Synthesis, characterization, anti-inflammatory and analgesic activity of transition metal complexes of 3-[1-(2-hydroxyphenyl) ethylideamino]-2-phenyl-3, 4-dihydroquinazolin-4(3H)-one

Article abstract of DOI:10.1002/aoc.1790

A new quinazolinone derivative, 3-[1-(2-hydroxyphenyl)ethylideamino]-2- phenyl-3,4-dihydroquinazolin-4(3H)-one (LH) was synthesized by the condensation of 2-hydroxyacetophenone-2-aminobenzoylhydrazone and benzaldehyde. The cyclization to form 1,2-dihydroquinazolinone was confirmed by IR, 1D and 2D HETCOR studies. Coordination compounds of Co(II), Ni(II), Cu(II) and Zn(II) of LH were synthesized and characterized using various physico-chemical studies like stoichiometric, conductivity, magnetic moment measurements and spectral techniques such as IR, NMR, UV-vis and EPR spectroscopy. The elemental analysis and thermal studies suggested a general stoichiometry [M(HEPDQ)Cl] for all the complexes. A four-coordinate geometry was assigned to all the complexes. The complexes along with the parent ligand were screened for their anti-inflammatory activity, using carrageenan-induced rat paw edema, and for their analgesic activity by Eddy's hot plate method. The activity of the ligand was enhanced on complexation with metal ions. This enhanced activity was attributed to the increased lipophilic nature of the complexes. Notable anti-inflammatory activity was observed for Ni(II), Cu(II) and Zn(II) complexes. The analgesic activity of the ligand was greater than the standard at 60 min. and at a 10 mg kg ^-1 dose, whereas the activity of Ni(II) and Cu(II) complexes at 10 mg kg^-1 dose was comparable with the standard used.

Full text of DOI:10.1002/aoc.1790

Full Paper
Received: 15 November 2010
Revised: 6 February 2011
Accepted: 10 February 2011
Published online in Wiley Online Library: 28 April 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1790
Synthesis, characterization, anti-inflammatory
and analgesic activity of transition metal
complexes of 3-[1-(2-hydroxyphenyl)
ethylideamino]-2-phenyl-3,4-
dihydroquinazolin-4(3H)-one
Rekha S. Hunoora, Basavaraj R. Patila, Dayananda S. Badigera,
Ramesh S. Vadavia, Kalagouda B. Gudasia,∗, V. M. Chandrashekharb
and I. S. Muchchandib
A new quinazolinone derivative, 3-[1-(2-hydroxyphenyl)ethylideamino]-2-phenyl-3,4-dihydroquinazolin-4(3H)-one (LH) was
synthesized by the condensation of 2-hydroxyacetophenone-2-aminobenzoylhydrazone and benzaldehyde. The cyclization to
form 1,2-dihydroquinazolinone was confirmed by IR, 1D and 2D HETCOR studies. Coordination compounds of Co(II), Ni(II), Cu(II)
and Zn(II) of LH were synthesized and characterized using various physico-chemical studies like stoichiometric, conductivity,
magnetic moment measurements and spectral techniques such as IR, NMR, UV-vis and EPR spectroscopy. The elemental analysis
and thermal studies suggested a general stoichiometry [M(HEPDQ)Cl] for all the complexes. A four-coordinate geometry was
assigned to all the complexes. The complexes along with the parent ligand were screened for their anti-inflammatory activity,
using carrageenan-induced rat paw edema, and for their analgesic activity by Eddy’s hot plate method. The activity of the ligand
was enhanced on complexation with metal ions. This enhanced activity was attributed to the increased lipophilic nature of the
complexes. Notable anti-inflammatory activity was observed for Ni(II), Cu(II) and Zn(II) complexes. The analgesic activity of the
ligand was greater than the standard at 60 min. and at a 10 mg kg−1 dose, whereas the activity of Ni(II) and Cu(II) complexes at
10 mg kg−1 dose was comparable with the standard used. Copyright ꢀ 2011 John Wiley & Sons, Ltd.
c
Keywords: 2,3-disubstituted quinazolinone; metal complex; anti-inflammatory activity; analgesic activity
Introduction
hydrazide with potential coordinating sites can form mononuclear
complexes with varied geometries.[15–21] We are particularly in-
terested in the coordination compounds of new 2,3-disubstituted
1,2-dihyroquinazolinones as a new class of anti-inflammatory
and analgesic agents. The appropriate substituent having an
additional ligating site at the N-3 position of the quinazoline
ring arranged strategically in the ligand backbone can give a
potential ligand with a definite geometry. In this regard a new
quinazolinone derivative with 2-hydroxyacetophenone bearing
an additional ligating site at N-3 position of the quinazolinone
ring has been prepared and characterized.
One of the most frequently encountered heterocycles in medic-
inal chemistry is 4(3H)-quinazolinone, with widespread applica-
tionsincludinganti-cancer,[1] anti-hypertensive,[2] antimicrobial,[3]
anti-convulsant[4] and other central nervous system activities.[5]
Quinazolin-4(3H)-ones with 2,3-disubstitution have been re-
ported to possess significant analgesic and anti-inflammatory
activities.[6–8] In particular, 1,2-dihydroquinazolinones were re-
ported to possess higher anti-inflammatory and analgesic activity
compared with fully aromatic quinazolinones.[9] Efforts to develop
andidentifynewmoleculesforanalgesicandanti-inflammatoryac-
tivities with minimal gastrointestinal ulceration side effects are the
currentarea of research. From this viewpoint, the metal complexes
of nonsteroidal anti-inflammatory drugs have been proven to re-
duce gastrointestinal toxicity with enhanced anti-inflammatory
activity, which has allowed their use as veterinary pharmaceutics
even in sensitive species, such as dogs, and offers considerable
potential for their application as human pharmaceutics.[10–12]
The coordination chemistry of 4(3H)-quinazolinone ligands has re-
ceivedmuchattentionbecauseofthepositiveeffectontheactivity
of these bioactive molecules on coordination with metal ions.[13,14]
Because of the flexibility around the N–N single-bond,
2,3-disubstituted quinazolinones derived from 2-aminobenzoyl-
The chelating behavior of hydrazones obtained by the reaction
of 2-aminobenzoylhydrazide and aldehydes has been reported
by many workers.[22–26] However our attempts to synthesize
hydrazone derived by condensing 2-aminobenzoylhydrazide with
∗
Correspondence to: Kalagouda B. Gudasi, Department of Chemistry, Karnatak
University, Pavate Nagar, Dharwad, Karnataka 580 003, India.
E-mail: kbgudasi@gmail.com
a
Department of Chemistry, Karnatak University; Pavate Nagar, Dharwad,
Karnataka 580003, India
b
H.S.K. College of Pharmacy; Bagalkot, Karnataka 587101, India
c
Appl. Organometal. Chem. 2011, 25, 476–483
Copyright ꢀ 2011 John Wiley & Sons, Ltd.

Transition metal complexes of LH
pyridine-2-carbaldehyde did not yield the Schiff base product. In-
stead we obtained a cyclized product, 1,2-dihydroquinazolinone.
The formation of the cyclized product was confirmed by 2D Het-
eronuclear Correlation and single-crystal X-ray diffraction studies
ofitsCo(II)complex.[16] Thereactioninbothpolarandnonpolarsol-
vents with 1 : 1 and 1 : 2 equivalents of 2-aminobenzoylhydrazide
and aromatic aldehyde yielded quinazolinone with a higher
yield in the latter case. This type of cyclization reaction has
been proposed by Fulop et al.[27] Using this strategy, various 1,2-
dihydroquinazolinones have been prepared and their structures
proved by single-crystal X-ray diffraction studies. Their chelating
behavior towards transition metals as well as lanthanides and their
antimicrobial activity has also been studied.[15–21] In our recent
communications we have reported a modified method for the
synthesis of 2,3-disubstituted 1,2-dihydroquinazolinones, which
involves the isolation of the final compound in two steps with a
higher yield. The quinazolinone ligands thus prepared were stud-
iedfortheircoordinationbehaviorandanti-inflammatoryandanal-
gesicactivities.[13,14] Asapartofourongoingstudyonthetransition
metal complexes of 2,3-disubstituted 1,2-dihydroquinazolinones
as new class of anti-inflammatory and analgesic agents and to
gain more insight in the structure–activity relationships, we
report the synthesis, characterization and anti-inflammatory
and analgesic activity studies of newly designed 3-[1-(2-
hydroxyphenyl)ethylideamino]-2-phenyl-3,4-dihydroquinazolin-
4(3H)-one and its Co(II), Ni(II), Cu(II) and Zn(II) complexes.
temperature and liquid nitrogen temperature on a Varian E-
4 X-band spectrometer using TCNE (tetracyanoethylene) as the
calibrant. Fast Atom Bombardment mass spectra of the complexes
were recorded on a Jeol SX 102/DA-6000 mass spectrometer/data
system using argon/xenon (6 kV, 10 ma) as the FAB gas.
Synthesis of 3-[1-(2-hydroxyphenyl)ethylideamino]-2-phenyl
-3,4-dihydroquinazolin-4(3H)-one (LH)
To a methanolic solution (50 ml) of 2-hydroxyacetophenone-2-
aminobenzoylhydrazone (2.69g, 10 mmol), an equimolar quantity
of benzaldehyde (1.06 ml, 10 mmol) was added and stirred for 2 h.
The colorless solid separated was filtered, washed repeatedly with
alcohol and dried in air. The compound was recrystallized from hot
ethanol, and the purity was checked by TLC on pre-coated silicagel
plates: Rf, 0.55 (hexane : EtOAc, 7 : 3); m.p., 250–253 ◦C; yield, 90%.
Synthesis of Co(II), Ni(II), Cu(II) and Zn(II) complexes (A1–A4)
The ligand, LH, was stirred with Co(II), Ni(II), Cu(II) and Zn(II)
chlorides in a 1 : 1 molar ratio in an ethanolic medium and the pH
of the solution was adjusted to around 7 by adding two to three
drops of ammonia; it was then refluxed on a water bath for over
2 h. The resulting precipitates of complexes were washed with
ethanol and chloroform and air-dried; yield, 50–60%.
Pharmacology
All the synthesized compounds were screened for analgesic and
anti-inflammatory activity in rats and mice. Wistar rats (230–250 g)
and Swiss mice (25–30 g) were used and the animals were kept at
26 2 ◦C with a relative humidity of 44–56% and a 12 h light/dark
cycle. All the animals were fed with standard diet and water ad
libitum. Approval for the experimental protocol was obtained from
Institutional Animal Ethics Committee (IAEC/2008/01-11/HSK) and
the same procedure was carried at H. S. K. College of Pharmacy,
Baglkot, India. Animalsthathadbeenfastedfor18–24 hwereused
fortheexperiments.Theanimalsweredividedinto12experimental
groups, each containing six animals. The test compounds were
suspended in 0.5% sodium carboxy methyl cellulose (Na-CMC)
and administered at doses of 3 and 10 mg kg−1 of body weight
(b.w.). Indomethacin and aspirin were administered as reference
standard drugs for anti-inflammatory and analgesic, respectively,
at a dose of 10 mg kg−1 b.w. The control group received 0.5%
Na-CMC in distilled water.
Experimental Section
Materials and General Methods
Methylanthranilate (S.D. Fine Chemicals, India), hydrazine hydrate
(Spectrochem, India), 2-hydroxyacetophenone (Himedia, India),
4-chlorobenzaldehyde (Spectrochem, India) and metal (II) chlo-
rides were of AR grade and used without further purification.
Solvents were distilled before use. 2-Aminobenzoylhydrazide[28]
and 2-hydroxyacetophenone-2-aminobenzoylhydrazone[29] were
prepared following the literature procedures.
Elemental analyses were carried out on a TruSpec CHN/CHNS
analyzer and metal complexes were analyzed for their metal
content gravimetrically (Co, Ni and Cu) and volumetrically through
EDTA titration (Zn) after decomposition with a mixture of HCl and
HClO4. The chloride content of the complexes was determined
gravimetrically as AgCl after decomposing the complexes with
HNO3. The IR spectra were recorded on a Nicolet 170 SX FT-IR
spectrometer in the 4000–400 cm−1 region using KBr disks. The
1H, 13C-NMR and 2D HETCOR spectra of the ligand and H, 13C-
1
Anti-inflammatory Activity
NMR spectra of Zn(II) complex were recorded in DMSO-d6 on a
Bruker Avance 400 MHz spectrometer operating at 400.13 MHz.
Electronic spectra were recorded on a Cary 50 Bio UV–vis
spectrophotometer in the 200–1000 nm range in DMF solutions.
Magnetic susceptibility measurements were carried out on a Gouy
balance using Hg[Co(SCN)4] as the calibrant and diamagnetic
corrections were made using Pascal’s constants. Conductance
measurements were recorded in DMF (10−3 M) using an ELICO-CM-
82 conductivity bridge with cell type CC-01 and cell constant 0.53.
Thermogravimetry and Differential Thermal Analysis studies were
carried out in the temperature range of 25–1000 ◦C usin◦g a TGA7
analyzer, Perkin-Elmer, USA, with a heating rate of 10 C min−1
in an N2 atmosphere. The Electron Paramagnetic Resonance
spectra of a polycrystalline Cu(II) complex were recorded at room
The anti-inflammatory activity of the test compounds was
[31]
evaluated as described by Winter et al.[30] and Diwan et al.
.
One hour after the administration of the test compounds, rats
in all groups were challenged with carrageenan (1% prepared in
0.4% NaCl) in the sub-plantar region of the right hind paw. The
paw volume was measured at different intervals of time (0.5, 1, 2,
3, and 5 h) using a digital plethysmometer (UGO Basil, Italy), and a
zero-hour reading, before administration of the carrageenan, was
taken. The percentage inhibition of the paw volume for each test
group was calculated using following equation:
percentage of inhibition (%) = [1 − volume in ml
(test compound)/volume in ml (control)] × 100
c
Appl. Organometal. Chem. 2011, 25, 476–483
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

R. S. Hunoor et al.
Scheme 1. Synthetic route for the preparation of LH.
Analgesic Activity
hydrogen bonding with carbonyl oxygen of another molecule.
This band in all the complexes shifted to a higher frequency
due to the breakdown of the intermolecular hydrogen bonding
after complexation. ν(C O), ν(C N) and ν(C–O) stertchings
were observed at 1647, 1610 and 1365 cm−1 respectively.
On complexation the stretching frequencies corresponding to
The Eddy and Leimback hot plate test[32] was carried out in mice
for evaluating analgesic activity. Albino mice of either sex were
divided into 12 groups, containing six animals each. Animals were
administered with control (0.4% NaCl), test compounds (3 and
10 mg kg−1) and aspirin (10 mg kg−1) as an aqueous suspension
of 1% sodium carboxy methyl cellulose. One hour after the
administration of compounds, mice were kept on a hot plate
pre-heated to 50 ◦C for 15 s. The reaction time between the mouse
reaching hot plate and licking its hind paw was noted. The cut-off
time was fixed at 15 s to prevent injury to the paw. The time taken
to lick the hind paw was recorded at 60, 120 and 180 min. Increase
in reaction time (time interval taken by animal to lick paw) was
considered as proportional to analgesic activity.
carbonyl and imine groups decreased by 30–47 and 17–25 cm−1
,
respectively, indicating the involvement of carbonyl oxygen and
azomethine nitrogen in the coordination. Absence of ν(OH) in all
the complexes is indicative of its participation in the coordination
of phenolic oxygen via deprotonation. Increase in the stretching
frequency of ν(C–O) in all the complexes is suggestive of the same.
Thus the title compound behaves as a monobasic tridetate ONO
ligand.
NMR Studies
Results and Discussions
In order to prove the formation of 1,2-dihydroquinazolinones
and complete assignment of the chemical shifts of the pro-
tons directly attached to the carbon, we carried out 2D HETCOR
spectral studies of LH. The numbering scheme for the assign-
ments of carbon and protons is given in Scheme 1. The spectral
assignments were made based on comparisons with NMR assign-
ments of 2-hydroxyacetophenone-2-aminobenzoylhydrazone[29]
and benzaldehyde.[33] The 1H-NMR and 13C-NMR data for LH and
its Zn(II) complex are given in Table 3. The 2D HETCOR NMR
spectrum (1H–13C) is displayed in Fig. 1.
The title compound was prepared in two simple steps as out-
lined in Scheme 1. In the first step 2-aminobenzoylhydrazide
was condensed with 2-hydroxyacetophenone to get 2-
hydroxyacetophenone-2-aminobenzoylhydrazoneandthishydra-
zone was treated with benzaldehyde in the second step to get
1,2-dihydroquinazolinone in 90% yield. The ligand has been well
characterized by IR, 1D and 2D NMR spectral studies. The metal
complexes (A1–A4) were prepared using respective metal chlo-
rides with the ligand in 1 : 1 molar ratio at pH 7. The analytical and
physico-chemical parameters of LH and its complexes are com-
piledinTable 1.Allthecomplexeswerenonhygroscopicandstable
at room temperature. The molar conductance data of the com-
The OH proton resonates as a singlet in the downfield region
(12.03 δ ppm) owing to its involvement in the hydrogen bonding
with azomethine nitrogen. The resonance owing to N1H, C2H and
methyl protons (C18H3) appeared as singlets at 7.51, 6.25 and 2.27
δ ppm. The aromatic protons were observed as multiplets in the
region 6.6–7.8 δ ppm. In the 1H-NMR spectrum of Zn(II) complex,
the signal corresponding to OH proton was absent, which is a clear
indication of involvement of phenolic oxygen in the coordination
by losing its proton. The methyl protons observed at 2.48 δ ppm
shifted downfield compared with LH, suggesting the coordination
through azomethine nitrogen.
plexes in DMF at 10−3 M was in the range 2–10 ꢀ−1 cm2 mol−1
which indicates the nonelectrolytic nature of the complexes.
,
Infrared Spectral Studies
Significant IR spectral bands of the ligand and its metal complexes
are presented in Table 2. A strong band at 3310 cm−1 in the
IR spectrum of ligand was assigned to ν(NH) while a broad
band around 2924 cm−1 was due to hydrogen-bonded ν(OH)
stretching.ThehydrogenonNHwasinvolvedintheintermolecular
13C NMR of LH showed a signal at 75.02 δ ppm assigned
to sp3 hybridized C2 carbon and proved the formation of 1,2-
c
wileyonlinelibrary.com/journal/aoc
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 476–483

Transition metal complexes of LH
Table 1. Analytical, electronic, spectral and magnetic moments of LH and its complexes
Elemental analysis found (calculated)
a
Compound
HECPDQ
Empirical formula
C22H19N3O2
Compound code
C
H
N
M
–
Cl
–
ꢁm
µeff (BM)
λmax (nm)
LH
73.90
(73.93)
58.53
5.40
(5.36)
3.51
11.66
(11.76)
8.83
1.2
333
[Co(HECPDQ)Cl]
[Ni(HECPDQ)Cl]
[Cu(HECPDQ)Cl]
[Zn(HECPDQ)Cl]
[Co(C22H18N3O2)Cl]
[Ni(C22H18N3O2)Cl]
[Cu(C22H18N3O2)Cl]
[Zn(C22H18N3O2)Cl]
A1
A2
A3
A4
13.59
(13.07)
13.65
7.30
(7.86)
8.23
5.31
2.35
4.80
9.43
4.1
674
411
(58.62)
58.97
(4.02)
3.84
(9.32)
8.19
Diab
1.91
Dia
(58.65)
58.15
(4.03)
3.55
(9.33)
9.35
(13.03)
14.46
(7.87)
7.35
311, 603
–
(58.02)
57.25
(3.98)
3.69
(9.23)
8.80
(13.95)
14.89
(7.79)
7.11
(57.79)
(3.97)
(9.19)
(14.30)
(7.75)
a ꢀ−1 cm2 mol−1
;
b Dia = diamagnetic.
Table 3. 1H and 13C NMR spectral data of LH and its Zn(II) complex
Table 2. Diagnostic IR bands for LH and its complexes
Compound ν(NH) ν(OH) phenolic ν(C O) ν(C N) ν(C–O)
LH
Zn(II) complex
1H
Position
13C
1H
13C
LH
A1
A2
A3
A4
3310s
3336s
2924 b
n.o.
1647s
1610s 1365 m
1600m 1585m 1373 s
1600m 1581m 1438 s
N1H
C2
–
7.51(s, 1H)
6.25 (s, 1H)
–
–
7. 51 (s, 1H)
3282 m
3355s
n.o.
75.03
74.30
176.11
–
6.25 (s, 1H)
n.o.
1610m
1587s
1375 s
C4
173.76
118.68
127.99∗
117.71
132.53
117.08
147.22
127.46
129.67∗∗
132.53
128.48
128.98
127.99∗
159.11
17.19
–
–
3264s
n.o.
1612 s 1593 s 1378 s
C5
–
C6
7.74 (m)
6.77 (m)
7.33 (m)
6.79 (m)
–
129.90
117.89
133.55
117.13
149.16
113.30
7.74 (m)
6.77 (m)
7.33 (m)
6.79 (m)
–
b = broad, m = medium, s = strong, n.o. = not observed.
C7
C8
C9
dihydroquinazolinone rather than hydrazone. Carbonyl carbon
and azomethine carbon were observed at 174.01 and 159.11
δ ppm, respectively. The 13C-NMR spectrum of Zn(II) complex
showed a downfield shift of the signals corresponding to carbonyl,
azomethine and C24 carbon, suggesting coordination through
carbonyl oxygen, azomethine nitrogen and phenolic oxygen.
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
OH
–
–
7.58 (m)
7.31 (m)
7.37 (m)
7.39 (m)
7.53 (m)
–
129.35∗∗ 7.58 (d, 1H, J = 7.2 Hz)
129.72∗
138.22∗
129.72
129.35∗∗
159.79
30.63
7.30 (m)
7.37 (m)
7.388 (m)
7.54 (m)
–
Electronic Spectral and Magnetic Moment Studies
2.27 (s, 3H)
–
2.48 (s, 3H)
–
Electronic spectra of LH and its complexes were recorded in order
to assign plausible geometry around the metal ions. Electronic
spectraoftheligandshowedstrongabsorptionat333 nmassigned
to π → π∗ transition. In the electronic spectrum of cobalt
139.17
129.67∗∗
114.53
134.04
118.36
160.32
–
134.13
128.55
114.59
130.13
116.73
169.92
–
7.60 (m)
6.82 (m)
7.35 (m)
6.86 (m)
–
7.61 (m)
6.82 (m)
7.40 (m)
6.86 (m)
–
4
complex, the band observed at 674 nm was due to 4A2 (F) → T1
(P) transition.[34] This assignment is supported by the µeff value
of 4.1 BM, which is consistent with a tetrahedral geometry.[35]
An intense absorption at 411 nm in the electronic spectrum of
nickel complex was due to phenolate → Ni(II) charge transfer
transition, suggesting square-planar geometry around Ni(II) ion,
which is confirmed by its diamagnetic nature.[36] A broad band
12.03 (s, 1H)
n.o.
m = multiplet, d = doublet, s = singlet; ∗
,
∗∗ might have appeared as
a single line; n.o., not observed.
in the electronic spectrum of Cu(II) complex with a peak maxima
2
at 603 was assigned to the combination of B1g
→
2A1g and
three complexes showed no weight loss in the region 30–200 ◦C,
indicating the absence of coordinated or lattice-held solvent
molecules. Weight losses of 83.4% (85.1%), 83.8% (85.1%) and
84.0% (85.1%) in the thermograms of Ni(II), Cu(II) and Zn(II) com-
plexes were due to the loss of ligand and a coordinated chlorine.
The plateau obtained after heating the complexes above 700 ◦C
corresponded to the formation of stable metal oxides and the
metal content thus calculated was in accordance with the metal
analyses.
2B1g
→
2Eg transitions as for a square-planar configuration
around it.[34] Another absorption at 311 nm was due to n → π∗
transition.
Thermal Studies
Thermal studies of Ni(II), Cu(II) and Zn(II) complexes were under-
taken in order to study their thermal stability and as supportive
data for the proposed molecular formulae. Thermograms of all the
c
Appl. Organometal. Chem. 2011, 25, 476–483
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

R. S. Hunoor et al.
Figure 1. 2D HETCOR NMR of LH. Expanded form of aromatic region is shown in the box inset.
Table 4. Anti-inflammatory activity of LH and its complexes (A1–A4)
Edema volume in ml (mean percentage inhibition)
Groups (dose)
0 h
0.5 h
1 h
2 h
3 h
5 h
Control
1.743 0.058
0.160 0.030∗∗
(90.08)
1.848 0.024
0.200 0.019∗∗∗
(89.18)
1.923 0.030
0.290 0.036∗∗∗
(84.91)
2.013 0.052
0.380 0.090∗∗∗
(82.01)
2.083 0.028
0.310 0.069∗∗∗
(85.11)
2.110 0.013
0.220 0.560∗∗∗
(89.57)
Indomethacin
(10 mg kg−1
)
LH
1.848 0.055
(0.00)
1.745 0.048
(5.57)
1.720 0.074
(10.55)
1.893 0.077
(5.96)
1.935 0.006
(7.10)
1.935 0.017
(8.29)
(3 mg kg−1
)
LH
1.828 0.088
(0.00)
1.810 0.144
(2.05)
1.743 0.073
(9.36)
1.828 0.097
(9.19)
1.875 0.056
(9.98)
1.960 0.037
(7.10)
(10 mg kg−1
)
)
)
)
)
A1
1.674 0.565
(3.95)
1.744 0.745
(5.61)
1.678 0.645
(12.71)
2.007 0.035
(0.32)
2.220 0.063
(0.00)
1.903 0.647
(9.81)
(3 mg kg−1
)
A1
1.714 0.313
(1.66)
1.643 0.056
1.756 0.462∗∗∗
1.755 0.064∗
1.787 0.068∗
1.866 0.066∗
(10 mg kg−1
(11.07)
(8.67)
(12.84)
(14.21)
(11.56)
A2
1.448 0.154
(16.92)
1.510 0.056∗∗
(18.29)
1.818 0.043∗∗∗
(5.40)
1.673 0.070∗
(16.89)
1.660 0.083∗∗
(20.30)
1.703 0.063∗∗
(19.28)
(3 mg kg−1
)
A2
1.533 0.020
(12.04)
1.588 0.039∗∗
1.548 0.045∗∗
1.503 0.074∗∗∗
1.583 0.131∗∗
1.693 0.123∗∗
(10 mg kg−1
(14.06)
(19.50)
(25.33)
(24.0)
(19.76)
A3
1.658 0.317
(4.87)
1.696 0.063
(8.22)
1.462 0.523∗∗∗
(23.97)
1.756 0.038
(12.74)
1.584 0.037∗∗
2.011 0.475
(3.44)
1.708 0.065∗
1.978 0.869
(6.25)
(3 mg kg−1
)
A3
1.724 0.052
(1.09)
1.695 0.068
(8.27)
1.451 0.063∗∗∗
1.954 0.043
(7.39)
(10 mg kg−1
(24.54)
(21.31)
(18.00)
A4
1.615 0.054
1.785 0.105
1.445 0.068
(24.85)
1.508 0.063∗∗∗
1.815 0.110
(9.83)
1.875 0.104
(9.98)
2.083 0.125
(3 mg kg−1
)
(7.34)
(3.40)
(1.27)
A4
1.495 0.061∗
(14.22)
1.460 0.031∗∗∗
(20.99)
1.820 0.032
(9.58)
1.803 0.074
(13.44)
1.633 0.087∗∗
(22.60)
(10 mg kg−1
(21.5)
Results expressed as means SEM (n = 6) ANOVA followed by Dunnett’s test. ∗∗∗ p < 0.001, ∗∗ p < 0.01, ∗ p < 0.05 when compared with the control
group.
LH = ligand, A1 = [Co(L)Cl], A2 = [Ni(L)Cl], A3 = [Cu(L)Cl], A4 = [Zn(L)Cl].
c
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Transition metal complexes of LH
Figure 2. Percentage inhibition of paw edema of the ligand and its metal complexes.
Figure 3. Analgesic activity of ligand (LH) and its metal complexes (A1–A4).
EPR Spectral Studies
slight increase is observed at 5 h. The results of anti-inflammatory
activity are summarized in Table 4. The activity of the ligand was
found to be independent of dose, but comparatively consistent
protection up to 5 h was observed at 10 mg kg−1. All complexes
at the higher dose exhibit enhanced activity compared with the
ligand. Compound A1 exhibited dose-dependent activity and was
found to be completely inactive at 2 and 3 h at the 3 mg kg−1 dose.
Compound A2 showed enhanced activity at both doses compared
with the ligand and exhibited good percentage protection up to
5 h. The activities of A3 and A4 were lower compared with A2,
but they possessed higher activity compared with the ligand.
Among all the compounds the highest activity was observed for
A2 with 25.33% inhibition of paw edema. When compared with
the standard, the activity of all the compounds was lower. The
compoundsexhibitedcomparativelygoodactivityat1 h,asshown
in the bar chart in Fig. 2.
The X-band EPR spectra of copper complex were recorded both
at room temperature (RT) and liquid nitrogen temperature (LNT)
as polycrystalline samples at a frequency of 9.1 GHz under a
field strength of 3000 G. The EPR spectrum of Cu(II) complex at
RT exhibited a broad unresolved signal giving only one g-value,
giso = 2.10. The broadening of the signals may be due to spin
relaxation. At LNT, the spectrum was well resolved with g-values
g1 = 1.99, g2 = 2.01 and g3 = 2.17, suggesting a rhombic
pattern. Observed g-values were less than 2.3, indicating the
covalent nature of the metal-ligand bonding.[37]
Anti-inflammatory Activity
The anti-inflammatory activity of LH and its transition metal
complexes was evaluated at two dose levels at 3 and 10 mg kg−1
body weight. The results show variation in the percentage
inhibition of carrageenan-induced rat paw edema from 0 to 5 h.
For all the complexes at both the dose levels a general trend
observed was that the activity gradually increased and attained
a peak value, then decreased; in some case after this decrease a
Carrageenan-induced rat paw edema induces inflammatory
mediators such as histamine, serotonin and cytokines, leading
to cascade inflammation reactions[39] over a short period time.
Later (up to 6 h), further augmentation of inflammation reaction
is mediated by prostaglandins derived from arachidonic acid
c
Appl. Organometal. Chem. 2011, 25, 476–483
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R. S. Hunoor et al.
Table 5. Analgesic activity of LH and its complexes
Reaction time (X SE) in seconds
Compound
Dose
Basal
60 min
120 min
180 min
Control
Aspirin
–
4.75 0.48
4.93 2.33∗
9.50 2.90
11.21 2.16∗∗
(6.28 0.16)
13.25 0.86
(5.50 1.03)
15.00 0.00
(6.50 2.26)
10.57 1.18
(3.94 0.97)
11.50 1.19
(4.38 0.03)
13.00 2.00
(5.00 2.00)
11.00 1.08
(2.50 0.92)
9.34 2.73
9.50 2.53
14.68 2.42∗∗∗
(9.75 0.10)
13.75 1.25
(5.25 0.64)
14.50 0.50∗
(6.0 1.76)
10.50 2.06
15.00 0.00∗∗∗
(10.07 2.33)
13.25 1.75
(5.50 0.14)
14.75 0.25∗
(6.25 2.01)
13.52 1.41∗
(5.89 0.89)
13.41 0.48∗
(6.29 1.15)
13.75 1.25
(5.75 1.25)
15.00 0.00∗∗
(6.50 2.00)
13.10 1.19
(6.39 0.05)
14.41 0.75∗∗
(7.59 0.36)
10.00 2.00
(6.25 0.35)
13.00 0.00
(6.30 1.11)
10
LH
LH
A1
A1
A2
A2
A3
A3
A4
A4
3
10
3
7.75 1.89
8.50 2.26
6.63 2.15
7.12 1.63∗
8.00 0.00∗
8.50 2.00∗
6.71 1.87
7.82 1.11∗
6.75. 1.60
6.70 1.11∗∗
12.21 0.53
(5.58 0.66)
12.75 1.64
(5.63 0.01)
12.50 1.50
(4.50 1.50)
13.00 0.82
(4.50 2.18)
12.02 1.65
(5.31 0.21)
13.54 1.63∗
(5.72 0.52)
11.00 0.00
(4.25 1.60)
12.00 0.00
(5.30 1.11)
10
3
10
3
(2.63 1.87)
11.42 1.53
(4.60 0.42)
10.00 2.92
(3.25 1.31)
10.50 1.19
(3.80 0.08)
10
3
10
∗ p < 0.05, ∗∗ p < 0.01, ∗∗∗ p < 0.001 when compared with the control group.
LH = ligand, A1 = [Co(L)Cl], A2 = [Ni(L)Cl], A3 = [Cu(L)Cl], A4 = [Zn(L)Cl].
by the action of prostaglandin H synthase. These results
suggest that the test compounds may exert their action
through inhibition of lecucocyte migration, reducing the cytokine
production and prostaglandin synthesis by inhibiting the activity
of cyclooxygenase enzyme activity.[38]
Analgesic Activity
The test for analgesic activity was performed by Eddy’s hot plate
method. This method is very useful to test the activity of the
drugs acting through CNS and can be screened easily. Each test
compound is screened at a lower dose level of 3 mg kg−1 and a
higher dose level of 10 mg kg−1. The time interval between the
moment, the mouse is introduced onto the hot plate (pre-heated
to 50 ◦C) and that when first begins to lick its hind paw is noted as
the reaction time. The increase in the reaction time compared with
the basal reading (the reaction time before the administration of
test compounds) is proportional to the analgesic activity of the
test compounds. The results of analgesic activity are summarized
in Table 5. LH exhibited excellent activity at 60 min. and its activity
at 10 mg kg−1 was found to be greater than that of the standard.
The activity of ligand at 60 min. was greater compared with all the
complexesandinsomecasesat120 min. also. Theactivityofallthe
complexes gradually increased from 60 to 120 min. and reaches
the peak point at 180 min., while ligand activity decreased from
60 to 120 min. and increased at 180 min. at both doses. LH, A1,
A3 and A4 exhibited dose-dependent activity while the activity
of A2 at 60 min. was greater at the lower dose than at the higher
dose. The activity of all the complexes was greater than that of
the ligand at 180 min. Among the complexes Cu(II) complex (A3)
Figure 4. Proposed structure for the complexes.
at 10 mg kg−1 at 180 min. exhibited the highest activity, but it is
lower compared with the standard. The analgesic activity chart for
the compounds at 180 min. is depicted in Fig. 3.
The superior activity of the complexes over the free ligand
may be explained with the help of Overtone’s concept and
Tweedy’s chelation theory.[39,40] Accordingly, the polarity of the
metal ion was reduced upon metal complexation which enhanced
the lipophilicity of the metal complexes, allowing their enhanced
penetration through cellular membranes.
Conclusions
A new 2,3-disubstituted 1,2-dihydroquinazolinone ligand hav-
ing potential ligating sites was synthesized by the condensation
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Appl. Organometal. Chem. 2011, 25, 476–483

Transition metal complexes of LH
of 2-hydroxyacetophenone-2-aminobenzoylhydrazone with ben-
zaldehyde in 90% yield. Co(II), Ni(II), Cu(II) ans Zn(II) complexes of
the same were synthesized and characterized. Physico-chemical
characterization revealed that the ligand behaves as monobasic
and coordinates to metal ions in a tridentate manner with ONO
donor sites. Tetrahedral geometry was assigned to Co(II) and Zn(II)
complexes, and square-planar for Ni(II) and Cu(II) complexes. The
tentatively proposed structure for complexes is given in Fig. 4.
The complexes showed enhanced anti-inflammatory activity com-
pared with the ligand. Complex A1 exhibited low activity while
the remaining complexes showed very good activity, with good
protection from carrageenan-induced paw edema up to 5 h. The
compounds achieved their activity by inhibiting the cyclooxyge-
nase enzyme. The analgesic activity of compounds was moderate
and the copper complex, A3, exhibited highest activity at higher
dose level. Enhanced activity of the complexes was due to the
increased liopophilic character owing to metal coordination.
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Acknowledgments
AuthorsthankIIScBangalore, IITMumbai, USICKarnatakUniversity
Dhawad, SAIF Cochin and Department of Physics, Karnatak
University Dharwad for NMR, EPR, IR, TG-DTA and magnetic
moment measurements, respectively. One of the authors, R.S.H., is
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