Synthesis and biological evaluation of asymmetric indole curcumin analogs as potential anti-inflammatory and antioxidant agents

Article abstract of DOI:10.3109/14756366.2012.743536

A series of asymmetric indole curcumin analogs were synthesized and evaluated as possible inhibiters of pro-inflammatory enzymes such as COX-2, pro-inflammatory cytokines as TNF-α and IL-6, trypsin and β-glucuronidase. They were also tested for antioxidant activities. The results showed that compounds 5e and 5h were found to be the most potent inhibitors of COX-2 (83.33%, 82.50%) and β-glucuronidase (67.80%, 64.12%). All the synthesized compounds exhibited promising activity against IL-6 in a range of 71-100% at 10 μM concentration. Compounds 5f, 5h, 5e, 5c and 5d showed significant inhibition against TNF-α (28-51%) and IL-6 (87-98%) with low toxicity (45-51%) against CCK-8 cells. With few exceptions, all other compounds were found to be good to excellent inhibitors of IL-6 and moderate inhibitors of TNF-α; however, the toxicity profiles of these compounds need to be ameliorated in further optimization studies. Amongst the tested compounds, 5c, 5b, 5j and 5g were found to possess excellent reducing activity and 5b, 5c and 5h were moderate DPPH (1,1-diphenyl-2-picryl hydrazine) radical scavengers.

Full text of DOI:10.3109/14756366.2012.743536

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ISSN: 1475-6366 (print), 1475-6374 (electronic)
J Enzyme Inhib Med Chem, 2014; 29(1): 7–11
2014 Informa UK Ltd. DOI: 10.3109/14756366.2012.743536
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Synthesis and biological evaluation of asymmetric indole curcumin
analogs as potential anti-inflammatory and antioxidant agents
Babasaheb P. Bandgar1, Santosh N. Kinkar2, Hemant V. Chavan1, Shivkumar S. Jalde2, Rafik U. Shaikh3, and
Rajesh N. Gacche3
2
1Medicinal Chemistry Research Laboratory, School of Chemical Sciences, Solapur University, Solapur, India, Organic Chemistry Research
3
Laboratory, School of Chemical Sciences, and School of Life Sciences, Swami Ramanand Teerth Marathwada University, Nanded, Maharashtra,
India
Abstract
Keywords
A series of asymmetric indole curcumin analogs were synthesized and evaluated as possible
inhibiters of pro-inflammatory enzymes such as COX-2, pro-inflammatory cytokines as TNF-a
and IL-6, trypsin and b-glucuronidase. They were also tested for antioxidant activities. The
results showed that compounds 5e and 5h were found to be the most potent inhibitors of
COX-2 (83.33%, 82.50%) and b-glucuronidase (67.80%, 64.12%). All the synthesized compounds
exhibited promising activity against IL-6 in a range of 71–100% at 10 mM concentration.
Compounds 5f, 5h, 5e, 5c and 5d showed significant inhibition against TNF-a (28–51%) and
IL-6 (87–98%) with low toxicity (45–51%) against CCK-8 cells. With few exceptions, all other
compounds were found to be good to excellent inhibitors of IL-6 and moderate inhibitors of
TNF-a; however, the toxicity profiles of these compounds need to be ameliorated in further
optimization studies. Amongst the tested compounds, 5c, 5b, 5j and 5g were found to possess
excellent reducing activity and 5b, 5c and 5h were moderate DPPH (1,1-diphenyl-2-picryl
hydrazine) radical scavengers.
Anti-inflammatory, antioxidant activity,
asymmetric indole curcumin analogs
History
Received 25 February 2012
Revised 24 August 2012
Accepted 22 October 2012
Published online 28 January 2013
Introduction
gastrointestinal side effects5–7. This is the reason why selective
COX-2 inhibition has become the important cellular target of a
number of chemical entities for the treatment of inflammatory
diseases and chemotherapy of cancer.
The pro-inflammatory enzymes such as cyclooxygenase-2 (COX-
2), trypsin and b-glucuronidase and pro-inflammatory cytokines
such as tumor necrosis factor-a (TNF-a) and interleukin-6 (IL-6)
have been described as important targets for the design and
development of novel and safe anti-inflammatory agents. Among
the pro-inflammatory enzymes, trypsin is a member of the serine
proteases family. These proteases are involved in initiation of
inflammation; serine protease inhibition has been considered
as one of the targets for design of anti-inflammatory drugs1.
The lysosomes of the polymorphonuclear neutrophils are rich
in b-glucuronidase. This enzyme is attributed as one of the
mediators for initiating the process of inflammation2. However,
COX-2 enzyme also plays an important role in the transformation
of the arachidonic acid to prostaglandins and thromboxane: an
important step for the recruitment of inflammation3. The COX-1
is housekeeping enzyme having constructive influence; however,
overexpression of COX-2 leads to more production of prosta-
glandins responsible for causing inflammation and it also
participates in the propagation of cancer4. This is consistent
with the idea that inhibition of COX-1 underlies the gastrointes-
tinal side effects of non-steroidal anti-inflammatory drug
(NSAIDs) and that NSAIDs selectivity toward inhibition of
COX-1 over COX-2 correlates with their ability to cause
The pro-inflammatory cytokines, IL-6 and TNF-a are impli-
cated in the pathogenesis of various inflammatory disorders such
as rheumatoid arthritis (RA), inflammatory bowel disease,
osteoarthritis, psoriasis, endotoxemia and/or toxic shock syn-
drome8–16. Apart from pro-inflammatory attributes these cyto-
kines have a wide array of functions for maintaining the normal
cellular physiology. For example, TNF-a can induce apoptosis
and secretion of cytokines such as IL-1, IL-6 and IL-10; it can
also activate T cells and other inflammatory cells. However, an
overabundance of TNF-a and IL-6 is attributed to the develop-
ment of various human ailments including inflammatory disor-
ders. Targeting the inhibition of cytokines, in particular TNF-a,
has been successful in several clinical trials for the treatment of
RA. Nevertheless, the TNF-a inhibition has been identified as one
of the attractive targets for the design and development of anti-
inflammatory agents17.
A large body of literature has been accumulated in the recent
past describing the importance of curcumin as one of the lead
molecules for the design and development of array of therapeutic
agents including anti-inflammatory, anticancer, antioxidant,
antiviral and antimicrobials18. Several analogs of curcumin have
been synthesized and evaluated for multifunctional pharmacolog-
ical application in a variety of diseases such as liver fibrosis,
Address for correspondence: Babasaheb P. Bandgar, Medicinal Chemistry
Research Laboratory, School of Chemical Sciences, Solapur University,
Solapur 413 255, India. Tel./Fax: 0091-217-2351300. E-mail: bandgar_
bp@yahoo.com
inflammation, cardiovascular diseases and cancer (Figure 1)19–21
.
The role of curcumin derivatives as antitumor agent, especially
targeting the tumor anti-angiogenesis is well described22.

8
B. P. Bandgar et al.
J Enzyme Inhib Med Chem, 2014; 29(1): 7–11
Figure 1. Some reported asymmetrical
curcumin analogs.
O
O
O
O
O
OH
HO
OH
HO
OH
OH
Curcumin
O
3,5,2',4'-Tetrahydrochalcone
O
H
N
H
O
N
R
O
O
N
HO
R=Aliphatic,Aromatic,Heteroaromatic
Antioxidant (IC = 4.3mM)
50
Several curcuminoid pyrazoles have been synthesized and NaOH and stirred for 10 min. To this reaction mixture indole-
described as new therapeutic agents in inflammatory bowl 3-carboxaldehyde was added and stirred at 25 ꢀC for 24 h. After
diseases targeting the matrix metalloproteinases23. A series of completion of reaction (TLC), the reaction mixture was poured
mono-carbonyl five-carbon linker curcumin analogs were syn- over crushed ice (25 g) and acidified with 10% aqueous
thesized and were found to inactivate pro-inflammatory cytokines HCl followed by basification with saturated Na2CO3 solution,
such as TNF-a and IL-6: important targets for the design of novel extracted with chloroform and organic layer was washed with
anti-inflammatory agents and tested as anticancer and anti- water, dried (anhydrous Na2SO4) and concentrated. Purification
angiogenic agents24. More recently, curcumin and its hydro- was carried out using silica gel column and a mixture of 0.5–1%
curcumin analogs were found to be potent DNA hypomethylating MeOH þ 1% liquor ammonia in chloroform as eluent to obtain
agents: an important event that has proven to be effective in AICAs in pure form.
restoring gene expression and normal patterns of differentiation
and apoptosis in malignant cells25.
The spectral data of some representative compounds are as
follows:
Taking the above circumstances into consideration we endeav-
ored to synthesize a series of asymmetric indole curcumin analogs
(AICAs) and evaluate the same for inhibition of major pro-
inflammatory enzymes such as COX-2, trypsin and b-glucuroni-
dase and pro-inflammatory cytokines such as TNF-a and IL-6,
along with their antioxidant potential.
N-(3-1H-indole-3-yl)acryloyl)phenyl)benzamide (5a)
Yellow solid, m.p. 182–185 ꢀC; 1H NMR (CDCl3, 300 MHz):
11.26 (bs, 1H, NH), 9.25 (bs, 1H, CONH), 8.23 (m, 2H, ArH),
7.82 (d, 1H, H-b), 7.56 (m, 5H, ArH), 7.23 (m, 3H, ArH), 7.02 (m,
3H, ArH), 7.06 (d, 1H, H-a), 6.96 (s, 1H, ArH); 13C NMR
(100 MHz, CDCl3): 190.2, 173.8, 148.1, 142.4, 140.5, 137.7,
136.2, 134.0, 134.5, 133.0, 132.8, 131.5, 130.1, 129.6, 128.0,
126.4, 125.2, 121.4, 115.7, 107.5; MS: m/z 367 (M þ 1).
Experimental
General
Chemicals were purchased from Aldrich Chemical Co.
(Milwaukee, WI). Thin layer chromotography (TLC) was per-
formed on an aluminum-backed silica plate with visualization
by UV-light. Melting points were determined with a digital
thermometer. IR spectra were recorded on a FT-IR spectro-
N-(3-1H-indole-3-yl)acryloyl)phenyl)-3-trifluoromethylbenza-
mide (5b)
Yellow solid, m.p. 162–165 ꢀC; 1H NMR (CDCl3, 300 MHz):
11.47 (bs, 1H, NH), 9.47 (bs, 1H, CONH), 8.38 (m, 2H, ArH),
7.86 (d, 1H, H-b), 7.80 (m, 2H, ArH), 7.78 (m, 2H, ArH), 7.32 (m,
3H, ArH), 7.24 (m, 3H, ArH), 7.09 (d, 1H, H-a), 6.98 (s, 1H,
ArH); 13C NMR (100 MHz, CDCl3): 191.8, 175.0, 148.6, 143.2,
143.0, 141.5, 141.3, 135.8, 134.7, 134.4, 134.0, 133.7, 133.5,
133.0, 128.6, 128.1, 127.2, 127.0, 124.9, 124.4, 123.2, 120.8,
114.7, 108.5; MS: m/z 435 (M þ 1).
1
photometer (Shimadzu 8300, Kyoto, Japan) and H NMR spectra
were recorded on 300 MHz instrument (Bruker Avance DRX 300,
Rheinstetten, Germany) in CDCl3 using tetramethylsilane as an
internal standard and chemical shifts are reported in ꢀ units. Mass
spectra were obtained with a Shimadzu LCMS-2010EV (Kyoto,
Japan).
General procedure for the synthesis of N-(3-acetyl
phenyl)benzamides
N-(3-1H-indole-3-yl)acryloyl)phenyl)-3-methylbenzamide (5c)
Yellow solid, m.p. 132–135 ꢀC; 1H NMR (CDCl3, 300 MHz):
11.02 (bs, 1H, NH), 9.14 (bs, 1H, CONH), 8.17 (m, 2H, ArH),
7.68 (d, 1H, H-b), 7.59 (m, 2H, ArH), 7.57 (m, 2H, ArH), 7.21 (m,
3H, ArH), 7.11 (m, 3H, ArH), 6.99 (d, 1H, H-a), 6.92 (s, 1H,
ArH), 2.14 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3): 187.2,
169.9, 145.2, 141.7, 140.6, 139.4, 138.5, 135.4, 134.2, 132.3,
132.2, 131.5, 130.3, 130.2, 127.9, 127.8, 127.0, 126.5, 123.8,
123.1, 120.4, 113.5, 106.2, 18.6; MS: m/z 381 (M þ 1).
1-(3-aminophenyl) ethanone (1 g, 7.40 mmol) was suspended in
20 ml 5% of sodium hydroxide solution in a well corked two necked
round bottom flask and to it was added 2 ml of various substituted
benzoyl chlorides, 0.5 ml at a time, with constant shaking and
stirring vigorously for 10 min, reaction mixture was heated under
reflux on water both at 70 ꢀC and at 80 ꢀC for 20 min until the odor
of the benzoyl chloride disappeared. Solid benzoyl derivative was
filtered and recrystallized from petroleum ether and ethyl acetate to
obtain an N-(3-acetyl phenyl)benzamide derivative.
N-(3-(3-1H-indole-3-yl)acryloyl)phenyl)-4-flurobenzamide (5e)
Yellow solid, m.p. 157–160 ꢀC; 1H NMR (CDCl3, 300 MHz):
11.40 (bs, 1H, NH), 9.22 (bs, 1H, CONH), 8.35 (d, 2H, ArH), 7.87
(d, 1H, H-b), 7.63 (d, 2H, ArH), 7.66 (m, 2H, ArH), 7.28 (m, 3H,
ArH), 7.18 (m, 3H, ArH), 7.08 (d, 1H, H-a), 6.97 (s, 1H, ArH);
General procedure for the preparation of AICAs
N-(3-acetyl phenyl)benzamide (219 mg, 1 mmol) was dissolved
in 10 ml of ethanol and to this was added 4 ml (40%) aqueous

DOI: 10.3109/14756366.2012.743536
Asymmetric indole curcumin analogs
9
13C NMR (100 MHz, CDCl3): 189.0, 170.4, 161.8, 147.5, 144.9, Cells were differentiated with phorbol myristate acetate.
142.7, 142.0, 135.3, 135.0, 134.9, 134.7, 133.8, 131.5, 130.6, Following cell plating, the test compound (10 mM) or vehicle
129.4, 127.0, 125.9, 125.1, 120.0, 114.7, 106.8; MS: m/z 385 using 0.5% DMSO was added to each well and the plate was
(M þ 1).
incubated for 30 min at 37 ꢀC. Finally, LPS (Escherichia coli
0127:B8) was added, at a final concentration of 1 mg/ml. Plates
were incubated at 37 ꢀC for 24 h, 5% CO2. Supernatants were
harvested and assayed for TNF-a and IL-6 by ELISA as described
by the manufacturer (BD Biosciences). The cells were simulta-
neously evaluated for cytotoxicity30 using CCK-8. Percent
inhibition of cytokine release compared to the control was
calculated.
COX-2 Inhibition microtiter assay
The assay was performed by using Colorimetric COX (human
ovine) Inhibitor Screening Assay Kit26. Briefly, the reaction
mixture of 100% initial activity wells contained 160 ml of assay
buffer, 150 ml of heme and 10 ml of COX-2 enzyme solution.
While the reaction mixture of inhibitor wells comprised of 150 ml
of assay buffer, 10 ml of heme, 10 ml of enzyme COX-2 and 10 ml
of the test samples (10 mM). The plates were carefully shaken for
5 s and were incubated for 5 min at 25 ꢀC. After 5 min incubation,
20 ml of the colorimetric substrate solution was added, followed
by the addition of 20 ml of arachidonic acid to all the wells. The
plates were shaken gently for few seconds and again incubated for
5 min at 25 ꢀC. The absorbance of all the wells was read at 590 nm
using Thermo make Automatic Ex-Microplate Reader (M
51118170) (Thermo, Ventaa, Finland). The COX-2 inhibition
activity (%) was calculated using the following formula12:
DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging
assay
The DPPH radical scavenging assay was performed as
described31. The reaction mixture contained 10 mM concentra-
tions of individual test sample (in absolute ethanol) and DPPH
radical (10ꢁ4 M in absolute ethanol) solution. The contents of the
reaction mixture were observed spectrophotometrically at 517 nm
after 20 min. Gallic acid was used a reference drug (86.30%).
Determination of the reducing power of AICAs
T
COX inhibition activity ð%Þ ¼ 1 ꢁ ꢂ 100,
The assay was carried out as per reported method32. The principle
of the method is that the antioxidants reduce Fe3þ of K3Fe(CN)6
to Fe2þ, the reducing power of AICAs was determined by the
decrease in absorption of K3Fe(CN)6 at 420 nm. The reaction
mixture contained 0.5 ml solution of individual AICAs (10 mM) in
3 ml of 1 mM potassium ferricyanide solution and the absorbance
was measured at 420 nm after 10 min incubation time. Ascorbic
acid (52.93%) was used as a reference compound.
C
where
T is the absorbance of the inhibitor well at 590 nm and
C is the absorbance of the 100% initial activity
without inhibitor well at 590 nm:
Trypsin inhibition assay
Results and discussion
The trypsin inhibition assay was carried out by employing a
previously reported method27. The method is based on the
measurement of inhibition of trypsin induced hydrolysis of bovine
serum albumin (BSA). Trypsin (0.075 mg/ml) was initially
incubated with 10 mM individual concentrations of test sample
of 0.1 ml for 20 min. The substrate BSA (6 g/100 ml, in 0.1 M
phosphate buffer, pH 7.6) was added after 20 min. The reaction
mixture was incubated for 25 min at 37 ꢀC. The reaction was
terminated by the addition 3 ml of CCl3COOH (5%, w/v). The
acid soluble fractions were obtained by centrifuging the contents
at 5000 RPM for 15 min. The amount of protein in the acid
soluble fractions was estimated by a method of Lowry et al.27.
Acetyl salicylic acid (10 mM) was used as a reference drug.
Chemistry
The compounds N-(3-acetyl phenyl) benzamides (3a–j) were
prepared by the reaction of 3-amino acetophenone with a variety
of benzoyl chlorides (2a–j) in the presence of sodium hydroxide
in ethanol at 80 ꢀC, whereas the Claisen–Schmidt condensation of
N-(3-acetyl phenyl) benzamides (3a–j) with indole-3-carboxyal-
dehyde 4 using sodium hydroxide in ethanol at room temperature
afforded the target AICAs (5a–j) in quantitative yield (Scheme 1).
All the synthesized compounds were characterized by IR,
1H NMR, 13C NMR and mass spectrometry analysis.
Biological evaluation
b-glucuronidase inhibition assay
All the synthesized AICAs 5a–j were tested for their in vitro anti-
inflammatory activity against pro-inflammatory enzymes, namely
COX-2, trypsin and b-glucuronidase at 10 mM concentration and
the results are summarized in Table 1. Among all the tested
compounds, 5e and 5h were found to be better inhibitors of COX-
2 (83.33% and 82.50%) than the acetylsalicylate reference while
other compounds were in the same range or with lower activities.
Compounds 5e, 5h and 5i showed moderate inhibitory activity
against trypsin and 5c, 5e, 5h and 5i showed significant activity
against b-glucuronidase whereas remaining compounds showed
poor inhibitory activity against both trypsin and b-glucuronidase.
Compound 5a (without functional groups) showed very poor
inhibition of COX-2, trypsin and b-glucuronidase; however,
substitution of electrophilic groups at p-position of phenyl ring
(5e, 5h) exhibited increase in inhibitory activity against COX-2,
trypsin and b-glucuronidase.
The effect of the AICAs on activity of b-glucuronidase was
studied using a method described by Demetrios et al.28. 10 mM
concentrations of test sample (0.1 ml) in 0.1 M acetate buffer pH
7.4 for 5 min at 37 ꢀC were preincubated with 0.8 ml of 2.5 mM p-
nitrophenyl-b-D-glucopyranosiduronic acid and 0.1 ml of b-glu-
curonidase was added. The mixture was incubated for 30 min.
Reaction was terminated by addition of 2 ml of 0.5 N NaOH. The
reaction mixtures were observed spectrophotometrically at
410 nm. Salicylic acid (10 mM) was used as a reference
compound.
Assay for TNF-a and IL-6 inhibition
Pro-inflammatory cytokine production by lipopolysaccharide
(LPS) in THP-1 cells was measured according to the method
described elsewhere29. Briefly, THP-1 cells were cultured in
RPMI 1640 culture medium containing 100 U/ml penicillin
and 100 mg/ml streptomycin containing 10% fetal bovine serum.
All the compounds 5a–j were also tested for their in vitro
inhibitory activity against pro-inflammatory cytokines, namely
TNF-a and IL-6. Some of the synthesized AICAs were observed

10 B. P. Bandgar et al.
J Enzyme Inhib Med Chem, 2014; 29(1): 7–11
(a)
(f)
(b)
(g)
(c)
(h)
(d)
(i)
(e)
(j)
Scheme 1. Synthetic route of asymmetrical indole curcumin analogs: (a) NaOH, EtOH, 80 ꢀC and (b) 40% NaOH, EtOH, RT.
Table 1. COX-2, trypsin and b-glucuronidase inhibitory activities (%) of Table 2. TNF-a and IL-6 inhibitory activities and cytotoxicity of AICAs.
AICAs (at 10 mM).
% Inhibition at 10 mM
Compound
R
COX-2 (%) Trypsin (%) b-Glu (%)
Compound
R
TNF-a
IL-6
Cytotoxicity
5a
5b
5c
5d
5e
C6H5
3-CF3C6H4
3-CH3C6H4
4-C(CH3)3C6H4
4-F C6H4
2-F C6H4
3-CN C6H4
4-MeOC6H4
4-ClC6H4
3-BrC6H4
–
12.00
33.34
34.38
43.34
83.33
38.88
30.00
82.50
48.25
32.40
35.10
ND
3.2
4.1
11.75
16.82
22.62
1.5
42.56
12.00
58.95
38.45
67.80
9.50
15.50
64.12
52.91
35.22
ND
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
C6H5
3-CF3C6H4
3-CH3C6H4
4-C(CH3)3C6H4
4-F C6H4
2-F C6H4
3-CN C6H4
4-MeOC6H4
4-ClC6H4
3-BrC6H4
–
87
88
39
28
48
51
59
45
32
48
71
84
100
100
95
93
98
87
71
93
78
79
91
67
57
62
49
45
51
45
63
47
53
49
00
00
5f
5g
5h
5i
5j
ASA
SA
9.7
25.08
20.64
12.50
88.34
ND
DMS (1 kM)
Curcumin
–
26.20
–
The results summarized are the mean values of n ¼ 2. ASA ¼ acetyl
salicylic acid, SA ¼ salicylic acid, ND ¼ not determined.
Results
DMS ¼ dexamethasone.
summarized
are
the
mean
values
of
n ¼ 2.
Table 3. DPPH radical scavenging and reducing activities (RA) of AICAs
(at 10 mM).
to be promising leads, possessing excellent IL-6 inhibitory
activity as compared to dexamethasone, a commercial anti-
inflammatory agent (Table 2).
Compound
R
DPPH (%)
RA (%)
Compound 5a and 5b showed excellent inhibition against both
TNF-a and IL-6, at 10 mM as compared to the dexamethasone
used as a standard as well as curcumin used as a parent
compound. Compounds 5e, 5c, 5d and 5h showed more than 90%
inhibition against IL-6, compounds 5f, 5j, 5i and 5g also showed
significant inhibition against IL-6 (87–71%) and compounds 5g,
5f, 5e, 5j and 5h were found to be moderate inhibitors (59–45%)
of TNF-a. The cytotoxicity profile indicates that the compound
5g (63%), 5b (62%), 5a (57%) and 5i (53%) were found to be
slightly toxic, while all other compounds were non-toxic.
On the other hand, all the synthesized compounds were also
evaluated for DPPH radical scavenging and reducing activity and
results are summarized in Table 3. Mostly, all the compounds
have shown significant DPPH radical scavenging and reducing
activity. The compound 5b (52.69%) was observed to be an
effective scavenger of DPPH radicals while 5c (78.68%), 5j
5a
5b
5c
5d
5e
5f
5g
5h
5i
C6H5
3-CF3C6H4
3-CH3C6H4
4-C(CH3)3C6H4
4-F C6H4
2-F C6H4
3-CN C6H4
4-MeOC6H4
4-ClC6H4
3-BrC6H4
–
41.92
52.69
45.96
43.65
44.23
44.61
29.80
45.78
41.89
43.18
80.86
ND
32.45
62.12
78.68
28.09
35.34
21.44
70.62
38.26
33.45
71.82
ND
5j
GA
AA
–
52.93
The results summarized are the mean values of n ¼ 2. GA ¼ gallic acid,
AA ¼ ascorbic acid, ND ¼ not determined, RA ¼ reducing activity.
(71.82%), 5g (70.62%) and 5b (62.12%) were identified as most methoxy at 4-position of benzoyl group seems to be the most
effective reducing agents. compatible structural configuration for the inhibition of COX-2,
While discussing the structure activity relationship it was trypsin and b-glucuronidase and for possessing significant
observed that the presence of lipophilic groups such as fluoro and antioxidant activity. In general, it was also observed that the

DOI: 10.3109/14756366.2012.743536
Asymmetric indole curcumin analogs 11
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antioxidant activity of the tested AICAs can be correlated with the
extent of pro-inflammatory enzyme inhibition to a greater extent.
The substitution at 4-position of benzoyl group seems to be
important for COX-2 inhibition as unsubstituted benzoyl group
showed very poor COX-2 inhibition. Also substitution of fluorine
at 2-position significantly reduces the inhibition of trypsin
and b-glucuronidase. The substitution at 3-position seems to be
pivotal for the antioxidant activity. Whereas the presence of
trifluoromethyl group at 3-position and fluorine at 4-position
seems to be the significant compatible structural configuration for
the inhibition of TNF-a and IL-6.
Conclusion
In conclusion, a new series of AICAs were synthesized and
evaluated for anti-inflammatory activities (COX-2, trypsin,
b-glucuronidase, TNF-a and IL-6) along with antioxidant activity.
The results of the present investigations indicate the importance
of these new compounds as potential candidates of anti-
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COX-2 and b-glucuronidase, 5f, 5h, 5e, 5c and 5d showed
promising activity against TNF-a and IL-6 with low cytotoxicity
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compounds such as 5a and 5b as inhibitors of TNF-a and IL-6 are
definitely encouraging, but the cytotoxicity of these compounds
limits the therapeutic applications. All the compounds were also
found to possess significant reducing activity and moderate DPPH
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Acknowledgements
H.V.C. is grateful to Council of Scientific and Industrial Research (CSIR),
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Declaration of interest
The authors report no conflicts of interest. The authors alone are
responsible for the content and writing of this article.
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