Synthesis, biological evaluation of 2,3-disubstituted-imidazolyl/benzimidazolyl-quinazolin-4(3H)-one derivatives

Article abstract of DOI:10.1007/s00044-016-1552-8

A series of disubstituted-quinazolin-4(3H)-ones derivatives have been synthesized and confirmed through IR, ¹H- and ¹³C-NMR, MS spectroscopy and elemental analysis. Synthesized compounds were screened for in vitro and in vivo anti-inflammatory using human red blood cell membrane stabilization method and carrageenan-induced rat paw edema. The antimicrobial potency was measured by disk diffusion method. The compounds with imidazole (3g) and benzimidazole nucleus (4b and 4f) displayed a significant anti-inflammatory activity by in vitro method. Moreover, the compounds 3d and 4a exhibited a significant anti-inflammatory activity in vivo. The compounds 3d, 3f and 4g were found to be active antimicrobial agents, when compared with reference drug ciprofloxacin and amphotericin B. Thus, these compounds can serve as promising leads for further biological studies.

Full text of DOI:10.1007/s00044-016-1552-8

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2016) 25:1125–1139
DOI 10.1007/s00044-016-1552-8
ORIGINAL RESEARCH
Synthesis, biological evaluation of 2,3-disubstituted-
imidazolyl/benzimidazolyl-quinazolin-4(3H)-one derivatives
Dilip A. Patil1
Sanjay J. Surana2
•
Received: 6 September 2014 / Accepted: 3 March 2016 / Published online: 19 March 2016
Ó Springer Science+Business Media New York 2016
Abstract A series of disubstituted-quinazolin-4(3H)-ones
derivatives have been synthesized and confirmed through
Introduction
1
IR, H- and 13C-NMR, MS spectroscopy and elemental
Pain and inflammation are very commonly associated with
numerous pathological conditions commonly prescribed
with nonsteroidal anti-inflammatory drugs (NSAIDs). Most
of the NSAIDs that are available in the market are known
to inhibit isoforms of the enzyme cyclo-oxygenase (COX),
a constitutive form, COX-1, and an inducible form, COX-
2, to elicit therapeutic effect. There is continuous devel-
opment of new drugs that have potent anti-inflammatory
activity, with minimum side effects and high safety margin
(Nathan and Ding, 2010). The design of effective agents
that have fast action and provide relief from pain and
inflammation is a major challenge for medicinal chemists.
The quinazolin-4-one ring system has been consistently
considered a promising molecule because of its broad-spec-
trum pharmacological activities, such as antitubercular
(Pattan et al., 2006), antibacterial (Gangwal et al., 2001),
antifungal (Bartroli et al., 1998; Priya et al., 2011; Al-Amiery
et al., 2014; Gali et al., 2014), anticancer (Jiang et al., 1990),
anti-HIV (Alagarsamy et al., 2004), anti-inflammatory (Chao
et al., 1999; Belligno and Amico-Roxas, 1972; Hunoor et al.,
2010; Zayed and Hassan, 2014; Zayed et al., 2015). The
choice of quinazolinone heterocycle as a central core was
fundamental due to its presence in the potent anti-inflam-
matory natural alkaloid rutaecarpine and tryptanthrin. Imi-
dazoles are among the oldest and most potent heterocyclic
compounds having antimicrobial activities (Martinez-Suarez
and Rodriguez-Tudela, 1995). Several studies have been
conducted on imidazoles for their antimicrobial activities
(Raghavendra et al., 2007), antitumor action (Raghavendra
et al., 2009) and anti-inflammatory activity (Soni et al., 2011;
Kuelzer et al., 2012; Fitzi et al., 1974).
analysis. Synthesized compounds were screened for in vitro
and in vivo anti-inflammatory using human red blood cell
membrane stabilization method and carrageenan-induced rat
paw edema. The antimicrobial potency was measured by
disk diffusion method. The compounds with imidazole (3g)
and benzimidazole nucleus (4b and 4f) displayed a signifi-
cant anti-inflammatory activity by in vitro method. More-
over, the compounds 3d and 4a exhibited a significant anti-
inflammatory activity in vivo. The compounds 3d, 3f and 4g
were found to be active antimicrobial agents, when com-
pared with reference drug ciprofloxacin and amphotericin B.
Thus, these compounds can serve as promising leads for
further biological studies.
Keywords Quinazolin-4(3H)-ones Á Anti-inflammatory Á
Antibacterial Á Antifungal
& Dilip A. Patil
dilipapatil@gmail.com
Sanjay J. Surana
sjsurana@yahoo.com
1
H. R. Patel Institute of Pharmaceutical Education
and Research, Karwand Naka, Dist-Dhule, Shirpur,
Maharashtra 425 405, India
2
R. C. Patel Institute of Pharmaceutical Education
and Research, Karwand Naka, Dist-Dhule, Shirpur,
Maharashtra 425 405, India
The synthesis of imidazole is of great interest because
the ring system is present in numerous compounds of
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Med Chem Res (2016) 25:1125–1139
therapeutic importance, e.g., bifonazole, etomidate,
econazole, butoconazole and tolazoline (Fig. 1). The ben-
zimidazole nucleus is present in drugs like emedastine,
astemizole and thiabendazole. The quinazolinone nucleus
is present in numerous compounds of biochemical impor-
tance, e.g., metolazone, gefitinib, doxazosin, raltitrexed,
diproqualone.
inflammatory and antimicrobial agent with reduced adverse
effects (Fig. 2). We report herein the 6,8-disubstituted-3-
[3-(1H-imidazol-1-yl)propyl]-2-methyl/phenyl-quinazolin-
4(3H)-ones and there in vitro and in vivo anti-inflammatory
and in vitro antimicrobial activities.
Drugs that serve dual anti-inflammatory, antimicrobial
functions will have greater potential than multidrugs regi-
men to treat inflammatory conditions that might be asso-
ciated with microbial infections, especially in patients with
impaired liver or kidney functions.
Materials and methods
All the chemicals and solvents used were purchased from
Sigma-Aldrich and other commercial suppliers. Melting
points were determined in open capillaries using digital
melting point apparatus (PEW). All the reactions were
monitored using aluminum-supported pre-coated thin-layer
chromatography (TLC) 60 F254 silica plates (Merck) and a
benzene/ethyl acetate solvent system. The spots were
The quinazolin-4-one and imidazole pharmacophores
have been selected so as to confer different substitution and
electronic environment that would affect the lipophilicity
and hence the activity of the target molecules.
1
The literature survey revealed that the presence of
quinazoline moiety, which can undergo substitution at the
heteroatom or the aromatic ring, is a necessary requirement
for the antibacterial and anti-inflammatory activities
(Mohamed et al., 2010; Grover and Kini, 2006). Moreover,
the diary heterocycles template was considered as a typical
model to inhibit COX-2 enzyme selectively (Palomer et al.,
2002). Quinazoline derivatives with either halogen- or
electron-rich substituent at 6th or 8th position are known to
promote activity against bacteria and inflammation (Tiwari
et al., 2006).
visualized using an ultraviolet (UV) lamp (254 nm). H
and 13C nuclear magnetic resonance (NMR) spectra were
recorded on a Bruker Avance III 500 MHz (AV 500)
instrument using DMSO-d6 or CD3OD as the solvent and
TMS as an internal standard. Mass spectra were recorded
on a JEOL GCMATE II GC–MS instrument with electron
impact as the source. Fourier transform infrared (FTIR)
spectra were recorded on a Shimadzu IRAffinity-1, with IR
solution FTIR control software, using KBr. Elemental
analysis was performed on an Elementar Vario EL III CHN
analyzer.
We were interested in preparing new quinazolinone
compounds bearing imidazole or benzimidazole moieties.
Molecular hybridization strategy (Viegas-Junior et al.,
2007) facilitates to achieve the objectives of forming tar-
geted compounds 3a–h and 4a–h as an active anti-
Chemistry
Compounds 3a–h and 4a–h were synthesized as depicted
in Scheme 1. The intermediates were prepared from
Fig. 1 Marketed drugs containing moieties, viz., imidazole (structures I–III), benzimidazole (structure IV) and quinazolinone (structures V–VII)
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Med Chem Res (2016) 25:1125–1139
1127
Fig. 2 Rational design of the
target quinazolinone derivatives
anthranilic acid or appropriately substituted anthranilic
acids (Bogert et al., 1907; Atkinson and Lufkin, 1963). The
reactions of the substituted anthranilic acids with refluxing
acetic anhydride yielded 6,8-substituted-2-methyl-4H-3,1-
benzoxazin-4-ones (2a–e) and those with benzoyl chloride
in dry pyridine gave 6,8-substituted-2-phenyl-4H-3,1-ben-
zoxazin-4-ones (2f–h). The subsequent reactions of 2a–h
with appropriate 2-aminoimidazoles or 2-aminobenzimi-
dazoles, in refluxing glacial acetic acid in the presence of
sodium acetate or in refluxing dry pyridine, yielded the
target compounds, i.e., 6,8-substituted-3-[3-(1H-imidazol-
1-yl)propyl]-2-methyl/phenyl-quinazolin-4(3H)-one (3a–
h) and 6,8-substituted-3-(1H-benzimidazol-2-yl)-2-methyl/
phenyl-quinazolin-4(3H)-one (4a–h). The yields, melting
points and molecular formula and molecular weight of the
synthesized compounds are listed in Table 1. The struc-
tures of the synthesized compounds were confirmed
through analytical and spectroscopic measurements.
The anthranilic acid reacts in pyridine solution with an
excess of benzoyl chloride to give 2-phenyl-4H-3,l-ben-
zoxazin-4-one (I; R = Ph) in high yield (Smalley et al.,
1966). The benzoyl chloride (2 mol) reacted with anthranilic
acid (1 mol) in pyridine solution to give (I; R = Ph) in
90–95 % yield. The excess of benzoyl chloride was involved
in the formation of the benzoxazinone. The aromatic acid
anhydrides can be prepared by treating an aqueous solution
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Med Chem Res (2016) 25:1125–1139
Scheme 1 Synthetic routes to compounds 3a–h and 4a–h
Table 1 Synthesis of 2,3-disubstituted-imidazolyl/benzimidazolyl-quinazolin-4(3H)-one (3a-h and 4a–h)
Comp
X1
X2
R
Mol. formula
Mol. wt.
m.p. (°C)
Yield (%)
3a
3b
3c
3d
3e
3f
H
H
CH3
CH3
CH3
Ph
C15H16N4O
268.3
426.1
337.2
330.3
490.1
401.2
313.3
394.2
276.2
434.0
345.1
338.3
496.1
407.2
321.2
402.1
213–215
278–279
281–283
223–224
256–257
245–246
221–222
267–268
238–239
268–269
279–281
211–212
264–265
268–269
216–218
198–199
67
54
63
75
47
44
52
53
67
63
66
62
74
68
78
69
Br
Cl
H
Br
Cl
H
C15H14Br2N4O
C15H14Cl2N4O
C
C
C
20H18N4O
Br
Cl
NO2
I
Br
Cl
H
Ph
20H18Br2N4O
20H18Cl2N4O
Ph
3g
3h
4a
4b
4c
4d
4e
4f
CH3
CH3
CH3
CH3
CH3
Ph
C15H15N5O3
C15H15IN4O
C16H12N4O
H
H
H
Br
Cl
H
Br
Cl
H
C16H10Br2N4O
C16H10Cl2N4O
C
C
C
21H14N4O
Br
Cl
NO2
I
Br
Cl
H
Ph
21H12Br2N4O
21H12Cl2N4O
Ph
4g
4h
CH3
CH3
C16H11N5O3
C16H11IN4O
H
of the sodium salt of an acid, with a molar proportion of acyl
halide in the presence of a catalytic amount of pyridine. The
reaction may, therefore, be considered as an intramolecular
nucleophilic displacement of benzoate ion from the
anhydride group by the carbonyl oxygen of the neighboring
amide function (Scheme 2, reaction A). Cyclization is pre-
sumably facilitated by a 1,6-interaction between the reacting
groups. Similarly, the reaction of acetic anhydride with
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Med Chem Res (2016) 25:1125–1139
1129
anthranilic acid gives the methyl benzoxazinone, probably
by displacement of hydroxyl ion from the carboxylic group
by the carbonyl oxygen of the neighboring amide function
(Scheme 2, reaction B).
Benzoxazinones were condensed with heterocyclic rings
to give compounds 3a–h and 4a–h. The probable mecha-
nism of the reaction involves, first the ring opening of
substituted-4H-3,1-benzoxazin4-one by the attack of
2-amino-heterocycle. This is the ring-opening step, fol-
lowed by the removal of water molecule to close the ring,
forming the title compounds (Scheme 3). The reactions of
benzoxazinones with simple primary amines such as thia-
zole and propyl-imidazole occur rapidly and follow path-
way A, whereas reactions with secondary amines and bulky
primary amines (benzimidazole and thiadiazole) occur
slowly and follow pathway B.
The reactions of 6,8-dibromo-2-methyl-3,l-benzoxazin-
4-one with primary amines RNH2 lead to slow formation of
the corresponding stable 2-acetamidobenzamides, and then,
cyclodehydration gives quinazolinones. The electronic and
steric effects associated with the substituent R at the
2-position and also the steric hindrance on the part of the
co-reactant amine are the significant factors that determine
selectivity via either pathways. The pathway A to pathway
B as well as the rate of conversion to products decreases
with increase in the bulk of R group (Laddha et al., 2006).
Scheme 3 Plausible mechanism for synthesis of substituted-
quinazolinones
hydroxide (0.61 mol). Glacial acetic acid (100 mL) was
added to this solution, and the reaction mixture was
immediately diluted with water (120 mL). The solid that
separated was filtered, washed with sodium bisulfate
(25 mL) and purified by recrystallization from a mixture of
methanol/water. Yield, 86 %; m.p., 210 °C.
Synthesis of 6,8-substituted-2-methyl-4H-3,1-benzoxazin-4-
2-Amino-5-iodobenzoic acid (1e)
one (2a–d)
The compound was prepared according to the method
described by Klemme (1940). A solution of anthranilic acid
(0.10 mol) in water (500 mL) containing potassium
hydroxide flakes (0.25 mol) was added to a solution of
iodine (0.18 mol) in water (250 mL) having potassium
The appropriate anthranilic acid (0.05 mol) was refluxed
with acetic anhydride (0.20 mol) for 1 h. The excess acetic
anhydride was distilled away under reduced pressure. The
products (6,8-disubstituted-2-methyl-4H-3,1-benzoxazin-4-
one) were separated and used without further purification.
Scheme 2 Plausible
mechanism for synthesis of 4H-
3,1-benzoxazinones
A
B
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Med Chem Res (2016) 25:1125–1139
6-Iodo-2-methyl-4H-3,1-benzoxazin-4-one (2e)
benzimidazole) (0.01 mol) in glacial acetic acid (40 mL),
and the reaction mixture was refluxed for 2–3 h. After the
completion of the reaction, the solvent was removed by
distillation under reduced pressure, and the residue washed
with water, filtered and recrystallized from suitable sol-
vents, gives up the target compounds, 6,8-disubstituted-3-
(1H-benzimidazol-2-yl)-2-methyl/phenyl-quinazolin-4(3H)-
ones (4a–h).
Benzoxazinone was synthesized using the procedure
described by Bogert et al., (1907). A mixture of anthranilic
acid (1e) (0.01 mol) and acetic anhydride (0.02 mol) was
refluxed for 1–2 h. The mixture was cooled. The residue
left behind after evaporation was washed with water and
recrystallized from ethanol, yielding the compound 2e.
Yield, 78 %; m.p., 155 °C.
Pharmacology
Synthesis of 6,8-disubstituted-2-phenyl-4H-3,1-benzoxazin-
The synthesized compounds were tested for in vitro and
in vivo anti-inflammatory activity and for antibacterial as
well as antifungal activity. Wistar rats of either sex,
excluding pregnant females, weighing 175–225 g of
70–95 days were used in these experiments. The acute
toxicity of the compounds was tested on albino mice
(15–25 g). The animals were maintained in colony cages at
25 2 °C and a relative humidity of 45–55 % under a
12-h light–dark cycle. Food (chaw pallets) and water were
provided to the animals ad libitum. All the compounds and
standard drugs were administered orally by gavage as
suspensions in 1 % carboxymethyl cellulose (CMC) pre-
pared in distilled water. The protocol for the experiments
with the animals was approved by the institutional animal
ethics committee (RCPIPER/IAEC/1/2011–2012).
4-one (2f–h)
A solution of the appropriate anthranilic acid (0.10 mol) in
dry pyridine (10 mL) was added dropwise to a solution of
benzoyl chloride (0.15 mol) in dry pyridine (10 mL) at a
temperature below 5 °C over a period of 20 min with
stirring. After the addition was completed, the mixture was
stirred for another 3 h at room temperature. After the
completion of the reaction, the mixture was poured into
crushed ice (150 g). The solid that separated (6,8-disub-
stituted-2-phenyl-4H-3,1-benzoxazin-4-one) was filtered,
washed with water, dried and recrystallized using
suitable solvents.
General procedure for synthesis of 6,8-disubstituted-3-[3-
(1H-imidazol-1-yl)propyl]-2-methyl/phenyl-quinazolin-
4(3H)-ones (3a–h)
In vitro anti-inflammatory activity
The lysosomal enzymes released during inflammation
produce a variety of disorders. This extracellular activity of
these enzymes is related to acute or chronic inflammation.
Since human red blood cell membranes are similar to
lysosomal membrane components, the prevention of
hypotonicity-induced HRBC membrane lysis was taken as
a measure of the anti-inflammatory activity of a drug.
HRBC membrane stabilization has been used to study anti-
inflammatory activity using prednisolone as standard drug
(Gandhidasan et al., 1991).
The fresh benzoxazin-4-one (0.01 mol) and sodium acetate
(0.01 mol) were added to a solution of 3-(1H-imidazol-1-
yl)-propan-1-amine (0.01 mol) in glacial acetic acid
(40 mL), and the reaction mixture was refluxed for 2–3 h.
Few reactions like 3 and 4 h were conducted using dry
pyridine. After the completion of the reaction, the solvent
was removed by distillation under reduced pressure, and
the residue was washed with water, filtered and recrystal-
lized from suitable solvents, yielding the target com-
pounds, 6,8-disubstituted-3-[3-(1H-imidazol-1-yl)-propyl]-
2-methyl/phenyl-quinazolin-4(3H)-ones (3a–h). Few com-
pounds like 3a, 3d, 3h, 4a, 4b and 4f were also synthesized
using a microwave (MW) synthesizer (Discover LabMate,
CEM, USA) with the reactants in the same ratio as that of
conventional route.
Blood samples were withdrawn from healthy volunteers
and were mixed with equal volumes of sterilized Alsever’s
solution (2 % dextrose, 0.8 % sodium citrate, 0.05 % citric
acid and 0.42 % sodium chloride). The mixtures were
centrifuged at 2500 rpm, and the packed cells were washed
with an isotonic sodium chloride solution (0.9 %, pH 7.2),
and a 10 % v/v suspension of the packed cells was pre-
pared in an isotonic sodium chloride solution.
General procedure for synthesis of 6,8-disubstituted-3-
(1H-benzimidazol-2-yl)-2-methyl/phenyl-quinazolin-4(3H)-
ones (4a–h)
Each assay mixture contained a 1 mL solution of
synthesized compounds and prednisolone (0.2, 0.4, 0.8
and 1.6 lM/mL), 1 mL of phosphate buffer (0.15 M, pH
7.2), 2 mL of hypotonic sodium chloride solution
(0.36 %) and 0.5 mL of HRBC suspension. In the control,
The fresh benzoxazin-4-one (0.01 mol) and sodium acetate
(0.01 mol) were added to a solution of 2-amino-(1H-
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Med Chem Res (2016) 25:1125–1139
1131
Bactericidal bioassay
2 mL of distilled water was used instead of the hypotonic
sodium chloride solution. All the assay mixtures were
incubated at 37 °C for 30 min and centrifuged at
3000 rpm. The hemoglobin content in the supernatant
solution was estimated using a UV–visible spectropho-
tometer (Shimadzu UV-1700) at 500 nm or 560 nm. The
percentage hemolysis was calculated assuming the
hemolysis produced in the presence of distilled water as
100 % using the formula:
The antibacterial activity of the synthesized compounds
was performed by the disk diffusion method and MIC by
twofold serial dilution method against few strains of Gram-
positive bacteria: Staphylococcus aureus ATCC 29213 and
Gram-negative bacteria: Escherichia coli ATCC 10536,
Pseudomonas aeruginosa ATCC 27853, Klebsiella pneu-
monia ATCC 31488.
The broth cultures of different bacterial strains were
swabbed on sterile Mueller–Hinton agar plates using sterile
swabs. The test compounds incorporated disks were placed
on the medium by help of sterile forceps, and the plates
were incubated at 37 °C overnight. Sterile disks (6 mm
diameter; HiMedia) were used for impregnating the test
compounds, and ciprofloxacin (CIP 5, HiMedia) disks
having 5 lg/disk of ciprofloxacin were used as standard. In
each experiment, test solutions were tested in duplicate.
The minimum inhibitory concentration by twofold serial
dilution method using nutrient broth of double strength was
determined.
Activity ð% prevention of lysisÞ
100 À OD of drug À treated sample
¼
 100
OD of control
In vivo anti-inflammatory activity
The anti-inflammatory activity was assessed using the
carrageenan-induced rat paw edema method (Winter et al.,
1963). The rats were divided into three groups (control,
drug-treated and standard drug-treated (reference control)),
each consisting of four animals, and 1 % CMC (control)
was administered orally. A standard drug (diclofenac
10 mg/kg) and the test compounds were administered at
doses of 20 mg/kg (on the basis of body weight of animals)
based on the basis of the literature (Achar et al., 2010;
Sondhi et al., 2002). The rats were challenged by a
0.05 mL solution of carrageenan (1 in 0.9 % saline)
injected subcutaneously into the plantar aponeurosis of the
left hind paw. The paw volume was measured using the
water displacement technique, using a plethysmometer
(Ugo-Basile, Italy). The paw volumes of the animals in the
three groups were measured 1, 2 and 3 h after carrageenan
treatment. The difference between the mean paw volume of
the control group and that of the standard drug-treated
group was considered 100 %. The difference between the
mean paw volume of the control group and that of each test
compound-treated group was expressed with reference to
the standard drug, and the percentage inhibition was cal-
culated. The percent anti-inflammatory activity was cal-
culated according to the formula
Antifungal activity
The in vitro antifungal activity of the synthesized com-
pounds was evaluated against Candida albicans ATCC
20408, Aspergillus niger ATCC 20266, Candida guillier-
mondii ATCC 20318 and Aspergillus flavus ATCC 20047
using the agar dilution method, with Sabouraud’s dextrose
agar (HiMedia). The fungi were inoculated onto Sabouraud
dextrose agar as in the disk diffusion method. The sterile
antibiotic disks were dipped in solution of test compounds
dimethylsulfoxide (DMSO). The disks containing test
compounds (100 lg) were placed on previously inoculated
plates and gently pressed. The plates were maintained for
15 min at 4 °C. Then, they were incubated at 37 °C for
48 h. Disks with DMSO absorbed in them were used for
the control. The area of the resulting inhibition zones on
the plates was measured in square millimeters. The data
reported are the averages of two experiments. The mini-
mum inhibitory concentration (MIC) was estimated using
the twofold serial dilution method.
1 À Vt
Percentage of inhibition of edema ¼
 100;
Vc
where Vt and Vc are the volumes of the edema in the right
paws of the rats in the drug-treated and control groups,
respectively.
Antimicrobial activity against multidrug-resistant strains
The synthesized compounds that were found to be potent in
the antimicrobial tests were further tested for their
antimicrobial potency against resistant strains of bacteria
and fungi, using disk diffusion on Mueller–Hinton agar and
Sabouraud dextrose agar, respectively. The microbial
strains used were S. aureus (ATCC 33592), P. aeroginosa
(ciprofloxacin resistant), C. albicans (ATCC MYA-574),
A. niger and A. flavus. The disks with the test compounds
Acute toxicity
Approximate lethal doses (ALD50) of representative
compounds were investigated by the method of Smith
(1960). For the compounds studied, the acute toxicity in
terms of ALD50 values was found to be [1000 mg/kg
when the drugs were administered by oral route.
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Med Chem Res (2016) 25:1125–1139
were placed on the medium using a pair of sterile forceps,
and the plates were incubated at 37 °C overnight. The disks
with DMSO were used as a negative control. The area of
the resulting inhibition zones on the plates was measured in
square millimeters.
quin, J = 1.5 Hz), 8.32 (d, 1H, quin, J = 1.5 Hz). 13C-
NMR (CD3OD) d: 24.7, 28.7, 41.5, 46.3, 112.8, 119.5,
122.8, 124.8, 128.6, 131.5, 135.4, 138.6, 148.3, 154.1,
162.7. EI-MS, m/z: 424.0. Anal. Calcd. for C15H14Br2N4O:
C, 42.28; H, 3.31; N, 13.15 %. Found: C, 42.19; H, 3.30;
N, 13.18 %.
Results and discussion
6,8-Dichloro-3-[3-(1H-imidazol-1-yl)propyl]-2-
methylquinazolin-4(3H)-one (3c)
The synthesis of the target compounds has been achieved
by adopting the synthetic route illustrated and outlined in
Scheme 1. The substituted benzoxazinones were appended
with the amino-heterocycles. The disappearance of C=O
stretching (cyclic lactone) of benzoxazinones around
1750–1720 cm-1 revealed the formation of corresponding
quinazolinone ring. The IR spectra of the quinazolinone
derivatives (3a–h and 4a–h) exhibited C=N stretching
vibration in the region of 1705–1600 cm-1 and C=O
stretching vibration (amide) in the region of 1693–
1644 cm-1. In the 1H NMR spectrum, protons of methyl at
2-position of quinazolinone ring exhibited singlet at
2.13–2.55 (d ppm) and the aromatic protons of phenyl rings
shown multiplets and doublets of doublets at 7.52–7.85 (d
ppm).
Yield, 63 %; m.p., 281–283 °C. IR (KBr, cm-1): 1675
(C=N), 1701 (C=O), 1567 (C=C), 708 (C–Cl), 3030 (arom.
CH str), 2916 (aliph. CH str). 1H-NMR (DMSO-d6) d: 2.55
(s, 3H, CH3), 2.68–2.74 (p, 2H, prop), 4.16–4.17 (t, 2H,
prop, J = 7.1 Hz), 4.23–4.25 (t, 2H, prop, J = 7.1 Hz),
6.71–6.75 (d, 1H, imid, J = 7.5 Hz), 7.17–7.18 (d, 1H,
imid, J = 7.5 Hz), 7.81 (d, 1H, quin, J = 0.4 Hz),
7.92–7.96 (t, 2H, imid 1, quin 1, J = 1.5, 0.4 Hz). 13C-
NMR (DMSO-d6) d: 24.3, 29.1, 41.1, 48.9, 120.8, 124.1,
126.8, 128.7, 129.2, 135.5, 135.6, 138.1, 153.5, 158.8,
162.3. EI-MS, m/z: 336.02. Anal. Calcd. for C15H14Cl2-
N4O: C, 53.43; H, 4.18; N, 16.62 %. Found: C, 53.39; H,
4.15; N, 16.58 %.
3-[3-(1H-imidazol-1-yl)propyl]-2-phenylquinazolin-4(3H)-
Analytical data of compounds
one (3d)
3-[3-(1H-imidazol-1-yl)propyl]-2-methylquinazolin-4(3H)-
Yield, 75 % (MW 79 %); m.p., 223–224 °C. IR (KBr,
one (3a)
cm-1): 1633 (C=N), 1668 (C=O), 1599 (C=C), 3050
1
(arom.CH str), 2925 (aliph. CH str). H-NMR (DMSO-d6)
Yield, 67 % (MW 78 %); m.p., 137–139 °C. IR (KBr,
d: 2.93–2.65 (p, 2H, prop), 4.06–4.09 (t, 2H, prop,
J = 7.1 Hz), 4.14–4.17 (t, 2H, prop, J = 7.1 Hz),
6.74–6.76 (d, 1H, imid, J = 7.5 Hz), 7.20–7.25 (d, 1H,
imid, J = 7.5 Hz), 7.53–7.56 (m, 3H, phen), 7.60–7.63 (m,
2H, quin), 7.73–7.76 (m, 1H, quin), 7.81–7.83 (dd, 2, phen,
J = 7.5, 1.5 Hz), 7.92 (s, 1H, imid), 8.03–8.04 (d, 1H,
quin, J = 7.5 Hz). 13C-NMR (DMSO-d6) d: 29.6, 40.8,
47.3, 119.4, 126.9, 127.5, 128.5, 131.8, 131.9, 134.5,
148.4, 157.2, 158.2. EI-MS, m/z: 330.2. Anal. Calcd. for
C20H18N4O: C, 72.71; H, 5.49; N, 16.96 %. Found: C,
72.61; H, 5.51; N, 16.98 %.
cm-1): 1693 (C=N), 1681 (C=O), 1573 (C=C), 3026
1
(arom.CH str), 2891 (aliph. CH str). H-NMR (CDCl3) d:
2.52 (s, 3H, CH3), 2.62–2.68 (p, 2H, prop), 4.03–4.12 (m,
4H, prop), 6.80–6.81 (d, 1H, imid, J = 7.5 Hz), 7.19 (d,
1H, imid, J = 7.5 Hz), 7.62–7.66 (m, 2H, quin), 7.73–7.78
(m, 1H, quin), 7.95 (s, 1H, imid), 8.09–8.10 (d, 1H, arom,
J = 7.5 Hz). 13C-NMR (CDCl3) d: 22.78, 29.74, 40.29,
47.01, 120.6, 120.8, 126.7, 127.3, 128.2, 133.5, 137.8,
146.8, 154.6, 161.3. EI-MS, m/z: 268.12. Anal. Calcd. for
C15H16N4O: C, 67.15; H, 6.01; N, 20.88 %. Found: C,
66.98; H, 6.02; N, 20.82 %. The data was in agreement
with the previous report (Strakovs et al., 2002).
6,8-Dibromo-3-[3-(1H-imidazol-1-yl)propyl]-2-
phenylquinazolin-4(3H)-one (3e)
6,8-Dibromo-3-[3-(1H-imidazol-1-yl)propyl]-2-
methylquinazolin-4(3H)-one (3b)
Yield, 47 %; m.p., 256–257 °C. IR (KBr, cm-1): (C=N),
(C=O), (arom. CH str), (aliph. CH str). H-NMR (DMSO-
1
Yield, 54 %; m.p., 278–279 °C. IR (KBr, cm-1): 1681
(C=N, 1644 (C=O), 1607 (C=C), 588 (C–Br), 3047 (arom.
d6) d: 2.66–2.71 (p, 2H, prop), 4.02–4.05 (t, 2H, prop,
J = 7.1 Hz), 4.10–4.13 (t, 2H, prop, J = 7.1 Hz),
6.65–6.66 (d, 1H, imid, J = 7.5 Hz), 7.14–7.15 (d, 1H,
imid, J = 7.5 Hz), 7.52–7.55 (m, 3H, phen), 7.83–7.85
(dd, 2H, phen, J = 7.5, 1.5 Hz), 7.94 (s, 1H, imid),
8.14–8.15 (d, 1H, quin, J = 1.5 Hz), 8.24–8.26 (d, 1H,
1
CH str), 2925 (aliph. CH str); H-NMR (CD3OD) d: 2.49
(s, 3H, CH3), 2.63–2.69 (p, 2H, prop), 4.09–4.18 (m, 4H,
prop), 6.75–6.78 (d, 1H, imid, J = 7.5 Hz), 7.22–7.23 (d,
1H, imid, J = 7.5 Hz), 7.98 (s, 1H, imid), 8.15 (d, 1H,
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Med Chem Res (2016) 25:1125–1139
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quin, J = 1.5 Hz). 13C-NMR (DMSO-d6) d: 28.8, 41.5,
46.9, 113.6, 120.6, 122.1, 124.7, 128.1, 128.2, 129.0,
130.4, 131.5, 137.3, 140.8, 155.2, 156.4, 161.2. EI-MS, m/
z: 487.8. Anal. Calcd. for C20H18Br2N4O: C, 49.00; H,
3.70; N, 11.42 %. Found: C, 49.08; H, 3.64; N, 11.49 %.
13C-NMR (CDCl3) d: 22.9, 30.0, 41.9, 44.5, 90.8, 118.5,
121.8, 128.6, 130.1, 135.4, 137.1, 143.1, 146.4, 154.1,
160.6. EI-MS, m/z: 394.0. Anal. Calcd. for C15H15IN4O: C,
45.70; H, 3.84; N, 14.21 %. Found: C, 45.73; H, 3.86; N,
14.23 %.
6,8-Dichloro-3-[3-(1H-imidazol-1-yl)propyl]-2-
3-(1H-benzimidazol-2-yl)-2-methylquinazolin-4(3H)-one
phenylquinazolin-4(3H)-one (3f)
(4a)
Yield, 44 %; m.p., 245–246 °C. IR (KBr, cm-1): 1589
(C=N), 1668 (C=O), 1557 (C=C), 752 (C–Cl), 3011 (arom.
CH str), 2957 (aliph. CH str). 1H-NMR (DMSO-d6) d:
2.70–2.75 (p, 2H, prop), 4.05–4.07 (t, 2H, prop,
J = 7.1 Hz), 4.13–4.16 (t, 2H, prop, J = 7.1 Hz),
6.79–6.80 (d, 1H, imid, J = 7.5 Hz), 7.23–7.49 (d, 1H,
imid, J = 7.5 Hz), 7.53–7.56 (m, 3H, phen), 7.83–7.86 (m,
3H, Phen 2, quin 1), 7.92 (s, 1H, imid), 7.94–7.96 (d, 1H,
quin, J = 1.5 Hz). 13C-NMR (DMSO-d6) d: 29.5, 41.4,
47.2, 120.2, 124.5, 125.6, 127.9, 128.7, 128.9, 129.5,
130.4, 134.9, 136.2, 138.1, 156.3, 159.5, 163.3. EI-MS, m/
z: 400.04. Anal. Calcd. for C20H18Cl2N4O: C, 59.86; H,
4.52; N, 13.96 %. Found: C, 60.01; H, 4.48; N, 14.05 %.
Yield, 67 % (MW 79 %); m.p., 238–239 °C. IR (KBr,
cm-1): 1693 (C=N), 1681 (C=O), 1573 (C=C), 3026
(arom. CH str), 2891 (aliph. CH str). 1H-NMR (CD3OD) d:
2.13 (s, 3H, CH3), 7.11–7.13 (q, 2H, benzim), 7.21–7.23 (q,
2H, benzim); 7.57–7.60 (m, 2H, quin), 7.72–7.75 (m, 1H,
quin), 8.05–8.07 (d, 1H, quin, J = 7.5 Hz). 13C-NMR
(CD3OD) d: 23.6, 115.1, 119.7, 123.7, 126.1, 126.5, 127.6,
133.8, 145.6, 148.9, 152.2, 161.6. EI-MS, m/z: 276.1. Anal.
Calcd. for C16H12N4O: C, 69.55; H, 4.38; N, 20.28 %.
Found: C, 69.59; H, 4.37; N, 20.29 %. The data was in
agreement with the previous report (Hazarkhani and Kar-
imi, 2003).
3-(1H-benzimidazol-2-yl)-6,8-dibromo-2-
3-[3-(1H-imidazol-1-yl)propyl]-2-methyl-6-
methylquinazolin-4(3H)-one (4b)
nitroquinazolin-4(3H)-one (3g)
Yield, 52 %; m.p., 221–222 °C. IR (KBr, cm-1): 1620
(C=N), 1672 (C=O), 1556 (C=C), 1517 and 1348 (C–NO2),
3080 (arom. CH str), 2922 (aliph. CH str). 1H-NMR
(CD3OD) d: 2.52 (s, 3H, CH3), 2.64–2.70 (p, 2H, prop),
4.02–4.04 (t, 2H, prop, J = 7.1 Hz), 4.10–4.11 (t, 2H,
prop, J = 7.1 Hz), 6.79–6.80 (d, 1H, imid, J = 7.5 Hz),
7.31 (d, 1H, imid, J = 7.5 Hz), 7.71 (d, 1H, quin,
J = 7.5 Hz), 7.89 (s, 1H, imid), 8.30–8.31 (dd, 1H, quin,
J = 7.5, 1.5 Hz), 8.58 (d, 1H, quin, J = 1.5 Hz). 13C-
NMR (CD3OD) d: 22.6, 27.5, 40.5, 45.4, 114.4, 117.5,
120.8, 124.2, 128.3, 128.6, 138.5, 143.7, 153.2, 154.2,
161.8. EI-MS, m/z: 313.0. Anal. Calcd. for C15H15N5O3: C,
57.50; H, 4.83; N, 22.35 %. Found: C, 57.54; H, 4.81; N,
22.38 %.
Yield, 63 % (MW 73 %), m.p., 268–269 °C. IR (KBr,
cm-1): 1643 (C=N quinazoline), 1702 (C=O), 1537 (C=C),
528 (C–Br), 3049 (arom. CH stretching), 2865 (aliph. CH
1
stretching). H-NMR (CD3OD) d: 2.19 (s, 3H, CH3), 5.14
(s, H, benzim), 7.11–7.13 (dd, 2H, benzim, J = 7.5,
1.5 Hz), 7.21–7.23 (dd, 2H, benzim, J = 7.5, 1.5 Hz),
8.17–8.18 (d, 1H, quin, J = 1.5 Hz), 8.27 (d, 1H, quin,
J = 1.5 Hz). 13C-NMR (CD3OD) d: 23.4, 113.8, 115.7,
121.8, 123.3, 125.1, 127.9, 131.7, 139.8, 149.5, 150.3,
152.9, 161.4. EI-MS, m/z: 431.8. Anal. Calcd. for C16
H10Br2N4O: C, 44.27; H, 2.32; N, 12.91 %. Found: C,
44.34; H, 2.31; N, 12.89 %.
3-(1H-benzimidazol-2-yl)-6,8-dichloro-2-
methylquinazolin-4(3H)-one (4c)
3-[3-(1H-imidazol-1-yl)propyl]-6-iodo-2-
methylquinazolin-4(3H)-one (3h)
Yield, 66 %; m.p., 279–281 °C. IR (KBr, cm-1): 1681
(C=N quinazoline), 1720 (C=O), 1573 (C=C), 785 (C–Cl),
3053 (arom.CH str), 2841 (aliph. CH str). 1H-NMR
(CD3OD) d: 2.18 (s, 3H, CH3), 5.21 (s, 1H, benzim),
7.07–7.09 (dd, 2H, benzim, J = 7.5, 1.5 Hz), 7.23–7.25
(dd, 2H, quin, J = 7.5, 1.5 Hz), 7.82–7.83 (d, 1H, quin,
J = 1.5 Hz), 7.96 (d, 1H, quin, J = 1.5 Hz). 13C-NMR
(CD3OD) d: 23.4, 115.4, 122.8, 123.9, 125.1, 126.8, 129.4,
134.2, 135.1, 149.3, 151.7, 159.1, 160.5. EI-MS, m/z:
344.03. Anal. Calcd. for C16H10Cl2N4O: C, 55.67; H, 2.92;
N, 16.23 %. Found: C, 55.69; H, 2.91; N, 16.18 %.
Yield, 53 % (MW 69 %); m.p., 267–268 °C. IR (KBr,
cm-1): 1589 (C=N), 1673 (C=O), 1511 (C=C), 523 (C–I),
3011 (arom. CH str), 2929 (aliph. CH str). 1H-NMR
(CDCl3) d: 2.46 (s, 3H, CH3), 2.61–2.67 (p, 2H, prop),
4.03–4.05 (t, 2H, prop, J = 7.1 Hz), 4.11–4.12 (t, 2H,
prop, J = 7.1 Hz), 6.73–6.74 (d, 1H, imid, J = 7.5 Hz),
7.22–7.25 (m, 1H, imid), 7.29–7.30 (d, 1H, quin,
J = 7.5 Hz), 7.96 (s, 1H, imid), 8.02–8.05 (dd, 1H, quin,
J = 7.5, 1.5 Hz), 8.53–8.54 (d, 1H, quin, J = 1.5 Hz).
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3-(1H-benzimidazol-2-yl)-2-phenylquinazolin-4(3H)-one
3-(1H-benzimidazol-2-yl)-6,8-dichloro-2-
(4d)
phenylquinazolin-4(3H)-one (4f)
Yield, 62 %; m.p., 211–212 °C. IR (KBr, cm-1): 1643
(C=N quinazoline), 1681 (C=O), 1587 (C=C), 3049 (arom.
Yield, 68 % (MW 77 %); m.p., 268–269 °C. IR (KBr,
cm-1): 1631 (C=N quinazoline), 1703 (C=O), 1591 (C=C),
756 (C–Cl), 3076 (arom. CH str), 2954 (aliph. CH str). 1H-
NMR (DMSO-d6) d: 5.05 (s, 1H, benzim), 7.06–7.09 (m,
2H, benzim), 7.25–7.28 (m, 2H, benzim), 7.49–7.51 (m,
3H, phen), 7.85–7.87 (m, 3H, Phen 2, quin 1), 7.96 (d, 1H,
quin, J = 1.5 Hz). 13C-NMR (DMSO-d6) d: 115.4, 122.9,
123.3, 125.4, 126.3, 128.3, 128.6, 128.7, 129.5, 130.4,
134.5, 135.2, 149.1, 156.5, 160.6, 163.4. EI-MS, m/z:
406.1. Anal. Calcd. for C21H12Cl2N4O: C, 61.93; H, 2.97;
N, 13.76 %. Found: C, 61.89; H, 2.95; N, 13.81 %.
1
CH str), 2937 (aliph. CH str). H-NMR (CD3OD) d: 5.03
(s, 1H, benzim), 7.09–7.12 (m, 2H, benzim), 7.24–7.27 (m,
2H, benzim), 7.53–7.55 (m, 3H, phen), 7.64–7.66 (m, 2H,
quin), 7.73–7.75 (dd, 1H, quin, J = 7.5 Hz), 7.83–7.86 (m,
2H, phen), 8.09–8.10 (d, 1H, quin, J = 7.5 Hz). 13C-NMR
(CD3OD) d: 115.9, 120.7, 123.1, 126.4, 126.5, 127.4,
128.3, 128.5, 128.7, 130.3, 133.3, 148.8, 149.4, 156.3,
160.7. EI-MS, m/z: 338.1. Anal. Calcd. for C21H14N4O: C,
74.54; H, 4.17; N, 16.56 %. Found: C, 74.67; H, 4.16; N,
16.51 %.
3-(1H-benzimidazol-2-yl)-2-methyl-6-nitroquinazolin-
3-(1H-benzimidazol-2-yl)-6,8-dibromo-2-
4(3H)-one (4g)
phenylquinazolin-4(3H)-one (4e)
Yield, 78 %; m.p., 216–218 °C. IR (KBr, cm-1): 1631
(C=N quinazoline), 1693 (C=O), 1591 (C=C), 1556 and
1323 (C–NO2), 3076 (arom. CH str), 2953 (aliph. CH str).
1H-NMR (MeOD) d: 2.21 (s, 3H, CH3), 5.19 (s, 1H, ben-
zim), 7.11–7.13 (dd, 2H, benzim, J = 7.5, 1.5 Hz),
7.21–7.23 (dd, 2H, benzim, J = 7.5, 1.5 Hz), 7.73–7.75 (d,
1H, quin, J = 7.5 Hz), 8.31–8.33 (dd, 1H, quin, J = 7.5,
1.5 Hz), 8.54 (d, 1H, quin, J = 1.5 Hz). 13C-NMR
(MeOD) d: 23.6, 115.4, 118.3, 121.8, 122.9, 124.4, 126.9,
128.8, 143.9, 149.4, 151.6, 153.4, 160.5. EI-MS, m/z:
Yield, 74 %; m.p., 264–265 °C. IR (KBr, cm-1): 1633
(C=N quinazoline), 1697 (C=O), 1591 (C=C), 574 (C–Br),
3078 (arom. CH str), 2953 (aliph. CH str). 1H-NMR
(DMSO-d6) d: 5.09 (s, 1H, benzim), 7.04–7.08 (m, 2H,
benzim), 7.22–7.25 (m, 2H, benzim), 7.51–7.53 (m, 3H,
phen), 7.80–7.83 (m, 2H, phen), 8.13–8.15 (d, 1H, quin,
J = 1.5 Hz), 8.31 (d, 1H, quin, J = 1.5 Hz). EI-MS, m/z:
493.8. Anal. Calcd. for C21H12Br2N4O: C, 50.84; H, 2.44;
N, 11.29 %. Found: C, 50.87; H, 2.45; N, 11.26 %.
Table 2 Anti-inflammatory activity (HRBC membrane stabilization potency) of compounds 3a–h and 4a–h
Compound
Prevention of HRBC membrane lysis (%) mean SEM
0.2 lM mL-1
0.4 lM mL-1
0.8 lM mL-1
1.6 lM mL-1
3a
3b
3c
3d
3e
3f
81.46 0.34
72.99 0.56
65.59 0.18
83.83 0.32
84.77 0.25
70.51 0.23
86.07 0.66
44.21 0.45
74.12 0.63
85.19 0.26
84.43 0.31
70.95 0.49
58.79 0.31
86.17 0.19
82.31 0.41
85.61 0.21
87.50 0.31
81.99 0.05
77.31 0.12
68.18 0.29
86.11 0.51
86.67 0.18
80.88 0.39
92.21 0.33
50.85 0.55
76.19 0.46
91.79 0.66
87.78 0.20
71.41 0.02
61.48 0.21
90.42 0.08
83.63 0.13
87.50 0.22
88.73 0.11
82.79 0.44
78.73 0.13
71.66 0.24
91.07 0.45
89.08 0.58
83.2 0.36
92.62 0.26
47.65 0.09
81.82 0.44
90.84 0.31
88.52 0.33
76.19 0.71
71.28 0.23
92.48 0.27
84.27 0.09
88.83 0.09
91.64 0.09
82.66 0.20
79.97 0.48
74.67 0.40
92.24 0.34
92.59 0.24
87.89 0.14
93.57 0.09
49.64 0.10
87.77 0.46
93.29 0.16
90.61 0.11
81.62 0.13
71.64 0.18
92.45 0.36
86.72 0.08
91.45 0.11
96.57 0.21
3g
3h
4a
4b
4c
4d
4e
4f
4g
4h
Std
Control: distilled water in the place of hypotonic saline solution
Values are expressed as mean SEM, n = 3/concentration; std: prednisolone
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Med Chem Res (2016) 25:1125–1139
1135
321.05. Anal. Calcd. for C16H11N5O3: C, 59.81; H, 3.45; N,
21.80 %. Found: C, 59.80; H, 3.43; N, 21.82 %.
found to be interesting. Compounds 3d, 3g, 4b and 4f were
found to be promising anti-inflammatory agents compared
with prednisolone. Compounds 3e, 4c and 4h displayed
parallel activity as of standard drug at the doses used, while
compounds 3a, 3f, 4a and 4g displayed anti-inflammatory
activity but seem to be slightly less active agents compared
with the standard drug. The results of the anti-inflammatory
activity studies are represented in Table 2.
3-(1H-benzimidazol-2-yl)-6-iodo-2-methylquinazolin-
4(3H)-one (4h)
Yield, 69 %; m.p., 198–199 °C. IR (KBr, cm-1): 1620
(C=N quinazoline), 1651 (C=O), 1591 (C=C), 540 (C–I),
3061 (arom. CH str), 2954 (aliph. CH str). 1H-NMR
(CD3OD) d: 2.14 (s, 3H, CH3), 5.23 (s, 1H, benzim),
7.11–7.32 (dd, 2H, benzim, J = 7.5, 1.5 Hz), 7.21–7.23
(dd, 2H, benzim, J = 7.5, 1.5 Hz), 7.29 (d, 1H, quin,
J = 7.5 Hz), 8.11–8.13 (dd, 1H, quin, J = 7.5, 1.5 Hz),
8.52 (d, 1H, quin, J = 1.5 Hz). 13C-NMR (CD3OD) d:
23.1, 94.9, 116.1, 122.3, 122.9, 124.5, 126.5, 136.4, 142.8,
145.4, 148.9, 152.0, 160.8. EI-MS, m/z: 401.9. Anal. Calcd.
for C16H11IN4O: C, 47.78; H, 2.75; N, 13.93 %. Found: C,
47.76; H, 2.75; N, 13.91 %.
The synthesized compounds were screened for anti-in-
flammatory activity using the carrageenan-induced rat paw
edema method (Winter et al., 1963). When compared with the
control all the compounds showed reduction in edema volume.
Compounds 3a, 3d, 3g, 4a, 4f and 4g had exhibited interesting
activity. Compounds 3d and 4a were found to be effective
agents capable of inhibiting the inflammation up to 65 %.
The anti-inflammatory activity of 3-[3-(1H-imidazol-1-
yl)propyl]-2-phenylquinazolin-4(3H)-one (3d) can be
attributable to the presence of imidazole ring and phenyl
substitution at 2-position of quinazolinone nucleus. How-
ever, the activity of derivative 3a was somewhat decreased
due to the presence of methyl group at 2-position of
quinazolinone ring. Also it has been observed a slight
incsrease in the activity of 3g, which might be due to nitro
group at 6-position on quinazolinone ring.
Anti-inflammatory activity
The in vitro anti-inflammatory activity of the synthesized
compounds was evaluated using the HRBC membrane
stabilization method (Sadique et al., 1987; Gandhidasan
et al., 1991; Shinde et al., 1999; Rajakumar et al., 2011;
Galhena et al., 2012). The response of the derivatives was
The replacement of imidazole by benzimidazole ring at
3-position of quinazolinone nucleus maintained anti-in-
flammatory potency of 3-(1H-benzimidazol-2-yl)-2-methyl-
Fig. 3 Anti-inflammatory potencies of compounds 3a–h and 4a–h as determined using the carrageenan-induced rat paw edema method
123

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Med Chem Res (2016) 25:1125–1139
quinazolin-4(3H)-one (4a), which has been somewhat
decreased due to the presence of the nitro group at 6-po-
sition of quinazolinone nucleus. The replacement of
2-phenyl and 6,8-dichloro groups on the quinazolinone
nucleus has slightly increased activity. Compounds 3a, 3g,
4f and 4g had displayed activity somewhat less to that of
diclofenac. The results for the active compounds are rep-
resented in Fig. 3.
E. coli and Klebsiella pneumoniae with MIC value of 32,
64 and 16 lg mL-1, respectively, and that of P. aerogi-
nosa with MIC 64 lg mL-1, equivalent to the standard
drug ciprofloxacin. Compound 3h showed greater inhibi-
tory potency against K. pneumonae, with an MIC of
32 lg mL-1, and 4h, against S. aureus, with an MIC of
8 lg mL-1. Compound 4h was also found to be equipotent
against P. aeroginosa and E. coli, with MICs of 64 and
32 lg mL-1, respectively. Compound 4g was also found to
be equipotent against S. aureus and P. aeroginosa, with
MICs of 16 and 8 lg mL-1, respectively, and 3g had MICs
of 32 and 64 lg mL-1 against E. coli and K. pneumonae,
respectively.
Antimicrobial activity
All the compounds were screened for in vitro antibacterial
and antifungal activity (Sharma et al., 2004, 2009). The
results are represented in Table 3. The compounds showed
a significant inhibition of the selected bacterial strains.
Compound 3d was able to inhibit the growth of S. aureus,
The antifungal activity data in Table 3 are average
values from two experiments. The MIC was estimated
using the twofold serial dilution method. Compounds 3b,
Table 3 Antimicrobial activity of synthesized compounds (3a–h and 4a–h)
Comp Zone of inhibition in mm (MIC value in lg mL-1
)
S. aureus
E. coli
P. aeroginosa
K. pneumonae C. albicans
A. niger
C.
gullerimondii
A. flavus
3a
3b
–
17.37 0.19
–
–
14.86 0.33 10.88 0.35 15.33 0.37 17.62 0.17
19.73 0.25 18.42 0.47 28.3 0.13
17.63 0.60 21.40 0.16 19.37 0.49
(32)
–
22.12 0.22
(8)
3c
20.55 0.15 13.56 0.14 29.29 0.12
19.34 0.4
19.59 0.24
(16)
–
16.66 0.24 14.11 0.23
3d
29.3 0.17
(32)
28.53 0.19 34.2 0.62
(64)
24.61 0.09 14.07 0.06 24.71 0.45 19.0 0.8
(16) (8) (64)
21.90 0.36
(8)
(64)
3e
3f
–
23.08 0.5
–
27.73 0.15
19.13 0.28
–
–
18.46 0.36
–
–
–
23.26 0.37
18.88 0.52 18.02 0.61 17.14 0.16 21.26 0.63
(8)
(16)
3g
3h
19.41 0.11 27.90 0.10
(32)
–
22.46 0.16
(64)
–
19.01 0.02 14.51 0.01 15.15 0.55
14.87 0.13 10.78 0.49 31.44 0.04
(128)
24.61 0.14 12.01 0.15 14.7 0.3
(32)
22.45 0.05
(16)
–
4a
4b
4c
13.02 0.19
–
–
–
–
–
–
–
13.7 0.1
–
18.11 0.25
17.62 0.30
15.39 0.02 8.91 0.27
13.57 0.03 12.32 0.17
12.58 0.26 13.0 0.38
13.29 0.43 18.4 0.02
19.67 0.14 16.43 0.39
22.56 0.11 19.05 0.37
27.69 0.41
(32)
19.28 0.44 17.41 0.23
(8)
–
4d
–
–
13.91 0.37 24.42 0.24
(32)
–
15.36 0.4
4e
4f
–
–
8.03 0.57
9.44 0.03
14.73 0.12
–
14.65 0.13
–
–
19.36 0.5
12.45 0.05 23.98 0.64 13.70 0.19 17.57 0.06
4g
28.99 0.21 19.36 0.16 34.1 0.08 (8) 19.05 0.41 13.83 0.42 16.1 0.8
(16)
–
23.59 0.24
(4)
4h
29.22 0.23 27.73 0.13 32.48 0.36
(8) (32) (64)
7.62 0.61
13.88 0.02
–
–
–
Cont
–
–
–
–
–
–
–
–
Cipro 29.16 0.15 28.63 0.21 30.94 0.51
Amp – – – – – –
23.68 0.35 – –
– –
– –
– –
– –
17.71 0.12 25.13 0.42 20.82 0.12 20.77 0.24
Values are expressed as mean SEM, n = 2
Cont control: DMSO (analytical grade), Cipro ciprofloxacin (CIP 5, HiMedia), Amp amphotericin B (Ap100, HiMedia); –, resistant; – –, not
tested
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Med Chem Res (2016) 25:1125–1139
1137
3c, 3f and 4c exhibited excellent antifungal potency against
C. albicans, with MICs of 32, 16, 8 and 8 lg mL-1
and 6-nitro functions on the quinazolinone ring, substituted
with the benzimidazole nucleus, has good potency against
K. pneumonae and S. aureus, with MICs of 8 and
16 lg mL-1. However, the derivative having a 6-iodo
group on the quinazolinone nucleus 3h has MIC
32 lg mL-1 against K. pneumonae, and 4h has good
antimicrobial activity against S. aureus and E. coli, with
MIC of 8 and 32 lg mL-1. Compound 3g, with a 6-nitro
group on quinazolinone, was found to be potent against
E. coli (MIC, 32 lg mL-1) and K. pneumonae (MIC,
64 lg mL-1).
,
respectively. Compounds 3b, 3d, 3f and 4g exhibited
activity against A. flavus, with MICs of 8, 8, 16 and
4 lg mL-1, respectively. Compound 3h was found to have
an MIC of 16 lg mL-1 against C. gullerimondii. Com-
pound 3d was found to be equipotent against A. niger and
C. gullerimondii, with MICs of 8 and 64 lg mL-1
,
respectively. 4d had an MIC of 32 lg mL-1 against A.
niger.
The motivating antimicrobial results of the synthesized
compounds imply further antimicrobial study against
resistant strains of microorganisms. Therefore, we had
screened them against several resistant strains of microor-
ganism. The compounds were found to be active against
resistant strains of S. aureus, P. aeroginosa, C. albicans, A.
niger and A. flavus. The data show that the resistant strain
of C. albicans was highly sensitive to the action of 3f (MIC
8 lg mL-1) and 4c (MIC 16 lg mL-1) (Table 4). The
strain of A. niger was sensitive to the action of 3d and MIC
of 8 lg mL-1, while A. flavus was sensitive to the action of
3b with an MIC 16 lg mL-1. Compound 4g was found to
be effective against A. flavus, P. aeroginosa and S. aureus
with MIC of 8, 16 and 64 lg mL-1, respectively.
The results show that few of the synthesized compounds
are of comparable potency as the standard drug cipro-
floxacin and amphotericin B against the selected patho-
genic strains. The compound with the propyl-imidazole
nucleus and a 2-phenyl ring 3d has comparable antimi-
crobial activity against S. aureus, E. coli and K. pneu-
monae. As shown in Table 3, replacement of the propyl-
imidazole moiety with the benzimidazole nucleus resulted
in some changes in the antibacterial activity against most
of the microorganisms. The compound 4g having 3-methyl
The structural features of the synthesized compounds
showed that the benzimidazole nucleus at the N3-position
of quinazolinone is useful in maintaining the antimicro-
bial activity. The 2-methyl at C-2 and the 6-nitro function
on the quinazolinone nucleus, along with the benzimida-
zole heterocycle (4g), was found to have the best results
in antifungal activity against A. flavus, with an MIC of
4 lg mL-1. The 3-imidazolyl derivative with no substi-
tutions at the 6,8-positions and a 2-phenyl on the quina-
zolinone ring (3d) was observed to be more potent than
amphotericin B against A. flavus, A. niger and C. gulle-
rimondii, with MICs of 8, 8 and 64 lg mL-1, respec-
tively. Compound 3b was found to be potent against C.
albicans (MIC, 32 lg mL-1
) and A. flavus (MIC,
8 lg mL-1) probably due to 6,8-dibromo substitution.
Compound 3c was potent against C. albicans (MIC,
16 lg mL-1) probably due to 6,8-dichloro substitution.
Compound 3f was found potent against C. albicans with
MIC 8 lg mL-1 and A flavus with MIC of 16 lg mL-1
.
The MIC of compound 3h against C. gullerimondii was
16 lg mL-1. Compounds 4c and 4d were found to be
active against C. albicans (MIC, 8 lg mL-1) and A. niger
(MIC, 32 lg mL-1).
Table 4 Antimicrobial activity of selected compounds against resistant strains of microbes
Compound
Zone of inhibition in mm (MIC value in lg mL-1
)
S. aureus (ATCC 33592)
P. aeroginosa
(ciprofloxacin resistant)
C. albicans (ATCC MYA-574)
A. niger
A. flavus
3b
3d
–
–
–
–
–
–
–
20.24 0.22 (16)
–
25.02 0.39
(8)
3f
–
–
18.42 0.37 (8)
–
–
4c
–
–
17.18 0.34 (16)
–
–
4g
26.51 0.38 (64)
28.94 0.08 (16)
–
33. 34 0.31 (16)
–
–
22.54 0.13 (8)
4h
–
–
–
–
-cont
?cont
–
–
–
–
29.18 0.16
34.52 0.31
17.02 0.14
24.19 0.16
20.22 0.18
–, not tested/resistant; ?cont, positive control (ciprofloxacin (CIP 5)/amphotericin B (Ap100)); -cont, negative control (DMSO, analytical grade)
123

1138
Med Chem Res (2016) 25:1125–1139
Belligno AM, Amico-Roxas Ottaviano G (1972) Anti-inflammatory
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1021/ja01958a012
Conclusions
In summary, in the present work we had successfully
synthesized a series of imidazolyl/benzimidazolyl substi-
tuted-2-phenyl/methyl-4(3H)-quinazolinone
derivatives
(3a–h, 4a–h) in good yields. The majority of the synthe-
sized compounds have good to moderate anti-inflammatory
and antimicrobial activity. Compounds 3g, 4b and 4f were
found to be equally active as prednisolone by in vitro
experiment; however, the compounds 3e, 4c and 4h dis-
played promising anti-inflammatory activity, and it might
be due to the presence of electron-withdrawing groups on
quinazolinone nucleus.
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HB (1999) Substituted isoquinolines and quinazolines as poten-
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The compounds 3a, 3d, 3g and 4a were found active in
terms of in vivo anti-inflammatory action. The derivatives
bearing the electron-withdrawing group retained the
activity, but in those lacking electron-withdrawing group
the activity was increased slightly.
The antimicrobial activities of the synthesized com-
pounds showed that compounds with five-member hetero-
cyclic imidazole (3b, 3c, 3d, 3f and 3h) as well as
compounds 4c, 4d, 4g and 4h with six-member benzimi-
dazole ring have promising inhibitory potencies approxi-
mating those of the standard drugs used against the selected
pathogenic strains.
Acknowledgments The authors thank SAIF, IIT, Madras, for the
NMR and GCMS spectra. Author DAP is thankful to Dr. U.K. Patil,
Manish and Mahesh. This author is grateful for the blessings of the
late Prof. Dr. R.A. Fursule.
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benzimidazolyl)-2-alkyl-4-(3H)-quinazolinones under micro-
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Compliance with ethical standards
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Conflict of interest The authors declare that they have no conflict
of interest.
Ethical approval All applicable international, national and/or
institutional guidelines for the care and use of animals were followed.
This article does not contain any studies with human participants
performed by any of the authors.
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