Pyrazolo[3,4-d]pyrimidine analogues: Synthesis, characterization and their in vitro antiamoebic activity

Article abstract of DOI:10.1007/s00044-012-0070-6

Pyrazolo[3,4-d]pyrimidine analogues were synthesized by treating 3-phenyl-1H-pyrazolo[3,4-d]pyrimidine-4-amine with different sulfonyl chlorides and triethylamine in dry dichloromethane. The structure of all the compounds was elucidated by spectral data a

Full text of DOI:10.1007/s00044-012-0070-6

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-012-0070-6
ORIGINAL RESEARCH
Pyrazolo[3,4-d]pyrimidine analogues: synthesis, characterization
and their in vitro antiamoebic activity
•
Shadab Miyan Siddiqui Attar Salahuddin
•
Amir Azam
Received: 5 December 2011 / Accepted: 19 April 2012
Ó Springer Science+Business Media, LLC 2012
Abstract Pyrazolo[3,4-d]pyrimidine analogues were syn-
thesized by treating 3-phenyl-1H-pyrazolo[3,4-d]pyrimidine-
4-amine with different sulfonyl chlorides and triethylamine in
dry dichloromethane. The structure of all the compounds was
elucidated by spectral data and their purity was confirmed by
elemental analysis. In vitro antiamoebic activity was performed
against HM1:IMSS strain of Entamoeba histolytica and two
compounds, 4 (IC50 = 0.57) and 6 (IC50 = 0.68), were found
better inhibitors than the reference drug metronidazole
(IC50 = 1.80). Further, both the compounds (4 and 6) were low
cytotoxic against the human breast cancer MCF-7 cell line in
the concentration range of 2.5–250 lM. These preliminary
results reveal that pyrazolo[3,4-d]pyrimidine analogues could
help in designing better molecules with enhanced antiamoebic
activity.
genotoxic to human cells (Bendesky et al., 2002). Fur-
thermore, resistance of E. histolytica to MNZ and relapses
of intestinal and hepatic amoebiasis have been reported
(Becker et al., 2011; Hwang et al., 2011). Therefore, new
effective antiamoebic agents are required.
Antiamoebic drugs, e.g. MNZ, tinidazole and ornidazole
(Fig. 1) have a basic core as imidazole ring having nitrogen
atoms at 1, 3 position. Structurally, the imidazoles and
pyrimidines are similar in having 1,3-dinitrogen system
(Fig. 2). In our earlier studies, the reduced forms of pyra-
zole that are known as pyrazoline and some pyrimidine
derivatives (Fig. 3) have been found to be endowed with
antiamoebic activities (Hayat et al., 2010, 2011; Abid et al.,
2009; Budakoti et al., 2007; Parveen et al., 2010, 2011).
In this context, pyrazole and pyrimidine are crucial nitrogen-
containing heterocyclic systems, which can provide
privileged scaffolds for the development of antiamoebic
compounds. Considering this perspective, it was planned to
integrate pyrazole and pyrimidine rings together in a single
molecular frame to form pyrazolo[3,4-d]pyrimidine phar-
macophore. Literature survey revealed that the replacement
of 1H of pyrazolo[3,4-d]pyrimidine system by some other
biologically active molecule drastically alters their phar-
macological properties (El-Sayed Ali, 2009). The intro-
duction of sulphonamide group is a provocative tactic in
drug designing for increasing pharmacological potency and/
or the absorption, distribution, metabolism, and excretion
(ADME) attributes of the lead chemical matter (Dai et al.,
2011). Recently, we have demonstrated that some azole-
based derivatives showed better antiamoebic activity than
MNZ (Siddiqui et al., 2012; Irfan et al., 2010). In this paper,
we herein report the synthesis of pyrazolo[3,4-d]pyrimidine
analogues having a sulphonamide linkages and their
in vitro antiamoebic activity against HM1:IMSS strain of
E. histolytica.
Keywords Pyrazolo[3,4-d]pyrimidine Á HM1:IMSS Á
Entamoeba histolytica Á Antiamoebic activity Á MTT assay
Introduction
Amoebiasis can be considered the most aggressive disease
of the human intestine (Salles et al., 2003). It is the second
leading cause of mortality due to a protozoan infection
(Lejeune et al., 2009). Entamoeba histolytica is the caus-
ative agent in humans and is responsible for 100,000
fatalities per annum (Ralston and Petri, 2011). Metroni-
dazole (MNZ), the first line medicament against amoebi-
asis, is potentially carcinogenic to humans because it is
S. M. Siddiqui Á A. Salahuddin Á A. Azam (&)
Department of Chemistry, Jamia Millia Islamia, Jamia Nagar,
New Delhi 110025, India
e-mail: amir_sumbul@yahoo.co.in
123

Med Chem Res
Results and discussion
of sodium hydride and dimethyl sulphate. Treatment of (1)
with hydrazine hydrate yielded 5-amino-3-phenyl-1H pyra-
zole-4-carbonitrile (2). Then the reaction of compound (2)
with formamide gave 3-phenyl 1H-pyrazolo[3,4-d]pyrimi-
dine-4-amine (3). Finally, the reaction of compound 3
(1 eq.), triethylamine (3 eq.) and alkyl or aryl sulfonyl
chlorides (1.2 eq.) in dry dichloromethane at 0 °C for about
2 h afforded the sulphonamide derivatives of pyrazolo
[3,4-d]-pyrimidine (4–11). The structure of all the com-
pounds was elucidated by spectral studies and their purity
was confirmed by elemental analyses (Scheme 1).
Chemistry
All the desired compounds were prepared by multistep
reaction starting from the synthesis of 2-(methoxy(phenyl)-
methylene)malononitrile (1), which was synthesized by
reacting benzoyl chloride with malononitrile in the presence
N
N
N
O2N
CH3
N
O2N
CH3
OH
N
O2N
CH3
N
Antiamoebic activity and cytotoxicity profile
O S
O
Cl
Ornidazole
OH
Metronidazole
Preliminary experiments were carried out to determine the in
vitro antiamoebic activity of the target compounds by mic-
rodilution method against the HM1:IMSS strain of E. his-
tolytica (Wright et al., 1988). All the experiments were
carried out in triplicate at each concentration level and
repeated thrice. The antiamoebic effect was compared with
the most widely used antiamoebic medication MNZ, which
had 50 % inhibitory concentration (IC50) 1.80 lM in our
experiments. All compounds showed IC50 values in the range
0.57–5.15 lM. In terms of IC50, it can be concluded that
compound (4) was endowed with the maximum activity
(IC50 = 0.57 lM) followed by compound 6 (IC50 = 0.68 lM),
Tinidazole
Fig. 1 Commercially available antiamoebic drugs bearing nitrogen-
containing heterocyclic ring
Fig. 2 Structural similarity
imidazole and pyrimidine rings
having 1,3-dinitrogen
N
N
N
H
N
Imidazole
pyrimidine
Fig. 3 Antiamoebic pyrimidine
compounds
O
Fe
N
N
N
N
N
N
N
N
N
IC50 = 0.62 µM
IC50 = 0.16 µM
Scheme 1 Synthesis of
pyrazolo[3,4-d]pyrimidine and
its analogues. Reagents and
conditions: a CNCH2CN, NaH,
THF, 0 °C/Me2SO4, 90 °C,
12 h, b N2H4.H2O/C2H5OH,
reflux 2 h, c HCONH2, 180 °C,
5 h, d RSO2Cl, Et3N, DCM, rt,
7 h
O
NC
CN
O
NC
(b)
Cl
(a)
N
H2N
N
H
( 1 )
( 2 )
(c)
NH2
N
NH2
(d)
N
N
N
N
N
H
N
N
O
S
O
R
( 3 )
( 4 - 11 )
123

Med Chem Res
malononitrile (219.1 mmol) in 100 mL THF was added
dropwise at 0 °C. The reaction mixture was then stirred
for 15 min at 0 °C then a solution of benzoyl chloride
(219.1 mmol) in 200 mL THF was added dropwise to the
reaction mixture. The solution was stirred at room tem-
perature for 45 min and then a solution of dimethyl sulfate
(262.92 mmol) in 50 mL of THF was added dropwise.
The reaction mixture was then allowed to reflux at 90 °C
overnight. The reaction mixture was quenched with satu-
rated ammonium chloride solution (120 mL) and con-
centrated to remove THF. The black residue was dissolved
in ethyl acetate (500 mL) and extracted with water. The
separated organic extract was washed with 100 mL brine
and dried over anhydrous sodium sulphate and concen-
trated to get crude product which was carried to next step
without purification.
MTT Assay
100
80
60
40
20
0
Control
4
6
MNZ
Concentration (µM)
Fig. 4 Percentage of viable cells after 48 h pre-treatment of human
breast cancer MCF-7 cells with compounds 4, 6 and MNZ, evaluated
by the MTT assay
while the remaining compounds showed IC50 value more
than that of the reference drug MNZ, and therefore were
considered to be inactive. Further, cytotoxicity of the com-
pounds having IC50 value less than MNZ was assessed by
MTT assay on human breast cancer MCF-7 cell line. A
confluent population of MCF-7 cells was treated with
increasing concentrations of compounds and the number of
viable cells was measured after 48 h by MTT cell viability
(CV) assay based on mitochondrial reduction of the yellow
MTT tetrazolium dye to a highly coloured blue formazan
product. This assay usually shows high correlation with
number of living cells and cell proliferation. The % CV
shown by the compounds (4, 6 and MNZ) at concentration
range of 2.5–500 lM is given in Fig. 4. The results showed
that all the compounds and MNZ were low cytotoxic in the
concentration range of 2.5–250 lM.
Synthesis of 5-amino-3-phenyl-1H-pyrazole-
4-carbonitrile (2)
A solution of compound (1) (219.1 mmol) and hydrazine
hydrate (876.4 mmol) in 500 mL ethanol was allowed to
reflux for 2 h. The mixture was concentrated and the res-
idue was diluted with ethyl acetate and washed with water.
The separated organic extract was dried over anhydrous
sodium sulphate and concentrated to get crude product
which was taken to next step without purification.
5-Amino-3-phenyl-1H-pyrazole-4-carbonitrile (2)
Yield: 90 %; m.p. 202 °C; Anal. calc. for C10H10N4: C
64.50, H 5.41, N 30.09 %; found: C 64.54, H 5.39, N
30.11 %. IR mmax (cm-1): 3442, 3303 (NH2), 3218 (NH),
1
2210 (CN); H NMR (DMSO-d6) d (ppm): 12.07 (s, 1H,
NH), 7.74–7.31 (m, 5H, Ar–H), 6.33 (s, 2H, NH2); MS (EI,
Experimental protocol
70 eV): m/z = 186.21 [M?].
Melting points (mp) were recorded on a KSW apparatus
and are uncorrected. Elemental analysis was carried out on
CHNS Elemental Analyzer vario MICRO, Elementar
Analysensysteme GmbH, Germany. IR spectra were
recorded on Perkine-Elmer model 1600 FT-IR RX1 spec-
Synthesis of 3-phenyl-1H-pyrazolo[3,4-d]pyrimidine-4-
amine (3)
A solution of compound (2) (63.54 mmol) in 300 mL
formamide was heated to 180 °C for 5 h. The reaction
mixture was cooled to room temperature then poured over
ice to get the crude dark brown precipitates of the product.
The solid was filtered and then kept for stirring in 150 mL
methanol for 15 min and again filtered. The solid precipi-
tates were again washed with 100 mL diethyl ether and
then dried under vacuum to get pure product.
1
trophotometer as KBr discs. The H NMR spectra were
recorded on Bruker Spectrospin DPX 300 MHz using
DMSO and CDCl3 as solvent and trimethylsilane (TMS) as
an internal standard. Chemical shift values are given in
parts per million (ppm) with respect to TMS. Mass spectra
were recorded by GC–MS (Perkin-Elmer Clarus 500 GC).
Synthesis of 2-(methoxy(phenyl)methylene)-
malononitrile (1)
3-Phenyl-1H-pyrazolo[3,4-d]pyrimidine-4-amine (3)
To a stirred suspension of 60 % NaH (438.21 mmol)
Yield: 50 %; m.p. 185 °C; Anal. calc. for C11H9N5:
C 62.55, H 4.29, N 33.16 %; found: C 62.59, H 4.33,
in 150 mL tetrahydrofuran (THF),
a
solution of
123

Med Chem Res
N 33.11 %; IR mmax (cm-1): 3470, 3308 (NH2), 3103 (NH);
1H NMR (DMSO-d6) d (ppm): 13.58 (s, 1H, NH), 8.21 (s,
1H, Ar–H), 7.68–7.44 (m, 5H, Ar–H), 6.71 (s, 2H, NH2);
MS (EI, 70 eV): m/z = 211.22 [M?].
1-[(4-Chlorophenyl)sulfonyl]-3-phenyl-1H-pyrazolo[3,4-
d]pyrimidine-4-amine (7)
Yield: 66 %; mp: 224 °C; Anal. calc. for C17H12N5O2ClS:
C 52.92, H 3.13, N 18.15, S 8.31 %; found: C 52.88, H
3.16, N 18.16, S 8.33 %; IR mmax (cm-1): 3443, 3306
(NH2), 1630 (C=N), 1365 (SO2); 1H NMR (CDCl3) d
(ppm): 8.60 (s, 1H, Ar–H), 8.22 (d, 2H, Ar–H,
J = 9.0 Hz), 7.97–7.44 (m, 7H, Ar–H), 5.59 (s, 2H, NH2);
MS (EI, 70 eV): m/z = 385.82 [M?].
Synthesis of sulphonamide derivatives of 3-phenyl-1H-
pyrazolo[3,4-d]pyrimidine-4-amine (4–11)
To a solution of compound (3) (1 eq) and triethylamine
(3 eq) in dry dichloromethane at 0 °C, alkyl or aryl sul-
fonyl chlorides (1.2 eq) were added. The reaction mixture
was stirred at 0 °C for about 2 h and the stirring was
continued at room temperature for about 5 h. After the
completion of the reaction, the reaction was quenched with
distilled water and extracted with dichloromethane
(3 9 15 mL). Finally, the separated organic layer was
washed with distilled water again and dried over anhydrous
Na2SO4. After removal of the solvent in vacuo, the residue
was purified by recrystallization from ethanol.
1-[(2,5-Dichlorophenyl)sulfonyl]-3-phenyl-1H-
pyrazolo[3,4-d]pyrimidine-4-amine (8)
Yield: 58 %; m.p: 210 °C; Anal. calc. for
C17H11N5O2Cl2S: C 48.58, H 2.64, N 16.66, S 7.63 %;
found: C 48.62, H 2.67, N 16.61, S 7.59 %; IR mmax
1
(cm-1): 3442, 3303 (NH2), 1630 (C=N), 1364 (SO2); H
NMR (DMSO-d6) d (ppm): 8.53 (s, 1H, Ar–H), 7.79–7.54
(m, 8H, Ar–H), 7.49 (s, 2H, NH2); MS (EI, 70 eV):
m/z = 420.27 [M?].
3-Phenyl-1-tosyl-1H-pyrazolo[3,4-d]pyrimidine-4-amine
(4)
1-(2-Naphthylsulfonyl)-3-phenyl-1H-pyrazolo[3,4-
d]pyrimidin-4-amine (9)
Yield 74 %; m.p. 212 °C; Anal. calc. for C18H15N5O2S: C
59.16, H 4.14, N 19.17, S 8.78 %; found: C 59.13, H 4.17,
N 19.16, S 8.80 %; IR mmax (cm-1): 3441, 3302 (NH2),
1629 (C=N), 1363 (SO2); 1H NMR (CDCl3) d (ppm): 7.94–
7.80 (m, 4H, Ar–H), 7.42–7.26 (m, 6H, Ar–H), 6.01 (s, 2H,
NH2), 2.43 (s, 3H, CH3); MS (EI, 70 eV): m/z = 365.40
[M?].
Yield: 56 %; m.p. 238 °C; Anal. calc. for C21H15N5O2S: C
62.83, H 3.77, N 17.45, S 7.99 %; found: C 62.81, H 3.80,
N 17.44, S 7.96 %; IR mmax (cm-1): 3467, 3306 (NH2),
1
1643 (C=N) 1389 (SO2); H NMR (DMSO): 8.21 (s, 1H,
Ar–H,), 8.05–7.95 (m, 3H, Ar–H), 7.86–7.60 (m, 9H, Ar–
H), 7.49 (s, 2H, NH2); MS (EI, 70 eV): m/z = 401.44
[M?].
1-[(4-Nitrophenyl)sulfonyl]-3-phenyl-1H-pyrazolo[3,4-
d]pyrimidine-4-amine (5)
3-Phenyl-1-(phenylsulfonyl)-1H-pyrazolo[3,4-
d]pyrimidine-4-amine (10)
Yield: 61 %; mp: 240 °C; Anal. calc. for C17H12N6O4S: C
51.51, H 3.05, N 21.20, S 8.09 %; found: C 51.54, H 3.01,
N 21.19, S 8.11 %; IR mmax (cm-1): 3469, 3306 (NH2),
1643 (C=N), 1391 (SO2); 1H NMR (CDCl3) d (ppm): 8.54–
8.37 (m, 3H, Ar–H), 7.95–7.39 (m, 7H, Ar–H), 5.85 (s, 2H,
NH2); MS (EI, 70 eV): m/z = 396.37 [M?].
Yield: 66 %; mp. 226 °C; Anal. calc. for C17H13N5O2S: C
58.11, H 3.73, N 19.93, S 9.13 %; found: C 58.13, H 3.71,
N 19.96, S 9.17 %; IR mmax (cm-1): 3463, 3308 (NH2),
1641 (C=N), 1387 (SO2); 1H NMR (DMSO-d6): 8.08–8.06
(m, 1H, Ar–H), 7.86–7.69 (m, 6H, Ar–H), 7.50 (s, 2H,
NH2); MS (EI, 70 eV): m/z = 351.38 [M?].
N-{4-[(4-Amino-3-phenyl-1H-pyrazolo[3,4-d]pyrimidin-1-
yl)sulfonyl]phenyl}acetamide (6)
3-Phenyl-1-(methyl sulfonyl)-1H-pyrazolo[3,4-
d]pyrimidine-4-amine (11)
Yield: 54 %; mp. 220 °C; Anal. calc. for C19H16N6O3S: C
55.87, H 3.95, N 20.58, S 7.85 %; found: C 55.84, H 3.96,
N 20.61, S 7.88 %; IR mmax (cm-1): 3470, 3302 (NH2),
1644 (C=N), 1397 (SO2); 1H NMR (DMSO): 13.77 (s, 1H,
NH), 8.96–8.78 (m, 1H, Ar–H), 8.44–8.00 (m, 2H, Ar–H),
7.88–7.24 (m, 9H, Ar–H and NH2), 3.67 (s, 3H, COCH3);
MS (EI, 70 eV): m/z = 408.43 [M?].
Yield: 65 %; mp: 202 °C; Anal. calc. for C12H11N5O2S : C
49.82, H 3.83, N 24.21, S 11.08 %; found: C 49.81, H 3.87,
N 24.19, S 11.12 %. IR mmax (cm-1): 3466, 3306 (NH2),
1
1642 (C=N), 1390 (SO2); H NMR (DMSO-d6): 8.51 (s,
1H, Ar–H), 7.57–7.35 (m, 5H, Ar–H), 7.65 (s, 2H, NH2),
2.43 (s, 3H CH3); MS (EI, 70 eV): m/z = 289.31 [M?].
123

Med Chem Res
Table 1 In vitro antiamoebic activity of 3-phenyl-1H-pyrazolo[3,4-d]pyrimidine-4-amine and its derivatives against HM1:IMSS strain of
E. histolytica and cytotoxicity profile of compounds 4, 6 and MNZ
NH2
N
NH2
N
N
N
N
N
N
N
H
O
S
R
O
( 4 - 11 )
( 3 )
Compound no.
R
Antiamoebic activity
Cytotoxicity profile
IC50 (lM)
SDa
IC50 (lM)
SDa
3
4
–
4.73
0.57
0.019
0.016
N.D.
N.D.
0.026
[250
CH3
NO2
5
6
2.52
0.68
0.013
0.017
N.D.
N.D.
[250
0.021
H
N
O
7
8
3.23
2.37
0.008
0.021
N.D.
N.D.
N.D.
N.D.
Cl
Cl
Cl
9
3.11
4.24
0.024
0.011
N.D.
N.D.
N.D.
N.D.
10
123

Med Chem Res
Table 1 continued
Compound no.
R
Antiamoebic activity
Cytotoxicity profile
IC50 (lM)
SDa
IC50 (lM)
SDa
11
CH3
5.15
0.027
N.D.
N.D.
1.80
0.029
[250
0.022
N
NO2
N
HO
N.D. not done
a
Standard deviation
In vitro antiamoebic assay
amoebae were fixed with methanol and when dried, stained
with (0.5 %) aqueous eosin for 15 min. The stained plate
was washed once with tap water, then twice with distilled
water and then allowed to dry. A 200-lL portion of 0.1 N
sodium hydroxide solution was added to each well to dis-
solve the protein and release the dye. The optical density of
the resulting solution in each well was determined at
490 nm with a microplate reader. The % inhibition of
amoebal growth was calculated from the optical densities
of the control and test wells and plotted against the loga-
rithm of the dose of the drug tested. Linear regression
analysis was used to determine the best fitting line from
which the IC50 value was found. The IC50 values are
reported in Table 1.
All the desired compounds were screened for in vitro
antiamoebic activity against HM1:IMSS strain of
E. histolytica by microdilution method (Wright et al.,
1988). E. histolytica trophozoites were cultured in culture
tubes using Diamond TYIS-33 growth medium. The test
compounds (1 mg) were dissolved in DMSO (40 mL, level
at which no inhibition of amoeba occurs) (Gillin et al.,
1982). The stock solutions of the compounds were pre-
pared freshly before use at a concentration of 1 mg/mL.
Twofold serial dilutions were made in the wells of 96-well
microtiter plate (costar). Each test includes MNZ as a
standard amoebicidal drug, control wells (culture medium
plus amoebae) and a blank (culture medium only). All the
experiments were carried out in triplicate at each concen-
tration level and repeated thrice. The amoeba suspension
was prepared from a confluent culture by pouring off the
medium at 37 °C and adding 5 mL of fresh medium,
chilling the culture tube on ice to detach the organisms
from the side of flask. The number of amoeba/mL was
estimated with the help of a haemocytometer, using trypan
blue exclusion to confirm the viability. The suspension was
diluted to 105 organism/mL by adding fresh medium and
170 lL of this suspension was added to the test and control
wells in the plate so that the wells were completely filled
(total volume, 340 lL). An inoculum of 1.7 9 104 organ-
isms/well was chosen so that confluent, but not excessive
growth, took place in control wells. Plate was sealed and
kept under nitrogen for 10 min before incubation at 37 °C
for 72 h. After incubation, the growth of amoeba in the
plate was checked with a low power microscope. The
culture medium was removed by inverting the plate and
shaking gently. Plate was then immediately washed with
sodium chloride solution (0.9 %) at 37 °C. This procedure
was completed quickly and the plate was not allowed to
cool in order to prevent the detachment of amoeba. The
plate was allowed to dry at room temperature and the
MTT assay
The human breast cancer MCF-7 cells were obtained from
NCCS (Pune, India). The cells were cultured in DMEM
(Sigma) with 10 % foetal bovine serum and 1 % penicillin/
streptomycin/neomycin. The effect of compounds (4) and
(6) and the standard drug MNZ on cell proliferation was
measured using an MTT-based assay (Mosmann, 1983).
Briefly, the cells (10,000/well) were incubated in triplicate
in a 96-well plate in the presence of various concentrations
of compounds (4), (6) as well as MNZ or vehicle (DMSO)
alone in a final volume of 200 lL at 37 °C and 5 % CO2 in
and humidified chamber for 48 h. At the end of this time
period, 20 lL of MTT solution (5 mg/mL in PBS) was
added to each well, and the cells were incubated at 37 °C in
a humidified chamber for 4 h. After 4 h, the supernatant
was removed from each well. The coloured formazan
crystal produced from MTT was dissolved in 200 lL of
DMSO, and then the absorbance (A) value was measured at
570 nm by a multiscanner autoreader. The following for-
mula was used for the calculation of the percentage of
CV: CV (%) = (A of the experimental samples/A of the
control) 9 100.
123

Med Chem Res
series of pyrazoline derivatives bearing quinoline tail. Eur J Med
Chem 45:4669–4675
Conclusion
Hayat F, Salahuddin A, Azam A (2011) Synthesis, characterization,
antiamoebic activity and cytotoxicity of new pyrazolo[3,4-
d]pyrimidine-6-one derivatives. J Enzyme Inhib Med Chem
26:472–479
Hwang EW, Cheung L, Mojtahed A, Cartwright CA (2011) Relapse
of intestinal and hepatic amoebiasis after treatment. Dig Dis Sci
56:677–680
Irfan I, Sawangjaroen N, Bhat AR, Azam A (2010) New dioxazole
derivatives: synthesis and effects on growth of Entamoeba
histolytica and Giardia intestinalis. Eur J Med Chem 45:1648–
1653
It was concluded that the compounds 4 and 6 showed better
antiamoebic activity than the reference drug MNZ and
found low cytotoxic against human breast cancer MCF-7
cell line. It is hoped that these preliminary results could
help in designing better molecules with enhanced anti-
amoebic activity.
Lejeune M, Rybicka JM, Chadee K (2009) Recent discoveries in the
pathogenesis and immune response towards Entamoeba histoly-
tica. Future Microbiol 4:105–118
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