Synthesis and characterization of novel indole derivatives reveal improved therapeutic agents for treatment of ischemia/reperfusion (I/R) injury

Article abstract of DOI:10.1021/jm100529e

To develop more potent therapeutic agents with therapeutic efficacy for ischemia/reperfusion (I/R) injury, we linked an antiinflammatory moiety (1,3-dioxane derivative) to the key pharmacophoric moiety of melatonin. We hypothesized that the resulting new indole derivatives might induce a synergistic protection against oxidative damage associated with I/R injury. Our results indicate that one of these indole derivatives (7) manifests potent antiinflammatory antioxidant effects and exerts a protective effect against skeletal muscle injury and associated lung injury following limb I/R in rats.

Full text of DOI:10.1021/jm100529e

J. Med. Chem. 2010, 53, 6763–6767 6763
DOI: 10.1021/jm100529e
Synthesis and Characterization of Novel Indole Derivatives Reveal Improved Therapeutic Agents for
Treatment of Ischemia/Reperfusion (I/R) Injury
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Wei Bi,* Yue Bi, Ping Xue, Yanrong Zhang, Xiang Gao, Zhibo Wang, Meng Li, Michele Baudy-Floc’h,
Nathaniel Ngerebara,† K. Michael Gibson,‡ and Lanrong Bi*,†
†Department of Chemistry, and ‡Department of Biological Sciences, Michigan Technological University, Houghton, Michigan 49931,
§Department of Surgery, Second Hospital of HeBei Medical University, Shijiazhuang 050000, P. R. China, UMR 6226 CNRS, ICMV,
Sciences Chimiques de Rennes, Universiteꢁ de Rennes I, F-35042 Rennes Cedex, France, and ^School of Basic Medical Sciences,
HeBei Medical University, Shijiazhuang 050000, P. R. China
Received April 30, 2010
To develop more potent therapeutic agents with therapeutic efficacy for ischemia/reperfusion (I/R) injury,
we linked an antiinflammatory moiety (1,3-dioxane derivative) to the key pharmacophoric moiety of
melatonin. We hypothesized that the resulting new indole derivatives might induce a synergistic protection
against oxidative damage associated with I/R injury. Our results indicate that one of these indole derivatives
(7) manifests potent antiinflammatory antioxidant effects and exerts a protective effect against skeletal
muscle injury and associated lung injury following limb I/R in rats.
Introduction
linked an antiinflammatory moiety (1,3-dioxane derivative) to
the key pharmacophoric moiety of melatonin with the objective
of developing a new indole derivative that would provide a
synergistic protection against downstream oxidative damage
associated with I/R injury. To examine the structure-activity
relationships, we have synthesized several related indole deriva-
tives with particular focus on the methoxy groups, the indole
heterocycle, and the spatial disposition.
Acute ischemia of the lower limb is frequently encountered in
many disease states and surgical procedures, including acute
atherosclerotic thrombosis, abdominal aortic aneurysm repair,
traumatic arterial injuries, and thromboembolic events in the
lower extremities.1 Although reperfusion is unavoidable, there is
evidence that reperfusion induces additional cellular injury. In
addition to muscle necrosis and edema, reperfusion of the
ischemic limb may lead to systemic complications such as
respiratory distress syndrome and multiple organ dysfunction.2
In relation to this, remote lung injury is associated with a high
degree of morbidity and mortality. Currently, there are no
completely effective treatments for remote organ injury.
Theprimaryliteratureindicates thatreactiveoxygenspecies
(ROSa) and inflammatory leukocytes play an important role
in the pathogenesis of limb I/R injury. Along these lines,
antioxidant therapy and/or inhibition of postischemic neutro-
phil infiltration may have therapeutic efficacy in various organs
during I/R injury.3 Melatonin represents an endogenous anti-
oxidant that can directly scavenge a variety of reactive oxygen
and nitrogen species, and it has been shown to have significant
protective effects in various experimental models of reperfusion
injury.4 Conversely, 1,3-dioxane derivatives have been reported
to possess antiinflammatory and anticancer properties and
protective effects against reperfusion injury via antiprolifera-
tive and antiinflammatory activities in human neutrophils and
tumor cells.5 Recently, we have characterized a new class of 2,5-
disubstituted 1,3-dioxanes, some of which possess antiinflam-
matory properties superior to those of aspirin.6 In contrast to
the classical, acidic NSAIDs (nonsteroidal antiinflammatory
drugs), the new 1,3-dioxane analogues are basic. To develop
more effective therapeutic agents to treat I/R injury, we have
Chemistry
Indole derivatives 3-10 can be readily prepared via a
Pictet-Spengler condensation. Starting from the mixed bisa-
cetal 1 at 50 ꢀC using oxalic acid and silica gel as the catalyst,
the mixed bisacetal is converted into the diastereomeric
aldehyde 2 in good yield (80%). On treatment of 2 with
5-methoxytryptamine in a Pictet-Spengler condensation,
(1R)-1-substituted indole derivative 3 was obtained stereo-
specifically in good yield. With tryptamine replacing 5-
methoxytryptamine in the Pictet-Spengler condensation,
the cyclization product 4 was obtained in high yield. However,
on treatment of 2 with L-tryptophan methyl ester in a Pictect-
Spengler condensation, two diasteresomers 5 and 6 were
obtained in yields of 55% and 30%, respectively. Subse-
quently, some difficulties were encountered during the depro-
tection of the N-phenylacetyl group of 3-6. We observed
racemization associated with the strong basic deprotection
conditions. To avoid this pitfall, we attempted to remove the
N-phenylacetyl protecting group of 3-6, employing enzy-
matic hydrolysis. Since penicillin acylase from Escherichia coli
can recognize a broad range of substrates, we examined this
enzyme and found that it was very useful in the removal of
N-phenylacetyl protecting groups of the dioxacycloalkanes.
Indeed, the mild and neutral enzymatic approach provided a
reliable avenue toward developing our desired compounds.
Thus, upon treatment of an aqueous solution of 3-6 with the
penicillin acylase at pH 6.0 and 37 ꢀC, the N-phenylacetyl
protecting group was removed almost quantitatively and
produced the expected 7-10 without undesired side reactions.
*To whom correspondence should be addressed. For W.B.: phone,
86-311-66002578; fax, 86-311-66002578; email, biwei8115@sohu.com. For
L.B.: phone, 1-906-487-1868; fax, 1-906-487-2061; e-mail, lanrong@mtu.edu.
a Abbreviations: I/R, ischemia/reperfusion; ROS, reactive oxygen
species; HOMO, highest occupied molecular orbital; TNF-R, tumor
necrosis factor-R; MDA, malondialdehyde; MPO, myeloperoxidase.
r
2010 American Chemical Society
Published on Web 08/23/2010
pubs.acs.org/jmc

6764 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 18
Scheme 1. Synthesis of Indole Derivatives 3-10a
Bi et al.
of the indole moieties. On the other hand, the indole structures
influence the antioxidant efficiency and properties of biological
systems at quite different extents and levels. For example, 7
displayed the most potent antiinflammatory activity (81.5%
inhibition). We hypothesize that the indole nucleus of 7
functions to maintain the two key pharmacophoric moieties
(5-methoxy group of melatonin and 1,3-dioxacycloalkane ring)
in an optimal configuration, allowing them to adopt the
required orientation for interactions within the receptor-bind-
ing pocket. Further, compared to the N-phenylacetyl substi-
tuted precursors 3-6, we propose that the uninhibited status of
the 5-amino moiety of the 1,3-dioxacycloalkanes of 7-10
results in a significant improvement of the antiinflammatory
activities and further suggests that the amino group may be
pivotal for maximal antiinflammatory capacity. As is well-
known in all pharmaceutical processes, a minor structural
alteration can lead to a marked influence of the antiinflamma-
tory activity, which raises the possibility that the improved
biological profiles observed for 7-10 might result from a
synergistic effect. Nonetheless, the formation of a hydrogen
bond with the 50-amino moiety may be critically important
during the receptor binding process. Thus, the potent antiin-
flammatory capacities of 7-10, at least partially, may result
from a facile protonation of the amine moieties, which in turn
facilitates better access of the molecule to the cellular mem-
brane. Of interest, although sharing common chemical struc-
tures, the antiinflammatory activity of (1S,3S)-10 was
significantly less (45.1% inhibition) than that of (1R,3S)-9
(74.3% inhibition). A similar trend was observed in (1R,3S)-5
(60.0% inhibition) and (1S,3S)-6 (40.6% inhibition). These
latter observations imply that the spatial disposition of the 1,3-
dioxane ring also plays an important role in the biological
activity of these indole derivatives.
a Reagents and conditions: (i) oxalic acid, silica gel; (ii) 5-methoxy-
tryptamine, tryptamine, L-tryptophane methyl ester; (iii) penicillin
acylase, room temp, pH 6.0.
Moreover, HPLC analysis indicated that no racemization
occurred during the enzymatic hydrolysis (Scheme 1).
Results and Discussion
With the indole derivatives in hand, we systematically under-
took an investigation of the antiinflammatory activity of these
compounds, beginning first with a xylene-induced ear edema
model assay. All of the newly synthesized compounds mani-
fested inhibition against xylene-induced ear inflammation in
mice when compared with vehicle (Table 1, See Supporting
Information), suggesting potent antiinflammatory activities for
derivatives 3-10. The most potent compounds, 7 and 9,
exhibited equivalent or even higher antiinflammatory activity
than the standard reference drug indomethacin. Subsequently,
3, 5, 7, 9 with substantial antiinflammatory activities were
administrated in a series of lower concentrations to develop a
detailed pharmacological activity profile. Oral administration
of 3, 5, 7, and 9 at doses of 5.0, 10.0, and 20.0 mg/kg yielded a
dose-dependent antiinflammatory response in the xylene-
induced mouse ear edema test (Table 2, see Supporting Infor-
mation). We observed a significant enhancement in the antiin-
flammatory capacity of 7 and 9 with doses above 5.0 mg/kg.
Compared to the parent compounds 1 and 2, the antiin-
flammatory activities of 3-10 were significantly enhanced. It is
known that indolic compounds are efficient free radical sca-
vengers and antioxidants.7 At sites of inflammation, increased
free radical activity is associated with activation of neutrophil
NADPH oxidase and/or the uncoupling of a variety of redox
systems.8 Such conditions generally result in impairment of the
antioxidant defense system. Thus, improving intracellular
responses via enhanced antioxidant capabilities may bolster
the maintenance of balance between ROS and antioxidant
defense systems. Accordingly, we hypothesize that the im-
proved antiinflammatory activities of the newly synthesized
3-10 may be linked to the antioxidant-enhancing contributions
Inflammation is a complex phenomenon involving multiple
cellular and molecular interactions in a variety of mechanistic
interactions. To further confirm their antiinflammatory activ-
ities, 3-10 were evaluated in the carrageenan-induced paw
inflammation rat model. Inflammation induced by carrageenan
is acute, nonimmune, and highly reproducible, and this model
system represents another useful phlogistic test system in which
to investigate the systemic nature of antiinflammatory agents.8,9
After subcutaneous injection of carrageenan, edema, hypera-
lgesia, and erythema immediately develop in the test subjects.
These signs of inflammation result from the concerted actions
of several proinflammatory agents (including bradykinin,
histamine, tachykinins, complement and reactive oxygen and
nitrogen species). In response, neutrophils migrate to sites
of inflammation and generate proinflammatory ROS.8,9 The
inflammatory response is readily quantified by an increase in
paw size (edema). As shown in Table 3 (see Supporting Informa-
tion), all of the newly synthesized indole derivatives effectively
inhibited paw edema at 3 h following carrageenan administra-
tion. Of note, 7 and 9 exhibited antiinflammatory activity
comparable to that of indomethacin. Accordingly, on the basis
of results in the murine ear edema model and the paw edema
carrageenan rat model, 7 and 9 exerted significant antiinflamma-
tory activity during the acute phase of inflammation.
The antiinflammatory effect of the newly synthesizedindole
derivatives in vivo most likely occurs via the inhibition
of certain key enzymes involved in inflammation and/or
cell signaling pathways. 1,3-Dioxane derivatives have been
reportedrecentlytopossessPKC(proteinkinase C) inhibitory
activity and exert antiinflammatory, anticancer, and reperfu-
sion injury protective effects via their antiproliferative and

Brief Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 18 6765
scavenging of reactive oxygen radicals and forming a stable
indole radical at the pyrrole ring. Interestingly, compared
with indole derivatives 7/9, although sharing the common
indole moiety and having similar chemical structures, the
respective precursors of 7/9, 3/5, displayed much weaker free
radical scavenging capacities. We propose that the bioavail-
ability of the respective compounds or the actual intracellu-
lar concentration might influence the extent of the free
radical scavenging effect in vitro. We speculate that indole
derivatives 7/9 possess enhanced hydrophilic and lipophilic
characteristics compared to precursors 3/5. It remains prob-
able that indole derivatives 7/9 are more effective at pene-
trating the biological membrane, and this may explain their
enhanced free radical scavenging capacity in vitro in com-
parison to their respective precursors.
Inrelation toantioxidantand antiinflammatory activities, 7
with the methoxy group appears more active than 9 which
lacks this group. We hypothesized that the electronic proper-
ties of the indole ring could be manipulated by the presence of
the 5-methoxy group in such a way to make 7 more likely to
react with radical species. Along these lines, we further hypo-
thesized that this radical scavenging effect might be ascribed
to the electron releasing properties of the ethereal oxygen,
making the doublet in the nitrogen atom more accessible for a
possible electron transfer. Alternatively, the introduction of a
5-methoxy group might result in higher antioxidant activity
by conferring higher stability to the aroxyl radical via electron
delocalization.
Figure 1. Possible mechanisms of action of indole derivatives.
antiinflammatory activities in human neutrophils and tumor
cells.5 Accordingly, we characterized the mechanism of ac-
tions of our new indole derivativesin a PKC inhibition assay.
However, preliminary findings indicated that most of these
newly synthesized compounds displayed weak PKC inhibi-
tory activity (data not shown), suggesting that PKC might not
bethetarget protein(atleastinvitro). Furtherexperimentsare
in progress to ascertain the protein target(s) of these indole
derivatives, with a particular focus on cyclooxygenase and
lipoxygenase and on phosphoinositide 3-kinase systems. Me-
chanistic insights for these new indole analogues may provide
beneficial information for the future development of anti-
ischemia agents.
During I/R injury, various ROS are produced and induce
cellular and tissue damage. Hydrogen peroxide (H2O2) in-
duces DNA strand breaks and base damage via a mechanism
requiring transition metal ions. Metals (i.e., copper ion) present
in biological systems can react with H2O2 via Fenton reactions
to produce hydroxyl radicals, which result in DNA strand
breakage. The hydroxyl radical can react rapidly with almost
any cellular biomolecule.8,9 Accordingly, we felt it was critically
important to evaluate the free radical scavenging activity of the
indole derivatives that manifested maximal antiinflammatory
activity (3, 5, 7, 9) against ROS, especially hydroxyl radicals.
Rat pheochromocytoma (PC12) cells originate from the
adrenal medulla and synthesize and release catecholamines.
These cells are very sensitive to oxidative stress. The PC12 cell
model system has been well established for in vitro ischemia
studies.10 Cell survival, as determined by MTT (3-(4,5-di-
methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduc-
tion, was markedly decreased after PC12 cells were exposed to
free radicals. We found that preincubation of PC12 cells with
the indole derivatives 7/9 or the incubation of cells with these
compounds following exposure to free radicals resulted in
improved viability of PC12 cells which was diminished by free
radical exposure, suggesting that derivatives 7/9 were efficient
scavengers of active radical species. Preincubating cells with7/
9 induced a stronger effect, and this probably was due to a
combination of antioxidant activity and membrane perme-
ability. From Table 4 (see Supporting Information), we
observed that 7 exhibited better radical scavenging activity
than 9. In particular, the scavenging effect of 7 is more
In relation to the above, we have proposed two possible
radical scavenging mechanisms for indole derivatives in Fig-
ure 1. Mechanism I involves electron transfer from the anti-
oxidant to the active radical, which produces a cation radical
and an anion. The electron transfer is followed by proton
transfer from the cation radical to the anion. A second
potential mechanism II involves direct transfer of hydrogen
between the antioxidant and the active radical.
The antioxidant activity and/or radical scavenging effect of
antioxidants is correlated with selected molecular and bio-
chemical parameters, such as the highest occupied molecular
orbital (HOMO) energy, the net charge, and the difference in
heat of formation between antioxidant and its radical, the
latter reflecting the O-H bond dissociation energy. Along
these lines, the ionization energy of the HOMO can be
employed as a measure of a compound’s capacity to partici-
pate in oxidant scavenging.11 Our preliminary findings sug-
gest thatthe linking of 1,3-dioxaneto the key pharmacophoric
moiety of melatonin increases the antioxidant potential. For
example, the HOMO energy of melatonin is -10.425 eV. In
comparison, the HOMO energy of compound 7 is -9.463 eV.
As a general rule, the higher the HOMO energy, the more
active the compound is as an antioxidant.11 Theoretically, 7
should possess higher radical trapping potential than melato-
nin. In addition, on the basis of the lowest energy conforma-
tions, the charge distributions, and the high positive charge of
the hydrogen atoms bound to the nitrogen atoms, we predict
that the indole cation radical of 7 possesses significant N-H
acidity and therefore can easily release protons, which may
facilitate free radical scavenging (Figure 2).
•
pronounced for OH and H2O2, suggesting that 7 is acting
as a scavenger of hydroxyl radicals generated through the
Fenton reaction. With regard to the effectiveness of 7/9 against
oxidative cellular death, we speculate that the antioxidant
activities of these indole derivatives are directly correlated
with the presence of the indole nucleus. The indole moiety of
7/9 most likely is the reactive center of interaction with
oxidants because of its high resonance stability and very
low activation energy barrier toward free radical reactions.
The antioxidative capacities of 7/9 may well be mediated via
Limb I/R injury drives the generation and transport of
numerous proinflammatory molecules (O2-, NO, H2O2, cy-
tokines, and arachidonic acid metabolites) into the systemic
circulation, which further promotes local and systemic
inflammation.1,2 Beyond the regional injury, limb I/R injury
may also yield a systemic inflammatory response resulting in

6766 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 18
Bi et al.
Figure 2. Predicted lowest energy conformations of melatonin and 7.
Figure 4. Hematoxylin-eosin-stained frozen cross-section of lung
tissue. (A-C) Representative lung tissue sections were taken from
the rats exposed to limb I/R injury. (D-F) Representative lung
tissue sections were taken from I/R injury þ 7 (20 mg/kg) treated
rats. Tissue sections were stained with H&E (hematoxylin and
eosin). Magnification: (A, D) ꢀ100; (B, E) ꢀ200; (C, F) ꢀ400.
the I/R group rats (Figure 3A-C). As well, there was also
significant remote organ injury in the lung, characterized by
increased permeability, edema, and neutrophil sequestration
(Figure 4A-C). Since free radical formation and inflamma-
tion play an important role in I/R injury, we investigated the
putative beneficial effects of 7 in limb I/R injury by monitor-
ing the change in serum tumor necrosis factor-R (TNF-R),
malondialdehyde (MDA), and myeloperoxidase (MPO) in
tissues.12,13 Hind limb I/R promotes the inflammatory
response by stimulating the production of inflammatory
cytokines and chemokines.1,2 TNF-R is an important media-
tor of local and remote organ injury following hind limb I/R.
We found that the TNF-R levels were dramatically increased
in the I/R injury group at the end of reperfusion compared to
that of the sham group (Table 5, see Supporting Information).
This indicated that the inflammatory damage induced by hind
limb I/R injury appeared to be systemic. In the treatment group
administered 7, there was a significant fall in the serum levels of
proinflammatory cytokines at the end of reperfusion period
compared to the I/R injury (e.g., no treatment) group, suggesting
that TNF-R increased in the systemic circulation following I/R
injury, which could be effectively inhibited by intervention with 7.
With regard to biomarkers of oxidative damage, MDA
(malondialdehyde) represents an important intermediate of
lipid peroxidation and therefore is generally taken as a represen-
tative surrogate for lipid peroxidation. We found that the MDA
levels of plasma and lung were significantly increased in the I/R
injury group compared to the sham group (Table 5, see
Supporting Information). Conversely, MDA levels in plasma
and lung were significantly lower than that of the I/R injury þ 7
Figure 3. Hematoxylin-eosin-stained frozen cross-section of skele-
tal muscle. (A-C) Representative muscle tissue sections were taken
from the rats exposed to limb I/R. (D-F) Representative muscle
tissue sections were taken from I/R þ 7 (20 mg/kg) treated rats.
Tissue sections were stained with H&E (hematoxylin and eosin).
Magnification: (A, D) ꢀ100; (B, E) ꢀ200; (C, F) ꢀ400.
multiple organfailure. The lungappears tobe a primary organ
susceptible to systemic inflammatory responses, likely related
to the high respiratory quotient. Remote lung injury, induced
by hind limb I/R injury, is characterized by accumulation of
inflammatory infiltrates, increased microvascular permeabil-
ity, alveolar capillary endothelial cell injury, and pulmonary
edema. Accordingly, we addressed the effects of regional and
systemic effects of I/R injury by examining if 7 could exert
protection against local and remote organ injury induced by
hind limb I/R injury in the rats. To perform these studies, we
employed a rubber band tourniquet model in the rat as the
model of hind limb I/R injury. In this rodent model, the
collateral blood flow around the femoral and iliac arteries can
be effectively occluded to ensure complete limb ischemia.
After 3 h of bilateral lower limb ischemia, tourniquets are
released and reperfusion is performed for 4 h. This model
system is associated with local and systemic proinflammatory
responses. We found that after 3 h of ischemia followed by 4 h
of reperfusion, muscle edema, neutrophil accumulation, and
muscle cell necrosis were apparent by histological analysis in

Brief Article
Journal of Medicinal Chemistry, 2010, Vol. 53, No. 18 6767
group. Elevated MDA levels in plasma and lung suggested
decreased levels of endogenous antioxidants and indicated that
7 significantly attenuated downstream lipid peroxidation and
cellular injury. This beneficial effect might be partly related to
the antioxidant and scavenging capacities of 7 for reactive •OH
and H2O2 species.
Acknowledgment. The authors are grateful to NASA
(Grant MSGC R85197), Research Excellence Fund (Grant
R01121), Natural Science Foundation of HeBei, China (Grant
062761266), and the Administration of Traditional Chinese
Medicine of HeBei Province (Grant 2007134) for support
of this research. The authors are also grateful to Professor
Hualiang Jiang for many helpful suggestions.
During hind limb ischemia/reperfusion, leukocytes may
reenter the systemic circulation. These activated neutrophils
may cause local and remote organ damage, especially in the
lungs. After adhering to the pulmonary microvascular en-
dothelium, neutrophils exert their toxic effects through the
release of proteolytic enzymes and free radicals.2 We found
that lung MPO activity in the I/R injury group was signifi-
cantly increased (Table5, see Supporting Information). Treat-
ment with 7 significantly attenuated this effect. The decrease
in lung MPO activity and attenuation of lung histopathology
(Figure 4D-F) indicated that 7 could protect the remote
organ (lung) against limb I/R injury. This protectiveeffect of7
most likely resulted from an inhibition of neutrophil infiltra-
tion and lipid peroxidation. This proposed inhibition is also
associated with tissue edema as evaluated by the W/D ratio
(wet to dry tissue weight ratio) (Table 6, see Supporting
Information), which revealed that 7 was effective at attenuat-
ing the lung damage associated with limb I/R injury.
Skeletal muscle ischemia is associated with an increase in
vascular permeability, which is characterized by swollen and
edematous muscle after acute limb injury. Our histological
results (Figure 3A-C) revealed a significant separation be-
tween muscle fiber bundles, suggesting the presence of inter-
stitial edema and increased microvascular permeability.
Microvascular permeability is an indicator of skeletal muscle
injury following hind limb I/R. As for other parameters
measured, this muscle edema was significantly attenuated
with 7 treatment (Figure 3D-F). As well, signs of pulmonary
edema consisting of interstitial thickening and a high degree of
neutrophil infiltration in the lung capillary vessels and inter-
stitium (Figure 4A-C) was vastly improved following inter-
vention with 7 (Figure 4D-F). The histological results further
confirmed that 7 could reduce the tissue edema and protect
local and remote organ against hind limb I/R injury. We
speculate that the efficacy in protection for indole deriva-
tive 7 against local and remote organ injury results from the
combined effects of inhibiting the release of free radicals and
proinflammatory cytokines.
Supporting Information Available: Details of the synthetic
procedures and characterization for 1-10 and details of biolo-
gical tests. This material is available free of charge via the
Internet at http://pubs.acs.org.
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Conclusion
We have designed and synthesized several related indole
derivatives with particular focus on the methoxy group, the
indole heterocycle, and the spatial composition. The antiin-
flammatory activities of all newly synthesized indole derivatives
3-10 were examined in the xylene-induced ear edema murine
model and the carrageenan-induced paw inflammation model
in the rat. The potent radical scavenging activity of 7 and 9 was
examined in rat pheochromocytoma (PC12) cell survival assays,
this cell line being exquisitely sensitive to free radical damage.
Considering its superior antiinflammatory and antioxidant
capacity, 7 was further evaluated in a hind limb I/R injury
animal model, which revealed its significant capacity to reduce
lipid peroxidation and local (muscle) and remote organ (lung)
injury induced by hind limb I/R injury in rats. These findings
suggest that indole derivative 7 may become an important agent
to attenuate the severity of I/R injury for future investigations,
although the precise cellular mechanism of action for this
compound remains to be determined.
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Hallenbeck, J. Development of an ischemic tolerance model in a
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