An in silico approach unveils the potential of antiviral compounds in preclinical and clinical trials as SARS-CoV-2 omicron inhibitors.

The increased transmissibility and highly infectious nature of the new variant of concern (VOC) that is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron and lack of effective therapy need the rapid discovery of therapeutic antivirals against it. The present investigation aimed to identify antiviral compounds that would be effective against SARS-CoV-2 Omicron. In this study, molecular docking experiments were carried out using the recently reported experimental structure of omicron spike protein in complex with human angiotensin-converting enzyme 2 (ACE2) and various antivirals in preclinical and clinical trial studies. Out of 36 tested compounds, Abemaciclib, Dasatinib and Spiperone are the three top-ranked molecules which scored binding energies of -10.08 kcal/mol, -10.06 kcal/mol and -9.54 kcal/mol respectively. Phe338, Asp339, and Asp364 are crucial omicron receptor residues involved in hydrogen bond interactions, while other residues were mostly involved in hydrophobic interactions with the lead molecules. The identified lead compounds also scored well in terms of drug-likeness. Molecular dynamics (MD) simulation, essential dynamics (ED) and entropic analysis indicate the ability of these molecules to modulate the activity of omicron spike protein. Therefore, Abemaciclib, Dasatinib and Spiperone are likely to be viable drug-candidate molecules that can block the interaction between the omicron spike protein and the host cellular receptor ACE2. Though our findings are compelling, more research into these molecules is needed before they can be employed as drugs to treat SARS-CoV-2 omicron infections.

Insights into plastome of Fagonia indica Burm.f. (Zygophyllaceae): organization, annotation and phylogeny.

The enhanced understanding of chloroplast genomics would facilitate various biotechnology applications; however, the chloroplast (cp) genome / plastome characteristics of plants like Fagonia indica Burm.f. (family Zygophyllaceae), which have the capability to grow in extremely hot sand desert, have been rarely understood. The de novo genome sequence of F. indica using the Illumina high-throughput sequencing technology determined 128,379 bp long cp genome, encode 115 unique coding genes. The present study added the evidence of the loss of a copy of the IR in the cp genome of the taxa capable to grow in the hot sand desert. The maximum likelihood analysis revealed two distinct sub-clades i.e. Krameriaceae and Zygophyllaceae of the order Zygophyllales, nested within fabids.

In silico analyses of major active constituents of fingerroot (Boesenbergia rotunda) unveils inhibitory activities against SARS-CoV-2 main protease enzyme.

Boesenbergia rotunda (L.) Mansf., commonly known as fingerroot is a perennial herb in the Zingiberaceae family with anticancer, anti-leptospiral, anti-inflammatory, antioxidant, antiulcer, and anti-herpes viral activities. While the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inhibitory activity of B. rotunda extract has been recently found, the active compounds contributing to this activity are yet unknown. The main protease (Mpro) enzyme is one of the most well established therapeutic targets among coronaviruses which plays a vital role in the maturation and cleavage of polyproteins during viral replication. The current work aims to identify active phytochemical substances from B. rotunda extract that can inhibit the replication of SARS-CoV-2 by using a combined molecular docking and dynamic simulation approaches. The virtual screening experiment revealed that fifteen molecules out of twenty-three major active compounds in the plant extract have acceptable drug-like characteristics. Alpinetin, Pinocembrin, and Pinostrobin have binding energies of -7.51 kcal/mol, -7.21 kcal/mol, and -7.18 kcal/mol, respectively, and can suppress Mpro activity. The stability of the simulated complexes of the lead compounds with the drug-receptor is demonstrated by 100-ns MD simulations. The binding free energies study utilizing molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) and molecular mechanics generalized Born surface area (MM-GBSA) show that the compounds and Mpro enzyme have favourable thermodynamic interactions, which are majorly driven by van der Waals forces. Thus, the selected bioactive phytochemicals from B. rotunda might be used as anti-SARS-CoV-2 candidates that target the Mpro enzyme.

Identification of SARS-CoV-2 inhibitors from extracts of Houttuynia cordata Thunb.

Houttuynia cordata Thunb., a perennial herb belonging to the Saururaceae family is a well-known ingredient of Traditional Chinese medicine (TCM) with several therapeutic properties. During the severe acute respiratory syndrome (SARS) outbreak in China, it was one of the approved ingredients in SARS preventative formulations and therefore, the plant may contain novel bioactive chemicals that can be used to suppress the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a virus for which there are currently no effective drugs available. Like all RNA viruses, SARS-CoV-2 encode RNA-dependent RNA polymerase (RdRp) enzyme which aids viral gene transcription and replication. The present study is aimed at understanding the potential of bioactive compounds from H. cordata as inhibitors of the SARS-CoV-2 RdRp enzyme. We investigated the drug-likeness of the plant's active constituents, such as alkaloids, polyphenols, and flavonoids, as well as their binding affinity for the RdRp enzyme. Molecular docking experiments show that compounds 3 (1,2,3,4,5-pentamethoxy-dibenzo-quinolin-7-one), 14 (7-oxodehydroasimilobine), and 21 (1,2-dimethoxy-3-hydroxy-5-oxonoraporphine) have a high affinity for the drug target and that the complexes are maintained by hydrogen bonds with residues like Arg553, Cys622 and Asp623, as well as hydrophobic interactions with other residues. The lead compounds' complexes with the target enzyme remained stable throughout the molecular dynamics simulation. Analysis of molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) and molecular mechanics generalized Born surface area (MM-GBSA) revealed the key residues contributing considerably to binding free energy. Thus, the findings reveal the potential of H. cordata bioactive compounds as anti-SARS-CoV-2 drug candidate molecules against the target enzyme.

Structure-based virtual screening of phytochemicals and repurposing of FDA approved antiviral drugs unravels lead molecules as potential inhibitors of coronavirus 3C-like protease enzyme.

Coronaviruses are enveloped positive-strand RNA viruses belonging to family Coronaviridae and order Nidovirales which cause infections in birds and mammals. Among the human coronaviruses, highly pathogenic ones are Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) and the Middle East Respiratory Syndrome coronavirus (MERS-CoV) which have been implicated in severe respiratory syndrome in humans. There are no approved antiviral drugs or vaccines for the treatment of human CoV infection to date. The recent outbreak of new coronavirus pandemic, coronavirus disease 2019 (COVID-19) has caused a high mortality rate and infections around the world which necessitates the need for the discovery of novel anti-coronaviral drugs. Among the coronaviruses proteins, 3C-like protease (3CLpro) is an important drug target against coronaviral infection as the auto-cleavage process catalysed by the enzyme is crucial for viral maturation and replication. The present work is aimed at the identification of suitable lead molecules for the inhibition of 3CLpro enzyme via a computational screening of the Food and Drug Administration (FDA) approved antiviral drugs and phytochemicals. Based on binding energies and molecular interaction studies, we shortlisted five lead molecules (both FDA approved drugs and phytochemicals) for each enzyme targets (SARS-CoV-2 3CLpro, SARS-CoV 3CLpro and MERS-CoV 3CLpro). The lead molecules showed higher binding affinity compared to the standard inhibitors and exhibited favourable hydrophobic interactions and a good number of hydrogen bonds with their respective targets. A few promising leads with dual inhibition potential were identified among FDA approved antiviral drugs which include DB13879 (Glecaprevir), DB09102 (Daclatasvir), molecule DB09297 (Paritaprevir) and DB01072 (Atazanavir). Among the phytochemicals, 11,646,359 (Vincapusine), 120,716 (Alloyohimbine) and 10,308,017 (Gummadiol) showed triple inhibition potential against all the three targets and 102,004,710 (18-Hydroxy-3-epi-alpha-yohimbine) exhibited dual inhibition potential. Hence, the proposed lead molecules from our findings can be further investigated through in vitro and in vivo studies to develop into potential drug candidates against human coronaviral infections.