Neoechinulin A as a Promising SARS-CoV-2 Mpro Inhibitor: In Vitro and In Silico Study Showing the Ability of Simulations in Discerning Active from Inactive Enzyme Inhibitors.

The COVID-19 pandemic and its continuing emerging variants emphasize the need to discover appropriate treatment, where vaccines alone have failed to show complete protection against the new variants of the virus. Therefore, treatment of the infected cases is critical. This paper discusses the bio-guided isolation of three indole diketopiperazine alkaloids, neoechinulin A (1), echinulin (2), and eurocristatine (3), from the Red Sea-derived Aspergillus fumigatus MR2012. Neoechinulin A (1) exhibited a potent inhibitory effect against SARS-CoV-2 Mpro with IC50 value of 0.47 µM, which is comparable to the reference standard GC376. Despite the structural similarity between the three compounds, only 1 showed a promising effect. The mechanism of inhibition is discussed in light of a series of extensive molecular docking, classical and steered molecular dynamics simulation experiments. This paper sheds light on indole diketopiperazine alkaloids as a potential structural motif against SARS-CoV-2 Mpro. Additionally, it highlights the potential of different molecular docking and molecular dynamics simulation approaches in the discrimination between active and inactive structurally related Mpro inhibitors.

Alkaloids in Future Drug Discovery.

Alkaloids are nitrogen-containing compounds, biosynthesized by both marine and terrestrial organisms, often with strong biological properties [...].

New C9 -Monoterpenoid Alkaloids Featuring a Rare Skeleton with Anti-Inflammatory and Antiviral Activities from Forsythia suspensa.

Forsyqinlingines C (1) and D (2), two C9 -monoterpenoid alkaloids bearing a rare skeleton, were isolated from the ripe fruits of Forsythia suspensa. Their structures, including absolute configurations, were fully elucidated by extensive spectroscopic data and ECD experiments. The plausible biogenetic pathway for compounds 1 and 2 was also proposed. In vitro, two C9 -monoterpenoid alkaloids showed anti-inflammatory activity performed by the inhibitory effect on the release of ß-glucuronidase in rat polymorphonuclear leukocytes (PMNs), as well as antiviral activity against influenza A (H1N1) virus and respiratory syncytial virus (RSV).

Marine Brominated Tyrosine Alkaloids as Promising Inhibitors of SARS-CoV-2.

There have been more than 150 million confirmed cases of SARS-CoV-2 since the beginning of the pandemic in 2019. By June 2021, the mortality from such infections approached 3.9 million people. Despite the availability of a number of vaccines which provide protection against this virus, the evolution of new viral variants, inconsistent availability of the vaccine around the world, and vaccine hesitancy, in some countries, makes it unreasonable to rely on mass vaccination alone to combat this pandemic. Consequently, much effort is directed to identifying potential antiviral treatments. Marine brominated tyrosine alkaloids are recognized to have antiviral potential. We test here the antiviral capacity of fourteen marine brominated tyrosine alkaloids against five different target proteins from SARS-CoV-2, including main protease (Mpro) (PDB ID: 6lu7), spike glycoprotein (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17), and non-structural protein 10 (nsp10) (PDB ID: 6W4H). These marine alkaloids, particularly the hexabrominated compound, fistularin-3, shows promising docking interactions with predicted binding affinities (S-score = -7.78, -7.65, -6.39, -6.28, -8.84 Kcal/mol) for the main protease (Mpro) (PDB ID: 6lu7), spike glycoprotein (PDB ID: 6VYB), nucleocapsid phosphoprotein (PDB ID: 6VYO), membrane glycoprotein (PDB ID: 6M17), and non-structural protein 10 (nsp10) (PDB ID: 6W4H), respectively, where it forms better interactions with the protein pockets than the native interaction. It also shows promising molecular dynamics, pharmacokinetics, and toxicity profiles. As such, further exploration of the antiviral properties of fistularin-3 against SARS-CoV-2 is merited.

Effect of the Phytochemical Agents against the SARS-CoV and Some of them Selected for Application to COVID-19: A Mini-Review.

BACKGROUND: The aim of the present review is to provide basic knowledge regarding the treatment of Coronavirus via medicinal plants. Coronavirus (COVID-19, SARS-CoV, and MERS-CoV) as a viral pneumonia causative agent, has infected thousands of people in China and worldwide. Currently, there is no specific medicine or vaccine available that can treat or prevent this virus and this has posed a severe threat to human health; therefore, there is an urgent need to develop a novel drug or anticoronavirus vaccine. However, natural compounds to treat coronaviruses are the most effective alternative and complementary therapies due to their diverse range of biological and therapeutic properties. METHODS: We performed an open-ended, English restricted search of Scopus database, Web of Science, and Pubmed for all available literature from Jan-March, 2020, using terms related to phytochemical compounds, medicinal plants and coronavirus. RESULTS: The view on anti-coronavirus (anti-CoV) activity in the plant-derived phytochemicals and medicinal plants gives a strong base to develop a novel treatment employing these compounds for coronavirus. Various phytochemicals and medicinal plant extracts have been revised and are considered as potential anti-CoV agents for effective control of the virus and future drug development. Herein, we discuss some important plants (Scutellaria baicalensis, Psorothamnus arborescens, Glycyrrhiza radix, Glycyrrhiza uralensis, Lycoris radiate, Phyllanthus emblica, Camellia sinensis, Hyptis atrorubens Poit, Fraxinus sieboldiana, Erigeron breviscapus, Citri Reticulatae Pericarpium, Amaranthus tricolor, Phaseolus vulgaris, Rheum palmatum, Curcuma longa and Myrica cerifera) that have emerged to have broad-spectrum antiviral activity. CONCLUSION: Nigella sativa has potent anti-SARS-CoV activity and it might be a useful source for developing novel antiviral therapies for coronavirus.