In vitro antioxidant activity and scavenging effects of some synthesized 4-Aminochalcones

Article abstract of DOI:10.14233/ajchem.2013.12441

A new series of substituted 4'-aminochalcones were synthesized by Claisen-Schmidt condensation of 4-aminoacetophenone with various substituted aromatic/heteroaromatic aldehydes. The antioxidant activity for all these compounds were studied on various reac

Full text of DOI:10.14233/ajchem.2013.12441

Asian Journal of Chemistry; Vol. 25, No. 1 (2013), 52-58
http://dx.doi.org/10.14233/ajchem.2013.12441
In vitro Antioxidant Activity and Scavenging Effects of Some Synthesized 4′-Aminochalcones
1
1,2
3,*
Y. RAJENDRA PRASAD , V. JHANSI RANI and A. SRINIVASA RAO
1
2
3
Department of Pharmaceutical Chemistry, University College of Pharmaceutical Sciences,Andhra University,Visakhapatnam-530 003, India
Department of Pharmacology, University College of Pharmaceutical Sciences Andhra University, Visakhapatnam-530 003, India
Department of Pharmaceutical Chemistry, Shri Vishnu College of Pharmacy, Vishnupur, Bhimavaram-534 202, India
*
Corresponding author: Fax: +91 8816 250863; E-mail: atlas1772@rediffmail.com
Received: 21 July 2011; Accepted: 9 July 2012)
(
AJC-11819
A new series of substituted 4'-aminochalcones were synthesized by Claisen-Schmidt condensation of 4-aminoacetophenone with various
substituted aromatic/heteroaromatic aldehydes. The antioxidant activity for all these compounds were studied on various reactive oxygen
species assays containing superoxide anion, hydroxyl radical,ABTS cation radical scavenging and inhibition of lipid peroxidation assays.
Chalcones 9 and 10 made up of 3,4,5-trimethoxyphenyl and 4-dimethylaminophenyl moieties as ring-B of chalcones respectively exhibited
maximum activity in various antioxidant assays, which may be due to the free radical scavenging activity. The present study revealed that
an electron releasing group at position 4 of the ring B of chalcone is essential for exhibiting significant antioxidant activity.
Key Words: 4'-Aminochalcones, Lipid peroxidation, Antioxidant activity, Scavenging effects.
Chalcones are also reported to display a number of interesting
INTRODUCTION
6
biological activities such as antimalarial , antimicrobial ,
7
8
9
10
11
antitubercular , antiviral , antileishmanial , cytotoxic , anti-
Several diseases caused by free radicals have been reported
such as atherosclerosis, cancer, liver cirrhosis, cancer, aging,
1
diabetes, etc. and the scavenging effects of these free radicals
12
13
cancer , antioxidant , antiinflammatory , analgesic , antihyper-
16
glycemic , antimutagenic and phosphodiesterase inhibitory
14
15
17
18
by the chemical compounds have great potential in amelio-
2
rating these disease progresses . Because of the human body
activities . The discovery of this class of compounds provides
an outstanding case history of modern drug development and
also points out the unpredictability of biological activity from
structural modification of a prototype leading molecule. As
part of our continuing efforts in this area, a series of some
new 4'-aminochalcones have been synthesized and evaluated
has an inherent mechanism to reduce free radical induced
injury by endogenous enzymes such as superoxide dismutase,
glutathione peroxidase, catalase and others such as ascorbic
acid (vitamin C) etc. When compared to the damage produced
to the body, these protective mechanisms are sometimes found
not to be sufficient. Hence, the exogenous antioxidants are
required to overcome the injuries produced by free radicals
and lipid peroxidation.
1
9,20
for their antiinflammatory and analgesic activities . The
present paper was aimed to investigate the free radical scaven-
ging and antioxidant activities of synthesized 4'-aminochalcones.
O
Flavonoids widely distributed in nature, possessing high
degree of antioxidant activity are found to be useful in this
3
type of injuries . An antioxidant which is capable of attacking
3
2"
6
'
1"
1
'
1
3"
5
'
_____
4"
_
_____
A
2
B
R"
R'
4
'
2'
6"
the reactive oxygen species along with inhibiting lipid
peroxidation process is of immense value in the effective
therapy of various diseases resulting from oxidative damage,
3'
5"
Fig. 1.
OH
4
e.g. curcumin, a popular and natural antioxidant .As chalcones
(
OH
OH
1,3-diaryl-2-propen-1-one, Fig. 1) are the precursors for
flavonoids, it has been hypothetized to have antioxidant
activity. The role of the chalcones as antipromoters becomes
evident. Isoliquiritigenin (Fig. 2), a trihydroxy chalcone has
O
5
been shown to inhibit TPA induced tumor promotion in mice .
Fig. 2.

Vol. 25, No. 1 (2013)
In vitro Antioxidant Activity and Scavenging Effects of Some Synthesized 4′-Aminochalcones 53
mixture was analyzed by TLC. Then the reaction mixture was
poured into ice water, if necessary acidified with dil. HCl and
extracted with ethyl acetate (3 × 50 mL). The combined organic
layer was washed with water, dried and concentrated in vacuuo.
The residue was purified on a column of silica gel using
hexane-ethyl acetate (4:1) as eluant affording pure chalcones
EXPERIMENTAL
Melting points were determined with an electrothermal
capillary melting point apparatus and are reported uncorrected.
Infrared (IR) spectra were recorded on a Perkin-Elmer BXF1
FT-IR spectrophotometer using KBr disc and the values are
-
1
1
13
expressed in cm . H and C nuclear magnetic resonance
NMR) spectra were recorded on a Bruker AMX 400 and 100
spectrophotometer respectively with tetramethylsilane (TMS)
as internal standard using CDCl as solvent and the values are
1
-16 in 37 to 81 ꢀ yield.
(
TABLE-1
SUBSTITUTED 4'-AMINOCHALCONES
3
expressed in δ ppm. Mass [EI-MS (70 eV)] spectra were
recorded on Agilent 1100 EI-Mass spectrophotometer. The
elemental analyses of the synthesized compounds were
recorded on Carlo Erba 1108 elemental analyzer and were
within ± 0.4 ꢀ of the theoretical values, unless otherwise noted.
Analytical TLC was performed on Silica Gel F254 plates
Comp.
Ar
Comp.
9
Ar
1
2
3
4
5
6
7
8
3-Bromophenyl
4-Methylphenyl
2-Chlorophenyl
3,4,5-Trimethoxyphenyl
4-Dimethylaminophenyl
9-Anthracenyl
4-Nitrophenyl
3-Pyridinyl
10
11
4
-Chlorophenyl
12
2,4-Dichlorophenyl
4-Fluorophenyl
13
14
2-Pyridinyl
(
Merck) with visualization by UV (254 nm) chamber with
4-Methoxyphenyl
3,4-Dimethoxyphenyl
15
4-Pyridinyl
protective filters. 4-Aminoacetophenone, substituted aromatic
and/or heteroaromatic aldehydes were purchased from E.
Merck (India) Ltd., Mumbai, India. All other materials used
were of analytical reagent grade.
16
2-Quinolinyl
1-(4'-Aminophenyl)-3-(3"-bromophenyl)-2-propen-1-
one (1): Orange crystals, yield 81 ꢀ, m.p. 168-171 ºC. IR
Chalcones (1 to 16) were obtained as following the
procedure given under Scheme-I by the reaction of 4-
aminoacetophenone with various substituted aromatic/
heteroaromatic aldehydes in the presence of aqueous alkali.
The absorption bands in IR spectra for primary amino group
-1
1
(
KBr, νmax, cm ): 3414, 3326, 1652, 1626, 1304, 1177. H
NMR (CDCl , 400 MHz, δ ppm): 4.20 (2H, br s, NH ), 6.72
1H, d, J = 16.0 Hz, CO-CH=), 7.27 (2H, d, J = 10.2 Hz, C-3'
3
2
(
and 5'-H), 7.57-7.49 (3H, m, C-4",5" and 6"-H), 7.70 (1H, d,
J = 16.0 Hz, Ar-CH=), 7.80 (1H, s, C-2"-H), 7.95 (2H, d, J =
-
1
-1
(
olefinic group (1600-1550 cm ) indicated the formation of
3350-3300 cm ), carbonyl group (1650-1600 cm ) and
13
1
1
1
3
0.0 Hz, C-2' and 6'-H). C NMR (CDCl , 100 MHz, δ ppm):
-1
87.59, 151.31, 141.26, 137.63, 132.79, 131.19, 130.65,
30.39, 128.43, 127.11, 123.50, 123.06 and 114.01. EI-MS,
1
the chalcones. The H NMR spectra (400 MHz, CDCl
3
) showed
a broad singlet between δ 4.15-4.22 for NH group, two
2
+
m/z: 302 [{M+H} ]. Anal. calcd. for C15
H, 4.00. Found: C, 59.60; H, 3.97.
H
12NOBr: C, 59.66;
doublets in between δ 6.50-7.50 for olefinic protons (J ≅ 16.0
Hz) indicates that E-geometrical isomers and the aromatic
1-(4'-Aminophenyl)-3-(4"-methylphenyl)-2-propen-1-
one (2): Yellow crystals, yield 65.78 ꢀ, m.p. 162-165 ºC. IR
13
protons appeared in between δ 6.00-9.00. In the C NMR
spectrum exhibited characteristic peaks between δ 190-180
for carbonyl group, δ 145-135 and δ 125-120 for olefinic
carbons confirming the chalcones structure. The mass spectra
-1
1
(
3
KBr, cm ): 3471, 3348, 1628 and 1602. H NMR (CDCl ,
4
NH
00 MHz, δ ppm): 2.42 (3H, s, C-4"-CH
3
), 4.20 (2H, br s,
2
), 6.81 (2H, d, J = 8.0 Hz, C-3' and 5'-H), 7.05 (1H, d, J =
+
showed the corresponding molecular ion peak [M ] as the base
1
5.8 Hz, CO-CH=), 7.23 (2H, d, J = 7.6 Hz, C-2" and 6"-H),
.53 (2H, d, J = 8.0 Hz, C-3" and 5"-H), 7.73 (1H, d, J = 16.0
peak and the fragmentation patterns was characteristic of
respective chalcones. The elemental analyses of all the newly
synthesized compounds confirmed their structures.
7
13
Hz, Ar-CH=), 8.03 (2H, d, J = 10.0 Hz, C-2' and 6'-H). C
NMR (CDCl , 100 MHz, δ ppm): 191.75, 159.05, 148.45,
42.81, 139.49, 136.23, 134.06, 131.17, 130.29, 129.68,
3
1
1
+
21.48 and 63.54. EI-MS, m/z: 238 [{M+H} ]. Anal. calcd.
2
H N
CH
3
Methanol, Aq. KOH
Room temperature
OHC
A
r
+
16 15
for C H NO: C, 81.08; H, 6.32. Found: C, 81.01; H, 6.32.
C
1
2 - 16 hours
1-(4'-Aminophenyl)-3-(2"-chlorophenyl)-2-propen-1-
one (3): Yellow crystals, yield 79.64 ꢀ, m.p. 108-111 ºC. IR
O
-1
1
(
KBr, νmax, cm ): 3384, 3332, 1647, 1607, 1340 and 1178. H
NMR (CDCl , 400 MHz, δ ppm): 4.09 (2H, br s, NH ), 6.62
2H, d, J = 8.8 Hz, C-3' and 5'-H), 7.26-7.21 (2H, m, C-4" and
H N
2
A r
3
2
C
(
O
5"-H), 7.37-7.34 (1H, m, C-6"-H), 7.41 (1H, d, J = 16.0 Hz,
CO-CH=), 7.67-7.64 (1H, m, C-3"-H), 7.85 (2H, d, J = 8.4
1
- 16
Hz, C-2' and 6'-H), 8.05 (1H, d, J = 15.8 Hz, Ar-CH=). EI-MS,
H12NOCl: C, 69.97;
Scheme-I: Synthesis of 4'-aminochalcones
+
m/z: 258 [{M+H} ]. Anal. calcd. for C15
7
Synthesis of chalcones, (1-16) : Potassium hydroxide
H, 4.70. Found: C, 69.90; H, 4.66.
1-(4'-Aminophenyl)-3-(4"-chlorophenyl)-2-propen-1-
one (4): Orange crystals, yield 66 ꢀ, m.p. 158-161 ºC. IR
(
10 ꢀ aqueous solution, 1 mL) was added to a stirred solution
of 4-aminoacetophenone (1 mmol) and a substituted aromatic/
heteroaromatic aldehyde (1 mmol) in methanol (10 mL)
-1
(KBr, νmax, cm ): 3459, 3341, 1645, 1629, 1346 and 1176. 1H
NMR (CDCl , 400 MHz, δ ppm): 4.17 (2H, br s, NH ), 6.72
(2H, d, J = 10.0 Hz, C-3' and 5'-H), 7.22 (1H, d, J = 16.0 Hz,
(
Scheme-I and Table-1). Stirring was carried out for at least
2-16 h at room temperature and each hour the reaction
3
2
1

5
4 Prasad et al.
Asian J. Chem.
CO-CH=), 7.38 (2H, d, J = 8.0 Hz, C-2" and 6"-H), 7.73 (2H,
d, J = 8.8 Hz, C-3" and 5"-H ), 7.93 (2H, d, J = 10.0 Hz, C-2'
(6H, s, C-4"-NMe ), 4.19 (2H, br s, NH
2
2
), 6.70 (2H, d, J =
10.0 Hz, C-3' and 5'-H), 6.88 (2H, d, J = 8.8 Hz, C-3" and 5"-
H), 7.39 (1H, d, J = 15.6 Hz, CO-CH=), 7.57 (2H, d, J = 8.0
Hz, C-2" and 6"-H), 7.76 (1H, d, J = 15.4 Hz, Ar-CH=), 7.94
and 6'-H), 8.02 (1H, d, J = 15.8 Hz, Ar-CH=). EI-MS, m/z:
H12NOCl: C, 69.97; H, 4.70.
+
58 [{M+H} ].Anal. calcd. for C15
2
+
Found: C, 69.90; H, 4.66.
-(4'-Aminophenyl)-3-(2",4"-dichlorophenyl)-2-
propen-1-one (5): Creamy yellow crystals, yield 87.73 ꢀ,
(2H, d, J = 8.0 Hz, C-2' and 6'-H). EI-MS, m/z: 267 [{M+H} ].
1
Anal. calcd for C17
H, 6.76.
18 2
H N O: C, 76.76; H, 6.82. Found: C, 76.69;
-1
m.p. 178-180 ºC. IR (KBr, νmax, cm ): 3436, 3362, 1651, 1609,
1-(4'-Aminophenyl)-3-(9"-anthracenyl)-2-propen-1-
one (11): Orange red crystals, yield 62.08 ꢀ, m.p. 173-176
1
1
343 and 1180. H NMR (CDCl
2H, br s, NH ), 6.71 (1H, d, J = 15.8 Hz, CO-CH=), 7.31
1H, d, J = 8.6 Hz, C-6"-H), 7.47 (2H, d, J = 10.0 Hz, C-3' and
3
, 400 MHz, δ ppm): 4.20
-1
1
(
(
2
ºC. IR (KBr, νmax, cm ): 3469, 3332, 1650, 1633 and 1356. H
NMR (CDCl , 400 MHz, δ ppm): 4.20 (2H, br s, NH ), 7.22
3
2
5
7
'-H), 7.56 (1H, d, J = 8.2 Hz, C-5"-H), 7.70 (1H, m, C-3"-H),
.93 (1H, d, J = 16.0 Hz, Ar-CH=), 8.06 (2H, d, J = 8.0 Hz,
(1H, d, J = 16.0 Hz, CO-CH=), 7.53-7.45 (4H, m, Ar-H-
anthracenyl), 7.57 (2H, d, J = 8.0 Hz, C-3' and 5'-H), 8.03
(1H, d, J = 15.8 Hz, Ar-CH=), 8.15-8.07 (2H, m, Ar-H-
anthracenyl), 8.30 (2H, d, J = 8.2 Hz, C-2' and 6'-H), 8.88-
+
C-2' and 6'-H). EI-MS, m/z: 292 (M ). Anal. calcd. for
C
15
H
11NOCl
2
: C, 61.70; H, 3.79. Found: C, 61.64; H, 3.77.
-(4'-Aminophenyl)-3-(4"-fluorophenyl)-2-propen-1-
one (6): Orange crystals, yield 66 ꢀ, m.p. 140-143 ºC. IR
+
1
8.45 (3H, m, Ar-H-anthracenyl). EI-MS, m/z: 324 [{M+H} ].
H17NO: C, 85.52; H, 5.30. Found: C, 85.44;
H, 5.26.
Anal. calcd. for C23
-1
1
(
KBr, νmax, cm ): 3460, 3340, 1628, 1603, 1345 and 1223. H
NMR (CDCl , 400 MHz, δ ppm): 4.20 (2H, br s, NH ), 6.62
2H, d, J = 8.4 Hz, C-3' and 5'-H), 7.03 (2H, d, J = 8.8 Hz,
C-2" and 6"-H), 7.38 (1H, d, J = 16.0 Hz, CO-CH=), 7.53
2H, d, J = 10.0 Hz, C-3" and 5"-H), 7.66 (1H, d, J = 16.0 Hz,
Ar-CH=), 7.85 (2H, d, J = 8.2 Hz, C-2' and 6'-H). EI-MS,
3
2
1-(4'-Aminophenyl)-3-(4"-nitrophenyl)-2-propen-1-
(
one (12): Orange crystals, yield 60 ꢀ, m.p. 182-184 ºC. IR
1
-1
(KBr, νmax, cm ): 3484, 3389, 1636, 1610, 1506 and 1341. H
NMR (CDCl , 400 MHz, δ ppm): 4.20 (2H, br s, NH ), 6.68
(
3
2
(2H, d, J = 10.0 Hz, C-3' and 5'-H), 6.72 (1H, d, J = 16.0 Hz,
CO-CH=), 7.66 (2H, d, J = 10.0 Hz, C-2" and 6"-H), 7.80
(1H, d, J = 16.2 Hz, Ar-CH=), 7.95 (2H, d, J = 9.8 Hz, C-2'
+
m/z: 242 [{M+H} ]. Anal. calcd. for C15H12NOF: C, 74.76; H,
5
.01. Found: C, 74.68; H, 4.97.
-(4'-Aminophenyl)-3-(4"-methoxyphenyl)-2-propen-
-one (7): Yellow crystals, yield 64.87 ꢀ, m.p. 108-111 ºC.
1
and 6'-H), 8.28 (2H, d, J = 10.0 Hz, C-3" and 5"-H). EI-MS,
+
m/z: 269 [{M+H} ]. Anal. calcd. for C15
1
H
12
2 3
N O : C, 67.22; H,
-1
IR (KBr, νmax, cm ): 3467, 3329, 1631, 1598, 1342 and 1230.
4.51. Found: C, 67.16; H, 4.47.
1-(4'-Aminophenyl)-3-(3"-pyridinyl)-2-propen-1-one
1
H NMR (CDCl
.20 (2H, br s, NH
2H, d, J = 10.0 Hz, C-3' and 5'-H), 7.43 (2H, d, J = 9.0 Hz,
C-3" and 5"-H), 7.60 (2H, d, J = 8.8 Hz, C-2" and 6"-H), 7.76
1H, d, J = 16.0 Hz, Ar-CH=), 7.94 (2H, d, J = 9.6 Hz, C-2'
3
, 400 MHz, δ ppm): 3.85 (3H, s, C-4"-OCH
3
),
4
2
), 6.71 (1H, d, J = 16.0 Hz, CO-CH=), 6.93
(13): Orange red crystals, yield 62.06 ꢀ, m.p. 160-163 ºC. IR
1
-1
(
(KBr, νmax, cm ): 3437, 3354, 1636, 1595 and 1342. H NMR
(CDCl , 400 MHz, δ ppm): 4.13 (2H, br s, NH ), 6.63 (2H, d,
3
2
(
J = 8.8 Hz, C-3' and 5'-H), 7.26 (1H, d, J = 8.0 Hz, C-5"-H),
7.52 (1H, d, J = 15.6 Hz, CO-CH=), 7.68 (1H, d, J = 16.0 Hz,
Ar-CH=), 7.86 (2H, d, J = 8.4 Hz, C-2' and 6'-H), 8.54-8.52
+
2
and 6'-H). EI-MS, m/z: 253 (M ). Anal. calcd. for C16H15NO :
C, 75.96; H, 5.97. Found: C, 75.88; H, 5.92.
13
1
-(4'-Aminophenyl)-3-(3",4"-dimethoxyphenyl)-2-
propen-1-one (8): Orange crystals, yield 72.43 ꢀ, m.p. 146-
(1H, m, C-4"-H), 8.78 (2H, d, J = 9.0 Hz, C-2" and 6"-H). C
NMR (CDCl , 100 MHz, δ ppm): 185.58, 154.01, 150.39,
149.93), 137.83, 134.72, 131.21, 130.98, 125.15, 124.48,
3
-1
149 ºC. IR (KBr, νmax, cm ): 3445, 3351, 1641, 1597, 1317
1
+
and 1260. H NMR (CDCl
C-3"-OCH ), 3.86 (3H, s, C-4"-OCH
.71 (2H, d, J = 8.0 Hz, C-3' and 5'-H), 7.13-6.79 (3H, m,
C-2",5" and 6"-H), 7.30 (1H, d, J = 15.8 Hz, CO-CH=), 7.64
1H, d, J = 15.8 Hz, Ar-CH=), 7.84 (2H, d, J = 8.4 Hz, C-2'
3
, 400 MHz, δ ppm): 3.84 (3H, s,
123.80 and 112.76. EI-MS, m/z: 225 [{M+H} ]. Anal. calcd.
3
3
), 4.21 (2H, br s, NH ),
2
12 2
for C14H N O: C, 75.06; H, 5.39. Found: C, 75.00; H, 5.35.
6
1-(4'-Aminophenyl)-3-(2"-pyridinyl)-2-propen-1-one
(14): Light orange crystals, yield 60.88 ꢀ, m.p. 146-150 ºC.
-1
(
IR (KBr, νmax, cm ): 3487, 3399, 1646, 1585, 1432 and 1336.
1
+
and 6'-H). EI-MS, m/z: 283 (M ). Anal. calcd. for C17
C, 72.15; H, 6.03. Found: C, 72.08; H, 6.00.
H
17
3
O N:
3 2
H NMR (CDCl , 400 MHz, δ ppm): 4.12 (2H, br s, NH ),
6.62 (2H, d, J = 8.8 Hz, C-3' and 5'-H), 7.22-7.19 (1H, m,
C-5"-H), 7.38 (1H, d, J = 15.0 Hz, CO-CH=), 7.65 (1H, m,
C-3"-H), 7.68 (1H, d, J = 8.0 Hz, C-4"-H), 7.93 (2H, d, J =
10.0 Hz, C-2' and 6'-H), 8.06 (1H, d, J = 8.8 Hz, C-6"-H),
1-(4'-Aminophenyl)-3-(3",4",5"-trimethoxyphenyl)-2-
propen-1-one (9): Yellow crystals, yield 70.55 ꢀ, m.p. 160-
-1
162 ºC. IR (KBr, νmax, cm ): 3469, 3344, 1630, 1604, 1316
1
+
and 1219. H NMR (CDCl
C-4"-OCH ), 3.93 (6H, s, C-3" and 5"-OCH
NH ), 6.71 (2H, d, J = 10.0 Hz, C-3' and 5'-H), 6.86 (2H, s,
C-2" and 6"-H), 7.43 (1H, d, J = 16.0 Hz, CO-CH=), 7.72
1H, d, J = 15.8 Hz, Ar-CH=), 7.94 (2H, d, J = 8.0 Hz, C-2'
3
, 400 MHz, δ ppm): 3.90 (3H, s,
8.60 (1H, d, J = 15.5 Hz,Ar-CH=). EI-MS, m/z: 225 [{M+H} ].
3
3
), 4.19 (2H, br s,
12 2
Anal. calcd. for C14H N O: C, 75.06; H, 5.39. Found: C, 75.00;
2
H, 5.35.
1-(4'-Aminophenyl)-3-(4"-pyridinyl)-2-propen-1-one
(15): Light orange yellow crystals, yield 55.38 ꢀ, m.p. 172-
(
+
-1
174 ºC. IR (KBr, νmax, cm ): 3439, 3334, 1643, 1593, 1414
and 6'-H). EI-MS, m/z: 313 (M ). Anal. calcd. for C18
H
19
4
O N:
1
and 1336. H NMR (CDCl
C, 69.07; H, 6.12. Found: C, 69.00; H, 6.07.
1
3
, 400 MHz, δ ppm): 4.16 (2H, br s,
-(4'-Aminophenyl)-3-(4"-dimethylaminophenyl)-2-
2
NH ), 6.63 (2H, d, J = 8.4 Hz, C-3' and 5'-H), 7.38 (2H, d, J =
propen-1-one (10): Orange red crystals, yield 66.50 ꢀ, m.p.
168-170 ºC. IR (KBr, νmax, cm ): 3474, 3432, 1620, 1597,
18.0 Hz, CO-CH= and C-3"-H), 7.60 (2H, d, J = 8.0 Hz, C-2"
and 6"-H), 7.85 (2H, d, J = 8.4 Hz, C-2' and 6'-H), 8.60 (2H,
+
d, J = 18.6 Hz, Ar-CH= and C-5"-H). EI-MS, m/z: 224 (M ).
-
1
1
346 and 1303. H NMR (CDCl
1
3
, 400 MHz, δ ppm): 3.05

Vol. 25, No. 1 (2013)
In vitro Antioxidant Activity and Scavenging Effects of Some Synthesized 4′-Aminochalcones 55
Anal. calcd. for C14
H
12
N
2
O: C, 75.06; H, 5.39. Found: C, 75.00;
of inhibition, which was calculated from the control where no
test compound was added.
H, 5.35.
1-(4'-Aminophenyl)-3-(2"-quinolinyl)-2-propen-1-one
16): Yellowish red crystals, yield 48.54 ꢀ, m.p. 162-165 ºC.
+
Determination of ABTS radical cation scavenging ac-
+
tivity: The ABTS radical cation scavenging activity of test
(
-1
1
IR (KBr, νmax, cm ): 3470, 3357, 1638, 1605, 1524, 1357. H
NMR (CDCl , 400 MHz, δ ppm): 4.15 (2H, br s, NH ), 6.73
2H, d, J = 8.0 Hz, C-3' and 5'-H), 7.70 (1H, d, J = 16.4 Hz,
compounds, ascorbic acid (as standard) was determined
23
3
2
according to Re et al. . Briefly, 5 mL of 7.0 mM ABTS was
(
reacted with 88.0 µL of 140 mM potassiumpersulfate over-
+
night in the dark to yield the ABTS radical cation. Prior to
+
use in the assay, the ABTS radical cation diluted with 50 ꢀ
CO-CH=), 7.93 (1H, d, J = 16.2 Hz, Ar-CH=), 8.06 (1H, d,
J = 10.0 Hz, C-2' and 6'-H), 8.40-7.61 (6H, m, Ar-H-
+
quinolinyl). EI-MS, m/z: 275 [{M+H} ]. Anal. calcd. for
ethanol for an initial absorbance of ≈ 0.700 (1:88 ratio) at 734
nm, with temperature control set at 30 ºC. Free radical scav-
C
18
14 2
H N O: C, 78.90; H, 5.15. Found: C, 78.83; H, 5.10.
+
Pharmacology: 2-Deoxy-D-ribose was purchased from
enging activity was assessed by mixing 1.0 mL dilutedABTS
Sigma chemical Co. (St. Louis, MO, USA). 2, 2'-azinobis-3-
ethylbenzothiozoline-6-sulfonic acid (ABTS) was purchased
from Sigma-Aldrich, Hyderabad, India. Nitroblue tetrazolium
radical cation with 10 µL of test antioxidant and monitoring
the change in absorbance at 0, 0.5, 1 min and again at 5 min
intervals until a steady state was achieved. The antioxidant
capacity of tested compounds were calculated and expressed
(NBT) was purchased from Sisco Research Laboratories Pvt.
Ltd., Mumbai, India. L-ascorbic acid and riboflavin were pur-
chased from Loba Chemicals, Mumbai, India. Thiobarbituric
acid was purchased from BDH Chemicals, Poole, UK.All other
materials and solvents used were of analytical reagent quality.
as IC50.
Determination of lipid peroxidation inhibitory activity:
Inhibition of lipid peroxidation was determined by the
2
4
thiobarbituric acid method . Different quantities of the com-
pounds were incubated at 37 ºC with 25 ꢀ (w/v) rat liver
homogenate (0.1 mL) containing Tris-Buffer (40 mM, pH 7.0),
KCl (30 mM), ascorbic acid (0.06 mM) and ammonium
ferrous sulphate (0.16 mM) in a total volume of 0.5 mL for
21
Determination of superoxide scavenging activity
Riboflavin photo reduction method: Superoxide scav-
enging activity of the compounds was determined by McCord
and Fridovich method, which depends on light induced
superoxide generation by riboflavin and the corresponding
reduction of nitrobluetetrazolium. The assay mixture contained
different quantities of the compounds and ethylene diamine
tetraacetic acid (6 µM containing 0.061 µM NaCN),
nitrobluetetrazolium (50 µM), riboflavin (2 µM) and phosphate
buffer (58 mM, pH 7.8) to give a total volume of 3 mL. The
tubes were uniformly illuminated with an incandescent light
1
h.At the end of the incubation period, 0.4 mL of the reaction
mixture was treated with 0.2 mL of sodium dodecyl sulphate
8.1 ꢀ), 1.5 mL thiobarbituric acid (0.8 ꢀ) and 1.5 mL of
(
acetic acid (20 ꢀ, pH 3.5). The total volume was then made
up to 4 mL by adding distilled water and kept in an oil bath at
95 ºC for 1 h. After the mixture had been cooled, 1 mL of
distilled water and 5 mL of butanol-pyridine mixture (15:1 v/v)
was added. Following vigorous shaking, the tubes were centri-
fuged and the absorbance of the upper layer containing the
chromophore was read at 532 nm. The percentage inhibition
of lipid peroxidation was determined by comparing the
absorbance values of the control and experimental tubes and
calculated IC50 values of all tested chalcones and standard from
their percentage inhibition values.
(
40 w) for 15 min and thereafter the optical density was
measured at 560 nm. The percentage inhibition of superoxide
production was evaluated by comparing the absorbance values
of control and experimental tubes. The inhibitory effects of
samples on the generation of superoxide anion were estimated
by the equation:
0 1 0
Inhibitory ratio = [(A - A ) ×100] / A
The IC50 values of chalcones tested for their antioxidant
activity against reactive oxygen species and inhibition of lipid
peroxidation are shown in Table-2.
where, A
0
is the absorbance with no addition of sample, A is
1
the absorbance with addition of sample. IC50 (the concen-
tration necessary for 50 ꢀ reduction) values were calculated
from the percentage of inhibition, which was calculated from
the control where no test compound was added.
RESULTS AND DISCUSSION
Chalcones were prepared by Claisen-Schmidt conden-
sation, starting from the reaction of 4-aminoacetophenone with
various substituted aromatic and heteroaromatic aldehydes
under basic conditions in the presence of alcohol to furnish
4'-aminochalcones 1 to 16, in good yield (37-81 ꢀ).A number
of α,β-unsaturated ketones possessed preferential reactivity
towards thiols , one of the identified mechanisms is the driving
force for the present study. Chalcones possessing such α,β-
unsaturated carbonyl entity, capable of acting as a soft
electrophile would attract only soft nucleophiles like thiols
but unlikely to react with hard nucleophiles like amino and
hydroxyl groups present on nucleic acids.
2
2
Determination of hydroxyl radical scavenging activity
Deoxyribose degradation method: Hydroxyl radical
scavenging activity was measured by studying the competition
between deoxyribose and the compounds for the hydroxyl
3+
2 2
radical generated from the Fe -ascorbate-EDTA-H O system.
25
The hydroxyl radical attacks deoxyribose and eventually
results in thiobarbituric acid reacting substances (TBARS)
formation. The reaction mixture containing deoxyribose (2.8
2 2
mM), ferric chloride (0.1 mM), EDTA (0.1 mM), H O (1 mM),
ascorbate (0.1 mM), phosphate buffer (20 mM, pH 7.4) and
various quantities of the compounds in a final volume of 1 mL
was incubated for 1 h at 37 ºC. Thiobarbituric acid reacting
substances method was proposed to measure deoxyribose
degradation. IC50 values were calculated from the percentage
Antioxidant activity: The in vitro antioxidant activity
and scavenging effects of the sixteen chalcones were evaluated
by using different reactive oxygen species assays containing

5
6 Prasad et al.
Asian J. Chem.
TABLE-2
IC50 VALUES OF 4'-AMINOCHALCONES (1 TO 16) AND ASCORBIC ACID
IC50 (µg/mL)
Compound Ar
a
b
+
ABTS cation radical
c
d
Superoxide radical
85.65 ± 1.30
86.02 ± 1.69
88.25 ± 1.33
78.84 ± 1.99
82.54 ± 1.57
79.73 ± 1.58
80.09 ± 1.21
80.65 ± 1.58
78.32 ± 1.59
78.87 ± 1.32
89.25 ± 1.99
85.31 ± 1.30
88.97 ± 1.53
89.65 ± 2.01
88.31 ± 1.34
88.87 ± 1.78
69.89 ± 0.82
Hydroxyl radical
204.33 ± 1.53
192.15 ± 2.18
185.14 ± 1.62
170.18 ± 1.43
207.21 ± 1.33
175.71 ± 1.61
179.01 ± 1.58
168.63 ± 1.55
158.18 ± 1.63
151.48 ± 1.09
198.22 ± 1.69
194.22 ± 1.76
189.63 ± 2.18
191.35 ± 2.03
185.21 ± 1.35
197.87 ± 1.48
113.50 ± 0.91
Lipid peroxidation
1
2
3
4
5
6
7
8
9
3-Bromophenyl
74.45 ± 0.96
64.85 ± 0.34
78.86 ± 1.56
55.87 ± 0.63
73.45 ± 1.69
61.06 ± 1.78
56.91 ± 0.68
52.89 ± 1.31
50.06 ± 1.41
50.36 ± 1.22
76.32 ± 2.66
62.32 ± 1.33
77.22 ± 1.38
75.36 ± 2.31
77.01 ± 2.06
77.98 ± 2.52
45.42 ± 1.24
600.85 ± 2.38
587.25 ± 2.32
612.12 ± 2.31
547.57 ± 3.50
650.32 ± 1.54
552.18 ± 2.98
575.97 ± 1.80
550.47 ± 1.97
547.18 ± 2.01
423.08 ± 2.26
652.25 ± 1.44
612.46 ± 2.99
617.74 ± 2.32
604.47 ± 1.29
624.46 ± 1.92
656.54 ± 1.75
488.62 ± 1.02
4-Methylphenyl
2-Chlorophenyl
4-Chlorophenyl
2,4-Dichlorophenyl
4-Fluorophenyl
4-Methoxyphenyl
3,4-Dimethoxyphenyl
3,4,5-Trimethoxyphenyl
4-Dimethylaminophenyl
9-Anthracenyl
1
0
1
2
3
4
5
6
1
1
1
1
1
1
4-Nitrophenyl
3-Pyridinyl
2-Pyridinyl
4-Pyridinyl
2-Quinolinyl
Ascorbic acid
All values are expressed as mean ± SD of 3 determinations
TABLE-3
INHIBITION OF SUPEROXIDE RADICAL USING RIBOFLAVIN PHOTO REDUCTION METHOD
ꢀ
Quantity (µg)
Compound
5
10
25
50
100
1
2
3
4
5
6
7
8
9
13.23 ± 1.25
15.70 ± 0.23
13.21 ± 0.54
11.76 ± 0.34
8.69 ± 0.18
8.98 ± 0.35
10.25 ± 1.02
11.19 ± 0.33
16.72 ± 0.23
17.46 ± 1.11
6.58 ± 1.04
16.88 ± 0.61
7.82 ± 053
5.48 ± 0.83
8.89 ± 0.64
7.32 ± 0.54
0.54 ± 1.01
18.56 ± 0.57
22.60 ± 0.20
21.35 ± 0.26
19.48 ± 0.15
16.60 ± 0.57
17.22 ± 0.44
17.64 ± 0.51
18.05 ± 0.38
22.77 ± 0.54
23.62 ± 0.75
12.54 ± 0.63
23.50 ± 0.75
15.32 ± 1.52
10.54 ± 0.74
21.60 ± 0.68
14.26 ± 0.52
0.78 ± 0.52
25.32 ± 1.21
30.26 ± 1.30
27.59 ± 1.23
29.77 ± 0.21
26.08 ± 0.35
28.46 ± 0.46
29.31 ± 0.87
29.24 ± 0.47
34.87 ± 0.74
35.95 ± 0.75
25.32 ± 078
33.44 ± 0.63
30.64 ± 054
23.20 ± 0.86
33.47 ± 0.63
30.25 ± 1.03
0.91 ± 0.63
38.54 ± 0.67
41.76 ± 0.17
37.58 ± 0.52
41.54 ± 0.21
41.89 ± 0.38
39.32 ± 0.55
40.28 ± 0.69
38.26 ± 1.35
41.99 ± 0.48
44.51 ± 0.55
30.52 ± 1.33
39.40 ± 0.54
41.55 ± 0.54
39.66 ± 0.79
44.06 ± 0.59
43.23 ± 0.23
9.32 ± 0.21
50.89 ± 0.52
52.87 ± 0.12
50.01 ± 1.32
53.30 ± 0.53
52.17 ± 0.23
50.93 ± 0.47
51.05 ± 1.05
51.98 ± 0.53
51.60 ± 0.69
53.08 ± 0.59
40.63 ± 0.87
53.31 ± 0.59
51.25 ± 0.58
51.89 ± 0.54
52.54 ± 0.79
51.05 ± 0.58
17.60 ± 0.48
1
1
1
1
1
1
1
0
1
2
3
4
5
6
Ascorbic acid
+
superoxide anion radical, hydroxyl radical, ABTS cation
radical and inhibition of lipid peroxidation.
results are expressed as percentage inhibition of hydroxyl
radical in relation to a control. All compounds in general
showed good hydroxyl radical scavenging activity, when each
tested at six dose levels (5, 10, 25, 50, 100 and 250 µg) and in
particular compounds 4, 6, 7, 8, 9 and 10 exhibited dose
dependant inhibition, which is comparable to that of the
standard drug ascorbic acid. Compound 10 carrying dimethyl-
aminophenyl ring as ring B of chalcone showed highest activity.
Superoxide scavenging activity: All the chalcones were
found to scavenge the superoxides generated by photoreduction
of riboflavin, when each tested at five dose levels (5, 10, 25,
5
0 and 100 µg). However, compounds 4, 6, 7, 9 and 10 showed
a dose dependent inhibition of superoxide radicals. Ascorbic
acid, the known antioxidant is employed in this study for
comparing the results. Compound 9 having 3, 4, 5-trimethoxy-
phenyl ring was the best among all the tested chalcones. The
mean values of inhibition for each compound at each concen-
tration level are presented in Table-3.
+
ABTS radical cation scavenging activity: The antioxidant
+
ability to scavenge the ABTS radical has been compared to
the standard ascorbic acid and is an excellent tool for deter-
mining the antioxidant activity of hydrogen donating anti-
oxidants and of chain breaking antioxidants. The percentage
Hydroxyl scavenging activity: Degradation of deoxyri-
3+
+
bose mediated by hydroxyl radicals generated by Fe /ascorbate/
EDTA/H system was found to be inhibited by the compounds
scavenging of ABTS by the compounds at different concen-
2 2
O
trations were shown in Table-5. Even though all compounds
showed a dose dependent scavenging activity, compounds 4,
6, 7, 8, 9 and 10 showed remarkable activity, comparable to
tested. Table-4 displays the hydroxyl scavenging activity of
the compounds when tested by the deoxyribose method and

Vol. 25, No. 1 (2013)
Compound
In vitro Antioxidant Activity and Scavenging Effects of Some Synthesized 4′-Aminochalcones 57
TABLE-4
INHIBITION OF HYDROXYL RADICAL USING DEOXYRIBOSE DEGRADATION METHOD
ꢀ
Quantity (µg)
5
10
25
50
100
250
1
2
3
4
5
6
7
8
9
16.31 ± 0.65
17.22 ± 0.37
15.45 ± 0.42
23.68 ± 0.42
20.24 ± 0.92
23.72 ± 0.75
24.21 ± 0.54
24.59 ± 0.98
20.67 ± 0.81
26.54 ± 1.05
10.47 ± 1.21
19.02 ± 0.88
10.54 ± 1.33
8.34 ± 0.45
12.68 ± 0.86
10.32 ± 1.24
2.43 ± 0.61
20.62 ± 1.05
23.94 ± 0.66
21.11 ± 0.87
26.84 ± 0.52
29.75 ± 1.20
28.81 ± 0.89
28.97 ± 1.21
29.83 ± 0.81
23.39 ± 0.63
34.49 ± 1.18
20.52 ± 0.52
28.74 ± 0.93
18.67 ± 0.54
15.56 ± 1.72
21.26 ± 1.16
15.45 ± 1.08
3.85 ± 1.05
28.65 ± 0.63
29.83 ± 0.82
28.47 ± 1.63
33.46 ± 0.84
33.47 ± 1.35
32.62 ± 0.66
34.55 ± 1.45
35.08 ± 0.82
35.32 ± 0.88
40.69 ± 1.06
29.58 ± 2.10
36.43 ± 1.05
29.31 ± 1.55
27.50 ± 0.71
31.71 ± 1.12
20.55 ± 0.54
4.33 ± 0.50
39.27 ± 0.62
40.33 ± 0.57
38.12 ± 1.05
36.96 ± 0.72
42.14 ± 1.19
42.37 ± 0.47
41.98 ± 0.55
42.74 ± 0.82
39.44 ± 0.84
45.34 ± 108
35.54 ± 0.68
46.96 ± 1.47
34.33 ± 0.71
33.98 ± 0.98
37.31 ± 0.94
31.11 ± 0.52
5.22 ± 1.52
41.23 ± 1.21
44.95 ± 0.88
40.19 ± 0.33
44.35 ± 0.84
45.46 ± 1.23
48.72 ± 1.02
48.04 ± 0.26
46.77 ± 0.82
43.57 ± 0.80
50.77 ± 1.07
42.97 ± 0.64
51.01 ± 0.66
41.87 ± 0.54
41.50 ± 0.98
42.53 ± 0.93
38.54 ± 0.21
15.47 ± 1.00
48.47 ± 0.34
50.83 ± 0.30
48.32 ± 0.57
52.52 ± 0.46
50.82 ± 0.85
53.81 ± 0.94
54.03 ± 0.55
54.42 ± 0.62
53.66 ± 0.95
56.02 ± 1.04
46.87 ± 0.87
52.63 ± 0.99
56.35 ± 1.04
57.31 ± 1.26
54.85 ± 1.09
49.51 ± 1.14
42.12 ± 2.68
10
11
12
13
14
15
16
Ascorbic acid
TABLE-5
INHIBITION OF ABTS CATION RADICAL SCAVENGING ACTIVITY OF TEST COMPOUNDS
+
ꢀ
Quantity (µg)
Compound
5
10
25
50
100
1
2
3
4
5
6
7
8
9
17.65 ± 1.21
18.86 ± 1.56
13.83 ± 0.98
17.67 ± 1.32
15.23 ± 0.56
18.92 ± 0.76
19.35 ± 1.65
15.70 ± 0.56
17.56 ± 0.65
10.52 ± 0.35
5.65 ± 1.25
20.70 ± 0.54
13.33 ± 1.88
11.71 ± 0.99
15.13 ± 1.68
5.65 ± 1.24
12.35 ± 0.59
20.91 ± 0.76
22.39 ± 1.78
18.54 ± 1.57
20.85 ± 0.68
18.98 ± 0.87
22.27 ± 1.02
23.35 ± 0.55
19.02 ± 0.72
21.53 ± 1.33
12.35 ± 1.24
14.24 ± 0.69
25.56 ± 1.02
16.69 ± 0.34
17.22 ± 1.22
17.22 ± 2.06
15.35 ± 1.33
23.46 ± 0.44
27.44 ± 1.65
30.54 ± 0.99
24.97 ± 0.68
27.35 ± 1.02
25.35 ± 1.22
28.21 ± 0.89
27.47 ± 0.68
25.64 ± 1.26
28.62 ± 2.31
19.26 ± 0.56
26.36 ± 1.55
35.55 ± 1.57
20.23 ± 0.53
21.40 ± 0.91
21.40 ± 0.91
19.48 ± 0.55
27.86 ± 0.65
36.15 ± 0.45
39.24 ± 0.44
35.24 ± 1.26
36.56 ± 0.78
32.32 ± 0.58
32.26 ± 1.25
34.24 ± 0.43
34.48 ± 0.38
34.84 ± 0.58
27.02 ± 0.65
30.21 ± 0.57
48.73 ± 1.21
25.54 ± 1.39
26.87 ± 0.67
26.97 ± 0.78
20.14 ± 1.11
35.58 ± 2.13
57.93 ± 0.67
62.43 ± 0.66
58.75 ± 0.54
56.47 ± 0.99
50.98 ± 1.68
47.91 ± 0.99
50.35 ± 1.98
56.55 ± 1.57
51.58 ± 1.26
46.64 ± 1.52
38.21 ± 1.35
65.21 ± 0.38
37.52 ± 1.76
40.90 ± 1.17
33.93 ± 2.11
30.35 ± 2.31
57.53 ± 0.78
10
11
12
13
14
15
16
Ascorbic acid
that of the standard drug ascorbic acid. Compound 9 and 10
showed maximum activity.
Inhibition of lipid peroxidation: Lipid peroxides
tested with such type of functional groups as substituent may
further conform this observation. Such observation is also
consistent with the earlier reports.As superoxides and peroxide
radicals are inevitable participants in the process of tumor
2
+
generated by the induction of Fe /ascorbate on rat liver
homogenate were found to be inhibited by the addition of
synthesized chalcones when tested by thiobarbituric acid
method, using ascorbic acid as standard. Table-6 exhibited the
percentage inhibition of lipid peroxidation of the compounds
tested. Compounds 4, 6, 7, 9 and 10 showed dose dependent
inhibitions when each tested at different dose levels (50, 100,
26
promotion .
It could be inferred from this study that substitution of
electron donating groups at the ortho and/or para positions of
the benzene ring could increase the antioxidant activity of the
chalcones.
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2
to be the most potent.
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TABLE-6
INHIBITION OF LIPID PEROXIDATION USING THIOBARBITURIC ACID METHOD
ꢀ
Quantity (µg)
Compound
50
100
200
300
500
750
1
2
3
4
5
6
7
8
9
15.22 ± 0.68
17.33 ± 1.12
8.66 ± 0.57
5.46 ± 0.39
10.48 ± 0.57
14.74 ± 1.39
10.58 ± 1.64
8.58 ± 1.01
18.90 ± 0.91
12.86 ± 0.84
8.65 ± 0.57
3.57 ± 0.49
5.87 ± 0.87
5.26 ± 0.63
6.45 ± 0.81
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21.37 ± 1.37
16.57 ± 1.31
15.43 ± 0.96
20.59 ± 1.10
19.92 ± 1.21
19.34 ± 0.55
19.02 ± 0.89
21.84 ± 0.91
22.07 ± 0.72
17.85 ± 0.87
19.44 ± 0.55
18.74 ± 1.14
16.22 ± 0.86
20.27 ± 1.09
9.67 ± 1.04
37.01 ± 0.83
22.34 ± 0.65
27.41 ± 0.86
20.94 ± 0.52
24.21 ± 1.12
29.21 ± 0.92
28.28 ± 1.22
28.65 ± 0.67
26.49 ± 0.92
33.19 ± 0.92
32.77 ± 1.07
22.45 ± 0.58
27.38 ± 1.06
30.28 ± 0.67
29.38 ± 1.08
30.41 ± 0.91
19.35 ± 0.87
51.65 ± 0.58
28.66 ± 0.87
32.25 ± 0.90
30.23 ± 0.98
32.42 ± 1.13
39.32 ± 1.23
43.42 ± 1.21
41.14 ± 0.59
39.17 ± 0.89
38.23 ± 1.04
39.83 ± 0.96
30.54 ± 1.52
35.71 ± 0.82
33.38 ± 0.97
32.01 ± 1.10
34.56 ± 1.13
25.07 ± 1.55
59.00 ± 0.35
39.38 ± 1.22
43.14 ± 1.54
41.05 ± 1.22
44.53 ± 0.98
45.62 ± 1.17
48.60 ± 1.15
48.24 ± 1.11
48.50 ± 0.82
48.31 ± 0.95
47.30 ± 0.88
41.21 ± 0.22
43.65 ± 0.83
40.56 ± 0.57
42.54 ± 0.93
41.93 ± 0.89
31.32 ± 0.74
74.33 ± 1.73
49.74 ± 0.34
54.43 ± 1.41
50.95 ± 0.38
54.29 ± 1.19
54.68 ± 1.68
54.97 ± 0.85
53.97 ± 1.34
54.85 ± 1.12
55.04 ± 1.12
53.94 ± 1.18
52.14 ± 0.68
55.15 ± 1.15
55.25 ± 0.54
55.26 ± 0.67
55.75 ± 0.94
40.47 ± 0.85
88.51 ± 1.28
10
11
12
13
14
15
16
Ascorbic acid
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6
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