Research Article |
Corresponding author: Neelaveni Thangavel ( nchellappan@jazanu.edu.sa ) Academic editor: Rumiana Simeonova
© 2024 Mohammed Albratty, Neelaveni Thangavel, Balakumar Chandrasekaran, Abdulkarim M. Meraya, Hassan Ahmad Alhazmi, Sankar Muthumanickam, Pandi Boomi, Natarajan Boopala Bhagavan, Safaa F. Saleh.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Albratty M, Thangavel N, Chandrasekaran B, Meraya AM, Alhazmi HA, Muthumanickam S, Boomi P, Bhagavan NB, Saleh SF (2024) Benchmarking docking, density functional theory and molecular dynamics studies to assess the aldose reductase inhibitory potential of Trigonella foenum-graecum compounds for managing diabetes-associated complications. Pharmacia 71: 1-10. https://doi.org/10.3897/pharmacia.71.e118949
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Inhibition of aldose reductase (AR) could be a beneficial strategy for managing diabetes-associated complications. Trigonella foenum-graecum (TFG) is used around the globe as a traditional medicine for the management of diabetes. Our study aimed to assess the potential of TFG phytocompounds as inhibitors of AR in the context of diabetes-related complications. Our research work employed molecular docking, density functional theory (DFT) and molecular dynamics (MD) to evaluate the efficacy of TFG compounds. The study compared the predictive power of AutoDock and AutoDock Vina docking software and found that AutoDock Vina performs better in ranking and discriminating actives and decoys. The research identified five compounds as potential AR inhibitors from fifty-eight reported TFG phytoconstituents. Tigogenin and Gitogenin stood out as the most promising AR inhibitors. The electronic properties of the compounds were analysed through DFT studies and provided insights into their binding potential. Finally, the results of MD simulations indicated that Tigogenin and Gitogenin bound robustly with AR throughout the simulation period. This study predicted the AR inhibitory potential of TFG compounds for managing diabetes-associated complications and supports further drug development from TFG. The benchmarking approach used in this study improves the accuracy and dependability of bioactivity prediction.
Benchmarking docking, aldose reductase, diabetic retinopathy, DFT, Trigonella foenum-graecum
Diabetes is a hormonal disorder involving deficient insulin secretion or action where glucose levels in the bloodstream are elevated (
Natural product datasets can be explored using in silico techniques like molecular docking and dynamics simulations to discover natural products for diabetes and related complications (
Molecular docking is a computational technique that predicts the binding affinity of a ligand to a protein and the ligand’s bioactive conformation. Based on molecular docking and molecular dynamics simulations, aldose reductase inhibitory compounds were identified. Further, it was observed that the phytochemicals of ginger exhibited higher docking scores, binding affinity and protein-ligand interactions than the phytochemicals of turmeric, garlic and TFG (
The study’s objective is to assess the AR inhibitory capacity of TFG’s chemical components using benchmarking molecular docking, followed by DFT analysis of TFG compounds and stability analysis of the binding of TFG’s compounds to AR using molecular dynamics (MD).
All the computational studies were carried out on a PC running Windows 7 Ultimate with an Intel Core i3 microprocessor, 4.00 GB of RAM and a 64-bit operating system. AutoDock 4.2.1 (ADock) (https://autodock.scripps.edu/download-autodock4/) and AutoDock Vina 1.1.2 (Avina) (https://vina.scripps.edu/downloads/) were used to benchmark molecular docking. Discovery Studio Visualizer 3.5 (https://discover.3ds.com/discovery-studio-visualizer-download) and PyMol 2.5 (https://pymol.org/2/) were employed to analyse the binding conformations and inter-molecular interactions. OpenBabel 3.1.1 (https://sourceforge.net/projects/openbabel/) was used to create PDBQT files for all test compounds and decoys. To validate and compare the docking results, an online tool called Screening Explorer (http://stats.drugdesign.fr/) was used.
The 3D crystal structure of AR (PDB accession number ID: 2INE with the best resolution 1.90 Å) was downloaded from the RCSB PDB (http://www.rcsb.org) in PDB format. The native ligand, cofactors, metal ions and water were removed from the protein structure. The residues that constitute the binding pocket of AR were analysed using the Computed Atlas for Surface Topography of Proteins (CASTp), a web-based tool for binding site prediction (http://cast.engr.uic.edu). The 3D structures of 58 TFG compounds and Epalrestat were obtained from the PubChem database (http://pubchem.ncbi.nlm.nih.gov/pccompound). The SDF file of 3D structures of decoys for the AR enzyme was downloaded from the DEKOIS 2.0 database (http://www.dekois.com).
The target protein in PDB format obtained from the above step was further processed by adding polar hydrogens and Gasteiger charges in Avina. This energy-minimised AR enzyme structure was saved as a PDBQT file and was used for docking the ligands in ADock and Avina. All test compounds, including TFG compounds, Epalrestat and decoys in SDF format, were loaded into Open Babel for conversion to PDBQT, during which the molecules are energy minimised by adding polar hydrogen and Gasteiger charges. The binding site was defined by positioning a grid box with a centre of X, Y and Z dimensions 18.61 X -11.39 X 17.71 Å and a size of 60 X 60X 65 Å, respectively, with a spacing value of 0.375 Å. Both ADock and Avina docking were performed using the exact dimensions mentioned above. The genetic algorithm parameter was set at 10 in ADock, while all other parameters were fixed at default values. In Avina docking, ten conformers were generated at a 3 kcal/mol energy gradient, while the rest of the parameters chosen were at their default numbers. Both software allowed the ligand flexibility; their rotatable bonds could move freely during docking. The energy calculations of protein-ligand complexes were done through the Lamarckian genetic algorithm in both software. The protein-ligand complexes with the least negative binding energy (∆G) indicate robust binding and favourable conformations were selected for analysing the interaction between the protein-ligand complexes (
Individual and comparative scoring methods were used to compare the results of ADock and Avina docking software (
DFT calculations were conducted to investigate the electronic properties of the best-forming TFG compounds. The calculation used Maestro’s Jaguar module with the B3LYP functional method and 6-31G* basis set. The electronic properties, such as the Highest Occupied Molecular Orbital (HOMO) energy, Lowest Unoccupied Molecular Orbital (LUMO) energy and its corresponding Band gap energy, were computed.
The GROMACS 4.3.1 package (https://www.gromacs.org/) with GROMOS43al force field was used to perform MD to evaluate the structural stability of protein-ligand complexes. The PRODRG online server (http://prodrg1.dyndns.org/) was utilised to create the ligand topology. The systems were equilibrated using a cubic box with dimensions of 10 × 10 × 10 nm³ and solvated with the Single Point Charge (SPC) water model. Appropriate counter ions (Na+ Cl-) were added to neutralise the systems. The steepest descent algorithm was employed for energy minimisation for 50,000 to eliminate weak van der Waals contacts. The Parrinello-Rahman barostat and modified Berendsen thermostat were applied to maintain constant pressure and temperature at 1 bar and 300 K, respectively, using the NPT and NVT ensemble. The MD simulations were conducted for 50 ns. The g_mmpbsa tool determined the binding free energy of the AR protein-Tigogenin and AR protein-Gitogenin complexes for the last 5 ns of the MD trajectories (
∆Gbind = Gdocked – (Genzyme + Gcompound),
wherein, Gdocked is the binding energy of the docked complexes of TFG compounds with AR, Genzyme and Gcompound are the energies of AR and TFG compounds in a solvent-filled system.
The binding pocket of AR protein was analysed using the CASTp web server and the results are depicted in Fig.
The benchmarking molecular docking protocol for assessing the AR inhibitory potential of TFG compounds utilising ADock and Avina involved 1200 decoys from the DEKOIS database (see Suppl. material
Software | Global metrics (Full threshold) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
auROC | TG | RIE | BEDROC | |||||||
AutoDock | 0.937 | 0.459 | 7.242 | 0.558 | ||||||
AutoDock Vina | 0.927 | 0.603 | 8.082 | 0.622 | ||||||
Partial metrics (5%) | ||||||||||
pauROC* | pTG* | Number of Actives | Number of decoys | TPF* | P(Act)* | EF5% | ||||
AutoDock | 0.034 | 0.638 | 5 | 1 | 0.102 | 0.542 | 17.80 | |||
AutoDock Vina | 0.102 | 0.806 | 6 | 0 | 0.119 | 0.792 | 21.36 |
The performance of docking software in distinguishing active and inactive compounds can be evaluated using the auROC/pauROC. A higher pauROC score at the top 5% retrieval indicates better discrimination by Avina at an early stage. The TG metric reflects the software’s ability to prioritise active compounds effectively across various ranked compounds in which Avina performed better. RIE evaluates the efficiency of docking software in terms of information gain per compound. A higher RIE value for prediction by Avina suggests a more robust ranking of compounds at the initial stage. BEDROC emphasises docking software’s early recognition ability by quantifying the enrichment of top-ranked compounds. A higher BEDROC score indicates early enrichment and Avina performed better. The TPF and P(Act) scores indicate better predictive power of Avina than ADock for activity prediction.
Table
Structures and binding energy scores of TFG compounds ranked by AutoDock Vina at the top 5% level.
Fig.
Intermolecular interactions of (a) Tigogenin, (b) Gitogenin, (c) Epalrestat with active-site amino acids of the enzyme aldose reductase. All the ligands are shown in all atoms’ green-coloured ball and stick-type representations. The names of amino acids with ID numbers are mentioned under each circle around each ligand. On the 2D figures analysis, green-coloured dotted lines indicate hydrogen bonding interactions involving electronegative elements like nitrogen and oxygen atoms; light purple-coloured dotted lines indicate π-alkyl interactions; violet-coloured dotted lines indicate π-sigma interactions. Light green colour amino acids without bonding represent van der Waals interactions, whereas, orange-red colour amino acids indicate unfavourable interactions. The light-blue halo surrounding the interacting residues represents the solvent-accessible surface that is proportional to its diameter.
We investigated the electronic and energetic states of the top two TFG compounds, Tigogenin and Gitogenin. Fig.
Thus, the result suggests that orbitals of such ligands are favourable for forming hydrogen bond interactions with binding site amino acid residues of AR.
The Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF) and hydrogen bond interactions of the docked complexes were analysed and presented (Fig.
Fig.
It is necessary to analyse the hydrogen bond interaction profile to determine the strength of the hydrogen bond between a ligand and a protein’s binding site. As illustrated in Fig.
The binding energy of the docked complexes was calculated using the last 10 ns of the MD trajectories with the MM/PBSA method implemented using the g_mmpbsa tool of GROMACS (
Binding energies of TFG compounds with aldose reductase computed by MM/PBSA method.
Compound | Evdw (kJ/mol) | Eelec (kJ/mol) | Gpolar (kJ/mol) | Gnonpolar (kJ/mol) | ∆Gbind (kJ/mol) |
---|---|---|---|---|---|
Tigogenin | −158.321 ± 11.055 | −25.831 ± 08.259 | 95.365 ± 11.705 | −15.659 ± 0.257 | −104.446 ± 13.954 |
Gitogenin | −155.361 ± 15.203 | −20.033 ± 05.002 | 84.587 ± 15.385 | −10.657 ± 08.325 | −101.464 ± 15.662 |
It is important to note that the binding energy is negatively impacted (stabilised) by Evdw, Eelec and Gnonpolar while positively affected (destabilised) by Gpolar. With both Tigogenin and Gitogenin, the binding energies with AR are below zero, indicating a strong affinity and interaction. In both complexes studied, van der Waals interactions contribute most to the binding energy.
Targeting AR is a beneficial strategy for the effective management of diabetes-associated complications. Predicting the inhibitory potential by benchmarking docking of compounds of the traditionally used herb TFG to AR is indispensable in drug discovery. The definition of the binding site of AR is the primary step in molecular docking. The predicted AR binding region surrounds Gly18, Thr19, Trp20, Lys21, Asp43, Val47, Tyr48, Lys77, Trp79, His110 and Trp111 which is anionic and the binding specificity aperture is surrounded by Trp111, Phe122, Gln183, Tyr209, Cys298, Ala299 and Leu300 residues.
ADock and Avina are popular types of software for molecular docking (
Density functional theory (DFT) calculations provide insights into drug molecules’ binding mechanisms and properties. It quantifies electrostatic interactions between drugs and target proteins, helping identify crucial binding interactions (
GROMACS software was utilised to conduct an MD simulation for 50 ns to explore the stability and conformational alterations of the docked complexes. The RMSD analyses revealed that the apoprotein and both complexes were stable and maintained their dynamic nature after achieving equilibrium. The RMSD plot confirmed that the complexes remained stable throughout the simulation. The RMSF plot provides information about how amino acid residues move over time (
TFG contains 0.6–1.7% of saponins. Tigogenin and Gitogenin, identified as AR inhibitors, are steroidal sapogenins (
In conclusion, combined benchmarking molecular docking, density functional theory calculations and molecular dynamics stability study have demonstrated the potential of Trigonella foenum-graecum compounds as natural alternatives for managing diabetes-associated complications. The study results show that Tigogenin and Gitogenin have strong inhibitory potential against aldose reductase, a key enzyme in the polyol pathway that leads to microvascular complications in diabetes. The docking and molecular dynamics simulations have predicted that both compounds bind well to the aldose reductase enzyme and the interactions exhibit excellent stability. Further research is needed to explore the efficacy of Trigonella foenum-graecum compounds in vivo and their long-term safety profile. The study aimed to increase the reliability of bioactivity prediction by utilising molecular docking benchmarking. The results from this approach could enhance the success rate in drug development of Trigonella foenum-graecum compounds, turning them into promising drug candidates.
The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through project number ISP-2024.
List of molecular weight matched decoys retrieved from DEKOIS 2.0
Data type: sdf
Explanation note: The list contains information about the ID number and molecular weights of decoys meant for aldose reductase, retrieved from the DEKOIS 2.0 database.