-osteoclastogenic
activity of 7-OG is mediated, in part, by the suppression of NF-κB and MAPK pathways.
Investigation of downstream target genes revealed a complete downregulation of NFATc1
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and Cath K. Additionally, treatment with this limonoid inhibited RANKL-induced activa-
tion of p38, MAPK, and Erk, as well as the nuclear localization of NF-κB. Taken together,
these ndings strongly suggest that 7-OG treatment interferes with osteoclast differentiation
at early stages following RANKL stimulation (Wisutsitthiwong et al., 2011). Limonoids
hold promise as potential therapeutic agents for osteoclast-related disorders.
FIGURE 14.17 Chemical structure of limonoid 7-oxo-7-deacetoxygedunin (45) isolated from Xylocarpus
moluccensis.
⏎
Dihydrochalcone and prenylated avone were identied from the bud of Artocarpus
altilis (Patil et al., 2002). Traditionally in Taiwan, the buds have been reported to possess
anti-inammatory and detoxifying effects (Chen et al., 1993). All the compounds
extracted from A. altilis demonstrated signicant inhibition activity against Cath K covers
(Figure 14.18). Compound (46) showed an IC50 value of 170 nM followed by compound
(47) with an IC50 value of 98 nM. Compound (48) was moderated inhibitor of Cath K with
IC50 values of 840 nΜ, respectively.
Biavones have been found to be potent inhibitors of Cath B and Cath K through
random screening, with some degree of selectivity for Cath B. Biavone compounds
were isolated and identied from acetone extracts of leaves and branches of Taxodium
mucronatum (Taxodiaceae) (49)–(51) and from methanol extracts of leaves of Cycas
guizhouensis (Cycadaceae) (52)–(54) (Figure 14.19). Zeng et al. (2006) demonstrated
that biavones are a novel class of cathepsin inhibitors from plants and exhibit a greater
degree of endopeptidase activity specically against Cath B. The kcat/Km value at pH 7.4
is much higher than that at pH 5.5, which means that, in weak neutral conditions, Cath B
can hydrolyze the endopeptidase substrate Z-FR-AMC more efciently. The pH preference
of Cath B against the substrate Z-FR-AMC was investigated in a pH-dependent prole at
pH 7.4 compared to pH 5.5. IC50 results indicated that under weak neutral conditions, the
inhibitory activities of biavones are slightly more potent than those under acidic conditions.
At pH 5.5, the IC50 range was 0.81–1.17 µM, and at pH 7.4, the IC50 range was 0.23–0.68
µM. These biavones are reversible Cath B inhibitors, according to inhibition and exible
335
docking experiments. The way these compounds bind and interact with Cath B makes them
effective inhibitors. According to the study, the new natural biavone inhibitors against
Cath B could open new strategies for developing innovative procedures for designing,
creating, and screening inhibitors of Cath B (Pan et al., 2005; Kassem et al., 2004).
FIGURE 14.18 Chemical structures of dihydrochalcone (46)–(47) and prenylated flavones (48) isolated
from Artocarpus altilis.
FIGURE 14.19 Chemical structures of biflavones isolated from Taxodium mucronatum (49)–(51) and Cycas
guizhouensis (52)–(54).
⏎
⏎
The Brazilian Cerrado biome is situated in the Central Brazilian highlands, encom-
2
passing approximately 2 million km
, which accounts for 23% of Brazil’s total land area.
336
It ranks as the second-largest vegetation formation on the South American continent,
trailing only the Amazon rainforest (Ratter et al., 1997). Known for its high biodiversity,
the Brazilian Cerrado is among the most diverse tropical savannas globally and represents
an arid ecosystem inhabited by native species adapted to its seasonally variable climate.
These woodland savannas are characterized by sparse canopies with scattered trees and
shrubs, some of which are endemic to the region. The Cerrado’s remarkable environmental
diversity positions it as one of the most biodiverse among all tropical savannas (Klink and
Machado, 2005). The Cerrado is an important and rich source of plants with unstudied
medicinal properties (Pinheiro and Monteiro, 2010). Ramalho et al. (2015) investigated
15 crude extracts from seven different Cerrado plants for the initial screening (125 µg/
mL). The most signicant inhibitory activity was observed in the ethanolic leaf extract of
Myrcia lingua Berg (Myrtaceae). The inhibition was higher than 90% against Caths L and B.
Bioactivity-guided fractionation resulted in the isolation of seven active polyhydroxylated
avonoids with and without glycosides (55)–(62) (Figure 14.20). The compounds showed
slightly more potency against Cath B. The most active compounds were (59) and (60) with
IC50 values of 4.9 and 8.2 µM, respectively. Polyhydroxylated avonols were shown to
be uncompetitive inhibitors against Cath B. Additionally, other avonoids isolated from
Esenbeckia grandiora Mart. (Rutaceae), Vochysia thyrsoidea Pohl. (Vochysiaceae), and
Byrsonima coccolo bifolia Kunth. (Malpighiaceae) were also evaluated for their inhibitory
activity against Cath B but did not show signicant inhibition at a concentration of 100 µM.
FIGURE 14.20 Chemical structures of polyhydroxylated flavonols (55)–(62) from Myrcia lingua Berg.
⏎
Rhizoma Drynariae (DR), usually named “Gol-Se-Bo” in Korean and “Gu-Sui-Bu”
in Chinese folk medicine, is one of the most frequently used herbs in traditional medicine for treating bone-related diseases. The biological effects of DR on in-vitro bone cell
culture, assessment of Cath K processing in bone cells, and examination of DR’s antibone
resorption activity have been investigated by analyzing inhibitory enzymatic activity
(Jeong et al., 2003). Dioscin (DR) demonstrates the potential to affect bone cell culture
without inducing cytotoxicity. The most efcacious concentration of DR for bone cells was
determined to be 100 µg/mL. When osteoclasts and osteoblasts, both types of bone cells,
were exposed to the PI3-kinase inhibitor wortmannin (WT), it resulted in the inhibition of
intracellular Cath K maturation. Likewise, the application of DR extracts to osteoclasts
containing long bone cells prevented the intracellular maturation of Cath K, indicating
337
that DR may impede the intracellular trafcking of pro-Cath K. The researchers conducted
experiments with WT and DR in the presence or absence of the mannose-6-phosphate
(M6P) receptor. Inhibition of Cath K in in-vitro bone resorption processing by both WT
and DR was observed in a dose-dependent manner, with similar potency observed for the
inhibition of Cath K processing.
The compounds Kushennol F (63) and Sohoravanone G (64) were isolated and identi-
ed from DR (Qiu et al., 2016) (Figure 14.21). Molecular docking and dynamics methods
showed that both compounds interact with Cath K. These compounds exhibited inhibitory
effects on the bone resorption process associated with Cath K. Biological studies were
conducted to verify the effects of these compounds on Cath K and its related bone resorption
process. Kushennol F (63) and Sohoravanone G (64) exhibited inhibitory activity against
Cath K, with IC50 values of 8.80 and 27.24 µM, respectively. The biological actions of KF
and SG on pit formation by osteoclasts were further conrmed using cultured RANKL-
induced osteoclastogenesis cells. The results clearly indicated that Kushennol F (63) and
Sohoravanone G (64) strongly suppressed osteoclastogenesis and inhibited Cath K-related
bone resorption. Signicantly, these two naturally derived compounds from plants have
displayed promising potential as novel inhibitors of Cath K, making them valuable for
potential applications in osteoporosis management.
FIGURE 14.21 Chemical structures of Kushennol F (63) and Sohoravanone G (64) isolated from DR.
⏎
The hexane and ethyl acetate (EtOAc) extracts of the stems of Bowdichia virgilioides
Kunth (Fabaceae) were assayed against Caths K, L, and V at a concentration of 125 µg/mL.
The extract with lower polarity (hexane) exhibited noteworthy inhibition against Caths L and
V, showing inhibitions of 91% and 97%, respectively . Similarly, the EtOAc extract displayed
inhibitory effects on Caths K, L, and V, with inhibitions of 70%, 97%, and 99%, respectively.
Bioassay-guided fractionation of the hexane and EtOAc extracts allowed the characterization
of lupeol, lupenone, β-sitosterol, and stigmasterol in mixture, a trans-p-coumaric acid ester
derivative, syringaresinol, bowdenol, 8-methoxycoumestrol, 3,4-hydroxy-7-methoxyisoavone, 7,3′-dihydroxy-4′-methoxyisoavone, and 5,4′-dihydroxy-7′-methoxyisoavone.
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All isolated compounds were tested at an initial concentration of 50 µg/mL against Caths K,
L, and V. The most potent compounds were the trans-p-coumaric acid ester derivative (65)
and 8-methoxycoumestrol (65) (Figure 14.22). The derivative of trans-p-coumaric acid (65)
displayed 78% inhibitory activity on Cath L, 94% inhibition on Cath V, and 49% inhibition
on Cath K. Likewise, 8-methoxycoumestrol (66) showed 55% inhibitory activity on Cath
L, 78% inhibition on Cath V, and 35% inhibition on Cath K. Similarly, the EtOAc fraction
from B. virgilioides containing similar phenolic compounds (8-methoxycoumestrol and
isoavones) showed inhibition on Cath K, L, and V of 70%, 97%, and 99%, respectively, at
a concentration of 125 µg/mL. The enzyme inhibitory activity of 8-methoxycoumestrol (67)
was determined for Cath V, showing an IC50 value of 17.4 µM (Silva et al., 2019).
FIGURE 14.22 Chemical structures of trans-p-coumaric acid ester derivative (65) and 8-methoxycoumestrol
(66) isolated from Bowdichia virgilioides Kunth.
⏎
Similarly, chalcone derivatives (67–70) were extracted from the ethanol extract of
the inner bark of Myracrodruon Urundeuva Allemão and individually assessed for their
inhibitory activity against Cath V (Sarria et al., 2018) (Figure 14.23). Compound (67)
exhibited the highest inhibitory potency, with an IC50 value of 0.42 μM. Additionally,
compounds (66) and (68) displayed signicant inhibition, with IC50 values of 0.7 and 1.4
μM, respectively. In contrast, compound (69) exhibited only moderate inhibition, with an
IC50 value of 24 μM. Notably, this marks the rst instance of dimeric chalcones being
identied as inhibitors of Cath V.
Natural polycyclic polyprenylated benzophenones (71)–(73) were isolated from
Garcinia brasiliensis (Martins et al., 2009) (Figure 14.24). Guttiferone A (71) showed
inhibition against Cath G, with an IC50 value of 2.7 µM, which is quite similar to the classical inhibitor chymostatin (2.1 µM) for this peptidase. Inhibition on Cath B was observed
at 2.1 µM. The presence of both the bicycle[3.3.1]-nonanetrione and 13,14-dihydroxy
substituted phenyl groups, as well as the keto-enol tautomeric form where the bridge
carbon is hydroxylated, enhances the inhibitory activity of the enzyme. The derivatives of
polyisoprenylated benzophenones that contain the bicycle[3.3.1]-nonanetrione moiety have
been shown to inhibit DNA topoisomerases and telomerase, as well as act as regulators in
mitogen-activated protein (MAP) kinase signal transduction pathways. The bicycle[3.3.1]nonanetrione is useful for antineoplastic therapy by decreasing the activity of MAP kinases
during mitosis in cancerous and tumoral tissues.
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FIGURE 14.23 Chemical structures of chalcone derivatives (67)–(70) isolated from Myracrodruon urundeuva
Allemão.
FIGURE 14.24 Chemical structures of polycyclic polyprenylated benzophenones (71)–(73) isolated from
Garcinia brasiliensis.
⏎
⏎
A compound library consisting of 270 chemical structures, including 111 NPs isolated
from Brazilian plants, was investigated through high-throughput screening to identify new
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potent inhibitors of Caths K, V, L, and S (Severino et al., 2011). This study evaluated
a series of different classes of secondary metabolites, including alkaloids, coumarins,
triterpenes, cinnamic acids, amides, lignans, avonoids, and limonoids. The most promising results against the cathepsins were obtained for alkaloid and avonoid derivatives.
Severino et al. (2011) described the rst study in the literature to use NPs as reversible and
competitive inhibitors of Cath V. A series of acridone alkaloids (75)–(86) isolated from the
methanol extract of the stem bark of Swinglea glutinosa showed potent inhibitory activity
(Figure 14.25). The alkaloids were found to be reversible and competitive inhibitors of
Cath V . Acridone (80) was the most effective inhibitor with an IC50 value of 1.2 µM and Ki
of 200 nM. The inhibitor interacts with the enzyme’s amino acids through hydrogen bonds
and van der Waals interactions. The predicted conformation within the binding pocket of
Cath V revealed that the inhibitor interacts via four hydrogen bonds. First, the 1-hydroxyl
substituent acts as a hydrogen bond donor to the main-chain carbonyl group of Gly23 at
the S1 pocket. Second, the oxygen atom of the 2-methoxy substituent accepts a hydrogen
bond from the NH2 side-chain of Gln19, which forms part of the oxyanion hole in Cath V.
Third, the 5-hydroxyl substituent binds to the S2 pocket, acting as a hydrogen bond donor
to the main-chain carbonyl group of Leu157. Finally , the 9-carbonyl group binds to the S3
pocket by accepting a hydrogen bond from the NH main-chain of Gly66. In addition to
these polar contacts, nonpolar interactions also contribute to the orientation of the inhibitor
in Cath V. The side-chains of Phe67 and Cys25 form van der Waals interactions with the
1-hydroxyl and 2,3,4-trimethoxy substituted rings, respectively. The SAR data conrms
that the inhibitory activity is improved by the presence of polar substituents at R1 (2-position) and less bulky groups at R4 (8-position).
Considering the signicant challenge of nding selective cathepsin inhibitors, a
complementary database for a small series of acridone alkaloids (74)–(84) was evaluated
against Cath L (Marques et al., 2016). The compounds showed signicant inhibition of
Cath L, with IC50 values ranging from 0.8 to 57 μM. Alkaloids (74), (75), and (80) were the
most potent in the series, with IC50 values of 0.9, 0.8, and 1.5 μM, respectively. For Cath V,
the IC50 values ranged from 1.2 to 48.0 μM, with compounds (76), (79), and (80) being the
most potent, with IC50 values of 2.2, 2.2, and 1.2 μM, respectively. The selectivity observed
in this small series was low, suggesting that these inhibitors are not capable of selectively
inhibiting Caths L and V. However, important information from the SAR data could be
visualized. The comparison of compounds (74) and (76) shows that the potency of these
compounds is not affected by the presence of the prenyl substituent group at C-8 in ring A.
Similarly, the same is observed when comparing compounds (74) and (75) in terms of the
presence of a methoxy group at C-4. Analyzing compounds (76) and (77), it was observed
that the inclusion of the prenyl group at C-4 of ring B leads to a signicant decrease in
potency by a factor of approximately 12 times. On the other hand, the absence of the prenyl
group at C-2 of ring B in compound (77) suggests that this group is crucial for establishing
afnity with these cathepsins. The intramolecular cyclization of the prenyl group (80), (82),
(83), and (84) signicantly reduces the potency of the compounds compared to prenylated
alkaloids (74), (75), (76), and (77), suggesting that the formation of a fourth ring hinders
the interaction of the inhibitor with the catalytic site. The data suggest that the acridone
alkaloids are satisfactorily positioned in the region of the enzyme’s catalytic site, allowing
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for important intermolecular interactions for molecular recognition. The aromatic rings A
and B can favor hydrophobic and van der Waals interactions, although this effect is less
pronounced in the case of tetracyclic compounds that hinder the planarity of the molecule
and, consequently, the hydrophobic interaction. Acridone alkaloids represent a potential
lead candidate for future medicinal chemistry, serving as new competitive inhibitors with
improved potency and afnity against Caths V and L.
FIGURE 14.25 Chemical structures of a series of acridone alkaloids (74)–(84) isolated from Swinglea glutinosa.
Triterpenoids have been identied as a new class of competitive inhibitors against
Cath L. Ramalho et al. (2014) have screened several natural triterpenes isolated from
plants (Figure 14.26). Three natural triterpenes, namely, 3-O-acetylursolic acid (85),
ursolic acid (86), and 3-epiursolic acid (87), were extracted from the stems of Myrcia
lingua Berg (Myrtaceae). 3-Oxoursolic acid (88) was identied from the stem bark of
Vochysia thyrsoidea (Vochysiaceae). Masticadienoic acid (89) and schinol (90) were
isolated from the fruit of Schinus terebinthifolius (Anacardiaceae). Interesting, the
⏎
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evaluated triterpenoids did not show signicant inhibition on Cath B (IC50 ˃ 250 µM).
Molecular docking studies and analysis of the binding patterns and interaction modes on
Cath B revealed that due the size and rigidity of the triterpenoid ring systems, they cannot
pass through the narrow V-shaped channel in the enzyme’s active site. Consequently, the
structure is unable to interact with the amino acids in subsites S2 and S3, which are
crucial for the inhibitory activity. On the other hand, triterpenoids were active against
Cath L. The most promising was 3-epiursolic acid (87) with IC50 values of 6.5 μM on
Cath L. 3-O-acetylursolic acid (85) and ursolic acid (86) showed signicant inhibition on
Cath L with IC50 value of 12.3 and 39.5 µM. The moderate inhibitory activity exhibited by
triterpenoids against Cath L suggests their potential to greatly assist in the development
of new inhibitors with increased potency against this enzyme (Ramalho et al., 2014).
FIGURE 14.26 Chemical structures of triterpenoids (85)–(90) isolated from different plants.
⏎
The dipeptide asperphenamate (91) was isolated from raw malt, a traditional medicine
used for the treatment of mammary gland hyperplasia (Ling et al., 2005) (Figure 14.27).
Asperphenamate (91) can inhibit the proliferation of cancer cells and showed cell death
through the induction of autophagy (Yuan et al., 2012). The inhibition of cathepsin by
asperphenamate (91) against Caths L, S, K, and B was evaluated, showing a moderate
inhibitory effect on Caths L and S with IC50 values of 91.23 and 171.11 µM, respectively
(Li et al., 2021; Yuan et al., 2018).
EBOV and Marburg virus (MARV) are members of the Filoviridae family, known for
causing severe hemorrhagic fevers in both humans and nonhuman primates, often with
mortality rates as high as 90%. In a study conducted by Cui et al. (2018), researchers
prepared 373 extracts from plants commonly used in traditional Chinese herbal medicine