Molecular docking, molecular dynamics simulations and reactivity, studies on approved drugs library targeting ACE2 and SARS-CoV-2 binding with ACE2.

The recent new contagion coronavirus 2019 (COVID-19) disease is a new generation of severe acute respiratory syndrome coronavirus-2 SARS-CoV-2 which infected millions confirmed cases and hundreds of thousands death cases around the world so far. Molecular docking combined with molecular dynamics is one of the most important tools of drug discovery and drug design, which it used to examine the type of binding between the ligand and its protein enzyme. Global reactivity has important properties, which enable chemists to understand the chemical reactivity and kinetic stability of compounds. In this study, molecular docking and reactivity were applied for eighteen drugs, which are similar in structure to chloroquine and hydroxychloroquine, the potential inhibitors to angiotensin-converting enzyme (ACE2). Those drugs were selected from DrugBank. The reactivity, molecular docking and molecular dynamics were performed for two receptors ACE2 and [SARS-CoV-2/ACE2] complex receptor in two active sites to find a ligand, which may inhibit COVID-19. The results obtained from this study showed that Ramipril, Delapril and Lisinopril could bind with ACE2 receptor and [SARS-CoV-2/ACE2] complex better than chloroquine and hydroxychloroquine. This new understanding should help to improve predictions of the impact of such alternatives on COVID-19. Communicated by Ramaswamy H. Sarma.

Introduction

In late 2019, a new generation of coronavirus appeared in Wuhan City in the Hubei Province in central China (Wang, Horby, et al., 2020; Zhu et al., 2020). This virus causes severe acute respiratory syndrome. The first case was reported on the 8th of December 2019 for many patients lived around the local Huanan Seafood Wholesale Market (Chan et al., 2020). The novel coronavirus was identified from the throat swab sample of a patient (Wang, Hu, et al., 2020). World Health Organization has abbreviated this novel coronavirus as 2019-nCoV then the pathogen was renamed to SARS-CoV-2(WHO, 2020). After that, World Health Oorganization declared the pandemic when the virus hit many other countries.

Human infections by the SARS coronavirus are known to be closely associated with interactions between the viral spike protein (S-protein) which has favorable binding affinity for the human Angiotensin-Converting Enzyme 2 (ACE2) (Böhm & Schneider, 2005; Li et al., 2005; Prabakaran et al., 2004; Veeramachaneni et al., 2020). Several studies have also provided evidence of the COVID-19 S-protein binding to the ACE2 receptor (Hoffmann et al., 2020; Lu et al., 2020; Wan et al., 2020).

Angiotensin-converting enzyme (ACE)-related carboxypeptidase is a zinc metallopeptidase ectoenzyme, which is predominantly found in the lungs (Skeggs et al., 1956). ACE2, is a type I integral membrane protein, which it consists of 805 amino acid residues with one Zn2+ essential for enzyme activity. ACE2 was implicated in the regulation of heart function and as a functional receptor for the coronavirus, which is linked to the severe acute respiratory syndrome (SARS). ACE2 is the cellular receptor for the new coronavirus (SARS-CoV-2) which is causing the serious pandemic COVID-19 (Hasan et al., 2020; Li et al., 2003; Towler et al., 2004; Yan et al., 2020).

In a recent study, it was suggested that the 2019-nCoV binds to the human ACE2 receptor via densely glycosylated spike (S) protein as the initiation step of the entry mechanism to human cells (Basit et al., 2020; Boopathi et al., 2020; Hoffmann et al., 2020). The entry of the virus depends on its binding with the cell surface units at site 1 and site 2 S1/S2 that contains Zn+2, an important cofactor for numerous viral proteins as well (Te Velthuis et al., 2010). Existence of this metallic ion facilitates the viral attachment to the surface of target cells. It is well known that zinc ions serve as intracellular second messenger and may trigger apoptosis or efficiently impair replication of a number of viruses and this effect may be based on direct inhibition (Alirezaei et al., 1999; Frederickson et al., 2005; Lazarczyk & Favre, 2008; Te Velthuis et al., 2010).

ACE2 exists in every human body but in different quantities (Gurley & Coffman, 2008). Patients, who suffer from hypertension, diabetes or cardiovascular diseases, have high concentration of ACE2 enzyme in their bodies (Fang et al., 2020; Gurley & Coffman, 2008; Zhou et al., 2020). These categories of people can be easily infected by coronavirus compared with children who have low concentration of ACE2 enzyme, their infection percentage is only 2% (Bunyavanich et al., 2020).

Blocking the active site of ACE2 by suitable pharmaceutical compound will prevent the virus entering to the human cells. Therefore, synthesis of such pharmaceutical compound is in great demand. Many scientists worldwide are trying to synthesise new drugs to stop spreading the new infectious disease. We think that this route takes a long time, at least 18 months, until the new vaccine will be available in the markets. Thus, using medicaments already exist is the shortcut to tackle such issue. In 2005, chloroquine was found as a potent inhibitor of SARS coronavirus infection and it was suggested to treat the new novel coronavirus SARS-CoV-2 with hydroxychloroquine (Adeoye et al., 2020; Amin & Abbas, 2020; Böhm & Schneider, 2005; Smith & Smith, 2020; Vincent et al., 2005). However, due to its cardiotoxicity hydroxychloroquine has been red flagged by USFDA for use as a prophylactic measure.

In this study, 18 drugs were selected to evaluate their binding with two receptors ACE2 and SARS-CoV-2 binding with ACE2 ([SARS-CoV-2/ACE2] complex). These drugs were chosen due to their similarities in structure with chloroquine and hydroxychloroquine in order to find an alternative drug for COVID-19.

Materials and methods

Molecular docking and molecular dynamics simulation was applied to the drugs selected from the DrugBank database (Wishart et al., 2018) to study their affinity with coronavirus antibody ACE2 receptor (PDB ID: 1R42) (Towler et al., 2004) and also study their affinity with the crystal structure of [SARS-CoV-2/ACE2] complex (PDB ID: 6M0J) (Lan et al., 2020) to select the most active drugs that inhibit COVID-19. Global reactivity descriptors of the selected drugs were calculated to understand their structures, stability and reactivity. The methodology of this work is illustrated in Figure 1.

Figure 1.

Schematic representation of the docking procedure, analysis of drugs and reactivity.

Molecule library preparation

The chemical structure of drugs inhibitors of ACE2 and similar structures were extracted from the DrugBank database (Wishart et al., 2018) in MDL Mol format and converted to 3 D format using Mervin Sketch (MarvinSketch, 2019). The structures were pre-optimized with semi-empirical AM1 method (Stewart, 2013) using Hyperchem 8.08 software (HyperChem, 2009). The structures were optimized using density functional theory DFT method by employing the B3LYP/6-31G basis set (Becke, 1997; Frisch et al., 2009) to obtain the most stable conformation, which was also used to calculate the global reactivity descriptors through Gaussian 09 (Frisch et al., 2009). The convergent value of maximum force, root-mean-square (RMS) force, maximum displacement and RMS displacement are set by default and achieved “YES”. All values are positive after calculation vibrational frequencies to drugs, those results indicate that the drugs are stable (Cavalli et al., 2006). The optimized structures were combined in one database on MOE software (Molecular Operating Environment (MOE), 2015) in order to study the affinity of ligands (Figure 2 and Table 1).

Figure 2.

The structures of selected drugs.

Table 1.

Names, accessions numbers and clinical indication of drugs.

Drugs names	Accessions Numbers	Clinical Indication
Chloroquine	DB00608  (APRD00468)	Anti-malarialAnti-inflammatoryAnti-parasitic
Hydroxychloroquine	DB01611	Anti-malarialAnti-parasiticAnti-rheumaticAnti-infective
Quinacrine	DB01103  (APRD00317)	Anti-infectiveAnti-malarialAnti-parasitic
Quinacrine mustard	DB02240  (EXPT02733)	Anti-parasitic
Piperaquine	DB13941	Anti-infectiveAnti-malarialAnti-parasitic
Ramipril	DB00178  (APRD00009)	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Trandolapril	DB00519  (APRD01269)	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Ramiprilat	DB14208	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Enalapril	DB00584  (APRD00510)	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Trandolaprilat	DB14209	Angiotensin-Converting Enzyme inhibitors
Lisinopril	DB00722  (APRD00560)	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Perindopril	DB00790  (APRD01178)	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
Enalaprilat	DB09477	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascularDecreased blood pressure
Delapril	DB13312	Angiotensin-Converting Enzyme inhibitorsAnti-hypertensiveCardiovascular
ORE-1001	DB12271  (DB06387)	Angiotensin-Converting Enzyme inhibitors
N-(2-Aminoethyl)-1-aziridineethanamine	DB15643	Angiotensin-Converting Enzyme inhibitors
Triethylenetetramine	DB06824	Copper chelator agent
Piperazine	DB00592 (APRD00225, DB11514)	Anti-parasiticAnti-infective

Receptor preparation

The crystal structure of the angiotensin-converting enzyme related carboxypeptidase ACE2 receptor (PDB ID: 1R42) (Towler et al., 2004) and Crystal structure [SARS-CoV-2/ACE2] complex (PDB ID: 6M0J) (Lan et al., 2020) were found in the Protein Data Bank. The enzymes were prepared by removing the N-acetyl-D-glucosamine in sequence editor. Because the water molecule in the active site of the target enzyme plays an important role, it was inserted in the active sites to ensure making a hydrogen bond between the ligand and the target (Böhm & Schneider, 2005; Klebe, 2006; Marechal, 2007).

Because Zn2+ is an important cofactor for many viral proteins, Zn2+ can inhibit the replication of ARN polymerase, two active sites containing zinc (Zn2+) in 1R42 and 6M0J enzymes were chosen as shown in Figures 3 and 4 respectively (Te Velthuis et al., 2010). After that, the protein structure was prepared by correcting the missing bonds, which were broken in X-ray diffraction, and then the hydrogen atoms were added (Table 2).

Figure 3.

Crystal structure of native human Angiotensin Converting Enzyme-related carboxypeptidase (ACE2) (PDB ID: 1R42).

Figure 4.

Crystal structure of [SARS-CoV-2/ACE2] complex (PDB ID: 6M0J).

Table 2.

Binding sites residues used as input for receptor grid generation during Induced Fit Docking.

Receptors	Sites	Residues
1R42	Site 1	1: (Arg73, Phe274, Pro346, Asp367, Leu370, Thr371, His374, Glu375, Glu402, Glu406, Ser409, Leu410, Ala413, Phe438, Gln442, Thr445, Ile446, Thr449, Thr453, Phe512, Tyr515, Arg518, Thr519, Gln522) 2 : (Zn804)
	Site 2	1 : (Phe40, Pro346, Thr347, Ala348, Asp350, Gly352, His374, Glu375, His378, Asp382, Tyr385, Phe390, Arg393, Asn394, His401, Glu402) 2: (Zn804)
6M0J	Site 1	1: (Tyr127, Asn149, Asp269, Trp271, Arg273, Phe274, Thr276, Tyr279, Lys288, Pro289, Asn290, Ile291, Asp292, Thr294, His345, Pro346, Thr365, Met366, Asp367, Leu370, Thr371, His374, Glu375, Glu402, Glu406, Ser409, Leu410, Ala413, Thr414, Pro415, Leu418 Phe428, Glu430, Asp431, Thr434, Glu435, Asn437, Phe438, Lys441, Gln442, Thr445, Ile446, Thr449, Leu503, Phe504, His505, Tyr515, Arg518, Thr519, Gln522, Phe523, His540) 3 :(Zn901)
	Site 2	1: (His345, Pro346, Thr347, Ala348, Glu375, His378, Asp382, His401, Glu402) 3 :(Zn901)

Molecular docking

All the docking and scoring calculations were performed using the molecular operation environment software (MOE) (Molecular Operating Environment (MOE), 2015). The crystal structure of human angiotensin converting enzyme (PDB entry: 1R42) (Towler et al., 2004) at a resolution of 2.20 Å and the crystal structure of [SARS-CoV-2/ACE2] complex (PDB entry: 6M0J) (Lan et al., 2020) at a resolution of 2.45 Å were obtained from the Protein Data Bank (Berman et al., 2020) .A resolution between 1.5 and 2.5 Å is considered as a good quality for docking studies (Didierjean & Tête-Favier, 2016; Venugopal et al., 2008). It is known that the best score of RMSD values should be near to 2 Å with an energy score less or equal to −7 Kcal/mol (Kellenberger et al., 2004; Ramalho et al., 2009). These two values are often used as criterion to validate the result of the molecular docking.

Global reactivity descriptors

Global reactivity indices are the most relevant traits, which can be derived from the conceptual density functional theory (DFT). They have important properties which enable us to understand the chemical reactivity and kinetic stability of compounds (Shahab et al., 2016). The global reactivity descriptors can be described by energy of the highest occupied molecular orbital (E, energy of the lowest unoccupied molecular orbital (E, energy gap (ΔE), global electrophilicity (ω), chemical potential (µ), chemical hardness (η), chemical softness (S) and nucleophilicity (N) (Defranceschi & C. Le Bris, 2000; Domingo et al., 2016; Harkati et al., 2017; Zekri et al., 2020). Those descriptors were calculated at B3LYP/6-31G using the following formulas:

(ΔE = ELUMO-EHOMO), (ω = µ2/2η), (µ = (ELUMO+EHOMO)/2), (η = (ELUMO- EHOMO)/2), (S = 1/(2 η)), (N = EHOMO (Nucleophile) – EHOMO (TCE)).

In this study, the global reactivity descriptors were calculated to compounds that have best result in docking with ACE2 and [SARS-CoV-2/ACE2] complex.

Molecular dynamics simulation

The molecular dynamics (MD) simulation study was carried out for the most promising drugs Delapril, Lisinopril and Ramipril to target [SARS-CoV-2/ACE2] complex (6M0J) using standard default parameter setting in the MOE software (Molecular Operating Environment (MOE), 2015).

There are four algorithms implemented in MOE software for MD simulations; the Nosé-Poincaré-Andesen (NPA), the Nosé-Hoover-Andersen (NHA), Berendsen velocity/position (BER) and Nanoscale Molecular Dynamics (NAMD). In this study, the NPA is: the most precise and the most sensitive, was used to study the molecular dynamics of ligands (Sturgeon & Laird, 2000). In MD calculations, MMFF94x force field, sphere shape, water as a solvent, six margins and delete far existing solvent with distance greater than four Å were selected to optimize the system.

Results and discussion

Molecular docking

Molecular docking was run for 18 ligands against the [SARS-CoV-2/ACE2] complex and the ACE2 receptor.

The binding affinities of the drugs into ACE2 active sites

Tables 3 and 4 present the results of docking the drugs in 1R42 at two selected pockets S1 and S2 respectively. The results, as shown in Table 3, indicate that only seven ligands have an interaction with the receptor in pocket S1. Delapril has the best docking score (-6.9809 kcal/mol) followed by Lisinopril (-6.6886 kcal/mol)) with RMSDs 2.2570 Å and 1.5417 Å respectively. On the other hand, Ramiprilat and Piperaquine had RMSDs more than 3 Å and Trandolaprilat, Chloroquine and Perindopril had RMSDs less than 1.5 Å, which this is inadequate .

Table 3.

The results obtained from docking of Drugs with 1R42 in site 1.

Drugs	S score (kcal/mol)	RMSD (Å)	Bonds between atoms of compounds and residues of active site 1 of 1R42
			Atom of compound	Atom of receptor	Involved receptor residues	Type of interaction bond	Distance (Å)	E (kcal/mol)
Chloroquine	−6.1074	1.1063	N-1	O	H2O 932	H-acceptor	2.79	−1
Delapril	−6.9809	2.2570	O-31	OG	Ser 409	H-donor	3.08	−0.7
			O-24	O	H2O 932	H-acceptor	2.84	−1.3
			O-25	NE2	Gln 442		3.16	−1.7
			C-43	5-ring	His 374	H-pi	3.71	−1
			6-ring	O	H2O 932	pi-H	4.08	−1.2
Lisinopril	−6.6886	1.5417	O-5	O	H2O 932	H-donor	3.24	−0.6
Perindopril	−6.5856	1.1260	O-42	NE2	Gln 442	H-acceptor	3.3	−0.8
Piperaquine	−6.6531	3.2826	6-ring	CD	Pro 346	pi-H	4.35	−0.8
Ramiprilat	−6.6703	4.3112	O-46	O	H2O 1075	H-donor	2.98	−1.6
			O-51	OE1	Glu 406		2.9	−2.3
				O	H2O 1099		2.89	−1.1
			O-45	NE2	Gln 442	H-acceptor	3	−1
Trandolaprilat	−6.7507	1.4433	N-45	OE1	Gln 442	H-donor	3.09	−1.6

Table 4.

The results obtained from docking of Drugs with 1R42 in site 2.

Drug	S score (kcal/mol)	RMSD (Å)	Bonds between atoms of compounds and residues of active site 2 of 1R42
			Atom of compound	Atom of receptor	Involved receptor residues	Type of interaction bond	Distance (Å)	E (kcal/mol)
Chloroquine	−5.5271	1.3462	N-17	O	Ala 348	H-donor	3.05	−2
			6-ring	6-ring	Trp 349	pi-pi	3.96	0
Delapril	−6.5831	2.0115	O-25	O	H2O 894	H-acceptor	2.9	−0.8
Enalapril	−6.1282	2.6836	C-28	5-ring	Trp 349	H-pi	3.86	−0.7
Enalaprilat	−5.9910	1.2547	O-40	N	Asp 350	H-acceptor	3.34	−1.3
			C-45	5-ring	Trp 349	H-pi	3.46	−2.6
Hydroxychloroquine	−5.6369	1.8041	O-2	O	Arg 393	H-donor	2.99	−0.8
			N-7	N	Asp 350	H-acceptor	3.13	−1.3
Lisinopril	−5.6358	1.7176	O-5	O	Arg 393	H-donor	3.19	−2.4
Perindopril	−6.2821	1.1895	O-23	5-ring	His 401	H-pi	3.51	−0.7
Piperazine	−3.4925	2.5032	C-5	5-ring	Trp 349	H-pi	3.86	−0.9
Quinacrine	−5.9184	1.1669	C-37	6-ring	Trp 349	H-pi	4.42	−0.6
			C-37	5-ring	Trp 349		3.8	−1.4
Ramipril	−6.1181	1.5054	O-46	N	Asp 350	H-acceptor	3	−3.2
			O-58	O	H2O 892		3.07	−1
Ramiprilat	−5.8613	1.8268	O-51	O	Leu 391	H-donor	2.92	−1.4
			O-46	ND2	Asn 394	H-acceptor	3.02	−0.8
			O-49	NZ	Lys 562		3.01	−5.7
			O-54	ND2	Asn 394		2.85	−0.9
Trandolaprilat	−5.7171	2.8424	O-53	O	H2O 952	H-donor	2.97	−2.2

Interactions were further examined for bond lengths and hydrogen bonds in site 1 and were illustrated in Figure 5. The results from this Figure 5 showed that Delapril interacts with three amino acids residues in three different interactions; H-donor with amino acid Ser409, H-acceptor with Gln442, H-pi with His374 as well as two H-acceptor and pi-H interactions with the water. The distance and energy binding of interaction are listed in Table 3.

Figure 5.

Compounds binding with 1R42 in site 1.

From Table 4, the docking results in pocket S2, it can be noticed that Delapril had the lowest docking score (-6.5831 kcal/mol) with RMSD (2.0115 Å) followed by Perindopril, Ramipril and Chloroquine with docking score and RMSD values of (-6.2821 Kcal/mol, 1.1895 Å), (-6.1181 Kcal/mol, 1.5054 Å) and (-5.5271 Kcal/mol, 1.3462 Å) respectively. Even in this site, Chloroquine had a good score but actually it had an inadequate RMSD value (1.3462 Å), which is less than the accepted limit 1.5 Å. The same things can be said for Enalaprilat, Perindopril and Quinacrine.

The interactions of drugs with site 2 were also examined and depicted in Figure 6. Figure 6 shows that Delapril had H-acceptor interaction with water, while Perindopril had H-pi interaction with amino acid His401. Meanwhile, Ramipril had H-acceptor interaction with amino acid Asp350 and H-acceptor with water and Chloroquine had H-donor interaction with amino acid Ala348 and pi-pi interaction with Trp349. The distance and the energy binding are presented in Table 4.

Figure 6.

Compounds binding with 1R42 in site 2.

The binding affinities of the drugs into [SARS-CoV-2/ACE2] complex active sites

Tables 5 and 6 show the results of docking of the drugs in 6M0J at two selected pockets S1 and S2 respectively. The results in pocket S1 revealed that Piperaquine had the lowest docking score (-8.6132 Kcal/mol) and RMSD (2.3325 Å) compared with Delapril and Hydroxychloroquine, which they had energy scores and RMSD values of (-7.5271 Kcal/mol, 2.1735 Å) and (-7.2272 Kcal/mol, 2.1035 Å) respectively. In spite of Delapril and Hydroxychloroquine did not have the lowest score, they have the best RMSD values. Lisinopril and Quinacrine Mustard had RMSD value less than 1.5 Å.

Table 5.

The results obtained from docking of Drugs with 6M0J in site 1.

Drugs	S score (kcal/mol)	RMSD (Å)	Bonds between atoms of compounds and residues of active site 1 of 6M0J
			Atom of compound	Atom of receptor	Involved receptor residues	Type of interaction bond	Distance (Å)	E (kcal/mol)
Chloroquine	−6.8442	1.9853	6-ring	6-ring	Phe 438	pi-pi	3.37	0
Delapril	−7.5271	2.1735	O-31	OE2	Glu 375	H-donor	3.01	−4.5
			O-25	NH2	Arg 514	H-acceptor	3.04	−1.4
			O-26	ZN	Zn 901	metallic	1.96	−2.1
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
			6-ring	OH	Tyr 515	Pi-H	3.38	−0.9
				6-ring	Tyr 510	pi-pi	3.93	0
Enalapril	−7.8671	1.9897	O-22	O	Pro 289	H-donor	3.39	−0.8
Enalaprilat	−6.9279	1.8459	O-446-ring	NZ	Lys 441	H-acceptor	3.16	−8.4
				6-ring	Phe 438	pi-pi	3.73	0
Hydroxychloroquine	−7.2272	2.1035	6-ring	CB	Phe 438	pi-H	3.82	−0.8
			6-ring	6-ring	Phe 438	pi-pi	3.81	0
Lisinopril	−7.5918	1.3368	N-11	NE2	Gln 442	H-acceptor	3.18	−2.8
			6-ring6-ring	CA	Asn 290	Pi-H	4.07	−0.8
				N	Ile 291		4.22	−0.9
ORE-1001	−7.3872	1.5557	Cl	O	Leu 410	H-donor	3.49	−0.8
			5-ring	CB	Phe 438	pi-H	4.43	−0.7
			6-ring	6-ring	Phe 438	pi-pi	3.37	0
Perindopril	−6.4327	2.4655	N-26	O	Ile 291	H-donor	3.21	−0.8
Piperaquine	−8.6132	2.3325	6-ring	6-ring	Phe 438	pi-pi	3.35	0
Quinacrine	−8.2350	1.6346	6-ring 6-ring	N	Ile 291	pi-H	4.81	−0.6
				N	Ile 291		3.98	−1.1
Quinacrine Mustard	−7.8570	1.4398	Cl-58	SD	Met 366	H-donor	3.74	−0.4
			6-ring6-ring	N	Ile 291	pi-H	3.98	−1.4
				6-ring	Phe 438	pi-pi	3.58	0
Ramipril	−7.7464	1.6166	O-58	N	Ile 291	H-acceptor	3.47	−0.8
Ramiprilat	−6.9943	2.4607	O-49	Zn	Zn 901	metallic	2.01	−3.9
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7

Table 6.

The results obtained from docking of Drugs with 6M0J in site 2.

Drugs	S score (kcal/mol)	RMSD (Å)	Bonds between atoms of compounds and residues of active site 2 of 6M0J
			Atom of compound	Atom of receptor	Involved receptor residues	Type of interaction bond	Distance (Å)	E (kcal/mol)
Chloroquine	−5.4920	2.3627	C-45	5-ring	His 401	H-pi	4.25	−0.9
Delapril	-8.1604	1.5603	O-26	ZN	Zn 901	metallic	2.13	−3.6
			Zn-901	NE2	His 374		2.4	−3.2
					His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
Enalapril	−6.7570	2.6763	O-14	ZN	Zn 901	metallic	2	−2.5
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
			C-52	5-ring	His 378	H-pi	3.88	−1
Hydroxychloroquine	−6.3125	1.8513	O-2	OE2	Glu 375	H-donor	2.86	−1.9
			O-2	ZN	Zn 901	metallic	2	−2.6
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
			C-47	5-ring	His 378	H-pi	4.12	−0.6
Lisinopril	−6.6966	1.9981	O-5	O	H2O 1004	H-donor	2.97	−2
			O-1	ZN	Zn 901	metallic	2.06	−2.3
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
			6-ring	N	Ile 291	pi-H	3.98	−1.1
ORE-1001	−6.2755	2.5319	N-6	OH	Tyr 515	H-acceptor	3.09	−2.1
			O-25	ZN	Zn 901	metallic	2.09	−2.3
			O-31	ZN	Zn 901		2.31	−0.9
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
Perindopril	−6.7968	2.2965	O-23	O	Glu 398	H-donor	2.84	−3.1
			N-26	OE1	Glu 402		3.11	−1.4
			C-46	OE2	Glu 375		3.49	−0.6
			O-16	O	H2O 1033	H-acceptor	2.86	−1.9
			O-25	NH2	Arg 514		2.91	−1.9
			O-42	ZN	Zn 901	metallic	1.97	−2.9
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
Ramipril	−7.6305	2.4853	O-53	ZN	Zn 901	metallic	2.13	−1.7
			O-58	ZN	Zn 901		2.44	−1.4
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
Ramiprilat	−7.1864	1.7252	O-45	Zn	Zn 901	metallic	1.94	−2.9
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
Trandolapril	−7.1160	1.9818	O-1	O	H2O 1030	H-acceptor	3.04	−1
			O-4	ZN	Zn 901	metallic	2.07	−3.8
			Zn-901	NE2	His 374		2.4	−3.2
				NE2	His 378		2.27	−5.7
				OE1	Glu 402		2.1	−5.6
				NE2	His 378	ionic	2.27	−11.7
				OE1	Glu 402		2.1	−14.4
				OE2	Glu 402		3.13	−3.7
			6-ring	CA	Glu 398	pi-H	3.63	−0.6

The results of the binding of drugs with 6M0J in site 1 are shown in Figure 7. From the Figure 7, It is apparent that Piperaquine had pi-pi interaction with amino acid Phe438, whereas Hydroxychloroquine had pi-H and pi-pi interactions with amino acid Phe438 and Delapril had numerous interactions; H-donor interaction with amino acid Glu375, H-acceptor with Arg514 and metallic interaction with zinc.

Figure 7.

Compounds binding with 6M0J in site 1.

The interaction of carboxylic functional group in Delapril with zinc motivates the zinc to interact with His374 by metallic interaction and with His378 and Glu402 by ionic and metallic interactions respectively. As mentioned above, zinc had an antiviral activity and this type of interaction may inhibit the COVID-19.

The results of docking of drugs with 6M0J in site 2 are shown in Table 6. According to the results in this site 2, almost all drugs make interacted in pocket S2 via zinc. Delapril showed excellent docking score −8.1604 Kcal/mol and RMSD 1.5603 Å compared with Perindopril, Lisinopril, Hydroxychloroquine and Ramipril with energy scores and RMSD values of (-6.7968 kcal/mol, 2.2965 Å), (-6.6966 Kcal/mol, 1.9981 Å), (-6.3125 Kcal/mol, 1.8513 Å) and (-7.6305 kcal/mol, 2.4853 Å) respectively.

Although in site 2, Enalaprilat, , Piperaquine, Piperazine, Quinacrine Mustard, Trandolaprilat and Quinacrine have interactions with the active site but they have unacceptable RMSD values.

In all pockets, , Triethylenetetramine and Piperazine had energy docking scores higher than −4 Kcal/mol, they had energy scores out of the accepted limit, therefore these compounds could not be considered. Also, in all results, Chloroquine had energy scores higher than Hydroxychloroquine and Delapril.

Figure 8 presents the interactions of drugs with 6M0J in site 2. From Figure 8, it can be seen that Delapril had a metallic interaction with Zn, meanwhile Zn interacts with three amino acids by two types of interactions. These are: two ionic and one metallic interactions with Glu402, one ionic and one metallic interactions with His378 and ionic interaction with His374.

Figure 8.

Compounds binding with 6M0J in site 2.

Perindopril had many interactions, three H-donor interactions with amino acids Glu398, Glu402 and Glu375, two H-acceptor with water and with amino acid Arg514 as well as metallic interaction with Zn. Meanwhile Zn had two ionic and metallic interactions, with amino acid Glu402, metallic and ionic interactions with amino acid His378 and metallic interaction with amino acid His374.

Hydroxychloroquine had H-donor interaction with amino acid Glu375, metallic interaction with Zn, H-pi interaction with amino acid His378, while Zn had the same interactions with these amino acids. Lisinopril had H-donor interaction with water and metallic interaction with Zn, whereas Zn interacts with the same amino acids. Ramipril had two metallic interaction with Zn. whereas Zn interacts with the same amino acids.

Global reactivity descriptors

The chemical reactivity descriptors were calculated and presented in Table 7. The EHOMO and ELUMO were obtained from GaussView (Dennington et al., 2016). The results of the global hardness and softness, which they are related to the stability of chemical system, as shown in Table 7, indicate that Ramipril, Chloroquine, ORE-1001 and Delapril are harder than the Hydroxychloroquine and other compounds.

Table 7.

HOMO and LUMO energy, energy gap ΔE and global reactivity indices µ, ω, η and N for drugs.

Drugs	HOMO (eV)	LUMO (eV)	ΔE (eV)	η (eV)	S (eV)	µ (eV)	ω (eV)	N (eV)
Chloroquine	−5.4861	−1.2232	4.2629	2.1315	173.6972	−3.3546	2.6398	3.1698
Delapril	−5.9438	−0.5853	5.3585	2.6792	138.1850	−3.2646	1.9888	2.7121
Enalapril	−5.7435	−0.7380	5.0055	2.5028	147.9282	−3.2407	2.0981	2.9124
Hydroxychloroquine	−6.5095	0.2797	6.7892	3.3946	109.0637	−3.1149	1.4291	2.1464
Lisinopril	−6.6328	−1.0583	5.5745	2.7873	132.8292	−3.8455	2.6527	2.0231
ORE-1001	−6.9346	−1.9323	5.0023	2.5011	148.0248	−4.4334	3.9292	1.7213
Perindopril	−5.6564	0.3793	6.0358	3.0179	122.6789	−2.6386	1.1534	2.9995
Piperaquine	−6.9269	0.0678	6.9947	3.4973	105.8603	−3.4296	1.6815	1.7290
Ramipril	−6.0807	−3.1299	2.9508	1.4754	250.9350	−4.6053	7.1873	2.5752
Ramiprilat	−6.4178	−0.3420	6.0758	3.0379	121.8712	−3.3799	1.8802	2.2381
Trandolapril	−6.1084	−0.7565	5.3519	2.6760	138.3537	−3.4324	2.2013	2.5475

Notes: the HOMO energy -8.6559 eV. of the reference system (TCE) had been calculated at DFT/B3LYP 6-31 G.

In addition, Ramipril have the smaller energy gap (ΔE = 2.9508 eV), Delapril and Lisinopril have smaller energy gaps than Hydroxychloroquine. Moreover, Ramipril, Chloroquine, ORE-1001 and Delapril have softness values higher than that of Hydroxychloroquine. These results indicate that Ramipril, Chloroquine, ORE-1001 and Delapril are more stable and more reactive than Hydroxychloroquine.

The electronic chemical potential (µ) for Perindopril (µ= −2.6386 eV) is higher than other compounds followed by Hydroxychloroquine, Enalapril and Delapril. According to these results, these compounds can exchange electron density with the environment efficiently (Azarhazin et al., 2019).

A further classification of organic molecules as strong (N > 3 eV), moderate (2.0 eV ≤ N ≤ 3.0 eV) and marginal nucleophilic (N < 2.0 eV) were obtained by analysis of a series of common nucleophilic species participating in polar organic reaction. Note that nucleophilicity value is referred to tetracyanoethylen (TCE) taken as a reference, because it presents the lowest EHOMO in a large series of molecule already investigated (Jaramillo et al., 2008). According to the results in Table 7, Chloroquine can be classified as strong nucleophile and the others as moderate nucleophile except ORE-1001, which is considered as marginal nucleophile.

The electrophilicity ω had become a potent tool for the study of the reactivity of organic compounds that can participate in polar reaction (Domingo et al., 2016; Srivastava, 2020). Ramipril had the highest electrophilicity value (ω = 7.1873 eV), whereas as Delapril had an electrophilicity value (ω = 1.9888 eV) higher more than that of Hydroxychloroquine (ω = 1.4291 eV).

Molecular dynamics simulation

In order to examine the conformational flexibilities of docked drug-receptor complexes and to attain dependable drug-receptor–binding affinities, the MD process combined with binding energy (MM-GBSA) (De Vivo et al., 2016; Kerrigan, 2013)calculations was run for 600 ps on the most promising drugs Delapril, Lisinopril and Ramipril to target [SARS-CoV-2/ACE2] complex (6M0J). The evaluated average MM-GBSA binding energies are given in Table 8.

Table 8.

Calculated MM-GBSA binding energies (in kcal/mol) for the Delapril, Lisinopril and Ramipril drugs against 6M0J over MD simulations.

Drugs	Site 1	Site 2
Delapril	−54	−45
Lisinopril	−33	−38
Ramipril	−46	−42

In general, it is apparent from this table that the selected three drugs exhibited considerable binding energies). In site 2, Delapril and Ramipril showed promising binding energies −54 and −46 kcal/mol respectively. On the other hand, Lisinopril showed relatively weak binding energy −33 kcal/mol. Whereas, in site 2, all three drugs Delapril, Lisinopril and Ramipril showed promising binding affinities with binding energies.

Figures 9 and 10 show the results of the atomic potential energy function during dynamic study calculation for Delapril, Lisinopril and Ramipril in the 6M0J at site 1 and 2 respectively. To explore the dynamic stability of the 6M0J/inhibitor drugs complexes, the time-dependent potential energy of the complex were calculated during MD trajectories. It is apparent in Figure 9, site 1, that complex A (6M0J/Delapril) achieved equilibrium around 300 ps. Meanwhile complex B (6M0J/Lisinopril) achieved the equilibrium around 350 ps. Whereas, complex C (6M0J/Ramipril) achieved the equilibrium stability around 400 ps. It can be seen from Figure 10, site 2, that the complex A achieved the equilibrium stability around 400 ps, complex B achieve the equilibrium stability around 400 ps, meanwhile complex C achieve the equilibrium stability around 350 ps.

Figure 9.

The evaluation of potential energy of complex of (A) Delapril, (B) Lisinopril and (C) Ramipril with 6M0J receptor site 1 as function of time.

Figure 10.

The evaluation of potential energy of complex of (A) Delapril, (B) Lisinopril and (C) Ramipril with 6M0J receptor site 2 as function of time.

In general, if the interaction energy between a residue and a ligand is lower than −0.8 Kcal/mol, the residue is regarded as an important residue in the molecular recognition of the ligand. For the 6M0J/Delapril complex A (Figure 11), the major favourable energy contributions (-2.2 to −1.4 kcal/mol) originate predominately from Glu375 (-1.4), H2O1030 (-1.5) and Trp203 (-2.2), As shown in Figure 11 the complex B had energy binding with Asp292 (-7.8) and Ala413 (-4.7). However, complex C did not interact in this site.

Figure 11.

Docked pose and binding interaction of (A) Delapril, (B) Lisinopril, (C) Ramipril with 6M0J in site 1.

It is clear from Figure. 12 that complex A had interactions in site 2 of 6M0J with Glu375 (-8.7) and Zn901 (-3.4), while complex B had the major favourable energy contributions (-0.6 to −6.2 kcal/mol) which originate predominately from Glu402 (-2.3), Asp382 (-6.2), H2O1033 (-1.3), Tyr510 (-2.8), H2O1004 (-1.5), His401 (-0.6) and Trp349 (-1). Nevertheless, His401 cannot be considered as an important residue.

Figure 12.

Docked pose and binding interaction of (A) Delapril, (B) Lisinopril, (C) Ramipril with 6M0J in site 2.

Complex C showed more favourable interactions with residues Glu402 (-3.8), H2O1030 (-1.3), H2O1002 (-0.9), Zn901 (-4.1) and Asp350 (-2).

Conclusion

The aim of the present research was to examine the binding of eighteen candidate drugs with ACE2 enzyme and [SARS-CoV-2/ACE2] complex using docking analysis. The docking ranking results in this study showed that some of these ligands might have the ability to inhibit SARS-CoV-2. The results of docking these ligands with ACE2 enzyme (1R42) in two pockets indicated that Delapril gave the lowest energy score and good RMSD value followed by Lisinopril (site1) and Ramipril (site 2). In addition, the docking results with 6M0J showed that only Delapril and Ramiprilat interacted with Zn in site 1, while in site 2 Delapril gave the best energy score followed by Ramipril. The drugs mentioned above presented good results with the two chosen enzymes compared with Chloroquine and Hydroxychloroquine. Moreover, the results obtained from global reactivity indices indicated that Ramipril is the most reactive drug, it had the highest electrophilicity value followed by ORE-1001, Chloroquine and Lisinopril. The most obvious finding to emerge from this study is that Ramipril, Delapril and Lisinopril gave good docking results compared with Chloroquine and Hydroxychloroquine. Also, Delapril, Lisinopril and Ramipril showed encouraging binding affinity, MM/GBSA energies, to [SARS-CoV-2/ACE2] complex. Further investigation and experimentation into Delapril, Lisinopril and Ramipril, which they are promising candidate drugs for COVID-19 patients, is strongly recommended.