Organoselenium compounds from purines: Synthesis of 6-arylselanylpurines with antioxidant and anticholinesterase activities and memory improvement effect

Article abstract of DOI:10.1016/j.bmc.2017.11.019

We describe here a simple method for the synthesis of 6-arylselanylpurines with antioxidant and anticholinesterase activities, and memory improvement effect. This class of compounds was synthesized in good yields by a reaction of 6-chloropurine with diaryl diselenides using NaBH₄ as reducing agent and PEG-400 as solvent. Furthermore, the synthesized compounds were evaluated for their in vitro antioxidant and acetylcholinesterase (AChE) inhibitor activities. The best AChE inhibitor was assessed on the in vivo memory improvement. Our results demonstrated that the 6-((4-chlorophenyl)selanyl)-9H-purine and 6-(p-tolylselanyl)-9H-purine presented in vitro antioxidant effect. In addition, 6-((4-fluorophenyl)selanyl)-9H-purine inhibited the AChE activity and improved memory, being a promising therapeutic agent for the treatment of Alzheimer's disease.

Full text of DOI:10.1016/j.bmc.2017.11.019

Accepted Manuscript
Organoselenium compounds from Purines: Synthesis of 6-arylselanylpurines
with antioxidant and anticholinesterase activities and memory improvement ef-
fect
Luis Fernando B. Duarte, Renata L. Oliveira, Karline C. Rodrigues, Guilherme
T. Voss, Benhur Godoi, Ricardo F. Schumacher, Gelson Perin, Ethel A.
Wilhelm, Cristiane Luchese, Diego Alves
PII:
S0968-0896(17)31923-5
https://doi.org/10.1016/j.bmc.2017.11.019
BMC 14071
DOI:
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
28 September 2017
7 November 2017
10 November 2017
Please cite this article as: Duarte, L.F.B., Oliveira, R.L., Rodrigues, K.C., Voss, G.T., Godoi, B., Schumacher, R.F.,
Perin, G., Wilhelm, E.A., Luchese, C., Alves, D., Organoselenium compounds from Purines: Synthesis of 6-
arylselanylpurines with antioxidant and anticholinesterase activities and memory improvement effect, Bioorganic
& Medicinal Chemistry (2017), doi: https://doi.org/10.1016/j.bmc.2017.11.019
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Organoselenium compounds from Purines:
Synthesis of 6-arylselanylpurines with
antioxidant and anticholinesterase activities
and memory improvement effect
Leave this area blank for abstract info.
Luis Fernando B. Duarte, Renata L. Oliveira, Karline C. Rodrigues, Guilherme T. Voss, Benhur Godoi,
Ricardo F. Schumacher, Gelson Perin, Ethel A. Wilhelm, Cristiane Luchese* and Diego Alves*

Bioorganic & Medicinal Chemistry
journal homepage: www.els evier.com
Organoselenium compounds from Purines: Synthesis of 6-arylselanylpurines
with antioxidant and anticholinesterase activities and memory improvement
effect
Luis Fernando B. Duartea, Renata L. Oliveirab, Karline C. Rodriguesb, Guilherme T. Vossb,
Benhur Godoic, Ricardo F. Schumachera, Gelson Perina, Ethel A. Wilhelmb, Cristiane
Lucheseb* and Diego Alvesa*
a Laboratório de Síntese Orgânica Limpa - LASOL - CCQFA - Universidade Federal de Pelotas - UFPel - P.O. Box 354 - 96010-900, Pelotas, RS, Brazil.
b Programa de Pós-Graduação em Bioquímica e Bioprospecção, Laboratório de Pesquisa em Farmacologia Bioquímica, Grupo de Pesquisa em
Neurobiotecnologia - GPN, CCQFA Universidade Federal de Pelotas, UFPel, Pelotas, RS, Brasil.
c Núcleo de Síntese, Aplicação e Análise de Compostos Orgânicos e Inorgânicos, Universidade Federal da Fronteira Sul - UFFS, Cerro Largo - RS - Brasil.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
We describe here a simple method for the synthesis of 6-arylselanylpurines with antioxidant and
anticholinesterase activities, and memory improvement effect. This class of compounds was
synthesized in good yields by a reaction of 6-chloropurine with diaryl diselenides using NaBH4
as reducing agent and PEG-400 as solvent. Furthermore, the synthesized compounds were
evaluated for their in vitro antioxidant and acetylcholinesterase (AChE) inhibitor activities. The
best AChE inhibitor was assessed on the in vivo memory improvement. Our results
demonstrated that the 6-((4-chlorophenyl)selanyl)-9H-purine and 6-(p-tolylselanyl)-9H-purine
presented in vitro antioxidant effect. In addition, 6-((4-fluorophenyl)selanyl)-9H-purine
inhibited the AChE activity and improved memory, being a promising therapeutic agent for the
treatment of Alzheimer’s disease.
Available online
Keywords:
Purine
Organoselenium compounds
Antioxidant
Acetylcholinesterase
Memory
2017 Elsevier Ltd. All rights reserved
.
1. Introduction
role in metabolic pathways, including hormonal metabolism and
immune function.6
1
Nucleoside analogues show significant roles in numerous
biological processes.1 There are five nitrogenous bases that form
the nucleosides, and two of them are purines (adenine and
guanine). Up till now, there are over 30 nucleoside analogues
approved for use as antiviral or cytotoxic agents and almost 50%
of these molecules containing structurally transformations on the
pyrimidine/purine ring.2 The structure of purines consist in a
pyrimidine fused to an imidazole and they are the most widely
distributed nitrogen heterocycles in nature.3 Therefore, synthetic
approaches have been developed for the synthesis of structurally
diverse purine derivatives, which possess several biological
activities such as antitumor, antitubercular, fungicidal and
antioxidant effects.4 The 6-position at the purine ring is a
principal modification place for many of these applications.5
Additionally, the interest in the organoselenium
pharmacology and chemistry has increased in the last two
decades due to a variety of selenium compounds that possess
biological activities. Organoselenium derivatives are considered
attractive synthetic targets, owing to their special structural
motifs and unique reactivity.7 Indeed, a number of important
pharmacological properties have been attributed to
organoselenium compounds, such as antioxidant,8 anti-
inflammatory,9
neuroprotective,10
anxiolytic-like,11
antihyperglycemic,12 among others.
In this sense, selenium-containing purines are an interesting
class of compounds since they combine the well-known
applicability of the purine skeleton with that of the selenium
moieties. Thus, the synthesis of selenium-containing purines13
has great significance and as example, alkylselanylpurines have
shown activity as an inhibitor of the growth of mouse leukemia
L121014 and could be used in the treatment of neural measles
virus infection.15
In the other hand, selenium is a trace element being
considered an essential dietary nutrient for all mammals. This
element presents several physiological functions as structural
component of diverse antioxidant enzymes, playing important
———
In view of the above mentioned, and according our interest in
the synthesis and biological evaluation of nitrogen-functionalized
organoselenium compounds,16 we report here our results on the
*Corresponding author: Phone/fax: +55 53 32757533,
e-mail: cristiane_luchese@yahoo.com.br and diego.alves@ufpel.edu.br

synthesis of 6-arylselanylpurines by reactions of 6-chloropurine
with diaryl diselenides and NaBH4 using PEG-400 as solvent. In
addition, the synthesized compounds were screened for their in
vitro antioxidant action and inhibitory effect on the cerebral
acetylcholinesterase (AChE) activity. Considering the obtained in
vitro results, we investigated the activity of compound with better
inhibitory effect on the AChE activity on the three stages of
memory (acquisition, consolidation and retrieval) in mice.
substituted nitrogen heterocycle 2b-f (0.5 mmol) was added and
the mixture was stirred at 60 °C for additional 1 hour. Then, the
reaction mixture was received in water (10 mL), extracted with
ethyl acetate (3 x 5 mL), dried over MgSO4, and concentrated
under vacuum. The residue was purified by column
chromatography on silica gel using
a mixture of ethyl
acetate/hexanes as the eluent. The new compounds were fully
characterized and the spectral data are provided in the Support
Information.
2.2. Biological assays
2.2.1 Animals
Male adult Swiss mice (25-35 g) from our own breeding
colony were used. The animals were kept on a separate animal
room, in a 12 h light/dark cycle, at a room temperature of 22
2ºC, with free access to food and water. Animals were used
according to the guidelines of the Committee on Care and Use of
Experimental Animal Resources, Federal University of Pelotas,
Brazil (CEEA 1974-2016).
Scheme 1. General scheme of the present work.
2. Materials and Methods
2.1. Chemistry
2.2.2.
scavenging activity
2,2’-Diphenyl-1-picrylhydrazyl
(DPPH)
radicals
In the DPPH assay, the reduction of DPPH radical by
antioxidants could be through the donation of hydrogen atom to a
free radical to remove the extra electron (which is responsible for
the activity of free radicals).17 A DPPH stable radical assay was
performed in accordance with Choi et al..18 Briefly, DPPH was
added to a medium containing compounds (3a-3g) at different
concentrations (1-200 µM). Compounds were solubilized in
dimethyl sulfoxide (DMSO) before the use. Compound 3h was
not used in the assay because it not solubilized efficiently in
DMSO. The medium was incubated for 30 min at room
temperature. For each assay, 3 independent experiments were
carried out in different days. The decrease in absorbance was
measured at 517 nm, which depicted the scavenging activity of
purine derivatives (3a-3g) against DPPH. The values were
expressed in % of blank: DPPH radicals scavenging activity =
(absorbance of sample x 100) / absorbance of blank.
The reactions were monitored by TLC carried out on Merck
silica gel (60 F254) by using UV light as visualizing agent and
5% vanillin in 10% H2SO4 and heat as developing agents. Proton
nuclear magnetic resonance spectra (1H NMR) were obtained at
300 MHz or 400 MHz on Bruker DPX 300 or DPX 400
spectrometers, respectively. Spectra were recorded in CDCl3 and
DMSO-d6 solutions. Chemical shifts are reported in ppm,
referenced to the signal of tetramethylsilane (TMS) as the
external reference or DMSO signals. Coupling constants (J) are
reported in Hertz. Abbreviations to denote the multiplicity of a
particular signal are s (singlet), d (doublet), dd (doublet of
doublet), t (triplet), q (quartet) and m (multiplet). Carbon-13
nuclear magnetic resonance spectra (13C NMR) were obtained at
75 MHz or 100 MHz on Bruker DPX 300 or DPX 400
spectrometer, respectively. Chemical shifts are reported in ppm,
referenced to the solvent peak of CDCl3 or DMSO-d6. Low-
resolution mass spectra were obtained with a Shimadzu GC-MS-
QP2010 mass spectrometer. High resolution mass spectra
2.2.3. 2,2'-Azino bis-3-ethylbenzothiazoline-6 sulfonic acid
(ABTS) radicals scavenging activity
ABTS is a protonated radical and it is used for evaluating the
scavenger activity of proton radicals.17 The ABTS radical assay
was performed in accordance with Re et al..19 In short, ABTS
was added to a medium containing purine derivatives (3a-3g) at
different concentrations (1-200 µM). Compounds were
solubilized in DMSO before the use. Compound 3h was not used
in the assay because it not solubilized efficiently in DMSO. The
medium was incubated for 30 min at room temperature. For each
assay, 3 independent experiments were carried out in different
days. The decrease in absorbance was measured at 734 nm,
which depicted the scavenging activity of purine derivatives (3a-
3g) against ABTS. The values were expressed in % of blank:
ABTS radicals scavenging activity = (absorbance of sample x
100) / absorbance of blank.
(HRMS) were recorded on
spectrometer 10416.
a
Bruker Micro TOF-QII
2.1.1. General procedure for the synthesis of 6-
arylselanylpurines 3a-h:
To a round-bottomed flask containing a solution of diorganyl
diselenide 1a-h (0.25 mmol) in PEG-400 (1.0 mL) under N2
atmosphere, was added NaBH4 (1.0 mmol). The resulting
solution was stirred for 1 hour at 60 °C, when its color changes
from yellow to colorless. After this, the 6-chloropurine 2a (0.5
mmol) was added and the mixture was stirred at 60 °C for
additional 1 hour. Then, the desired product was precipitated
when the pH was adjusted to 6 using 6 N HCl. The product was
collected, washed with H2O and then purified by
recrystallization. The new compounds were fully characterized
and the spectral data are provided in the Support Information.
2.2.4. AChE activity assay
Animals were killed by inhalation of isoflurane, and cerebral
cortex were quickly removed, placed on ice and homogenized
1:10 (w/v) in Medium I (0.32 M sucrose, 5.0 mM HEPES, 0.1
mM ethylenediaminetetraacetic acid disodium salt) buffer. The
homogenate was centrifuged at 2400xg at 4ºC for 15 min to yield
the low-speed supernatant (S1) fraction that was used in the
assays. For each assay, 3 independent experiments were carried
out in different days, using different animals. The AChE activity
2.1.2. General procedure for the synthesis of N-
Heterocycle-SePh 3i-m:
To a round-bottomed flask containing a solution of diphenyl
diselenide 1a (0.25 mmol) in PEG-400 (1.0 mL) under N2
atmosphere, was added NaBH4 (1.0 mmol). The resulting
solution was stirred for 1 hour at 60 °C, when its color changes
from yellow to colorless. After this, the appropriated chlorine

of cerebral cortex was performed according to the method of
Ellman et al.20 with some modifications, using acetylthiocholine
iodide as a substrate. An aliquot of 50 µl of the S1 (protein of 2.8
mg/ml) was pre-incubated for 2 min at 25ºC in the presence of
compounds 3a-3g, at different concentrations (1-200 µM) in a
medium containing potassium phosphate buffer 100 mM, pH 7.5.
Compounds were solubilized in DMSO before the use.
Compound 3h was not used in the assay because it not
solubilized efficiently in DMSO. Enzymatic reaction was
initiated by adding 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB)
to a final concentration of 0.5 mM and acetylthiocholine to a
final concentration of 0.8 mM. The rate of hydrolysis of
acetylthiocholine iodide was measured at 412 nm through the
release of the thiol compound which when reacted with DTNB,
produces the color-forming compound thionitrobenzene (TNB).
The activity of AChE was expressed as µmol
acetylthiocholine/h/mg protein. The protein concentration was
measured by the method of Bradford21 using bovine albumin
serum (1 mg/ml) as a standard.
the data were analyzed using a non-paired t-test and the results
were expressed as mean standard error medium (S.E.M.).
Values of p < 0.05 were considered statistically significant.
3. Results and Discussion
3.1. Chemistry
In the last years our research group has continuously explored
the potential of NaBH4/PEG-400 as reaction system to promote
different synthetic transformations.7e,24 Thus, based in our
previous works and considering that there are no reports of the
use of this system to promote the insertion of organochalcogen
moieties into purine nucleus, we decided to study the efficiency
of this reaction medium to promote the functionalization of
purine derivatives by employing different diaryl diselenides as
source of organochalcogen nucleophilic species. First, in a
mixture of diphenyl diselenide 1a (0.25 mmol) in PEG-400 (1.0
mL) under N2 atmosphere, we added NaBH4 (1.0 mmol) and the
reaction was stirred for 1 hour at 60 °C. After this time, the 6-
chloropurine 2a (0.5 mmol) was added and the mixture was
stirred at 60 °C for additional 1 hour. Through this protocol the
desired 6-phenylselanyl-purine 3a was successfully obtained in
96% yield, after 1h (Table 1, entry 1). Importantly, the use of
only 0.5 equivalent of PhSeSePh on this experiment suggests that
both “PhSe” moieties are being consumed for the final product
formation, which represents an advantage of this method
regarding to atom economy.
2.2.5. Behavioral tasks - In vivo
Considering the in vitro results of purine derivatives on the
cerebral AChE activity, compound with better inhibitory effect
was used on the behavioral tasks. Mice were allowed to
acclimatize to the holding room for 2 h before the behavioral
procedure. All manipulations were conducted in the light phase.
2.2.5.1. Step-down inhibitory avoidance:
Table 1. Variability in the synthesis of 6-arylselanylpurines.a
Non-spatial long-term memory was investigated using a step-
down inhibitory avoidance task according to the method of
Sakaguchi et al.,22 with modifications in the intensity of electric
shock and in the exposure time. Each mouse was placed on the
platform, and the latency to step-down (four paws on the grid)
was automatically recorded in training and test sessions. In the
training session, upon stepping down, the mouse received a 0.5
mA scrambled foot shock for 2 s. Test sessions were performed
24 h later, with the same procedure except that no shock was
administered after stepping down; an upper cut-off time of 300 s
was set. Six to eight animals were used per group. Compound 3e,
which inhibited AChE activity in vitro, was given 30 min before
training (acquisition), immediately post-training (consolidation),
or 30 min before test (retrieval), at the dose of 10 mg/kg of body
weight (intragastrically (i.g.)). Control animals received vehicle
(canola oil 10 ml/kg of body weight, i.g.).
Product
(Yield)b
Product
(Yield)b
Entry
1
Entry
5
3a (96%)c
3e (55%)
2.2.5.2. Open-field test:
Spontaneous locomotor and exploratory activities were
measured in the open-field test.23 The open-field was made of
plywood and surrounded by walls 30 cm in height. The floor of
the open-field, 45 cm in length and 45 cm in width, was divided
by masking tape markers into 9 squares (3 rows of 3). Each
animal was placed individually at the center of the apparatus and
observed for 4 min to record the locomotor (expressed by number
of segments crossed with the four paws) and exploratory
(expressed by the number of time rearing on the hind limbs)
activities. Six to eight animals were used per group. The
locomotor and exploratory activities were evaluated after the test
session of the step-down inhibitory avoidance task.
2
3
4
6
7
8
3b (74%)
3c (65%)
3d (87%)
3f (86%)
3g (95%)
3h (55%)
2.2.6. Statistical analysis
For in vitro assays, statistical analysis was performed using a
one-way ANOVA followed by the Newman–Keuls test when
appropriated and the results were expressed as mean standard
derivation (S.D.). Maximal inhibition (Imax
- maximum
percentage that an inhibitor reduced a response) was calculated at
the most effective concentration used. For in vivo experiments,

a
Reactions were performed using diorganyl diselenide 1a-h (0.25 mmol),
Interestingly, when 4,7-dichloroquinoline and 2,6-
dichloroquinoxaline were submitted to the same reaction
conditions the desired heterocycles 3i e 3m were isolated in
excellent yields and these transformations carried out with high
regioselectivity since in all cases only one chlorine atom was
replaced by the organochalcogen group (see Scheme 2).
NaBH4 (1.0 mmol) in PEG-400 (1 mL) at 60 °C under N2 atmosphere for 1 h.
After this, 6-chloropurine 2a (0.5 mmol) was added and the mixture was
b
stirred at 60 °C for additional 1 hour. Yields are given for isolated products.
c One reaction was performed in a 5 mmol scale and the desired product 3a
was obtained in 90% yield.
Encouraged by this promising result we have focused on
verify the versatility of this synthetic methodology using
differently substituted diaryl diselenides. These tests showed that
this synthetic approach is not sensitive to electronic effects from
the substituents in the aromatic rings of the diselenides. Diaryl
diselenides bearing neutral, donating and electron-withdrawing
groups afforded the expected 6-arylselanyl-purines 3a,d-g in
good to excellent yields (Table 1, entries 1,4-7). On the other
hand, the target heterocycles 3b, 3c and 3h were obtained in 74,
65 and 55% yields, respectively. These results suggest that the
reaction behavior has being affected by steric hindrance from the
methyl groups bonded to the aromatic rings of the diselenides
(Table 1, compare entries 2,3 and 8).
These results increase the synthetic importance of this
methodology once the preservation of a chlorine atom in the final
product structure allows further functionalization of the
heterocycle units by using several synthetic tools.
3.2. Biological assays
3.2.1. In vitro antioxidant activity of purine derivatives: DPPH
and ABTS radicals scavenging activities
Synthetic radicals DPPH and ABTS have been used for the
determination of scavenger mechanism of antioxidants
molecules.25 In the DPPH assay, antioxidant molecules donate
hydrogen to free radical, removing the extra electron, which is
responsible for the damage caused by free radical. In the present
study, it was verified that compound 3f demonstrated DPPH
radical scavenging activity at concentrations equal to 200 µM
(Table 2). The Imax of compound 3f was 32%. Compounds 3a, 3b,
3c, 3d, 3e and 3g, at all concentrations used, did not show DPPH
radical scavenging activity (Table 2).
Like radical DPPH, ABTS radical is also used to check the
scavenger activity of antioxidants.26 In the ABTS assay,
protonated ABTS radical is used to evaluate the scavenger
activity of proton radicals, which are an important attribute of
antioxidant molecules.17 Our results showed that compounds 3b
and 3f presented a significant ABTS radical scavenging activity
at concentrations equal to or greater than 100 µM, while
compound 3a demonstrated scavenger activity at concentrations
equal to 200 µM (Table 3). The Imax values of compounds 3a, 3b
and 3f were 13.5, 38.5 and 27.4%, respectively. Compounds 3c,
3d, 3e and 3g, at all concentrations used, did not present ABTS
radical scavenging activity (Table 3).
Scheme 2. Variability in the synthesis of N-Heterocycle-SePh.
In order to extend the scope and confirm the versatility of the
synthetic method different chlorine substituted nitrogen
heterocycles were submitted to the same reaction condition in the
presence of diphenyl diselenide 1a. When the 2-chloropyrimidine
and 2-chloroquinoxaline were employed as substrates the
3.2.1. In vitro AChE activity assay
AChE is an enzyme with a key role in cholinergic
neurotransmission by hydrolyzing the acetylcholine to acetate
and choline in the synaptic cleft.27 AChE inhibitors are strategies
of treatment to Alzheimer’s disease.28 Nowadays, the Food and
Drug Administration (FDA) approved four AChE inhibitors for
the treatment of Alzheimer’s disease (tacrine, donepezil,
galanthamine and rivastigmine). However, these drugs have low
bioavailability and undesirable side effects. Thus, this study
reported inhibitory effect of purine derivatives (3a-3g) on AChE
activity in cerebral cortex of mice.
corresponding
2-phenylselanyl-pyrimidine
3j
and
2-
phenylselanyl-quinoxaline 3k were isolated in 97 and 80% yields
(Scheme 2). By employing the 2,3-dichloroquinoxaline as
starting reagent under the optimized reaction conditions the 2,3-
bis(phenylselanyl)quinoxaline 3l was obtained in excellent yield
by the replacement of the two chlorine atoms by both “PhSe”
moieties from the diphenyl diselenide.
Table 2. Effect of purine derivatives 3a-3g in the DPPH radical scavenging activity.
Purine derivatives
3a
3b
3c
3d
3e
3f
3g
Blank
1 µM
100.0 10.0
99.4 0.9
100.0 10.0
100.7 0.5
100.0 10.0
100.2 0.4
100.0 10.0
99.8 0.6
100.0 10.0
99.4 1.0
100.0 10.0
100.0 1.0
100.0 10.0
99.7 0.4
10 µM
99.4 0.2
95.1 1.1
90.1 2.1
99.7 0.8
96.3 0.7
93.0 1.8
100.0 0.7
99.3 0.5
98.7 0.4
99.7 0.9
98.5 0.4
97.5 0.5
99.4 0.6
98.6 1.0
98.0 1.4
98.8 1.5
85.9 2.6
68.0 3.3*
99.4 0.9
99.4 0.6
99.0 1.8
100 µM
200 µM
Data are reported as mean S.D. of 3 independent experiments. DPPH radical scavenging activity was expressed as % of blank. * p < 0.05 as compared with the
blank group (one-way ANOVA/Newman-Keuls).

Table 3. Effect of purine derivatives 3a-3g in the ABTS radical scavenging activity.
1.
Purine derivatives
3a
3b
3c
3d
3e
3f
3g
100.0 10.0
99.9 0.7
98.8 0.6
93.2 0.8
86.5 0.6*
100.0 10.0
100.1 1.9
98.0 1.3
81.7 4.7*
61.5 7.4*
100.0 10.0
99.3 0.7
96.9 2.0
97.7 1.3
94.8 1.4
100.0 10.0
100.9 1.0
98.1 1.6
97.1 0.3
93.5 0.9
100.0 10.0
99.7 2.1
100.9 1.1
99.7 1.2
96.9 0.4
100.0 10.0
99.5 1.2
98.4 1.1
86.5 1.8*
72.6 1.2*
100.0 10.0
99.4 1.1
98.9 0.4
97.9 1.3
97.6 0.7
Blank
1 µM
10 µM
100 µM
200 µM
Data are reported as mean S.D. of 3 independent experiments. ABTS radical scavenging activity was expressed as % of blank. * p < 0.05 as compared with the
blank group (one-way ANOVA/Newman-Keuls).
Table 4. Effect of purine derivatives 3a-3g on AChE activity in cerebral cortex of mice.
Purine derivatives
3a
3b
3c
3d
3e
3f
3g
9.6 0.5
7.8 1.5
9.6 0.5
8.7 2.4
9.6 0.5
7.9 1.2
9.6 0.5
10.4 1.6
9.6 0.5
6.6 0.6*
9.6 0.5
7.2 1.7
9.6 0.5
7.9 0.9
Control
1 µM
7.6 1.1
7.7 1.0
7.6 1.1
9.3 2.9
8.9 2.4
8.9 1.9
7.6 1.0
7.1 1.5
6.3 0.9*
11.3 2.4
11.0 3.0
8.8 2.3
6.5 0.4*
6.6 1.7*
6.6 1.3*
7.3 1.2
7.8 1.6
7.8 1.4
8.9 1.7
8.2 1.3
8.2 1.6
10 µM
100 µM
200 µM
Data are reported as mean S.D. of 3 independent experiments. AChE activity was expressed as µmol acetylthiocholine/h/mg protein. * p < 0.05 as compared
with the control group (one-way ANOVA/Newman-Keuls).
Table 4 shows the effect of purine derivatives (3a-3g) on
AChE activity in cerebral cortex of mice. Compounds 3c and 3e
significantly inhibited the cerebral cortex AChE activity at
concentrations equal to or greater than 200 and 1 µM,
respectively. The Imax values were 34.4% for compound 3c and
31.2% for compound 3e. Compound 3e had an inhibitory effect
on the AChE activity at concentrations less than 3c. Purine
derivatives 3a, 3b 3d, 3g and 3f had no effect in inhibiting AChE
activity in cerebral cortex of mice.
respectively) the step-through latency in comparison to the
control group. Acquisition, consolidation and retrieval are stages
of memory29 and we verify that purine derivative 3e caused a
cognitive enhancement in the memory phases of consolidation
and retrieval.
Administration of compound 3e pre-training, immediately
post-training and before test did not cause impairment in the
locomotor activity (number of crossings) and exploratory
behavior (number of rearing) of mice assessed by the open-field
test (data not shown).
3.2.1. Behavioral tasks – In vivo
Progressive loss of memory is a major feature of Alzheimer’s
disease. Memory can be defined as the record of information
representation acquired through experiences, and it is a process
that has several stages.29 Moreover, cholinergic system has a key
function in the memory.30 Thus, considering the in vitro results of
purine derivatives on the AChE activity, compound 3e was used
to investigate its effect in improving memory in mice.
4. Conclusion
In summary, we describe a simple method for the synthesis of
6-arylselanylpurines with antioxidant and anticholinesterase
activities, as well as in improving memory. This method involves
the reaction of the commercial available 6-chloropurine with
nucleophilic selenium species, generated in the system
(ArSe)2/NaBH4/PEG-400. The reactions are suitable to a range of
diorganyl diselenides and proceeded efficiently at 60 °C under N2
atmosphere furnishing the products in moderated to excellent
yields. Biological studies revealed the promising antioxidant
effects of the synthesized arylselanyl purine derivatives.
Moreover, it was evidenced the inhibitory effect on the cerebral
AChE activity by a purine derivative (compound 3e) containing
fluorine in the chemical structure. Still, this purine derivative
administrated in mice caused cognitive enhancement in the
memory phase of consolidation and retrieval in the step-down
Figure 1 shows the effect of purine derivative 3e on the step-
down inhibitory avoidance task in mice. During the training
session in the step-down inhibitory avoidance task, there was no
difference in the step-through latency time among groups.
Compound 3e administered 30 min before the training
(acquisition) did not change the step-through latency time (Figure
1A). However, administration immediately after the training
session (consolidation) (Figure 1B) and 30 min before the test
session (retrieval) (Figure 1C) increased (around 52 and 44%,

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We are grateful for the financial support and scholarships
from the Brazilian agencies CNPq (408874/2016-3,
400150/2014-0 and 447595/2014-8), FAPERGS (PRONEM
16/2551-0000240-1 and PRONUPEQ 16/2551-0000526-5),
FINEP and CAPES. CNPq is also acknowledged for the
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