Mol 2 Net Docking Studies and ADMET Profile of Streblusol E , Anti-Hepatitis B viral Agent of Streblus Asper

Background: Streblusol E, a phenolic phytoconstituents of Streblus asper is a potential antihepatitis B viral agent. Objective: Current study is to mechanistically analyze the probable site of action for streblusol E. Material and methods: Streblusol E has been docked with EF3CaM adenylyl cyclase(1PK0), deoxycytidine kinase(2NOA), human nucleoside diphosphate kinase(3FKB), human Hepatitis B Viral Capsid(1QGT) and hepatitis B X-interacting protein(3MSH) proteins using GRIP docking methodology. Results: Results revealed its preferential intractability towards 1PK0 i.e. EF3-CaM adenylyl cyclase and 1QGT i.e. human hepatitis B viral capsid(HBCAG) compared with reference ligand like adefovir diphosphate(active metabolite of adefovir), lamivudine, tenofovir monophosphate(active metabolite of tenofovir) and tenofovir diphosphate(active metabolite of tenofovir). Drug metabolism and pharmacokinetics studies did affirm that Streblusol E possessed all the desired drug Likeness potential. According to Derek Nexus predictions, Streblusol E did not carry potential toxicities like carcinogenicity, mutagenicity genotoxicity and developmental toxicity, providing further impetus for discovery and clinical development of semi-synthetic analogs of Streblusol E. Conclusion: The present study successfully denotes the docking studies and ADMET profile of streblusol E from Streblus asper. SciForum Mol2Net, 2015, 1(Section B), pages 1-13, Proceedings 2 http://sciforum.net/conference/mol2net-1


Introduction
Traditional medicinal plants have been recognized for their therapeutic benefits for centuries.However, there is still lack of the evidence for the clarification of their typical mechanism of action (Sripanidkulchai et al., 2009).Streblus asper, family Moraceae, commonly known as Sihora, is a rigid shrub or medium sized tree distributed in South China and South Asia (Aeri et al., 2012;Jun et al., 2012).S. asper was used by traditional healers as remedy for hepatitis B virus in South China.
Streblusol E (Fig. 1), a phenolic phytoconstituent of S. asper was proved to have potential anti-hepatitis B viral activity (anti-HBV activity), but its mechanism is still unknown for the world.Anti-HBV activity was evaluated in HepG2.2.15 cell line stably transfected with the HBV genome.Test concentrations were 4, 20, 100 and 200 µM.The levels of HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) were assayed with ELISA.IC50 value reported was 153.7 µM for HBsAg while for HBeAg, it is 23.1 µM (Jun et al., 2012).In purview of this, we tried to mechanistically analyze the probable site of anti-HBV action and to find out the pharmacophores present.
So aim of current study was to dock streblusol E with specific protein responsible for the virulence of HBV and analyze the site of action and also to evaluate its drug likeness by calculating drug metabolism, pharmacokinetics and toxicity by in silico route.
As per the Lipinski rule of five, Streblusol E stands a good chance to be drug (Table 2).Further the logs of 3.244 and logP of 2.664 made it a good molecule which will be having better dissolution and bioavailability because of its absorption via human intestine also.hERG channel inhibition is also below 5, which is good signal.As plama protein binding is high, so the half life of the drug, Streblusol E is expected to be high and have a longer duration of action.Streblusol E will not be able to cross blood brain barrier, so side effect will not be related to that of brain like nausea etc.As this molecule is not a Pgp substrate, so likeliness of resistance will be minimal.
Moreover, as per the data of Derek Nexus, Streblusol E doesn't have potential toxicities like carcinogenicity, mutagenicity, genotoxicity and developmental toxicity, but found to be possible hepatotoxic, skin sensitizer and can damage chromosome Table 3).
These results will certainly attract the attention of researchers worldwide to derivatize streblusol E and clinically developed this class to reach bedside as alternative and complementary medicine for the treatment of acute or chronic hepatitis B viral infection.

Materials and Methods
Proteins used for GRIP Docking EF3-CaM complexed with PMEApp (1PK0): Adefovir dipivoxil, a drug approved to treat chronic infection of hepatitis B virus, effectively inhibit EF-induced cAMP accumulation by inhibiting calmodulin(CaM)-activated adenylyl cyclase (Shen et al., 2004).
Deoxycytidine kinase complexed with Lamivudine & ADP (2NOA): L-nucleoside analogs represent an important class of small molecules for treating both viral infections and cancers.
These pro-drugs achieve pharmacological activity only after enzymecatalyzed conversion to their tri-phosphorylated forms.Crystal structure of human deoxycytidine kinase (dCK) in complex with the L-nucleosides (-)-beta-2',3'-dideoxy-3'-thiacytidine (3TC), an approved anti-human immunodeficiency virus (HIV) agent and troxacitabine (TRO), an experimental anti-neoplastic agent was used.The first step in activating these agents is catalyzed by dCK.The capability of dCK to phosphorylate both D-and L-nucleosides and nucleoside analogs derives from structural properties of both the enzyme and the substrates themselves (Sabini et al., 2007).
NDPK H122G and Tenofovir-diphosphate (3FKB): Tenofovir is an acyclic phosphonate analog of deoxyadenylate used in AIDS and hepatitis B therapy.Tenofovir diphosphate, its active form can be produced by human nucleoside diphosphate kinase (NDPK), but with low efficiency, and that creatine kinase is significantly more active (Koch et al., 2009).
Human Hepatitis B Viral Capsid (HBCAG) (1QGT): Hepatitis B is a small enveloped DNA virus that poses a major hazard to human health.The crystal structure of the T = 4 capsid has been used.The monomer fold is stabilized by a hydrophobic core that is highly conserved among human viral variants.Association of two amphipathic alpha-helical hairpins results in formation of a dimer with a four-helix bundle as the major central feature.The capsid is assembled from dimers via interactions involving a highly conserved region near the C terminus of the truncated protein used for crystallization.The major immunodominant region lies at the tips of the alpha-helical hairpins that form spikes on the capsid surface (Wynne et al., 1999).
Hepatitis B X-interacting protein at high resolution (3MSH): Hepatitis B X-interacting protein (HBXIP) is a ubiquitous protein that was originally identified as a binding partner of the hepatitis B viral protein HBx.HBXIP is also thought to serve as an anti-apoptotic cofactor of survivin, promoting the suppression of procaspase-9 activation (Garcia-Saez et al., 2011).

Docking studies
Vlife MDS 4.4 is very robust software with inclusion of all the necessary simulation modules.The structure of streblusol E in the study has been drawn in the 2D drawing application (2D Draw app) of MDS 4.3, followed by its conversion into 3D form by using default conversion procedure.Best conformer with the minimum energy was used for the docking analysis (Singla and Bhat, 2010;Singla et al., 2013).Molecular docking energy evaluations are usually carried out with the help of scoring function like dock score, PLP score, potential of mean force (PMF) score, steric and electrostatic score, etc.The PLP function is incorporated by the MDS Vlife Science software in the GRIP docking method which calculates the ligandreceptor binding affinity in terms of the PLP score.The PLP score is designed to enable flexible docking of ligands to perform a full http://sciforum.net/conference/mol2net-1conformational and positional search within a rigid binding site.Streblusol E was docked into the active site of 1PK0, 1QGT, 2NOA, 3FKB and 3MSH that can be obtained in the cocrystallized with adefovir diphosphate, lamivudine, tenofovir monophosphate & tenofovir diphosphate or by the use of cavities.The parameters fixed for docking simulation was like this-number of placements: 50, rotation angle: 10o, exhaustive method, ligand-wise results: 10, scoring function: PLP score.By rotation angle, ligand would be rotated inside the receptor cavity to generate different ligand poses inside the receptor cavity.By placements, the method will check all the 50 possible placements into the active site pocket and will result out best placements out of 50.After docking simulation, the best docked conformer of streblusol E and reference ligands were then checked for their interactions with targeted proteins like hydrogen bonding, hydrophobic, pi-staking/aromatic, charge and vanderwaal's interactions (Igoli et

In Silico Prediction of Toxicity
Using Derek Nexus module in StarDrop(liaison between Optibrium Ltd. and LHASA ltd), probability of Streblusol E to exert toxicity against various toxicological endpoints like carcinogenicity, mutagenicity, genotoxicity etc were calculated and reporting under four reasoning level like • No Report -no evidence of toxicity or nothing to report • Probable-there is atleast on strong argument for the proposition and none against it • Plausible -the weight of evidence supports the proposition • Equivocal -there is an equal weight of evidence for and against the proposition (Lhasa Ltd.; Segall and Barber, 2014).

Conclusions
Streblusol E, bioactive from Streblus asper has potential to inhibit hepatitis B virus.Its in silico studies with various target proteins further strengthens its efficacy as anti-hepatis B viral agents.

Figure 5 .
Figure 5. Hydrogen bonding of Streblusol E with Human Hepatitis B Viral Capsid(1QGT); Blue Broken Line-Hydrogen Bonding.

Table 1 .
Docking studies of streblusol E and reference ligands with various targeted proteins.

Table 2 .
ADME profile prediction of Streblusol E.