Synthesis, docking, in vitro and in vivo antimalarial activity of hybrid 4-aminoquinoline-1,3,5-triazine derivatives against wild and mutant malaria parasites

Article abstract of DOI:10.1111/cbdd.12490

A new series of hybrid 4-aminoquinoline-1,3,5-triazine derivatives was synthesized by a four-step reaction. Target compounds were screened for in vitro antimalarial activity against chloroquine-sensitive (3D-7) and chloroquine-resistant (RKL-2) strains of Plasmodium falciparum. Compounds exhibited, by and large, good antimalarial activity against the resistant strain, while two of them, that is 8g and 8a, displayed higher activity against both the strains of P. falciparum. Additionally, docking study was performed on both wild (1J3I.pdb) and quadruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) type pf-DHFR-TS to highlight the structural features of hybrid molecules. A series of hybrid 4-aminoquinoline was synthesized and evaluated for antimalarial activity against chloroquine-sensitive (3D-7) and chloroquine-resistant (RKL-2) strains of P. falciparum.

Full text of DOI:10.1111/cbdd.12490

Received Date : 26-Jun-2014
Revised Date : 21-Nov-2014
Accepted Date : 24-Nov-2014
Article type : Research Article
Synthesis, docking, in vitro and in vivo antimalarial activity of hybrid 4-
aminoquinoline-1,3,5-triazine derivatives against wild and mutant malaria
parasites
Hans Raj Bhat1*, Udaya Pratap Singh1,5, Prashant Gahtori2, Surajit Kumar Ghosh3, Kabita
Gogoi4, Anil Prakash4, Ramendra K. Singh5
1 Drug Design & Discovery Laboratory, Department of Pharmaceutical Sciences, Sam Higginbottom Institute of
Agriculture, Technology & Science, Deemed University, Allahabad, 211007 India
2 Faculty of Pharmacy, Uttarakhand Technical University, Dehradun, 248007 India
3 Department of Pharmaceutical Sciences, Dibrugarh University, Dibrugarh, 786004 India
4 Regional Medical Research Centre, ICMR, Dibrugarh, 786005 India
5
Nucleic Acids and Antiviral Research Laboratory, Department of Chemistry, University of Allahabad,
Allahabad, 211002 India
Corresponding author:
Hans Raj Bhat (E-mail: pharmahans@gmail.com)
Phone: +91-9616574197 Fax: +91-532-2684394
Running head title
Bhat et al.: Synthesis and antimalarial activity of 4-aminoquinoline and 1,3,5-triazine
conjugates.
This article has been accepted for publication and undergone full peer review but has not
been through the copyediting, typesetting, pagination and proofreading process which may
lead to differences between this version and the Version of Record. Please cite this article as
an 'Accepted Article', doi: 10.1111/cbdd.12490
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Abstract
A new series of hybrid 4-aminoquinoline 1,3,5-triazine derivatives was synthesized by a four-
step reaction. Target compounds were screened for in vitro antimalarial activity against
chloroquine-sensitive (3D-7) and chloroquine-resistant (RKL-2) strains of P. falciparum.
Compounds exhibited, by and large, good antimalarial activity against the resistant strain
while two of them, i.e., 8g and 8a displayed higher activity against both the strains of P.
falciparum.Additionally, docking study was performed on both wild (1J3I.pdb) and
qradruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) type pf-DHFR-TS to highlight
the structural features of hybrid molecules.
Key word: Aminoquinoline, 1,3,5-triazine, antimalarial, docking.
Introduction
According to the recent report of the World Health Organization (WHO), an
estimated 3.3 billion people were at risk of malaria and approximately 80% malaria cases
were observed in African region [1]. Accordingly, discovery of novel antimalarial
compounds endowed high therapeutic efficiency along with antimalarial potential against
resistance strains is always a topic of interest [2,3]. In this regard, 1,3,5-triazine derivatives
received considerable attention, for instance, proguanil, a prodrug of cycloguanil belongs to
1,3,5-triazine containing antimalarial drug act via arresting of Plasmodium
falciparum dihydrofolate reductase-thymidylate synthase (pf-DHFR-TS), an enzyme required
in biochemical processes that are vital for parasite growth [4, 5]. Impressed by the
antimalarial efficacy of proguanil, various derivatives of 1,3,5-triazine were also synthesized
in search of novel drug entity, e.g., cycloguanil, chlorcycloguanil, clociguanil, WR99210 [6].
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In our previous studies, we have designed several analogues of 1,3,5-triazine with 4-
aminoquinoline as effective antimalarial agents [7]. During the course of study it has been
observed that the structure–activity relationship (SAR) could be exemplified on the nature of
linker between 4-aminoquinoline and 1,3,5-triazine pharmacophore and variety of fragment
attached to the other two wings of 1,3,5-triazine moties [8,9]. The SAR of antimalarial agents
clearly suggests the use of basic compounds and its strong influence on the antimalarial
activity [10]. The structural input drawn from our previous studies has allowed us to devise
new series of compounds where two pharmacophores i.e., 4-aminoquinoline and 1,3,5-
triazine have been tethered via 2-(piperazin-1-yl) ethylamine basic linker. These targeted
molecules were subsequently screened against chloroquine sensitive (3D-7) and chloroquine
resistant (RKL-2) strains of Plasmodium falciparum. Furthermore, molecular docking study
was also performed to get insight of essential key structural requirements for antimalarial
activity.
Methods and Materials
The solvents and reagents of analytical grade were used without further purification. Melting
points were determined on a Veego MPI melting point apparatus and FT-IR (2.0 cm-1, flat,
1
smooth, abex) were recorded on Perkin Elmer RX-I Spectrophotometer. H-NMR spectra
13
were recorded on Bruker Avance II 400 NMR and C-NMR spectra on Bruker Avance II
100 NMR spectrometer in DMSO-d6 using TMS as internal standard. Mass spectra were
obtained on VG-AUTOSPEC spectrometer equipped with electrospray ionization (ESI)
source. Elemental analysis was carried out on Vario EL-III CHNOS elementor analyzer.
The desired compounds 3, 6, 7a-i and 8a-i were synthesised using the protocols as outlined in
Scheme 1. Initially the synthesis of compound 3 was achieved by the nucleophilic
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substitution of N–aminoethyl piperazine (2) at the C-4 chloro of 4,7-dichloroquinoline (1).
The mono-substituted 1,3,5-triazines, such as 4,6-dichloro-N-(4-nitrophenyl)-1,3,5-triazin-2-
amine (6) was accomplished by the nucleophilic substitution of the Cl atom of the 2,4,6-
trichloro-1,3,5-triazine (4) with p-nitro aniline (5) in the presence of saturated solution of
NaHCO3. Further, the synthesis of di-substituted 1,3,5-triazines 7a-i was accomplished by the
nucleophilic substitution at one of the Cl atom of compound 6 with different primary and
secondary amines (a-i), as presented in scheme 1. The final targeted compounds (8a-i) were
realised upon treating 7a-i with compound 3.
The synthesis of intermediate compounds 3, 6, 7a-i was performed according earlier reported
procedure [9,11].
General procedure for synthesis of compounds 8a-i
A solution of respective di-substituted 1,3,5-triazine compounds 7a-i (0.01eq.) and
compound 3 (0.01 eq.) and K2CO3 (0.01 eq.) in 1,4-dioxane was refluxed for 8-9h. The
completion of reaction was monitored by TLC using ethanol:acetone (1:1) as mobile phase.
The reaction mixture was filtered and concentrated under reduced pressure. The resulting
residue was re-crystallised from ethanol to afford the desired products 8a-i.
The spectral and analytical data of final compounds as well as the intermediates were given
in Supplementary information
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Antimalarial Activity
Preparation of parasites
The chloroquine sensitive 3D-7 and chloroquine resistant RKL-2 strains (Rourkela, Orissa,
India) of P. falciparum were routinely maintained in stock cultures in medium RPMI-1640
supplemented with 25mmol HEPES, 1% D-glucose, 0.23% sodium bicarbonate and 10% heat
inactivated human serum. The asynchronous parasites were synchronized after 5% D-sorbitol
treatment to obtain only the ring stage parasitized cells. For carrying out the assay, the initial
ring stage parasitaemia of 1.0 % at 3.0 % haematocrit in a total volume of 200 µL of medium
RPMI-1640 was uniformly maintained.
In-vitro antimalarial assay
The in-vitro antimalarial assay was carried out according to microassay process described by
Reickmann and co-workers using 96 well-microtitre plates [12] with minor modifications. A
stock solution of 5mg/mL of each test compound was prepared in DMSO and subsequent
dilutions were prepared with culture medium. The test compounds in 20 µL volume at two
concentrations, i.e., 5 µg/mL and 50 µg/mL in triplicate wells were incubated with
o
parasitized cell preparation at 37 ºC in CO2 incubator set at 37 C and 5% CO2 level . After
40h of incubation, the blood smears were prepared from each well and stained with Giemsa
stain. The level of parasitemia in terms of percentage dead rings along with trophozoites was
determined by counting a total of 100 asexual parasites (both live and dead) in each smear
microscopically using chloroquine and proguanil as reference drugs.
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In vivo antimalarial assay
The in vivo drug response was evaluated in swiss albino mice infected with P. berghei, which
is innately sensitive to chloroquine [13]. The mice (20 5 g) was inoculated with 1x107
parasitized RBC on day 0 and treatment was administered to a group of five mice from day 0-
4, once daily. The aqueous suspension of compounds were prepared with 2.5µl of 30%
ethanol and diluted with Milli Q grade water. Initially, the efficacy of test compounds was
evaluated at 5 mg/kg/day and required daily dose was administered in 0.2 ml volume via
intraperitoneal route. Parasitaemia levels were recorded from thin blood smears between day
4. The mean value determined for a group of 5 mice was used to calculate the percent
suppression of parasitaemia with respect to the untreated control group. Mice treated with
chloroquine served as reference control.
Molecular docking studies
The 3D X-ray crystal structure of wild type (1J3I.pdb) and qradruple mutant (N51I, C59R,
S108 N, I164L, 3QG2.pdb) pf-DHFR-TS were used as starting model for this study. The
protein was prepared, docked and its interaction with different ligands was studied using
Discovery Studio 2.5 (Accelrys Software Inc., San Diego; http://www.accelrys.com).
Preparation of receptor
The target wild and qradruple mutant pf-DHFR proteins without co-crytallised ligands were
taken and the bond order corrected. The hydrogen atoms were added and their positions
optimized using the all-atom CHARMm (version c32b1) forcefield with Adopted Basis set
Newton Raphson (ABNR) minimization algorithm until the root mean square (r.m.s) gradient
for potential energy was less than 0.05 kcal/mol/Å [14,15]. Using the 'Binding Site' tool panel
available in DS 2.5, the minimized protein structure was defined as receptor, the binding site
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was defined as volume occupied by the ligand in the receptor, and an input site sphere was
defined over the binding site with a radius of 5 Å. The center of the sphere was taken to be
the center of the binding site, and side chains of the residues in the binding site within the
radius of the sphere were assumed to be flexible during refinement of postdocking poses. The
receptor having defined binding site was used for the docking studies.
Ligand setup
Using the built-and-edit module of DS 2.5, various ligands were built, all-atom CHARMm
forcefield parameterization assigned and then minimized using the ABNR method. A
conformational search of the ligand was carried out using a stimulated annealing molecular
dynamics (MD) approach. The ligand was heated to a temperature of 700 K and then
annealed to 200 K. Thirty such cycles were carried out. The transformation obtained at the
end of each cycle was further subjected to local energy minimization using the ABNR
method. The 30 energy-minimized structures were then superimposed and the lowest energy
conformation occurring in the major cluster was taken to be the most probable conformation.
Docking
Docking, a significant computational method, was used to predict the binding of the ligand
to the receptor binding site by varying position and conformation of the ligand keeping the
receptor rigid. LigandFit [15] protocol of DS 2.5 was used for the docking of ligands with
wild and quadruple mutant pf-DHFR proteins [16]. The LigandFit docking algorithm
combines a shape comparison filter with a Monte Carlo conformational search to generate
docked poses consistent with the binding site shape. These initial poses are further refined by
rigid body minimization of the ligand with respect to the grid based calculated interaction
energy using the Dreiding forcefield [17]. The receptor protein conformation was kept fixed
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during docking, and the docked poses were further minimized using all-atom CHARMm
(version c32b1) forcefield and smart minimization method (steepest descent followed by
conjugate gradient) until r.m.s gradient for potential energy was less than 0.05 kcal/mol/Å.
The atoms of ligand and the side chains of the residues of the receptor within 5 Å from the
center of the binding site were kept flexible during minimization.
Results and discussion
The hybrid molecules were synthesized following the standard protocols as discussed
previously. While, the structure of final derivatives were ascertained on the basis various
1
spectral analysis viz., FT-IR, H-NMR,13C-NMR and Mass. The spectroscopic data are in
good arrangement with the proposed structures.
Antimalarial activity and structure-activity relationship
In vitro antimalarial screening data against chloroquine-sensitive (3D-7) and chloroquine
resistant (RKL-2) strains of P. falciparum at 5 µg/mL and 50µg/mL doses are provided in
table 1. Hybrid compounds 8a-i killed parasitemia ranging from 8.0-36.0 % at 50µg/mL and
5.0-20.5% at 5 µg/mL in the case of 3D-7 and 22-45.3% at 50µg/mL and 9.6-22.3% at 5
µg/mL in the case of RKL-2 strains, indicating marginally better activity against the resistant
strain. The compound 8g bearing aliphatic analogs such as semicarbazide containing 1,3,5-
triazine moeity was found to exhibit highest activity against both the strains at 50µg/mL
concentration. However, compounds 8a-c synthesized by incorporation of aryl groups on
1,3,5-triazine nucleus exhibited moderate to low activity against both the strains. Compound
8a substituted with morpholine on 1,3,5-triazine registered 25.5 % parasitemia kill against
chloroquine-sensitive and 38.3 % parasitemia kill against chloroquine resistant strain at 50
µg/mL. Furthermore, compound 8b showed 16 % parasitemia kill against chloroquine-
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sensitive and 36.6 % parasitemia kill against chloroquine resistant strain at 50 µg/mL. The
compound 8c substituted with phenol on 1,3,5-triazine showed 8% parasitemia kill against
chloroquine–sensitive and 34.6% parasitemia kill against chloroquine resistant strain.
Compounds 8d and 8h with single methyl group at para and ortho position of the phenyl ring
substituted on 1,3,5-triazine base, respectively, registered a remarkable 13.5 % and 26.5%
parasitemia kill against chloroquine-sensitive and 36.6 % and 22% parasitemia kill against
chloroquine-resistant strain at 50 µg/mL. The introduction of thiosemicarbazide on the 1,3,5-
triazine base resulting in compound 8e increased the antimalarial activity against both the
stains with parasitemia kill of 29 % and 28 % at 50 µg/mL. Among the compounds having
thiourea on 1,3,5-triazine moeity, compound 8f showed 18 % parasitemia kill against
chloroquine-sensitive and 40.6% parasitemia kill against chloroquine-resistant strain. The
hybrid derivative 8i with amine group substituted on 1,3,5-triazine ring, recorded 14 %
parasitemia kill against chloroquine-sensitive and 34.6 % parasitemia kill against
chloroquine-resistant strain at 50 µg/mL.
Among the synthesized derivatives, 8g were identified as most potent molecule and thus it
subsequently evaluated for in vivo antimalarial efficacy against chloroquine sensitive rodent
malaria parasite (P. berghei) in swiss albino mice model using Peters’ 4-day suppressive test
using chloroquine as reference drug at the dosage of 5 mg/kg body weight. As depicted in
table 2, compound 8g, bearing semicarbazide demonstrate good suppression of parasitaemia
(64.5%) with mean survival time 21.3+4.0 days in comparison to the mean survival time of
22.1 9.2 days obtained with the reference drug chloroquine at 5 mg/kg body weight. Results
revealed that introducing more basic semicarbazide moiety (8g) resulted in the highest
supression of parasitaemia and the highest mean survival time for treated mice.
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The structure-activity relationship (SAR) studies, emerged from the screening data showed
in Figure 1, indicated that the aliphatic substituent at the 1,3,5-triazine ring such as
thiosemicarbazide (8e), thiourea (8f), semicarbazide (8g) and amine (8i) played a vital role in
the activity. While incorporation at p-OH (8c), p-CH3 (8h), p-OCH3 (8b) and o-CH3 (8d)
aromatic ring substituted on 1,3,5-triazine ring reduced the antimalarial activity, the
introduction of basic moieties, like thiosemicarbazide (8e), semicarbazide (8g), thiourea (8f),
mopholine (8a), and ammonia (8i) at 1,3,5-triazine ring enhanced the activity suggesting that
the basic moiety at 1,3,5-triazine was important for antimalarial activity. Our studies
indicated that compounds 8b and 8c with (p-OCH3 and p-OH) substituents on phenyl ring at
1,3,5-triazine ring showed mild to moderate activity against both the strains of P. falciparum.
Furthermore, methyl group substituted at ortho and para position of aryl ring (8d and 8h)
also showed mild to moderate activity.
Molecular Docking Study
In the given docking protocol, we had carried out molecular dynamics simulations, which
calculated the time dependent behaviour of a molecular system and provided detailed
information on the fluctuations and conformational changes of proteins. These methods are
now routinely used to investigate the structure, dynamics and thermodynamics of biological
molecules and their complexes. The CHARMM force field was also applied to the designed
molecules, which added the deficient hydrogen atoms in the molecules, minimized energy to
stable conformation and analysed the structure for efficient binding with protein. The
program can read or model structures, minimize the energy by first- or second-derivative
techniques, perform a normal mode or molecular dynamics simulation, and analyse the
structural, equilibrium, and dynamic properties as determined in these calculations [18].
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The docking studies of all compounds 8a-i were performed into the binding pocket of both
wild type (1j3i.pdb) and qradruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) Pf-
DHFR-TS. The docking results and docked conformations of ligands in the active site are
illustrated in Table 3, while the docking interaction of compound 8g being the most active
one, showed in Figure 2 and Figure 3. In this study, we had found that the molecules formed
stable interactions with wild and mutant Pf-DHFR-TS enzyme by bringing change in the
conformation of the protein.
In a pioneering study by Yuvanyama et al., it has been found that the carboxylate oxygen
atoms of Asp54 were involved in hydrogen bond formation with N3 and N4-amino nitrogen
atoms of WR99210 (a 1,3,5-triazine containing pre-clinical molecule as Pf-DHFR-TS
inhibitor) or with N1 and N2 amino nitrogen atoms of Pyr, as expected for this class of
inhibitors [19]. Similarly, our compound showed the formation of hydrogen bond with the
carboxylate oxygen atoms of Asp54 through the involvement of NH groups of 1,3,5-triazine
phenyl and semicarbazide in wild-type. Other non-bonded π –π interactions between 1,3,5-
triazine phenyl and 1,3,5-triazine ring with Phe58 were also observed. The π - + interactions
between 1,3,5-triazine phenyl (NO2 group) with Phe58 and Leu40 in wild and mutant Pf-
DHFR-TS were also observed. In in-vitro antimalarial activity results showed that the
compound 8g showed highest antimalarial activity against wild-type strain of P. falciparum,
which was confirmed by the interactions with Ser111. Further, in mutant Pf-DHFR-TS
showed no favorable interactions with critical amino acid residues viz. Ala16, Cys50, Asn51,
Cys59 and Ser108. Most of the derivatives bind in more or less similar manner with
substituted phenyl ring and triazine nucleus occupying the interior of the deep cleft of the
active site by the formation of hydrogen bonds while the quinoline moiety formed π-π, π-+,
π-σ interactions with different amino acid residues of the receptor molecule.
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After molecular docking analysis of target compounds, it is imperative to discern
between sound and bad docking solution, thus scoring function is deemed as a worthy option
for it. These functions are traditionally either physics-based or knowledge based and differ
mainly in the derivation of the mathematical models. The major implication of the scoring
function is rest with their power to calculate the intensity of the non-covalent interaction,
called as binding affinity, and other parameters between ligand and receptor after they have
been bobbed. So, to better see the molecular interaction and their correlation with biological
action, two molecules viz., highly active (8g) and non-active (8c) compounds were rigorously
analysed through various scoring parameters. The outcomes were presented in table 4.
It has been found that compound 8g being as highly active in bioassay showed
prominent values for PLP1 and PLP2 than its non-active counterpart (8c). Piecewise Linear
Potential (PLP) is a quick and simple docking function that has been presented to elucidate
the protein ligand binding affinities in an effective manner. The PLP scores are measured in
arbitrary units and higher PLP scores indicate stronger receptor-ligand binding. On
comparing the PLP scores, compound 8g was found much active than 8c against quardruple
mutant form which is found in agreement with anti-malarial activity. In the case of the wild
type model, compound 8g showed lesser affinity than mutant model, but significantly higher
than non active compound 8c.
The PMF scoring functions were developed on the basis of statistical analysis of the 3D
structures of protein-ligand complexes. These were found to correlate well with protein-
ligand interaction. The scores are computed by summing pairwise interaction terms over all
interatomic pairs of the receptor-ligand complex. Compound 8g was again turned out as
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efficient legend (144.52) by exhibiting higher PMF score than 8c (121.82) against the
quadruple mutant protein model. Further, the same pattern is also revealed on comparing the
PMF values against wild-type. These results are found in better correlation with in-vitro and
in-vivo anti-malarial activity.
In order to better understand the ligand-protein interaction, molecules (8g and 8c) were
further analysed on the basis dock score. The most active molecule 8g presented significantly
higher values against quardruple mutant than compound 8c. While, the same correlation held
true for wild type protein model, i.e., 8g is found more active than 8c. It was understood that,
compound 8g was appreciably more active than 8c for both the protein model, showing
higher correlation with in-vitro and in- vivo antimalarial activity.
Conclusion:
In conclusion, a new series of hybrid 4-aminoquinoline 1,3,5-triazine was designed and
synthesized. In the present series, compound 8g showed good in vitro antimalarial activity
against both chloroquine sensitive as well as resistant strains of P. Falciparum and also
excellent in vivo antimalarial activity against P. Berghei. Activity results indicated that
compound 8g may be utilized as lead molecules for further chemical modifications to
improve their therapeutic potential as antimalarial agents.
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Acknowledgement
The financial support from the Department of Science and Technology (DST), New Delhi,
India is gratefully acknowledged (Grant no. SR/SO/HS-125/2010). Authors are also thankful
to S.A.I.F., Punjab University, Chandigarh, India for providing spectroscopic data.
Conflict of interest: Authors declare no conflict of interest.
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Figures and Schemes captions
Scheme 1 : Reagents and conditions: R-H (a-i) various amines, (i) Reflux 1hr at 80oc
followed by 6-8 h at 120-130oC (ii) Acetone, 0-5 oC 3h, NaHCO3 (iii) Acetone, 40-45 oC, 5 h,
NaHCO3 (iv) 1,4-dioxane 120-130 oC, 8-9h, K2CO3
Figure 1. SAR of hybrid 4-aminoquinoline 1,3,5-triazine derivatives
Figure 2.Docking pose of hybrid compound 8g in the active site of wild pf-DHFR-TS.
(Ligand stick colored by atom type, where, Grey: C, Green: Cl, Blue: N, White: H, while the
vital neighboring amino acid residues were colored according to interpolated charges.)
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Figure 3.Docking pose of compound 8g in the active site of qradruple mutant type pf-DHFR-
TS. (Ligand stick colored by atom type, where, Grey: C, Green: Cl, Blue: N, White: H, while
the vital neighboring amino acid residues were colored according to interpolated charges.)
Table 1: In vitro antimalarial activity of Hybrid derivatives 8(a-i).
% dead asexual parasites
Compounds
3D-7*
RKL-2#
$5µg/ml
5.0
$50µg/ml
25.5
$5µg/ml
20.3
$50µg/ml
38.3
8a
20.5
6.5
16.0
8.0
19.6
20.6
16.0
15.0
18.3
22.3
9.6
36.6
34.6
36.6
28.0
40.6
45.3
22.0
34.6
8b
8c
8d
8e
8f
6.5
13.5
29.0
18.0
36.0
26.5
14.0
11.5
5.0
22.0
19.5
9.5
8g
8h
8i
14.3
49.5
-
-
Chloroquine
(0.7µg/ml)
45.0
50
Chloroquine
(1.2µg/ml)
50
Proguanil
(˃200µg/ml)
*- Wild P. falciparum parasite (Chloroquine sensitive)
#- Mutant P. falciparum parasite (Chloroquine resistant)
$- Test dosage
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Table 2: In vivo antimalarial evaluation of representative lead compound against P. berghei
in swiss albino mice model
Treatment
Mean % parasitaemia
inhibition
Mean survival time (MST) of treated
mice
(days SD)
22.09 9.22
21.3 4.04
90.35
64.50
Chloroquine
8g
Dosage 5mg/kb/day
Table 3: Docking interaction of hybrid derivatives 8(a-i) in wild and qradruple mutant pf-DHFR-TS
Wild type pf-DHFR-TS
Donor/acceptor
Hydrogen bond
Qradruple mutant pf-DHFR-TS
Donor/acceptor Non-
hydrogen bond bonded
forces
Binding
energy(Kcal/mol
)
Non-
bonded
forces
Binding
energy
(Kcal/mol
)
Compou
nd
Quinoline-NH…..
SER167
-72.45
Quinoline-
NH…..
SER167
8a
-35.54
π-σ
-
Quinoline
—THR107
π-+
Quinoline ring-
N….. SER108
Phenyl
NO—
PHE58
1,3,5-triazine-
phenyl-
NH……SER 111
11.27
8b
1,3,5-triazine-
phenyl-
NO…….ALA16
-85.11
-81.41
π-π
π-π
Phenyl—
PHE58
Phenyl—
PHE116
Quinoline-
NH….. LYS49
π-+
Phenyl NO-
---PHE58
1,3,5-triazine-
phenyl-
NH….ILE164
-44.44
8c
1,3,5-triazine-
Phenyl NO………
SER120,
π-π
π-π
Phenyl—
PHE58
Phenyl—
PHE116
π-σ
ARG159,
1,3,5-triazine
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Phenyl
OH….ASP54
Quinoline
Piperazine-
PHE58
ARG122
1,3,5-triazine
Phenyl
OH….LYS49
1,3,5-triazine-
phenyl
NH….SER111
-47.28
8d
1,3,5-triazine-
Phenyl NO………
ARG59
-110.55
π-π
π-+
Phenyl—
PHE58
π-+
Phenyl—
ARG122
Phenyl
NO—
PHE58
Quinoline-NH…..
SER167
-39.77
1,3,5-triazine-
NH…TYR170
1,3,5-triazine-
NH…ASP54
1,3,5-triazine
thiosemicarbazi
de-
8e
2.00
-
π-π 1,3,5-
triazine—
PHE58
1,3,5-triazine –
phenyl-
NH…..ILE164
π-σ
Quinoline
–ARG59
1,3,5-triazine-
Thiosemicarbazie-
NH2…..ILE164,
TYR170
NH2…..THR18
5
1,3,5-triazine-
thiourea
NH2……TYR170
-39.65
1,3,5-triazine-
Phenyl
NH……SER11
1
8f
-21.77
π-σ
π-+
Triazine—
LEU46
Quinoline--
-ARG59
π-+
phenyl-
NO---
PHE58
1,3,5-triazine-
thiourea
NH……SER11
1
1,3,5-triazine-
phenyl
NH……SER111
4.74
1,3,5-triazine-
phenyl
NO……SER16
7
1,3,5-triazine-
phenyl
NH…TYR170
1,3,5-triazine
semicarbazide-
NH…..ASP54
1,3,5-triazine-
semicarbazide-
NH2….CYS15
8g
-9.66
π-π
π-π
Phenyl—
PHE58
π-+
1,3,5-
triazine—
PHE58
Phenyl NO-
--PHE58
π-+
Phenyl-
NO---
LEU40
1,3,5-triazine-NH
……SER167
72.74
1,3,5-triazine-
phenyl
8h
-84.21
π-π
π-+
Phenyl—
Quinoline--
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NH…SER111
PHE58
-ARG59
1,3,5-triazine
NH…..SER111
π-σ
Phenyl
NO—
PHE58
-
8i
π-π
18.27
Quinoline ring
N…..SER120
π-+
-35.43
Phenyl—
PHE58
Quinoline--
-ARG59,
ARG122
1,3,5-triazine-
phenyl
π-+
Phenyl NO-
--PHE58
NH…SER111
Table 4: Docking scores of compound 8g and 8c
Wild type pf-DHFR-TS
Quadruple mutant pf-DHFR-TS
Dock
Score
70.25
-PMF
65.78
57.68
-PLP1
-PLP2
Dock
Score
-PMF
-PLP1 -PLP2
Scoring
parameter
8g
111.99 94.73
103.84 92.72
141.90 144.52 150.9 140.42
76.68 121.82 88.32 97.82
68.92
8c
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This article is protected by copyright. All rights reserved.