Synthesis of new phenylcarbamoylbenzoic acid derivatives and evaluation of their in vitro antioxidant activity

Article abstract of DOI:10.1007/s00044-011-9677-2

In this study, new derivatives of phenylcarbamoylbenzoic acid were synthesized and evaluated for their in vitro antioxidant activity. The target compounds were prepared by bonding pharmacophoric moieties possessing antioxidant activity, including hydrazon

Full text of DOI:10.1007/s00044-011-9677-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:1633–1640
DOI 10.1007/s00044-011-9677-2
ORIGINAL RESEARCH
Synthesis of new phenylcarbamoylbenzoic acid derivatives
and evaluation of their in vitro antioxidant activity
•
Waleed A. Bayoumi Magda A. Elsayed
Received: 21 February 2011 / Accepted: 19 May 2011 / Published online: 3 June 2011
ꢀ Springer Science+Business Media, LLC 2011
Abstract In this study, new derivatives of phenylcarba-
moylbenzoic acid were synthesized and evaluated for their
in vitro antioxidant activity. The target compounds were
prepared by bonding pharmacophoric moieties possessing
antioxidant activity, including hydrazones, acid hydrazides,
imino, Schiff’s bases, and phthalimides with phenylcarba-
moylbenzoic acid via simple and efficient synthetic strat-
egies. The structures of the newly synthesized compounds
were confirmed by physical and spectral data. The in vitro
antioxidant activity was carried out using ABTS antioxi-
dant assay. All the tested compounds showed low antiox-
idant activity except compound 7, which showed moderate
antioxidant activity compared with ascorbic acid.
conditions are used and high or almost quantitative yields
are obtained (Argade and Balasubramaniyan, 2000; Feuer
and Asunskis, 1962). Biologically, many of the amides and
hydrazides of 1,2-dicarboxylic acids and their derivatives
are characterized by low toxicity and wide variety of bio-
logical and pharmacological activity (Lange et al., 1979;
Dolzhenko et al., 2002, 2003).
A collection of biological activity and acute toxicity
data of several substituted amides and hydrazides of
1,2-dicarboxylic acids and their derivatives was reviewed
(Koz’minykh, 2006).
Antioxidants are molecules, natural, or synthetic, capa-
ble to interact with free radicals and stop their chain
reactions before essential vital molecules are damaged
(Aruoma, 1998). Owing to the contribution and implication
of oxidative stress in many human diseases, antioxidants
are intensively studied in medicinal chemistry and phar-
macology (Knight, 1998; Mates et al., 1999). Their main
use is for treatment, prevention, or protection against many
disease conditions.
Keywords Synthesis ꢀ Phenylcarbamoylbenzoic acid ꢀ
Hydrazone ꢀ Acyl hydrazone ꢀ Phthaloyl derivatives ꢀ
Antioxidant activity
Introduction
Diverse biological and pharmacological activities of this
class of organic compounds were reported by many
workers. The literature survey did not reveal any study
about the antioxidant activity of phenylcarbamoylbenzoic
acid derivatives. Recently, Phthalic acid was reported to
alter the antioxidant system of specific type of plant,
leading to the formation of reactive oxygen species (Bai
et al., 2009). In this study, phthalic acid as a precursor for
phenylcarbamoylbenzoic acid, was chemically modified by
conversion into amides and hydrazide derivatives.
The objective of this research is to investigate and dis-
cover the expected antioxidant activity of this class of
compounds via design, synthesis, and in vitro antioxidant
screening of selective representatives of phenylcarbamoyl-
benzoic acid derivatives bearing pharmacophoric moieties.
Monoamides of 1,2-dicarboxylic acid and their derivatives
started receiving significant chemical and biological
interest since the later part of the last century by many
Russian workers (Koz’minykh, 2006). From a chemical
point of view, monoamides of 1,2-dicarboxylic acids,
especially monoamides of succinic, maleic, and phthalic
acids (Fig. 1), are easily obtained under mild conditions
(Filho et al., 2003). They can be regarded as precursors for
cyclic imides synthesis, in which facile dehydration
W. A. Bayoumi (&) ꢀ M. A. Elsayed
Department of Pharmaceutical Organic Chemistry, Faculty of
Pharmacy, University of Mansoura, Mansoura 35516, Egypt
e-mail: waleedbayoumi@mans.edu.eg
123

1634
Med Chem Res (2012) 21:1633–1640
Fig. 1 General formulas of
most famous 1,2-dicarboxylic
acid amides (R1, R2,
R3 = different alkyl and aryl
derivatives)
The synthesis was achieved through construction of different
series of phenylcarbamoylbenzoic acid derivatives (mainly,
amides, hydrazides of phthalic acid, and their derivatives)
conjugated and bonded with a variety of pharmacophoric
moieties possessing antioxidant activity. These, include
9a, b by condensation with the appropriate aromatic ketone
in refluxing glacial acetic acid. 1,3-Dioxoisoindolin-2-yl-
imino 10 was obtained by condensing the acid hydrazide 7
with phthalic acid anhydride in refluxing glacial acetic acid.
¨
hydrazones derivatives (Angelo et al., 2003; Gu¨rkok et al.,
Antioxidant screening
¨
2009), acid hydrazide (Gu¨rkok et al., 2009), imino deriva-
tives (Vukovic et al., 2010), Schiff’s bases (Chen et al., 2003;
Guo et al., 2005), and phthalimide derivatives (Shankar
et al., 2000).
All the newly synthesized compounds 1–10 were evaluated
for their potential in vitro antioxidant activity by pre-
liminary qualitative screening using L-ascorbic acid as a
positive control according to ABTS antioxidant assay
method (Re et al., 1999; Miller and Rice-Evans, 1997).
ABTS is an abbreviation to 2,20-azino-bis(3-ethyl-
benzthiazoline-6-sulfonic acid) diammonium salt, a radical
cation decolonization test and is also a spectrophotometric
method widely used for the assessment of antioxidant
activity of various substances. It is applicable for both
lipophilic and hydrophilic compounds. The radical cation
(ABTS•?) was generated by oxidation of ABTS with
potassium persulfate. The absorbance is bleached by anti-
oxidants because of their capacity to reduce the preformed
radical. The % inhibition of the absorbance was calculated
to indicate the inhibition of superoxide production and to
measure the antioxidant activity.
Results and discussion
Chemistry
The synthetic methodologies for obtaining the newly syn-
thesized compounds were illustrated in Schemes 1, 2, and
3. Starting compounds, carbamoyl hydrazone 2 (Scheme 1)
and carbamoyl acid hydrazide 7 (Scheme 2), were prepared
by condensing hydrazine hydrate in refluxing ethanol with
ketone 1 and carboxylic acid ester 6, respectively. Both 1
(Dolzhenko et al., 2003) and 6 were prepared from the
corresponding aromatic amines; 4-aminoacetophenome
and ethyl 4-aminobenzoate through nucleophilic acylation
with phthalic acid anhydride in the presence of ethyl ace-
tate as a solvent, in a typical phthalic acid monoamide
formation reaction (Koz’minykh, 2006).
The results of the antioxidant screening (scavenger
activity) are listed (Table 1). The bar-chart of the % of
inhibition of the absorbance is shown (Fig. 2). All com-
pounds showed low antioxidant activity except compound
7 (carrying the carboxylic acid hydrazide moiety), which
showed moderate antioxidant activity, in comparison to
L-ascorbic acid. The results also revealed that the core
nucleus ‘‘phenylcarbamoylbenzoic acid’’ even after chem-
ical modification with pharmacophores, showed a low
in vitro antioxidant activity.
Starting compounds 2 and 7 were converted to different
derivatives through reaction with the appropriate aromatic
aldehydes, aromatic ketone, and phthalic acid anhydride; to
afford the target compounds 3–5 (Scheme 1) and 8–10
(Scheme 3).
The ketone hydrazone 2 afforded the benzylidene
hydrazono derivatives 3a–c by condensation with the
appropriate aromatic aldehyde in refluxing ethanol and
phenyl ethylidene hydrazono derivatives 4a, b by con-
densation with the appropriate aromatic ketone in refluxing
glacial acetic acid. 1,3-Dioxoisoindolin-2-yl-imino 5 was
obtained by reacting the ketone hydrazone 2 with phthalic
acid anhydride in refluxing glacial acetic acid.
Experimental
Chemistry
Melting points were determined on Fisher-Johns melting
point apparatus and were uncorrected. Elemental Microa-
nalyses were within 0.04% with theoretical calculated
On the other hand, the acid hydrazide 7 afforded the
benzylidene acyl hydrazono derivatives 8a–c by conden-
sation with the appropriate aromatic aldehyde in refluxing
ethanol and phenyl ethylidene acyl hydrazono derivatives
1
values. H NMR spectra were recorded on Bruker Ac 250
FT NMR spectrometer (250 MHZ) in DMSO-d6 or CDCl3
123

Med Chem Res (2012) 21:1633–1640
1635
Scheme 1 Synthesis of 2-((4-(1-hydrazonoethyl)phenyl)carbamoyl)
benzoic acid and its hydrazone and phthaloyl derivatives. Reagents
and conditions: (i) hydrazine hydrate, ethanol, reflux; (ii) aromatic
aldehyde, ethanol, reflux; (iii) acetophenone, glacial acetic acid,
reflux; (iv) phthalic acid anhydride, glacial acetic acid, reflux
Scheme 2 Synthesis of 2-((4-(hydrazinecarbonyl)phenyl)carbamoyl)benzoic acid. Reagents and conditions: (i) ethyl acetate, stirring, room
temperature; (ii) hydrazine hydrate, ethanol, reflux
using TMS as internal standard; chemical shifts in ppm
were expressed in d units. MS analyses were performed on
JEOL JMS-600H spectrometer. Reaction times and purity
of compounds were decided and checked using TLC on
Silica gel plates 60 F245 E. Merck, and the spots were
visualized by UV (366, 245 nm). Compound 1 was pre-
pared in a 65% yield, according to the published procedure
(Dolzhenko et al., 2003).
123

1636
Med Chem Res (2012) 21:1633–1640
Scheme 3 Synthesis of acyl
hydrazone and phthaloyl
derivatives of
phenylcarbamoylbenzoic acid.
Reagents and conditions: (i) the
appropriate aromatic aldehyde,
ethanol, reflux; (ii) the
appropriate acetophenone,
glacial acetic acid, reflux; (iii)
phthalic acid anhydride, glacial
acetic, reflux
2-((4-(1-Hydrazonoethyl)phenyl)carbamoyl)benzoic
acid (2)
Table 1 Results of ABTS antioxidant assay
Tested
compounds
Absorbance
of samples
(mean)
% Inhibition
of
superoxide
production
A mixture of 1 (2.83 g, 10 mmol) and hydrazine hydrate
99% (5 g, 0.1 mol) in absolute ethanol (30 ml) was
stirred under reflux for 5 h. The product formed was
collected by filtration, dried, and recrystallized from
isopropyl alcohol to afford pure compound. Pale yellow
crystals, mp 212–214ꢁC, yield 81%. Analysis for
C16H15N3O3 (297.31), Calcd.: C, 64.64; H, 5.09; N,
14.13; Found: C, 64.49; H, 5.00; N, 13.92. 1H NMR
(DMSO-d6): d 2.95 (s, 3H, CH3), d 6.98 (s, 2H, NH2,
D2O exchangeable), d 7.68–8.39 (m, 8H, Ar–H), d 9.65
(s, 1H, NH, D2O exchangeable), d 11.00 (s, 1H, COOH,
D2O exchangeable). MS m/z (% Rel. Int.): 297 (15.56,
M?).
Control
0.512
0.051
0
Ascorbic
acid
90.04
1
0.474
0.419
0.446
0.385
0.394
0.462
0.458
0.491
0.491
0.229
0.467
0.412
0.490
0.499
0.461
0.469
7.42
2
18.16
12.87
24.80
23.02
9.85
3a
3b
3c
4a
4b
5
10.63
4.19
6
4.09
7
55.21
8.78
(Un)substituted benzylidenehydrazono derivatives 3a–c
8a
8b
8c
9a
9b
10
19.53
4.29
A mixture of 2 (0.59 g, 2 mmol) and the appropriate aro-
matic aldehyde (2 mmol) in absolute ethanol (30 ml) was
refluxed for 5 h, then allowed to cool to room temperature.
The formed precipitate was filtered, dried, and recrystal-
lized from dioxan to afford pure products.
2.63
9.95
8.39
123

Med Chem Res (2012) 21:1633–1640
1637
Fig. 2 Bar-chart of the %
inhibition of absorbance of the
tested compounds
2-((4-(1-(Benzylidenehydrazono)ethyl)phenyl)
carbamoyl)benzoic acid (3a)
and recrystallized from glacial acetic acid to afford pure
products.
Yellow crystals, mp 241–43ꢁC, yield 61%. Analysis for
C23H19N3O3 (385.42), Calcd.: C, 71.67; H, 4.97; N, 10.90;
1
Found: C, 71.52; H, 5.09; N, 10.78. H NMR (DMSO-d6):
2-((4-(1-((1-Phenylethylidene)hydrazono)ethyl)phenyl)
carbamoyl)benzoic acid (4a)
d 2.14 (s, 3H, CH3), d 7.48–8.21 (m, 13H, Ar–H), d 8.42 (s,
1H, N=CH–), d 9.98 (s, 1H, CONH, D2O exchangeable), d
11.00 (s, 1H, COOH, D2O exchangeable). MS m/z (% Rel.
Int.): 385 (7.34, M?).
Yellow crystals, mp 241–43ꢁC, yield 61%. Analysis for
C24H21N3O3 (399.44), Calcd.: C, 72.16; H, 5.30; N, 10.52;
1
Found: C, 72.10; H, 5.22; N, 10.61. H NMR (DMSO-d6):
d 2.13 (s, 6H, two CH3), d 7.51–8.20 (m, 13H, Ar–H), d
9.99 (s, 1H, CONH, D2O exchangeable), d 11.00 (s, 1H,
COOH, D2O exchangeable). MS m/z (% Rel. Int.): 399
(14.63, M?).
2-((4-(1-((4-Chlorobenzylidene)hydrazono)ethyl)phenyl)
carbamoyl)benzoic acid (3b)
Yellow crystals, mp 204–206ꢁC, yield 73%. Analysis for
C23H18ClN3O3 (419.86), Calcd.: C, 65.79; H, 4.32; N,
10.01; Found: C, 65.65; H, 4.27; N, 10.08. 1H NMR
(DMSO-d6): d 2.13 (s, 3H, CH3), d 7.37–8.21 (m, 12H, Ar–
H), d 8.65 (s, 1H, N=CH–), d 10.74 (s, 1H, CONH, D2O
exchangeable), d 11.25 (s, 1H, COOH, D2O exchangeable).
MS m/z (% Rel. Int.): 419 (3.12, M?).
2-((4-(1-((1-(4-(2-Carboxybenzamido)phenyl)ethylidene)
hydrazono)ethyl)-phenyl)amino)benzoic acid (4b)
Yellow crystals, mp 241–43ꢁC, yield 61%. Analysis for
C32H26N4O6 (562.57), Calcd.: C, 68.32; H, 4.66; N, 9.96;
Found: C, 68.39; H, 4.71; N, 9.87. 1H NMR (DMSO-d6): d
2.15 (s, 6H, two CH3), d 6.99–8.20 (m, 16H, Ar–H), d 9.99
(s, 2H, two CONH, D2O exchangeable), d 11.00 (s, 2H,
two COOH, D2O exchangeable). MS m/z (% Rel. Int.): 562
(9.78, M?).
2-((4-(1-((4-Methoxybenzylidene)hydrazono)ethyl)
phenyl)carbamoyl)-benzoic acid (3c)
Yellow crystals, mp 241–43ꢁC, yield 61%. Analysis for
C24H21N3O4 (415.44), Calcd.: C, 69.39; H, 5.10; N, 10.11;
1
Found: C, 69.43; H, 5.06; N, 10.23. H NMR (DMSO-d6):
2-((4-(1-((1,3-Dioxoisoindolin-2-yl)imino)ethyl)phenyl)
carbamoyl)benzoic acid (5)
d 2.12 (t, 3H, =C–CH3), d 3.79 (s, 3H, OCH3), d 7.18–8.22
(m, 12H, Ar–H), d 8.48 (s, 1H, N=CH–), d 9.84 (s, 1H,
CONH, D2O exchangeable), d 11.00 (s, 1H, COOH, D2O
exchangeable). MS m/z (% Rel. Int.): 415 (10.89, M?).
A mixture of 2 (0.59 g, 2 mmol), phthalic acid anhydride
(0.30 g, 2 mmol), and catalytic amount of sodium acetate
(0.1 g) in glacial acetic acid (20 ml) was refluxed for 5 h
and allowed to cool to room temperature. The precipitated
solid was filtered, dried, and recrystallized from glacial
acetic acid to afford pure product. Orange crystals, mp
267–69ꢁC, yield 78%. Analysis for C24H17N3O5 (427.41),
Calcd.: C, 67.44; H, 4.01; N, 9.83; Found: C, 76.51; H,
Phenylethylidenehydrazono derivatives 4a, b
A mixture of 2 (0.59 g, 2 mmol), acetophenone (0.24 g,
2 mmol) or 1 (0.57 g, 2 mmol), and catalytic amount of
sodium acetate (0.1 g) in glacial acetic acid (20 ml) was
refluxed for 5 h. The resultant solution was allowed to
stand overnight. The precipitated solid was filtered, dried,
1
4.20; N, 10.02. H NMR (DMSO-d6): d 2.35 (s, 3H, CH3),
d 7.52–8.20 (m, 12H, Ar–H), d 9.84 (s, 1H, CONH, D2O
exchangeable), d 11.00 (s, 1H, COOH, D2O exchangeable).
MS m/z (% Rel. Int.): 427 (12.63, M?).
123

1638
Med Chem Res (2012) 21:1633–1640
2-((4-(Ethoxycarbonyl)phenyl)carbamoyl)benzoic acid (6)
2-((4-(2-(4-Chlorobenzylidene)hydrazinecarbonyl)phenyl)
carbamoyl)benzoic acid (8b)
A solution of ethyl 4-aminobenzoate (8.26 g, 50 mmol) in
ethyl acetate (80 ml) was gradually added under vigorous
stirring to a suspension of phthalic acid anhydride (7.41 g,
50 mmol) in ethyl acetate (100 ml). Stirring was continued
for 3–4 h (TLC). The formed product was filtered, washed
with ethyl acetate (2 9 25 ml), air-dried, and recrystallized
from dioxan. White crystals, mp 219–221ꢁC, yield 75%.
Analysis for C17H15NO5 (313.30), Calcd.: C, 65.17; H,
4.83; N, 4.47; Found: C, 65.31; H, 4.76; N, 4.99. 1H NMR
(DMSO-d6): d 1.32 (t, 3H, CH3), d 4.30 (q, 2H, CH2), d
7.55–7.97 (m, 8H, Ar–H), d 9.99 (s, 1H, CONH, D2O
exchangeable), d 11.00 (s, 1H, COOH, D2O exchangeable).
MS m/z (% Rel. Int.): 313 (6.39, M?).
Yellow crystals, mp 254–56ꢁC, yield 68%. Analysis for
C22H16ClN3O4 (421.83), Calcd.: C, 62.64; H, 3.82; N,
9.96; Found: C, 62.56; H, 3.79; N, 10.04. 1H NMR
(DMSO-d6): d 7.34–8.20 (m, 12H, Ar–H), d 8.44 (s, 1H,
N=CH), d 9.95 (s, 1H, CONH, D2O exchangeable), d 10.55
(s, 1H, CONH–N, D2O exchangeable), d 11.00 (s, 1H,
COOH, D2O exchangeable). MS m/z (% Rel. Int.): 421
(6.63, M?).
2-((4-(2-(4-Methoxybenzylidene)hydrazinecarbonyl)
phenyl)carbamoyl)-benzoic acid (8c)
Yellow crystals, mp 237–39ꢁC, yield 79%. Analysis for
C23H19N3O5 (417.41), Calcd.: C, 66.18; H, 4.59; N, 10.07;
Found: C, 66.25; H, 4.47; N, 9.96. 1H NMR (DMSO-d6): d
3.79 (s, 3H, OCH3) d 6.95–8.20 (m, 12H, Ar–H), d 8.43 (s,
1H, N=CH), d 9.99 (s, 1H, CONH, D2O exchangeable), d
10.57 (s, 1H, CONH–N, D2O exchangeable), d 11.00 (s,
1H, COOH, D2O exchangeable). MS m/z (% Rel. Int.): 417
(8.78, M?).
2-((4-(Hydrazinecarbonyl)phenyl)carbamoyl)benzoic
acid (7)
A mixture of 6 (3.13 g, 10 mmol) and hydrazine hydrate
(5 g, 99%) in ethyl alcohol (50 ml, 95%) was heated under
reflux for 8 h. The formed precipitate was collected by
filtration, washed with ethanol, dried, and crystallized from
isopropyl alcohol. White crystals, mp 246–248ꢁC, yield
68%. Analysis for C15H13N3O4 (299.28), Calcd.: C, 60.20;
Phenylethylidenehydrazinecarbonyl derivatives 9a, b
1
H, 4.38; N, 14.04; Found: C, 60.03; H, 4.51; N, 13.78. H
NMR (DMSO-d6): d 7.65–8.20 (m, 8H, Ar–H), d 8.96 (s,
1H, CONHNH2, D2O exchangeable), d 9.92 (s, 1H,
CONHC6H4–, D2O exchangeable), d 11.00 (s, 1H, COOH,
D2O exchangeable). NH2 protons seemed to be exchanged
by the solvent. MS m/z (% Rel. Int.): 299 (13.40, M?).
A mixture of 7 (0.60 g, 2 mmol) and acetophenone (0.24 g,
2 mmol) or 1 (0.57 g, 2 mmol) in acetic acid (20 ml, 96%)
was refluxed for 5 h and allowed to cool to room temper-
ature. The precipitated solid was filtered, dried, and re-
crystallized from glacial acetic acid to afford pure
products.
(Un)substituted benzylidenehydrazinecarbonyl
derivatives 8a–c
2-((4-(2-(1-Phenylethylidene)hydrazinecarbonyl)phenyl)
carbamoyl)benzoic acid (9a)
A mixture of 7 (0.60 g, 2 mmol) and the appropriate aro-
matic aldehyde (2 mmol) in absolute ethanol (30 ml) was
refluxed for 5 h and allowed to cool to room temperature.
The formed crystalline product was separated by filtration,
dried, and recrystallized from ethanol:acetone (1:1) to
afford pure products.
Orange crystals, mp 272–74ꢁC, yield 67%. Analysis for
C23H19N3O4 (401.41), Calcd.: C, 68.82; H, 4.77; N, 10.47;
1
Found: C, 68.86; H, 4.70; N, 10.54. H NMR (DMSO-d6):
d 2.54 (s, 3H, CH3), d 7.34–8.21 (m, 13H, Ar–H), d 9.86 (s,
1H, CONH, D2O exchangeable), d 10.16 (s, 1H, CONH–N,
D2O exchangeable), d 11.00 (s, 1H, COOH, D2O
exchangeable). MS m/z (% Rel. Int.): 401 (11.98, M?).
2-((4-(2-Benzylidenehydrazinecarbonyl)phenyl)
carbamoyl)benzoic acid (8a)
2-((4-(1-(2-(4-(2-Carboxybenzamido)benzoyl)hydrazono)
ethyl)phenyl)-carbamoyl)benzoic acid (9b)
Yellow crystals, mp 223–25ꢁC, yield 73%. Analysis for
C22H17N3O4 (387.39), Calcd.: C, 68.21; H, 4.42; N, 10.85;
1
Found: C, 68.34; H, 4.56; N, 10.77. H NMR (DMSO-d6):
Orange crystals, mp [300ꢁC, yield 45%. Analysis for
C31H24N4O7 (564.54), Calcd.: C, 65.95; H, 4.28; N, 9.92;
Found: C, 65.91; H, 4.33; N, 9.98. 1H NMR (DMSO-d6): d
2.59 (s, 3H, CH3), d 7.57–8.24 (m, 16H, Ar–H), d 9.86 and
d 10.10 (s, 2H, two CONH, D2O exchangeable), d 10.84 (s,
1H, CONH–N, D2O exchangeable), d 11.00 (s, 2H, two
d 7.32–8.20 (m, 13H, Ar–H), d 8.44 (s, 1H, N=CH), d 9.95
(s, 1H, CONH, D2O exchangeable), d 10.55 (s, 1H,
CONH–N, D2O exchangeable), d 11.00 (s, 1H, COOH,
D2O exchangeable). MS m/z (% Rel. Int.): 387 (18.23,
M?).
123

Med Chem Res (2012) 21:1633–1640
1639
COOH, D2O exchangeable). MS m/z (% Rel. Int.): 564
(2.56, M?).
Conclusion
It was observed that compound 7, carrying the acid
hydrazide moiety, showed moderate antioxidant activity
(55.21% inhibition), in comparison to L-ascorbic acid. The
rest of the tested compounds showed low antioxidant
activity.
2-((4-((1,3-Dioxoisoindolin-2-yl)carbamoyl)phenyl)
carbamoyl)benzoic acid (10)
A mixture of 7 (0.60 g, 2 mmol), phthalic acid anhydride
(0.30 g, 2 mmol), and catalytic amount of sodium acetate
(0.1 g) in glacial acetic acid (20 ml) was refluxed for 5 h
and allowed to cool to room temperature. The precipitated
solid was filtered, dried, and recrystallized from glacial
acetic acid to afford pure product. Orange crystals, mp
228–230ꢁC, yield 72%. Analysis for C23H15N3O6 (429.38),
Calcd.: C, 64.34; H, 3.52; N, 9.79; Found: C, 64.53; H,
3.46; N, 9.83. 1H NMR (DMSO-d6): d 7.62–8.17 (m, 12H,
Ar–H), d 8.82 (s, 1H, CONH–N, D2O exchangeable), d
10.02 (s, 1H, CONH, D2O exchangeable), d 11.96 (s, 1H,
COOH, D2O exchangeable). MS m/z (% Rel. Int.): 429
(8.45, M?).
Acknowledgments The authors are grateful to Dr. Hany N. Baraka,
Department of Pharmacognosy, Faculty of Pharmacy, Mansoura
University, for carrying out the antioxidant assay.
References
Angelo QM, George KB, Cezar SG, Ricardo GO, Antonio A, Marcelo
H-L (2003) Pyridoxal isonicotinoyl hydrazone inhibits iron-
induced ascorbate oxidation and ascorbyl radical formation.
Biochim Biophys Acta 1620(1–3):15–24
Argade NP, Balasubramaniyan V (2000) Ring closure reactions
of suitably ortho-substituted maleanilic acids: an avenue for
heterocycles. Heterocycles 53(2):475–488. doi:10.3987/REV-
99-525
ABTS antioxidant assay
Aruoma OI (1998) Free radicals, oxidative stress, and antioxidants in
human health and disease. JAOCS 75(2):199–212. doi:10.1007/
s11746-998-0032-9
Preparation of reagents
Bai R, Ma F, Liang D, Zhao X (2009) Phthalic acid induces oxidative
stress and alters the activity of some antioxidant enzymes in
roots of Malus prunifolia. J Chem Ecol 35(4):488–494. doi:
10.1007/s10886-009-9615-7
Chen A, Taguchi T, Aoyama S, Sugiura M, Haruna M, Wang M,
Miwa I (2003) Antioxidant activity of a Sciff base of pyridoxal
and aminoguanidine. Free Radic Biol Med 35(11):1392–1403.
doi:10.1016/j.freeradbiomed.2003.08.014
Dolzhenko AV, Kolotova NV, Kozminykh VO, Syropyatov BY,
Kotegov VP, Godina AT (2002) Hypoglycemic effect of several
substituted amides and acylhydrazides of succinic acid. Phar-
mazie 57(11):776–778
Dolzhenko AV, Koz’minykh VO, Kolotova NV, Burdi NZ, Kotegov
VP, Novoselova GN, Syropyatov BY (2003) Substituted amides
and hydrazides of dicarboxylic acids. Part 17. Synthesis and
antibacterial and anticonvulsant activity of some amides and
acylhydrazides of phthalic acid. Pharm Chem J 37(7):342–344.
doi:10.1023/A:1026307221989
ABTS solution was prepared as 0.1 g/100 ml. MnO2
solution 25 mg/ml was used instead of potassium persul-
fate. All reagents were prepared in phosphate buffer (pH 7,
0.1 M). The two reagents ABTS/MnO2 (2:3) were mixed
and centrifuged. The supernatant was obtained as green–
blue solution (ABTS•? radical solution). This color
remained stable more than 1 h. The absorbance was
adjusted at ca., 0.2 at 734 nm. L-Ascorbic acid solution was
prepared as 2% solution: 1 g/50 ml distilled water. Each
test sample was used in concentration of 0.01 mg/ml in
methanol/phosphate buffer (1:1).
Starting assay
900 ll of (ABTS/MnO2) was added to cuvette of spectro-
photometer (SPEKOL 11), and the absorbance was mea-
sured at 734 nm, against a blank, made of methanol/
phosphate buffer (1:1).
Feuer H, Asunskis JP (1962) The chemistry of cyclic hydrazides.
VIII. The preparation of substituted N-aminomaleimides and
their conversion to N-substituted maleic hydrazides. J Org Chem
27(12):4684–4686. doi:10.1021/jo01059a530
ˆ
Filho VC, Campos F, Correa R (2003) Chemical aspects and
900 ll of (ABTS/MnO2) mixture was added to 100 ll
standard L-ascorbic acid, and the absorbance was measured
against blank: methanol/phosphate buffer (1:1) ? 100 ll
of L-Ascorbic acid.
therapeutic potential of cyclic imides: a review. Quim Nova
26(2):230–241
Guo Z, Xing R, Liu S, Yu H, Wang P, Li C, Li P (2005) The synthesis
and antioxidant activity of the Schiff bases of chitosan and
carboxymethyl chitosan. Bioorg Med Chem Lett 15(20):4600–
4603. doi:10.1016/j.bmcl.2005.06.095
900 ll of (ABTS/MnO2) mixture was added to 100 ll of
sample, and the absorbance was measured against blank:
methanol/phosphate buffer (1:1) ? 100 ll of sample).
% Inhibition of absorbance for each of the tested
compound was calculated from the following equation:
% Inhibiton = [Abs(control) - Abs(test)]/Abs(control).
¨
Gu¨rkok G, Coban T, Suzen S (2009) Melatonin analogue new indole
hydrazide/hydrazone derivatives with antioxidant behavior:
synthesis and structure-activity relationships. J Inhib Med Chem
24(2):506–515. doi:10.1080/14756360802218516
Knight JA (1998) Free radicals: their history and current status in
aging and disease. Ann Clin Lab Sci 28(6):331–346
123

1640
Med Chem Res (2012) 21:1633–1640
Koz’minykh VO (2006) Synthesis and biological activity of substi-
tuted amides and hydrazides of 1,4-dicarboxylic acids. Pharm
Chem J 40(1):8–17. doi:10.1007/s11094-006-0048-0
LangeJ,RumpS,IlczukI,LapszewiczJ,RabsztynT,WalczynaK(1979)
Synthesis and properties of cyclic derivatives of succinic acid with
anticonvulsant activity Part 3. Pharmazie 34(12):794–795
Mates JM, Perez-Gomez C, Nunez de Castro I (1999) Antioxidant
enzymes and human diseases. Clin Biochem 32(8):595–603
Miller NJ, Rice-Evans C (1997) Factors influencing the antioxidant
activity determined by the ABTS? radical cation assay. Free
Rradic Res 26:195–199. doi:10.3109/10715769709097799
Re N, Pellegrini A, Proteggente A, Pannala MY, Evans CR (1999)
Antioxidant activity applying an improved ABTS radical cation
decolorization assay. Free Radical Biol Med 29:1231–1237. doi:
10.1016/S0891-5849(98)00315-3
Shankar RA, Hideg K, Zweier JL, Kuppusamy P (2000) Targeted anti-
oxidant properties of N-[(tetramethyl-3-pyrroline-3-carboxamido)
propyl]phthalimide and its nitroxide metabolite in preventing
postischemic myocardial injury. J Pharmacol Exp Ther 292(3):
838–845
Vukovic N, Sukdolak S, Solujic S, Niciforovic N (2010) An efficient
synthesis and antioxidant properties of novel imino and amino
derivatives of 4-hydroxy coumarins. Arch Pharm Res 33(1):5–15.
doi:10.1007/s12272-010-2220-z
123