Antihyperglycemic activity of naphthylchalcones

Article abstract of DOI:10.1016/j.ejmech.2009.12.017

The purpose of the present work was to investigate, following previous works, naphthylchalcones as antihyperglycemic agent in glucose loaded animal model, insulin secretion as well as the action of these compounds on glucose uptake in a target tissue of insulin. The naphthylchalcones were found to have an acute serum glucose-lowering effect in hyperglycemic normal rats. In addition, chalcones 2 and 4 stimulated significantly the insulin secretion induced by glucose. These results suggest that the presence of nitro group and their position in the phenyl rings are responsible for the antihyperglycemic activity of chalcones. Additionally, the effect of chalcones on serum glucose-lowering seems to be a consequence of insulin secretion and these chalcones represent potential compounds with strong antihyperglycemic properties.

Full text of DOI:10.1016/j.ejmech.2009.12.017

European Journal of Medicinal Chemistry 45 (2010) 1332–1337
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Antihyperglycemic activity of naphthylchalcones
Rosangela Guollo Damazio a, Ana Paula Zanatta a, Luisa Helena Cazarolli a,
b
b
b
´
Louise Domeneghini Chiaradia , Alessandra Mascarello , Ricardo Jose Nunes ,
b
a,
*
´
Rosendo Augusto Yunes , Fatima Regina Mena Barreto Silva
a
´
ˆ
´
´
Departamento de Bioquımica, Centro de Ciencias Biologicas, Universidade Federal de Santa Catarina Campus Universitario,
´
Bairro Trindade, Cx. Postal 5069, CEP: 88040-970, Florianopolis, Santa Catarina, Brazil
b
´
ˆ
´
´
´
Departamento de Quımica, Centro de Ciencias Fısicas e Matematicas, Universidade Federal de Santa Catarina Campus Universitario,
Bairro Trindade, CEP: 88040-900, Floriano´polis, Santa Catarina, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
The purpose of the present work was to investigate, following previous works, naphthylchalcones as
antihyperglycemic agent in glucose loaded animal model, insulin secretion as well as the action of these
compounds on glucose uptake in a target tissue of insulin. The naphthylchalcones were found to have an
acute serum glucose-lowering effect in hyperglycemic normal rats. In addition, chalcones 2 and 4 stimu-
lated significantly the insulin secretion induced by glucose. These results suggest that the presence of nitro
group and their position in the phenyl rings are responsible for the antihyperglycemic activity of chalcones.
Additionally, the effect of chalcones on serum glucose-lowering seems to be a consequence of insulin
secretion and these chalcones represent potential compounds with strong antihyperglycemic properties.
Ó 2009 Elsevier Masson SAS. All rights reserved.
Received 21 August 2009
Received in revised form
25 November 2009
Accepted 8 December 2009
Available online 16 December 2009
Keywords:
Chalcones
Insulin secretion
Hyperglycemia
Structure–activity relationship
1. Introduction
Recently it was demonstrated that chalcone derivatives from
aryloxypropanolamines show potential antihyperglycemic effect in
Chalcones are compounds previously formed in natural synthesis
of flavonoids in plants and are known to exhibit several biological
activities such as apoptosis induction, an anti-proliferative action in
various cancer cell types, inhibition of pro-inflammatory mediators,
antiplatelet activity, potential antimalarial activity, among others
[1–7]. It is well known that different substituents at different posi-
tions on the core structure of chalcones (Fig. 1) determine biological
activity as well as the specificity of action [8–13].
Several studies have been demonstrated that chalcones either
from natural sources or synthetic chalcone can influence carbohy-
drate pathways, especially glucose metabolism. These studies show
that chalcones are effective antihyperglycemic or hypoglycemic
agents as much in vitro as in vivo experimental models [8,9,14]. It
has been reported that sulfonamide chalcones act as a potent new
hyperglycemic and diabetic rats [17]. It has been demonstrated that
chalcone derivatives from 3,4-methylenedioxybenzaldehyde, with
a nitro group at position 30 or 40, were able to improve glucose
tolerance curve in hyperglycemic normal rats. Based on that
promissory effect of chalcones on serum glucose-lowering effect in
hyperglycemic rats [12], the aim of this study was to investigate the
acute antihyperglycemic activity of chalcones with naphthyl group
substituting one phenyl ring in the core structure, and nitro group
as substituent in different positions of the other phenyl ring, on
serum glucose levels, on the potential insulin secretatogue effect as
well as the action of these compounds in a target tissue to insulin,
soleus muscle.
2. Chemistry
class of a-glucosidase inhibitors [10,15]. Also, it has been demon-
strated that chalcones stimulate glucose uptake and potentiate
insulin-stimulated glucose uptake in adipocytes [11], and chalcones
isolated from plants show insulin-like activities, stimulate the
induction of preadipocyte differentiation to adipocytes and
improve the glucose uptake in adipocytes [16].
Nine naphthylchalcones were prepared by aldolic condensation
between acetophenones and aldehydes, in methanol, under basic
conditions (Fig. 2). Chalcones 1, 2, 3, 6 and 7 are derived from
2-naphthaldehyde, chalcones 4 and 5 are derived from 2-naph-
thylacetophenone and chalcones 8 and 9 are derived from 1-naph-
thaldehyde, in order to observe the influence of the presence and of
the position of nitro group at A- and B-rings. The obtained yields
were between 54% and 97%. The structures of the compounds were
* Corresponding author. Tel.: þ55 48 3721.6912; fax: þ55 48 3721.9672.
E-mail address: mena@mbox1.ufsc.br (F.R.M. Barreto Silva).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.12.017

R.G. Damazio et al. / European Journal of Medicinal Chemistry 45 (2010) 1332–1337
1333
positions on the core structure of chalcones determine several
biological activity [3,19]. Among the several activities, was demon-
strated that synthetic methoxychalcone derivatives were able to
influence the biosynthesis of prostaglandins PGE2 and this activity is
related to differences in the positions of methoxyl groups [20], and it
was recently observed that the presence of substituents that
increase the electronic density of the A ring appear to be necessary
for potential inhibitory action of the chalcones towards a protein
tyrosine phosphatase (PtpA) from Mycobacterium tuberculosis [21].
Chalcones with nitro group at position 3 or 4 in the B ring
showed different profile of action, when administered to the
hyperglycemic rats. The compound 4 with nitro group at position 3
in the B ring, showed an effective antihyperglycemic action on
serum glucose levels over the time studied. However, chalcone 5,
with nitro group at position 4 in the B ring, did not influence the
serum glucose levels (Fig. 4A and B), contrasting to that showed in
the Fig. 3B. These results points that the position of the nitro group
is responsible for the antihyperglycemic activity of chalcones and
are in agreement with others studies that demonstrate that the
position of the substituents in the rings modifies the several bio-
logical activity of the chalcones [21,22].
Additionally, to verify the role of nitro group in the glycemia
levels, it was performed the oral glucose tolerance tests of chalcone
6 with 2-naphthyl group as B ring (and with the phenyl ring
without substituents as A ring) and chalcone 7 with the 2-naphthyl
group as A and B rings. Both chalcones were unable to modify the
serum glucose levels, reinforcing the functional activity of nitro
group in the rings to the chalcone biological activity (Fig. 5A and B).
It was also investigated the influence of the 1-naphthyl group as B
ring in the presence of nitro group at position 30 or 40 in the A ring on
serum glucose levels. The chalcone 8 and 9 produced serum glucose
lowering in the oral glucose tolerance curve by 18, 32 and 13% and 17,
21 and 14% at 15, 30 and 60 min, respectively, when compared to the
hyperglycemic control group (Fig. 6A and B). Taking into account the
positions of 1-naphthyl group as B ring in the chalcones 8 and 9 both
of them demonstrated similar antihyperglycemic activity when
compared to chalcones with 2-naphthyl group as B ring (Fig. 3B).
Based on the structure management demonstrated in this study, the
structure relationship of substituents on the core structure of chal-
cones with their activity seems to be an attractive pattern to opti-
mize the anti-diabetic potency of chalcone derivates.
O
2'
A
5'
2
1'
6'
1
3'
4'
3
4
B
6
5
Fig. 1. Core structure of chalcones.
confirmed by melting points and by chemical identification data: 1H
NMR, 13C NMR and IR. 1H NMR specters revealed that all structures
were geometrically pure and configured E (JH
¼ 16.0 Hz).
a
–Hb
3. Results and discussion
3.1. Effect of chalcones on serum glucose levels in hyperglycemic
rats
It was examined the effect of chalcones derived from 2-naph-
thylacetophenone and 1- and 2-naphthaldehyde with the corre-
spondent nitrobenzaldehydes and nitroacetophenones respectively,
on serum glucose levels in hyperglycemic normal rats. In a wide
number of experiments reported in the literature the dosage chosen
is between 4 and 25 mg/kg [17,18]. Also, based on previous studies
with chalcones in hyperglycemic in vivo model, the dosage chosen to
the present study was 10 mg/kg [12]. As expected, after starting the
oral glucose tolerance test, serum glucose level was significantly
increased when compared with zero time of the respective hyper-
glycemic control group (Fig. 3B). In all experiments, the vehicle (corn
oil) was not able to modify the hyperglycemic profile over time
studied (data not shown).
The oral administration of chalcone 1 and chalcone 2, with nitro
group at position 30 and 40 in the A ring, respectively, and with group
2-naphthyl as B ring showed significant, acute and lasting anti-
hyperglycemic activity. The treatment with chalcone 1 and chalcone
2 decreased serum glucose levels in the oral glucose tolerance curve
by 24, 25 and 14% and 22, 25 and 19% at 15, 30 and 60 min respec-
tively, when compared to the hyperglycemic control group (Fig. 3A
and B). Based on that results, the effect of chalcone 3 (with nitro
group at position 20 in the A ring), was studied. However, this
chalcone was not able to modify the profile of the glucose tolerance
curve, demonstrating the importance of nitro substituent at posi-
tion 30 or 40 in the A ring to biological activity (Fig. 3B).
3.2. Effect of chalcones on insulin secretion
Glucose-induced insulin secretion is an essential element in the
control of fuel homeostasis. It is a complex metabolic process in
pancreas, primarily driven by closure of ATP-sensitive potassium
channels, activation of voltage-dependent calcium channels and
subsequent insulin secretion in response to glucose metabolism in
It has been recently demonstrated that chalcone derivatives
from 3,4-methylenedioxybenzaldehyde, with different substituents
at position 30 or 40 in the A ring, were able to decrease the glycemia
in hyperglycemic normal rats on oral glucose tolerance curve [12].
Also, it has been documented that selected substituents at different
the b-cell [23]. Many compounds can increase insulin secretion in
vitro and are useful tools to the mechanisms of stimulus-secretion.
However, sulfonylureas were the only drugs used to stimulate
insulin secretion in patients with type 2 diabetes [24]. The most
efficient chalcones that were able to decrease serum glucose levels
in hyperglycemic rats, chalcones 2 and 4, were selected to study
their role as insulin secretagogues.
Insulin is the most important hormone in the regulation of
blood glucose concentrations and glucose is the primary stimulus
for insulin secretion [25,26]. As demonstrated in Fig. 7, the glucose-
induced insulin secretion was increased 128% at 15 min in hyper-
glycemic rats when compared with euglycemic group, returning to
the basal levels after 30 min. The rapid increase in serum insulin
levels observed in this figure confirms, in this model, the classical
profile of glucose-stimulated insulin secretion and these results are
according to that reported by Frangioudakis et al. (2008) [27].
O
O
O
a
R
OCH3
H
R'
R
R'
+
1 R = 3-NO2, R'= 2-naphthyl
2 R = 4-NO2, R'= 2-naphthyl
3 R = 2-NO2, R'= 2-naphthyl
4 R = 2-naphthyl, R'= 3-NO2
5 R = 2-naphthyl, R'= 4-NO2
6 R = phenyl, R'= 2-naphthyl
7 R = 2-naphthyl, R'= 2-naphthyl
8 R = 3-NO2, R'= 1-naphthyl
9 R = 4-NO2, R'= 1-naphthyl
Fig. 2. Synthesis of chalcones. a) KOH/MeOH, r.t., 24 h.

A
O
NO2
O
O
O2N
O2N
Chalcone 1
Chalcone 2
Chalcone 3
Hyperglycemic Control
Hyperglycemic + Chalcone 1 10 mg/kg
Hyperglycemic + Chalcone 2 10 mg/kg
Hyperglycemic + Chalcone 3 10 mg/kg
B
230
180
130
80
***
***
**
0 15 30
60
180
Time (min)
Fig. 3. (A) Structure of chalcone 1, (2E)-1-(30-nitrophenyl)-3-(2-naphthyl)-2-propen-1-one; chalcone 2, (2E)-1-(40-nitrophenyl)-3-(2-naphthyl)-2-propen-1-one; and chalcone
3, (2E)-1-(20-nitrophenyl)-3-(2-naphthyl)-2-propen-1-one; (B) Effect of chalcones 1, 2 and 3 on oral glucose tolerance curve. Values are expressed as mean ꢀ S.E.M; n ¼ 8. Significant
at **P ꢁ 0.01 and ***P ꢁ 0.0001 in relation to hyperglycemic control.
O
O
A
NO2
NO2
Chalcone 4
Chalcone 5
B
Hyperglycemic Control
Hyperglycemic + Chalcone 4 10 mg/kg
Hyperglycemic + Chalcone 5 10 mg/kg
230
180
130
80
**
***
0 15 30
60
180
Time (min)
Fig. 4. (A) Structure of chalcone 4, (2E)-1-(2-naphthyl)-3-(3-nitrophenyl)-2-propen-1-one; and chalcone 5, (2E)-1-(2-naphthyl)-3-(4-nitrophenyl)-2-propen-1-one; (B) Effect of
chalcones 4 and 5 on oral glucose tolerance curve. Values are expressed as mean ꢀ S.E.M; n ¼ 8. Significant at **P ꢁ 0.01 and ***P ꢁ 0.0001 in relation to hyperglycemic control.

O
O
A
Chalcone 6
Chalcone 7
Hyperglycemic Control
Hyperglycemic + Chalcone 6 10 mg/kg
Hyperglycemic + Chalcone 7 10 mg/kg
B
230
180
130
80
0 15 30
60
180
Time (min)
Fig. 5. (A) Structure of chalcone 6, (2E)-1-phenyl-3-(2-naphthyl)-2-propen-1-one; and chalcone 7, (2E)-1,3-di(2-naphthyl)-2-propen-1-one; (B) Effect of chalcones 6 and 7 on oral
glucose tolerance curve. Values are expressed as mean ꢀ S.E.M; n ¼ 8.
O
A
O
O2N
O2N
Chalcone 8
Chalcone 9
Hyperglycemic Control
B
Hyperglycemic + Chalcone 8 10 mg/kg
Hyperglycemic + Chalcone 9 10 mg/kg
230
180
***
***
***
130
80
0 15 30
60
180
Time (min)
Fig. 6. (A) Structure of chalcone 8, (2E)-1-(30-nitrophenyl)-3-(1-naphthyl)-2-propen-1-one; and chalcone 9, (2E)-1-(40-nitrophenyl)-3-(1-naphthyl)-2-propen-1-one; (B) Effect of
chalcones 8 and 9 on oral glucose tolerance curve. Values are expressed as mean ꢀ S.E.M; n ¼ 8. Significant at ***P ꢁ 0.0001 in relation to hyperglycemic control.

1336
R.G. Damazio et al. / European Journal of Medicinal Chemistry 45 (2010) 1332–1337
stimulated glucose uptake in adipocytes [11]. Also, chalcones iso-
Euglycemic group
Hyperglycemic Control
lated from plants show strong insulin-like activities and improve
the glucose uptake in adipocytes [16]. On the other hand, there is no
report on chalcone stimulatory effect on glucose uptake in muscle
cells. Than, we selected the chalcone 2 (based on the influence of
this compound on serum glucose levels as well as on insulin
secretion), to assess their effect on 14C-DG uptake in soleus muscle.
Based on the dose–response curve of chalcones on glucose
uptake in adipocytes, the Fig. 8 shows the in vitro effect of chalcone
2 (10ꢂ4, 10ꢂ7 and 10ꢂ9 M) on glucose uptake in soleus muscle after
60 min of incubation. No stimulatory effect was observed to chal-
cone 2 on glucose uptake compared with control group. Addi-
tionally, any alteration on serum glucose levels in diabetic rats was
observed after this chalcone treatment (data not shown).
Hyperglycemic + Chalcone 2
Hyperglycemic + Chalcone 4
1.50
1.25
1.00
0.75
0.50
0.25
**
*
#
**
4. Conclusion
These results show that the position of the nitro group is
responsible for the antihyperglycemic activity of chalcones. Addi-
0
15
30
60
tionally, it points that b-pancreatic cells are an important target to
Time (min)
particular chalcones to act quickly on the glucose management and
on the glucose homeostasis. Chalcone 2 in vivo was able to
ameliorate significantly the glucose tolerance curve and induced
insulin secretion, indicating this chalcone as a potential insulin
secretagogue. Studies are underway in order to clarify the mecha-
Fig. 7. Effect of chalcones 2 and 4 (10 mg/kg)onserum insulin levelsinhyperglycemic rats.
Values are expressed as mean ꢀ SEM; n ¼ 8. Significant at #P ꢁ 0.01 in relation to eugly-
cemic group; Significant at *P ꢁ 0.05, **P ꢁ 0.01 and in relation to hyperglycemic control.
Additionally, the treatment with chalcone 2 and 4 potentiated the
glucose effect on insulin secretion in hyperglycemic rats after 30
and 60 min, compared to the hyperglycemic control group. The
stimulatory effect of chalcone 2 and 4 in insulin secretion was
around 27% and 48% at 30 min and 104% and 88% at 60 min,
respectively, when compared with respective time-course in
hyperglycemic control group (Fig. 7). Also, in the presence of
chalcones, a sustained high insulin serum levels is observed during
this time-course studied. So, the antihyperglycemic effect of chal-
cones observed on serum glucose lowering in hyperglycemic rats
seems to be a consequence of insulin secretion.
nism of action of chalcones on in vitro
5. Experimental protocols
5.1. Materials
b-cells.
Enzyme-linked immunosorbent assay (ELISA) for quantitative
determination of rat insulin (catalogue no. EZRMI-13 K) was
purchased from Millipore (St Charles, MO, USA). [U-14C]-2-deoxy-
D-
glucose ([14C]-DG), specific activity 10.6 GBq/mmol, and biode-
gradable liquid scintillation were obtained from Perkin Elmer Life
and Analytical Sciences (Boston, MA). Salts and solvents were
purchased from MerckÒ AG (Darmstadt. Germany). Reagents used
in synthesis are obtained commercially from Sigma–AldrichÒ and
MerckÒ.
3.3. Effect of chalcone 2 on 14C-glucose uptake in rat soleus muscle
It has been demonstrated the effect of 20-benzyloxychalcone
derivatives stimulate glucose uptake and potentiate insulin-
5.2. Chalcone synthesis
Control
[10-4 M]
[10-7 M]
[10-9 M]
All chalcones were prepared by magnetic agitation of aldehydes
and acetophenones, in methanol and KOH (50% v/v), at room
temperature for 24 h. Distilled water and 10% hydrochloric acid were
added to the reaction for total precipitation of the compounds, which
were then obtained by vacuum filtration and later recrystallized in
dichloromethane and hexane. The structures were identified by their
melting points, 1H and 13C nuclear magnetic resonance spectroscopy
(NMR) and infrared spectroscopy (IR). The chalcones 3, 4, 5 and 7
were previously cited, respectively, by Tollari et al. [28], Thirunar-
ayanan [29], Deshpande et al. [30] and Bowen et al. [31]. The
compounds 1, 2, 6, 8 and 9 were previously described by us [21].
1.5
1.0
0.5
5.3. Experimental animals
Male Wistar rats weighing 180–210 g were used. The rats were
housed in plastic cages in an air-conditioned animal room and fed
on pellets (Nuvital, Nuvilab CR1, Curitiba, PR, Brazil), with free
access to tap water. Room temperature was controlled at 21 ꢃC with
a 12 h light: 12 h dark cycle. Animals described as fasted had been
deprived of food for 16 h but allowed free access to water. All the
animals were monitored carefully and maintained in accordance
with the ethical recommendations of the Brazilian Veterinary
0.0
Chalcone 2
Fig. 8. Effect of chalcone
expressed as mean ꢀ S.E.M; n ¼ 4 in duplicate for each group.
2
on 14C-glucose uptake in soleus muscle. Values are

R.G. Damazio et al. / European Journal of Medicinal Chemistry 45 (2010) 1332–1337
1337
Medicine Council and the Brazilian College of Animal Experimen-
tation (CEUA protocol PP00117/UFSC).
Acknowledgements
This study was supported by grants and fellowships from Con-
´
´
5.4. Determination of serum glucose levels
selho Nacional de Desenvolvimento Cientıfico e Tecnologico-Brasil
(CNPq) and PIBIC-CNPq/Universidade Federal de Santa Catarina
´
Program. Coordenaça˜o de Pessoal de Nıvel Superior (CAPES-
Blood samples from the tail vein were collected, centrifuged and
the serum was used to determine the glycemia by the glucose
oxidase method [12,32].
`
PGFAR), and Fundaça˜o de Amparo a Pesquisa do Estado de Santa
Catarina (FAPESC). R. G. D. and L. H. C. are registered on the PGFAR-
UFSC. A. P. Z. is registered on the PG-Biochemistry-UFSC. L. D. C. and
A. M. are registered on the PGQMC-UFSC. The authors express their
appreciation to Dr. Danilo Wilhelm Filho and to the laboratory of Dr.
5.5. Study of chalcones on glucose tolerance curve
ˆ
¨
Fasted normal rats were divided into different groups of eight
rats. Group I, hyperglycemic control rats that received glucose (4 g/
kg; 8.9 M); Group II, treated hyperglycemic rats that received
vehicle (corn oil): Group III, treated hyperglycemic rats that
received different chalcones (1, 2, 3, 4, 5, 6, 7, 8 and 9) (10 mg/kg);
For all oral treatments, 0.5 mL of each substance was given by oral
gavage and the serum glucose levels were measured immediately
prior to, and at 15, 30, 60 and 180 min after, treatment. After
centrifugation, serum samples were used to determine serum
glucose levels or for the insulin measurement.
Tania Silvia Frode for experimental support.
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