CXCR4 inhibitory activity analysis of linoleic acid isolated from ethanolic extract of Cayratia trifolia (L.): An molecular docking simulation

Abstract

Chemokine Receptor type 4 (CXCR4) is the increasing interest as a drug target, which is involved in many disease states including more than 23 types of cancer and several immunodeficiency disorders. On the other hand, the chemical constituents of medicinal plant are helpful in the discovery of therapeutic agents. Therefore the main aim of the study was to analyze the inhibitory activity of linoleic acid against CXCR4. Previous studies the natural compound of linoleic acid was isolated and identified from ethanolic extract of Cayratia trifolia. The molecular docking analysis was carried out to find the CXCR4 inhibitory activity of the isolated compound. Results, the isolated compound of linoleic acid possess comparable good Glide score and Glide energy when compared with FDA approved drug. Based on the results, it can be concluded that, the isolated compound of linoleic acid may act as novel inhibitor aginst CXCR4 and further it can be lead to development of therapeutic agent for variety of cancers and other disorders. © 2015, International Journal of Pharmacognosy and Phytochemical Research. All Rights Reserved.

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International Journal of Pharmacognosy and Phytochemical Research 2015; 7(4); 781-784
ISSN: 0975-4873
Research Article
*Author for Correspondence
CXCR4 Inhibitory Activity Analysis of Linoleic Acid Isolated from
Ethanolic Extract of Cayratia trifolia (L.): An Molecular Docking
Simulation
Chella Perumal P1,Pradeep Kumar Reddy C2,Pratibha P1, Sowmya S1, Priyanga S3, Devaki
K3, Poornima K3, Ramkumar S3, Gopalakrishnan VK1*
1Cancer Biology and Medicinal Chemistry Unit, Department of Biochemistry & Bioinformatics,
Karpagam University, Coimbatore, Tamil Nadu, India-641 021.
2Laboratory of Conformational Diseases, Biological Research Centre, Hungarian Academy of Sciences,
Szeged-6726, Hungary.
3Department of Biochemistry, Karpagam University, Coimbatore, Tamil Nadu, India-641 021.
Available Online: 21st July, 2015
ABSTRACT
Chemokine Receptor type 4 (CXCR4) is the increasing interest as a drug target, which is involved in many disease states
including more than 23 types of cancer and several immunodeficiency disorders. On the other hand, the chemical
constituents of medicinal plant are helpful in the discovery of therapeutic agents. Therefore the main aim of the study
was to analyze the inhibitory activity of linoleic acid against CXCR4. Previous studies the natural compound of linoleic
acid was isolated and identified from ethanolic extract of Cayratia trifolia. The molecular docking analysis was carried
out to find the CXCR4 inhibitory activity of the isolated compound. Results, the isolated compound of linoleic acid
possess comparable good Glide score and Glide energy when compared with FDA approved drug. Based on the results, it
can be concluded that, the isolated compound of linoleic acid may act as novel inhibitor aginst CXCR4 and further it can
be lead to development of therapeutic agent for variety of cancers and other disorders.
Keywords: Cayratia trifolia (L.); Linoleic acid; CXCR4; Molecular docking analysis.
INTRODUCTION
The chemokine gradients are playing significant role
movement of cells in a variety of normal and pathologic
processes. Cancers have a complex chemokine network
that may influence the leucocyte infiltrate and
angiogenesis1. Malignant cells can also state the
chemokine receptors and respond to chemokine gradients
and this may be associated with the development and
spread of cancer. Different cancers express different CC
and CXC chemokine receptors and the corresponding
ligands are sometimes expressed at sites of tumour
spread2,3. There is one chemokine receptor, however,
Chemokine Receptor type 4 (CXCR4) is a G-protein-
coupled membrane receptor which is present in various
cell types. It is increasing interest as a drug target and it
can be involved in many disease states including more
than 23 types of cancer and several immunodeficiency
disorders4. CXCR4 has been shown to play a critical role
in (breast) cancer progression and metastatic spread. It
has been reported that 69% of ductal carcinoma in situ
(DCIS) lesions are CXCR4-positive. Over-expression of
CXCR4 has also been suggested to be of value for
imaging applications5. As a number of reviews have
recently been published highlighting CXCR4 as a target
in HIV and its role in cancer metastasis6.
Consideration of the bioactive compounds from the
medicinal plant is helpful to discovery of therapeutic
agents as well as new sources of economic materials like
oil and gums7. Secondary metabolites from medicinal
plants have demonstrated to be an excellent reservoir of
new medical compounds8. Numbers of bioactive
compounds are present in medicinal plants which are
widely used against variety of diseases9.Cayratia trifolia
(L.) is the medicinal plant belongs to the family of
Vitaceae, commonly known as Fox grape in English is
native to India, Asia and Australia. It is a perennial
climber having trifoliated leaves with (2-3 cm), long
petioles and ovate to oblong-ovate leaflets. Flowers are
small greenish white brown in color. Fruits are fleshy,
juicy, dark purple or black, nearly spherical, about 1 cm
in diameter10. The whole plant is used as anti diuretic, in
tumors, neuralgia and splenopathy. It has been reported to
contain huge amount of bioactive compounds such as
yellow waxy oil, steroids, terpenoids, flavonoids and
tannins11. The bark extract has been reported to have
antiviral, antibacterial, antiprotozoal, hypoglycemic,
anticancer and diuretic activities in animal models12.
Therefore, the aim of the present research work is to
analyze the inhibitory activity of linoleic acid (Isolated

Chella Perumal P et al.. / CXCR4 Inhibitory Activity…
IJPPR, Volume 7, Issue 4, August 2015- September 2015 Page 782
Table 1: GlideScores and GlidEnergies of various
ligands with CXCR4 (the natural compounds are
identified from ethanolic extract of Cayratia trifolia (L.)
and carboplatin is a FDA approved drug) complexes are
given as calculated from the molecular docking studies.
S
.
N
o
Compounds
Glide Score
Glide
Energy
1
Linoleic acid
-4.585
-32.114
2
Carboplatin (FDA
drug)
-6.024
-25.039
Table 2: ADME properties of selected compounds as
predicted by using QikProp module of Schrodinger suite
are listed.
S.
N
o
Ligands
Molecula
r Weight
(g/mol)
H-
Bond
dono
r
H-Bond
accepto
r
Log
P
O/W
1
Linoleic
acid
280.44
1
2
5.84
2
Carboplati
n FDA
144.12
0
2
1.35
from ethanolic extract of Cayratia trifolia) against
CXCR4 computational molecular analysis.
MATERIALS AND METHODS
Computational molecular analysis
Ligand selection preparation
Based on the previous studies, the isolated compound of
linoleic acid13 and FDA approved drug of Carboplatin
(standard drug for comparison) were selected and
prepared using the LigPrep 2.4 module from Schrodinger
suit14 for molecular docking analysis. The structure of
each ligands were optimized by means of the OPLS 2005
force field using a default setting.
Preparation of protein structure
The high resolution crystal structure of (3D structure)
CXCR4 was retrieved from the Protein Data Bank (PDB
ID: 3OE6) and it was prepared by protein preparation
wizards (standard methods) that are available in grid-
based ligand docking with energetics15. Protein was
optimized using sample water orientation and minimized
by using RMSD 0.30 Å and OPLS (2005) force field.
Active site prediction
The binding pockets (active site) and functional residues
in CXCR4 were identified and characterized by Site- Map
5.5 module from Schrodinger suit16. SiteMap calculation
begins with an initial search step that identifies or
characterizes- through the use of grid points- one or more
regions on the protein surface that may be suitable for
binding ligands to the receptor. Contour maps were then
generated, hydrogen binding possibilities, hydrophilic
maps, produced hydrophobic are may guide the protein-
ligand docking analysis17.
Molecular docking analysis
The docking analysis was performed by using the
standard precision (SP) which is Standard mode of Glide
5.6 (Gridbased Ligand Docking with Energetic) module
from Schrodinger suit18. The selected natural compound
of linoleic acid and FDA approved drug were docked in
to the binding site of CXCR4 using Glide modiule. The
scaling Vander Waals radii were 1.0 in the receptor grid
generation. Grid was prepared with the bounding box set
on 20Aº. The co-ordinates of this enclosing box with the
help of the active site residues to be set default. The force
field is using for the docking protocol is OPLS_2005. The
docked lowest-energy complexes were found in the
majority of similar docking conformations19.
ADME properties prediction
The CXCR4 ligands of linoleic acid and FDA drug were
checked for their ADME properties using QikProp 2.3
module20. It helps to analyze the pharmacokinetics and
pharmacodynamics of the ligands by accessing the drug
like properties. The significant ADME properties such as
Molecular weight (MW), H-Bond donor, H Bond
acceptor and log P (O/W) were predicted.
RESULTS AND DISCUSSION
In India, great number of plant species had been screened
for their pharmacological properties but still vast wealth
of rare species is unexplored21. Medicinal plants are at
interest to the field of novel drug development, as most of
the drug industries depend on medicinal plants for the
production of novel bioactive compounds22. The isolated
bioactive compound of linoleic acid posses many
biological activities such as anti-inflammatory, anti-
microbial and anti-diabetic activities23. The best active
site (binding pocket/site) was preferred based on the site
score and hydrophobic/hydrophilic areas, which holds
better binding cavity24. The binding site residues of
CXCR4 were predicted and it may involve in the binding
of substrate and small molecule. Thus, all these residues
were confirmed as CXCR4 active site residues and picked
to generate grid in the centroid of these residues for
molecular docking approach.
Normally the molecular docking study is used to predict
the binding orientation of small molecule drug candidate
to their protein targets in order to predict the affinity and
activity of the small molecule. In the docking results of
linoleic acid and FDA approved drug of Carboplatin were
complexes with CXCR4 protein shown in Table 1.
Among that the natural compound of linoleic acid has
good binding affinity when compared with FDA drug.
In the CXCR4-linoleic acid complex (Figure 1) possess
Glide score of -4.585 and Glide energy of -32.114
kcal/mol, when compared with CXCR4/carboplatin
complex which has Glide score of -6.02 and Glide energy
of -25.03 kcal/mol. The linoleic acid strongly binds in
hydrophobic region of CXCR4 at LYS239 residue. In the
same way CXCR4/carboplatin complex also possess good
affinity (Figure 2).
Chemokines and chemokine receptors regulate the
physiological movement of immune cells in the body25.
Among the family of chemokine and chemokine
receptors mediating tumor cell invasion and metastasis,
CXCL12/CXCR4 has gained a central role in different
types of tumors in mediating tumor growth, angiogenesis

Chella Perumal P et al.. / CXCR4 Inhibitory Activity…
IJPPR, Volume 7, Issue 4, August 2015- September 2015 Page 783
and metastasis. In prostate cancer cells, CXCL12 and
CXCR4 play a key role in invasion and metastasis,
leading to development and expansion of osseous
metastasis26,27. Thus, targeting CXCR4 can have dual
effects on inhibiting primary tumor growth and metastasis
or mono effect on inhibiting either tumor growth or
metastasis28. In the molecular docking analysis the
highest negative value of glide score and glide energy
indicated that, these complexes may have good affinity29
and this compound may act as good CXCR4 inhibitor.
The ADME properties prediction of linoleic acid was
under acceptable range. The limitations of ADME
properties are: not more than 5 hydrogen bond donors,
not more than 10 hydrogen bond acceptor, molecular
mass less than 500 daltons, an octanol- water partition
coefficient log P not greater than 5 (Table 2).
CONCLUSION
In the present, the isolated and identified natural
compound of linoleic acid was analyzed for their
inhibitory activity against CXCR4 using molecular
docking analysis and the drug like properties also were
predicted. In the results, linoleic acid was strongly binds
with CXCR4 when compared with FDA drug. The
ADME properties of these compounds were acceptable
range. Therefore, based on the results, it can be
concluded that, the isolated bioactive compound of
linoleic acid may work as novel inhibitor against CXCR4
and it may leads to development of drug agents for
variety of cancers and other disorders.
CONFLICT OF INTEREST STATEMENT
The authors declare that there is no conflict of interests
regarding the publication of this paper.
ACKNOWLEDGEMENT
The authors are thankful to our Chancellor, Chief
Executive Officer, Vice-Chancellor and Registrar of
Karpagam University for providing facilities and
encouragement. Our grateful thanks to Indian Council of
Medical Research (ICMR), New Delhi for providing the
financial support (File No: BIC/11(19)/2013) to this
research work. We extend our deepest thanks to Dr. D.
Jeya Sundra Sharmila, Karunya University for providing
us an opportunity to use Schrodinger Suite (in silico
analysis).
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Figure 1: Docking complex of CXCR4 with A) Linoleic acid and B) FDA approved drug generated by using Glide-SP
module of Schrodinger suite are shown in this figure. The proteins, ligands and binding pockets are represented in
ribbon, sticks and surface models, respectively.
Figure 2: Residues of the CXCR4 that are within 4 Å proximities to A) Linoleic acid and B) FDA approved drug are
illustrated in 2D graphics. Dotted arrow lines denote ‘Hydrogen bonds’ between the corresponding atoms.

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IJPPR, Volume 7, Issue 4, August 2015- September 2015 Page 784
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