Introduction

to the family of lentiviruses. HIV types 1 and 2 (HIV-1 and HIV-2) causes Acquired immunodeficiency syndrome (AIDS). During the course of AIDS in humans, immune system begins to fail which leads to life- threatening opportunistic infections or malignancies associated with the progressive failure of the immune system [1,2]. HIV/AIDS remains a persistent problem around the world. Till 2013, 35 million people were detected worldwide living with HIV/AIDS. Sub-Saharan Africa remains most severely affected due to HIV. In Sub-Saharan Africa, 1 in every 20 adults living with HIV. This accounts for nearly 71% of the people living with HIV worldwide [3]. India is the third highest number of estimated people living with HIV in the world. According to the National AIDS Control Organization (NACO) report 2014, the estimated number of people living with HIV/AIDS in India during 2012 was 20.89 lakh [4].

to the family of lentiviruses. HIV types 1 and 2 (HIV-1 and HIV-2) causes Acquired immunodeficiency syndrome (AIDS). During the course of AIDS in humans, immune system begins to fail which leads to life- threatening opportunistic infections or malignancies associated with the progressive failure of the immune system [1,2]. HIV/AIDS remains a persistent problem around the world. Till 2013, 35 million people were detected worldwide living with HIV/AIDS. Sub-Saharan Africa remains most severely affected due to HIV. In Sub-Saharan Africa, 1 in every 20 adults living with HIV. This accounts for nearly 71% of the people living with HIV worldwide [3]. India is the third highest number of estimated people living with HIV in the world. According to the National AIDS Control Organization (NACO) report 2014, the estimated number of people living with HIV/AIDS in India during 2012 was 20.89 lakh [4].

to the family of lentiviruses. HIV types 1 and 2 (HIV-1 and HIV-2) causes Acquired immunodeficiency syndrome (AIDS). During the course of AIDS in humans, immune system begins to fail which leads to life- threatening opportunistic infections or malignancies associated with the progressive failure of the immune system [1,2]. HIV/AIDS remains a persistent problem around the world. Till 2013, 35 million people were detected worldwide living with HIV/AIDS. Sub-Saharan Africa remains most severely affected due to HIV. In Sub-Saharan Africa, 1 in every 20 adults living with HIV. This accounts for nearly 71% of the people living with HIV worldwide [3]. India is the third highest number of estimated people living with HIV in the world. According to the National AIDS Control Organization (NACO) report 2014, the estimated number of people living with HIV/AIDS in India during 2012 was 20.89 lakh [4].

At present, there are no defined vaccines or drugs available to cure HIV infected patients. Currently, nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) are anti-HIV class of drugs are exercised around the world [5]. Most HIV-infected patients in resource limited settings receive a first-line triple combination of lamivudine, nevirapine, stavudine or zidovudine. This combination antiretroviral therapy (ART) provides many benefits but it also creates more adverse events like peripheral neuropathy, hypersensitivity and life-threatening hepatotoxicity in HIV patients which hamper treatment adherence [6].

Chemokine receptors are critical regulators of cell migration in the context of immune surveillance, inflammation and development. In 2013, it is reported that G protein-coupled chemokine receptor CXCR4 is an important targets for HIV infection [7]. CXCR4 is a major co-receptor for T-cell-tropic HIV-1 [8]. Due to this, till now numerous efforts have been made to develop a new class of anti-HIV agents that target CXCR4 as an additional or alternative therapy to standard HAART. The first FDA approved CXCR4 antagonist, plerixafor/ AMD3100 is used to mobilize hematopoietic stem cells, which are collected for use in stem cell graft in patients with hematological cancers. Plerixafor was initially developed to interfere with SDF-1/CXCR4 interaction and shows promise for HIV infection, cancers and autoimmune diseases such as rheumatoid arthritis. However, this drug is expensive because of the difficulty in its total synthesis. Therefore, there is an urgent need for the discovery of new CXCR4 antagonists that are cost-effective, potent and safe [9]. Phytochemicals have been an important and safe source of lead compounds in drug discovery and development.

Moringa oleifera, Lam (M. oleifera) is a member of the Moringaceae family. This edible plant is also known as drumstick tree, horseradish tree and malunggay. Moringa oleifera, Lam is native to the sub-Himalayan tracts of India, Pakistan, Bangladesh and Afghanistan and it is consumed as food [10,11]. Phytochemical analyses have shown that M. oleifera leaves are particularly rich in potassium, calcium, phosphorous, iron, vitamins A and D, essential amino acids, as well as such known antioxidants such as β-carotene, vitamin C and flavonoids [12-15]. In many regions of Africa, from traditional days M. oleifera is widely consumed for self-medication by patients affected HIV/ AIDS [16]. However, the benefit for the treatment or prevention of HIV disease or infection by using either dietary or topical administration of M. oleifera preparations is not quite wellknown. There is room to exploit the potential M. oleifera in the battle against HIV. In the present study, attempt has been made to answer the role of M. oleifera in HIV treatment using CXCR4 as a target receptor.

Materials and Methods

Data Set

Phyto constituents and standard drug compounds could be downloaded from the database (https://pubchem.ncbi.nlm.nih.gov/search/search.cgi) and generate the small molecule compounds to identify potential CXCR4 antagonist screening. A three-dimensional structure of CXCR4 chemokine GPCR protein could be offered from the Protein Data Bank (PDB ID: 3ODU).

Receptor Optimization

Receptor was optimized using Discovery Studio version-4 Accelrys Software. The energy minimization of modeled protein was performed by SPDV and its score was obtained. Then the active sites of these proteins were obtained from online active site prediction tool. The Ramachandran plot was obtained to study the favorable regions with residues present.

Ligands Optimization

Drug molecule and phyto constituents optimization, addition of charges and hydrogen bonds was carried out using Autodock tools.

Computational Docking Studies

The docking of selected protein with three drug molecules was performed by using Auto dock 4. The docking calculations were verified using docking server [17]. Gasitier partial charges were added to ligand. Nonpolar hydrogen atoms were merged and rotatable hydrogen bonds were defined. Docking calculations were carried out on receptor. Essential hydrogen atoms, kollaman charges and savlavation parameters were added affinity (grid) maps 25 Å grid points and 0.500 Å were generated using the auto grid program. Auto dock parameters set and distance dependent dielectric functions were used in the calculation of the van der Waals and the electrostatic terms, respectively. Docking simulations were performed using Lamarckian algorithm (LGA) and Solis and Wet local search methods [18]. Initial position torsion and orientation of the drug molecules were set randomly. All rotatable torsions were released during docking. Each docking experiment was derived from 10 different runs that were set to terminate after 250000 energy calculations. The population size was set to 150. During search the translational step 0.2 Å and quaternion and torsion step 5 were applied [19].

Results

Docking is done by Auto dock 4 for CXC4 structure with control drug (6,6-dimethyl-5,6-dihydroimidazo [2,1- b] [1,3] thiazol-3-yl) methyl N,N’ dicyclo hexylimidothio carbamate and selected phyto constituents of Moringa oleifera. Docking energies for (6,6-dimethyl-5,6-dihydroimidazo[2,1-b] [1,3] thiazol-3- yl) methyl N,N’ dicyclo hexylimido thio carbamate (-9.17Kcal/mol), 2-Pyrrolidinone (-3.35 kcal/mol), Linalool oxide (-4.12 kcal/ mol), Upiol (-4.15 kcal/mol),1,2- Benzene dicarboxylic acid, bis (2-ethyl hexyl) ester (-5.56 kcal/mol), Ellagic acid (-6.10 kcal/ mol), Gallic acid (-4.38 kcal/mol), Ferulic acid (-4.81 kcal/mol), Vanillin (-4.23 kcal/mol), 1,2,3-Cyclopentanetriol (-4.09 kcal/ mol), Astragalin (-5.69 kcal/mol), Aurantiamide acetate (-6.02 kcal/mol), Chlorogenic acid (-5.89 kcal/mol), Isoquercetin (-5.52 kcal/mol), Crypto-chlorogenic acid (-4.66 kcal/mol), Kaempferol (-5.90 kcal/mol), Niaziminin (-3.96 kcal/mol) (Table 1). Interaction tables of drug and all phyto constituents have shown the non-covalent interactions occurring between active site residues and respective drug and phyto constituents (Table 2-18). The docking study showed that Ellagic acid and Aurantiamide acetate as a promising anti-HIV candidate when they are compared with 6,6- dimethyl-5,6-dihydroimidazo [2,1-b] [1,3] thiazol-3- yl) methyl N,N’ dicyclo hexylimidothio carbamate. However, further in vitro and in vivo studies of individual phyto constituents are needed to validate their biological potential. Ball and socket model of respective drug molecule and phyto constituents interacting with active site are shown in (Figure 1-16). In the present investigation, we found that tryptophan 94 and histidine113 from the active site of CXCR4 contributed to hydrophobic interaction with Ellagic acid and Aurantiamide acetate. The nature of amino acids presentat the active site of receptor is an important to understand interaction studies with ligand. In case of Aurantiamide acetate hydrophobic interactions were contributed by histidine113 and Iso leucine 284. These three amino acids plays crucial role in the docking and non- covalent interaction and defined as the amino acids that can interact with all the selected ligands. Thus these amino acids may play important role in target function of CXCR4.

Discussions

Moringa oleifera known for its high nutritional and therapeutic potential, only since last two decades serious efforts has been made to explore this plant scientifically. Phytochemical analyses have shown that M. oleifra is rich in phenolic acids, flavonoids, alkaloids, phytosterols and glycosides. These phytochemical classes contributing to its diversified pharmacological activities viz. analgesic, anti- inlammatory, antihypertensive, antioxidant, antitumor, antiarthritic, antispasmodic, antiurolithic and hepato protective, etc. In the present investigation 16 phytochemicals of M. oleifera were docked against CXCR4 receptor. After molecular docking study of selected phytoconstituents and considering their docking score, two compounds viz. ellagic acid and aurantiamide acetate are found to be promising candidate against the CXCR4 receptor. Literature survey has shown that ellagic acid and aurantiamide acetate contribute to diverse pharmacological properties. Ellagic acid (EA) is known to possess multiple biological activities, such as inhibition of proliferation, angiogenesis, oxidation, HIV protease and other processes involved in inflammation and carcinogenesis [20-23]. Whereas, Aurantiamide acetate showed significant antiinflammatory/antiarthritic and analgesic activity mediated via inhibition of TNF-alpha, IL-2 and other cytokines [24]. In vitro and in vivo studies demonstrate that aurantiamide acetate may suppress the growth of human malignant gliomas via inhibiting intracellular autophagic flux [25]. From the above references and our research findings, we suggest the possibility of ellagic acid and aurantiamide acetate to develop as a CXCR4 antagonist. However, further in vitro and in vivo studies needed to validate their biological potential.

Conclusion

Based on the above discussion, we have observed that ellagic acid and aurantiamide acetate is promising candidate against the CXCR4 receptor. The results of present investigation may possibly provide the rationale behind the use of M. oleifera in HIV infected patients. In future, there is a great need to work on the active principles from M. oleifera to formulate the best alternative formulations alone or in combinations with ART drugs to increase the quality of life of patients.

Acknowledgement

Authors are grateful to the Haffkine Institute for Training, Research & Testing for providing the opportunity to conduct present investigation.

Supplementary Material

Graphical abstract.

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  Figure 1: 2-Pyrrolidinone ball and stick model.

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  Figure 2: Linalool oxide ball and stick model.

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  Figure 3: Upiol ball and stick model.

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  Figure 4: --------------------

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  Figure 5: Ellagic acid ball and stick model.

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  Figure 6: Gallic acid ball and stick model.

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  Figure 7: Ferulic acid ball and stick model.

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  Figure 8: Vanillin ball and stick model.

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  Figure 9: 1,2,3-Cyclopentanetriol ball and stick model.

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  Figure 10: Astragalin ball and stick model.

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  Figure 11: Aurantiamide acetate ball and stick model.

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  Figure 12: Chlorogenic acid ball and stick model.

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  Figure 13: Isoquercetin ball and stick model.

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  Figure 14: Crypto-chlorogenic acid ball and stick model.

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  Figure 15: Kaempferol ball and stick model.

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  Figure 16: Niaziminin ball and stick model.

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  Table 1: CXCR4 chemokine GPCR inhibitors docked against 3ODU.

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  Table 2: (6,6-dimethyl-5,6-dihydroimidazo[2,1-b][1,3] thiazol- 3-yl)methyl N,N’-dicyclohexylimidothiocarbamate interaction.

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  Table 3: 2-Pyrrolidinone interaction.

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  Table 4: Linalool oxide interaction.

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  Table 5: Upiol interaction.

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  Table 6: 1,2-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester interaction.

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  Table 7: Ellagic acid interaction.

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  Table 8: Gallic acid interaction.

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  Table 9: Aurantiamide acetate interaction.

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  Table 10: Chlorogenic acid interaction.

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  Table 11: Isoquercetin interaction.

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  Table 12: Crypto-chlorogenic acid interaction..

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  Table 13: Kaempferol interaction.

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  Table 14: Niaziminin interaction.

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  Table 15: Ferulic acid interaction.

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  Table 16: Vanillin interaction.

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  Table 17: 1,2,3-Cyclopentanetriol interaction.

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  Table 18: Astragalin interaction.