Dual action spirobicycloimidazolidine-2,4-diones: Antidiabetic agents and inhibitors of aldose reductase-an enzyme involved in diabetic complications

Article abstract of DOI:10.1016/j.bmcl.2012.11.039

The desired 3-(arylsulfonyl)spiroimidazolidine-2,4-diones were synthesized by reacting spiroiminoimidazolidine-2,4-dione with arylsulfonyl chlorides. Spiroimidazolidine-2,4-dione was in turn synthesized from norcamphor. Structures of the synthesized molecules were established by modern spectroscopic techniques. The synthesized compounds were screened for in vivo antidiabetic activity and aldose reductase inhibition. Compounds 2a, 2b and 2g exhibited excellent dual activity, compound 2a being most prominent. These results reveal that the synthesized compounds may serve as the molecule of choice to treat diabetes and diabetic complications using a single medication.

Full text of DOI:10.1016/j.bmcl.2012.11.039

Bioorganic & Medicinal Chemistry Letters 23 (2013) 488–491
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Dual action spirobicycloimidazolidine-2,4-diones: Antidiabetic agents and
inhibitors of aldose reductase-an enzyme involved in diabetic complications
Zafar Iqbal a, Sher Ali b, Jamshed Iqbal b, Qamar Abbas c, Irfan Zia Qureshi c, Shahid Hameed a,
⇑
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
b Department of Pharmaceutical Sciences, COMSATS Institute of Information Technology, Abbottabad 45320, Pakistan
c Department of Animal Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
The desired 3-(arylsulfonyl)spiroimidazolidine-2,4-diones were synthesized by reacting spiroiminoimi-
dazolidine-2,4-dione with arylsulfonyl chlorides. Spiroimidazolidine-2,4-dione was in turn synthesized
from norcamphor. Structures of the synthesized molecules were established by modern spectroscopic
techniques. The synthesized compounds were screened for in vivo antidiabetic activity and aldose reduc-
tase inhibition. Compounds 2a, 2b and 2g exhibited excellent dual activity, compound 2a being most
prominent. These results reveal that the synthesized compounds may serve as the molecule of choice
to treat diabetes and diabetic complications using a single medication.
Received 7 August 2012
Revised 24 October 2012
Accepted 12 November 2012
Available online 24 November 2012
Keywords:
Diabetic complications
Aldose reductase
Enzyme inhibition
Imidazolidinediones
Hypoglycemic agents
Ó 2012 Elsevier Ltd. All rights reserved.
Abnormal glucose metabolism causes an increase in the blood
glucose level in diabetic patients. Prolonged hyperglycemia plays
an important role in the development of diabetic complications
such as atherosclerosis, neuropathy, end stage renal failure and
blindness.1 One of the important biochemical pathways that
impair the function and structure of cells is the polyol pathway.2
Polyol pathway consists of two steps, aldose reductase (ALR2,
E.C.1.1.1.21) is the first enzyme involved in this pathway convert-
ing glucose into sorbitol using NADPH as a co-factor. Sorbitol
dehydrogenase then converts sorbitol into fructose. Under normal
glucose level in blood, glucose is converted into glucose-6-phos-
phate by hexokinases. As there is high affinity of hexokinases for
glucose substrate, very small amount of glucose converts into
sorbitol. In hyperglycaemic condition, aldose reductase converts
glucose into sorbitol because of the saturation of hexokinases.
Glucose influx is very low in this pathway under euglycemic
conditions.3,4 Once sorbitol is accumulated inside the cell, it cannot
diffuse easily across the cell membrane causing increase in the
osmotic pressure of the cell, which plays an important role in
etiology of diabetic complications.5
Decrease in myo-inositol is observed in the peripheral tissues
because of the accumulations of sorbitol in cells. Decreased myo-
inositol causes the reduction in Na+, K+-ATPase activity, which
plays an important role in nerve conduction.6 Because of the
activation of polyol pathway, as there is overutilization of NADPH,
a lot of homeostatic processes are compromised. Depletion of
NADPH results in reduction of nitric oxide causing circulatory
abnormalities.6 Blindness is due to the retinopathy or cataract
formation. Diabetes is the major risk factor for the development
of cataract and retinopathy. The risk of complications is lower if
glucose level remains normal in blood, but strict glycemic control
is extremely difficult.7
Inhibition of aldose reductase is, therefore, a potential target of
drug action. The aim of the present work was to design and synthe-
size molecules to achieve the treatment of diabetics with a single
medication that will not only control the glucose level but also re-
duce acute complications produced by abnormal glucose concen-
trations and increased aldose reductase activity. Although,
thiazolidinediones and their analogues have long been used for
the treatment of diabetes and to lower the aldose reductase activ-
ity, there are still a number of concerns regarding their long term
safety.8 Weight gain, hepatotoxicity9 and edema10 are some of
the side effects of thiazolidinediones. Similarly, it has been
reported that thiazolidinedione treated diabetic hypertensive pa-
tients are at a high risk for angina, congestive heart failure, cerebral
vascular accident and myocardial infarction.11 Imidazolidinedi-
ones, on the other hand, are cyclic urea derivatives and exhibit
Aldose reductase, the enzyme involved in the first step of polyol
pathway, has been found in retina, nervous tissues, kidney, aorta
and lens, that is tissues in which diabetic complications appear.
⇑
Corresponding author. Tel.: +92 51 9064 2133; fax: +92 51 9064 2241.
E-mail addresses: shahidhameed@daad-alumni.de, shameed@qau.edu.pk (S.
Hameed).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.11.039

Z. Iqbal et al. / Bioorg. Med. Chem. Lett. 23 (2013) 488–491
489
diverse biological activities, such as antitumor,12 antiarrhythmic,13
anticonvulsant14 and herbicidal.15 Therefore, we planned to com-
bine the sulfonylureas and imidazolidinediones in a single mole-
cule, arylsulfonylspiroimidazolidinediones, to further our
previous work on antidiabetic agents.16,17 The target compounds
exhibited very good in vivo hypoglycemic activity and an excellent
in vitro aldose reductae inhibition. As a result, the compounds have
the potential to find use as hypoglycemic agents and in the treat-
ment of diabetic complications, in a single medication.
Spiroimidazolidine-2,4-dione (1) consisting of norcamphoryl
residue was obtained by employing Bucherer–Bergs reaction
(Scheme 1).18 Compound (1) was purified by repeated recrystalli-
zations in ethanol-water solvent pair affording a yield of 81%.
Spiroimidazolidine-2,4-dione was coupled with different arylsulfo-
nyl chlorides in presence of triethylamine and DMAP as a catalyst
to afford the desired 3-arylsulfonylspiroimidazolidine-2,4-diones
(2a–g).19
synthesis of compounds 2a–g was also confirmed in 13C NMR spec-
tra by the appearance of signals for C-2 and C-4 in the range of
150.2–151.6 and 172.7–173.8 ppm, respectively. The additional
carbonyl carbons in compound 2g resonated at d = 181.6 and
181.9 ppm. The synthesis of compounds 2a–g was further
confirmed in the mass spectra. A weak molecular ion peak was ob-
served in all the cases. The characteristic loss of SO2 and ArSO2 was
also observed for all the compounds. The isotopic M + 2 peaks were
present in the mass spectra of compounds 2b and 2c, confirming
the presence of halogen atoms in these molecules.
Plasma glucose measurements: The synthesized compounds were
tested for their antidiabetic potential on male albino rats. Plasma
glucose concentration dropped gradually and significantly on
A
600
NC
DC
The newly synthesized compounds were characterized by mod-
ern spectroscopic techniques. The spiroimidazolidine-2,4-dione (1)
was identified in the IR spectrum by the presence of two peaks at
3270 and 3217 cmÀ1 assigned to the N–H of the imide and amide
groups. The strong absorption bands at 1772 and 1704 cmÀ1 were
assigned to two carbonyl groups. The synthesis of compound (1)
was confirmed in the 1H NMR spectrum where two broad singlets
appeared at 10.56 and 8.44 ppm. These signals were assigned to
the protons of imido and amido groups, respectively. 13C NMR
spectrum exhibited two low intensity signals at 157.1 and
179.8 ppm for two carbonyl group.
The coupling of spiroimidazolidine-2,4-dione (1) with arylsulfo-
nyl chlorides was indicated in the IR spectra by the appearance of
peaks for anti-symmetric and symmetric O@S@O absorptions in
the range of 1392–1313 cmÀ1 and 1191–1141 cmÀ1, respectively.
The presence of only 1 peak for the N–H stretching in the range
of 3300–3100 cmÀ1 also indicated the successful synthesis of 3-
arylsulfonylspiroimidazolidine-2,4-diones (2a–g). The structures
of 3-arylsulfonylspiroimidazolidine-2,4-diones (2a–g) were con-
firmed using 1H NMR spectroscopy. The appearance of relatively
broad N–H signal in the range of 7.94–9.12 ppm confirmed the
coupling of arylsulfonyl group. The disappearance of the low field
signal N-H signal confirmed that the arylsulfonylation has taken
500
400
300
200
100
0
DGT
2a
2a
1
2
3
4
5
6
7
8
Time (hr)
450
400
350
300
250
200
150
100
50
B
NC
DC
DGT
2b
2b
place at position
3
of spiroimidazolidine-2,4-dione. The
norcamphoryl protons resonated in the region of 1.0–3.5 ppm.
The aromatic protons were observed as two doublets for com-
pounds 2a–e, while as multiplets in case of compounds 2f and
2g. The methyl protons in compound 2a resonated at d = 2.46,
while the methoxy protons in 2e appeared at d = 3.87 ppm. The
0
1
2
3
4
5
6
7
8
Time (hr)
O
i) KCN
C
600
500
400
300
200
100
0
ii) (NH4)2CO3
iii) HCl
HN
NC
DC
DGT
2g
O
2g
NH
55 ºC, aq. ethanol
O
(1)
Et3N
ArSO2Cl
DMAP
*
2a: Ar = 4-CH3C6H4
2b: Ar = 4-ClC6H4
2c: Ar = 4-BrC6H4
O
N
2d: Ar = 4-NO2C6H4
2e: Ar = 4-OCH3C6H4
2f: Ar = 4-(2-naphthyl)
2g: Ar = 4-(2-anthraquinonyl)
HN
SO2Ar
1
2
3
4
5
6
7
8
O
Time (hr)
(2a-g)
Scheme 1. Synthesis of 3-arylsulfonylspiroimidazolidin-2,4-diones (2a–g).
Figure 1. Significant lowering of plasma glucose in diabetic rats treated with
compounds 2a, 2b and 2g. ⁄⁄P <0.001.

490
Z. Iqbal et al. / Bioorg. Med. Chem. Lett. 23 (2013) 488–491
Table 1
Plasma glucose concentration (mg/dl) in healthy rats, diabetic rats, diabetic rats treated with glibenclamide, and diabetic rats treated with compounds 2a–g
Time (h)
NC
DC
DGT
2a
2b
2c
2d
2e
2f
2g
0
1
2
3
4
5
6
7
100 3.53
104 4.30
108 4.06
98 8.74
106 6.20
105 4.47
103 3.03
108 3.52
297 5.38
274 4.73
251 2.91
263 10.67
291 6.40
275 3.53
285 8.66
280 6.51
385 8.94
350 7.90
289 10.17
250 3.53
239 4.30
220 5.70
170 7.07
150 9.35
399 4.11
506 3.45
421 4.30
305 3.53
225 6.51
163 4.63
128 2.55a
114 2.91a
395 3.53
392 6.44
287 4.63
283 6.81
280 2.23
215 2.23
143 6.81a
128 8.95a
265 3.62
289 1.93
273 3.15
357 3.27
353 4.42
352 1.99
337 4.82
245 5.64
388 3.16
399 3.01
429 2.12
482 3.89
421 3.23
349 3.56
502 4.95
542 6.66
650 5.38
413 2.94
353 1.42
544 5.32
570 7.69
565 2.42
600 6.39
620 5.15
330 4.10
210 2.28
389 1.99
393 2.92
471 2.92
401 3.66
414 4.34
430 2.80
491 2.91
460 7.07
399 5.78
338 5.14
281 6.51
187 4.63
99 2.91a
86 4.30a
NC: normal control; DC: diabetic control; DGT: diabetic glibenclamide treated; comparisons were made between and within treatment groups.
Values represent mean SEM.
a
P <0.001.
Table 2
ALR2 inhibitory activity data
0.5
Compounds
IC50 SEMa
(lM)
0.4
0.3
0.2
0.1
0.0
2a
2b
2c
2d
2e
2f
2g
Sulindac
1.8 0.006
5.59 0.07
15.4 1.7
13.1 0.05
4.4 0.18
3.8 0.02
No Inhibitor
4.5 0.014
0.293 0.08b
20 (µM) 2a
Linear (No Inhibitor)
Linear (20 (µM) 2a)
a
n = 3.
Reported IC50: 0.374
b
l
M by Zheng et al.20
-10.0
-5.0
0.0
5.0
10.0
15.0
NADPH (mM) 1/Cp
2.5
2.0
1.5
1.0
0.5
0.0
Figure 3. Inhibitory effect of compound 2a on calf lens aldose reductase. Linewe-
aver–Burk plot by using NADPH, in the presence and absence of inhibitor (2a): (
no inhibitor; ( ) 20 lM 2a (uncompetitive type of inhibition).
)
No Inhibitor
Table 3
ALR1 inhibitory activity data
20 (µM) 2a
Linear (No Inhibitor)
Linear (20 (µM) 2a)
Compounds
IC50 SEM (lM)
2a
2b
2c
2d
116.7 2.97
61.1 0.85
43.2% (0.6 mM)
44.8 1.99
-5.0
0.0
5.0
10.0
15.0
D,L-Glyceraldehyde (mM) 1/S
2e
40.2 0.07
2f
2g
36.8% (0.6 mM)
41.6% (0.6 mM)
IC50: 57.4 0.89 (l
M)a
Figure 2. Inhibitory effect of compound 2a on calf lens aldose reductase. Linewe-
aver–Burk plot in the presence and absence of Inhibitor (2a): ( ) no inhibitor; (
20 M 2a (uncompetitive type of inhibition).
)
Valproic acid
l
a
Reported IC50: 56.1 ( 2.7) by Stefek and co-workers.22
treatment with compounds 2a, 2b and 2g. Euglycemic concentra-
tions were obtained 6 h after treatment with the respective com-
pounds and decreased further at 7 h post dosage. Mean plasma
glucose concentrations in compound 2a treated rats at 6 and 7 h
post treatment were 128 1.55 and 114 2.91, respectively, com-
pared to 0 or 1 h post treatment (F = 1260.28; P <0.001; Fig. 1A).
For compound 2b, the mean plasma glucose concentrations were
143 6.81 and 8.15 at 6 and 7 h, respectively (F = 335.90; P
<0.001; Fig. 1B). Similarly, mean plasma glucose concentrations of
compound 2g treated rats were 99 2.93 and 86 4.30 at 6 and
7 h post treatment, respectively (F = 738.37; P <0.001; Fig. 1C). Glu-
cose concentration did not decrease where rats were treated with
compounds 2c–f. Table 1 shows complete data sets in control and
compound treated rats. The present results show that compounds
2a, 2b and 2g possess potent glucose lowering activity, while com-
pounds 2c–f appear to be ineffective in lowering plasma glucose.
Overall compound 2g seems to be more promising than 2a and
2b in achieving euglycemic level. Importantly, all the three com-
pounds showed a greater glucose lowering activity as compared
to glibenclamide, a well known antidiabetic sulphonylurea drug.
Enzyme inhibition: Compounds 2a–g were also evaluated for
inhibition of the partially purified enzyme ALR2 extracted from
the calf eye. Sulindac was used as a reference drug (Table 2).
In the next step, the enzyme kinetics were determined using
compound 2a which was found most active at a concentration of
20
l
M. The type of inhibition was found to be uncompetitive when
-glyceraldehyde (Fig. 2) as a
it was observed in relation with
D,L
substrate and NADPH as a cofactor (Fig. 3). The Km value of ALR2,
was calculated as 0.537 mM, while the reported value is
0.585 mM.21
The Km value of ALR2 using NADPH was found to be 91.05
while reported value is 54
M.13 The series of arylsulfonylspiroim-
idazolidinediones was also tested on aldehyde reductase (ALR1),
lM,
l

Z. Iqbal et al. / Bioorg. Med. Chem. Lett. 23 (2013) 488–491
491
highly homologous enzyme to ALR2, partially purified from kid-
neys of calf. The results are tabulated in Table 3 as IC50 values. Val-
proic acid was used as positive control to validate the ALR1 assay.
In this assay, the most potent compound against ALR2 was
found to be 2a with a methyl group attached at position 4 of the
benzene ring. Compounds 2f and 2g also revealed excellent inhib-
itory activity, however, compound 2f having a naphthyl group as
an aryl moiety is more potent than 2g where naphthyl group is re-
placed with anthraquinyl group. The activity decreases little bit,
when halogen group is attached with the aryl moiety. The IC50
value of compound 2b with a chlorine atom attaches to the para-
exhibited excellent hypoglycemic activity and were more potent
than the standard drug glibenclamide, a well known 2nd genera-
tion antidiabetic drug. Compound 2a was also the most potent
inhibitor of ALR2. Rest of the compounds also revealed very good
activity against ALR2. The activity against ALR1 was synthesized
compounds also exhibit selectivity towards ALR2 over ALR1.
Supplementary data
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.bmcl.2012.
11.039. These data include MOL files and InChiKeys of the most
important compounds described in this article.
position of aryl group was found to be 5.59
lM, while it decreased
further to 15.4 M when bromine atom is present as a substituent
l
at the same position in compound 2c. The activity remains almost
the same when bromine was replaced with NO2 group, hence com-
References and notes
pound 2d showed IC50 value of 13.1
was used as a substituent again a good activity with IC50 value of
4.4 M was observed. In the next step, we determined the enzyme
lM. When a methoxy group
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l
kinetics using the most active compound (2a) in the series. A de-
crease in Km and Vmax values was observed in presence of inhibitor
2a, suggesting an uncompetitive type inhibition mechanism. This
means that in hyperglycaemic condition where the glucose level
is high, the inhibitory efficiency of the drug would not decrease.
The synthesized compounds were also evaluated for ALR1 inhibi-
tion. Compounds 2d and 2e showed a more potent activity than
5. Wick, A. N.; Drury, D. R. Am. J. Physiol. 1951, 166, 421.
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standard with an IC50 value of 44.8
lM and 42.2 lM, respectively,
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2012, 143, 497.
17. Kashif, M. K.; Ahmad, I.; Hameed, S. ARKIVOC 2008, xvi, 311.
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(resumed) 1962, 2789.
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21. Stefek, M.; Snirc, V.; Djoubissie, P. O.; Majekova, M.; Demopoulos, V.; Rackova,
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as compared to 57.4 M of the standard. The activity decreases
l
when a halogen atom is attached with the aryl group of arylsulfo-
nylspiroimidazolidinediones. Methoxy and nitro group attachment
caused the compound to become potent against ALR1.
It may be observed from the comparison of ALR1 and ALR2
activities that most of the synthesized compounds show selectivity
against ALR2 as compared to ALR1. Compound 2g is around 150-
fold more potent inhibitor of ALR2 than ALR1. Similarly, compound
2a is almost 100-fold and compound 2b about 10-fold more potent
towards ALR2 than ALR1. This selectivity towards ALR2 over ALR1
is desirable to minimize toxicity and side effects.
In conclusion, the synthesis of spirobicycloimidazolidine-2,4-
diones was successfully accomplished. The synthesized com-
pounds were evaluated for in vivo hypoglycemic activity on male
albino rats and inhibition of ALR1 and ALR2 extracted from the kid-
ney and eye of the calf, respectively. Compounds 2a, 2b and 2g