In silico evaluation of flavonoids as potential inhibitors of SARS-CoV-2 main nonstructural proteins (Nsps)-amentoflavone as a multitarget candidate.

Despite the development of vaccines against COVID-19 disease and the multiple efforts to find efficient drugs as treatment for this virus, there are too many social, political, economic, and health inconveniences to incorporate a fully accessible plan of prevention and therapy against SARS-CoV-2. In this sense, it is necessary to find nutraceutical/pharmaceutical drugs as possible COVID-19 preventives/treatments. Based on their beneficial effects, flavonoids are one of the most promising compounds. Therefore, using virtual screening, 478 flavonoids obtained from the KEGG database were evaluated against non-structural proteins Nsp1, Nsp3, Nsp5, Nsp12, and Nsp15, which are essential for the virus-host cell infection, searching for possible multitarget flavonoids. Amentoflavone, a biflavonoid found mainly in Ginkgo biloba, Lobelia chinensis, and Byrsonima intermedia, can interact and bind with the five proteins, suggesting its potential as a multitarget inhibitor. Molecular docking calculations and structural analysis (RMSD, number of H bonds, and clustering) performed from molecular dynamics simulations of the amentoflavone-protein complex support this potential. The results shown here are theoretical evidence of the probable multitarget inhibition of non-structural proteins of SARS-CoV-2 by amentoflavone, which has wide availability, low cost, no side effects, and long history of use. These results are solid evidence for future in vitro and in vivo experiments aiming to validate amentoflavone as an inhibitor of the Nsp1, 3, 5, 12, and 15 of SARS-CoV-2.

(-)-Epicatechin Is a Biased Ligand of Apelin Receptor.

(-)-Epicatechin (EC) is part of a large family of biomolecules called flavonoids and is widely distributed in the plant kingdom. Several studies have shown the beneficial effects of EC consumption. Many of these reported effects are exerted by activating the signaling pathways associated with the activation of two specific receptors: the G protein-coupled estrogen receptor (GPER), a transmembrane receptor, and the pregnane X receptor (PXR), which is a nuclear receptor. However, the effects of EC are so diverse that these two receptors cannot describe the complete phenomenon. The apelin receptor or APLNR is classified within the G protein-coupled receptor (GPCR) family, and is capable of activating the G protein canonical pathways and the ß-arrestin transducer, which participates in the phenomenon of receptor desensitization and internalization. ß-arrestin gained interest in selective pharmacology and mediators of the so-called "biased agonism". With molecular dynamics (MD) and in vitro assays, we demonstrate how EC can recruit the ß-arrestin in the active conformation of the APLN receptor acting as a biased agonist.

PXR is a target of (-)-epicatechin in skeletal muscle.

(-)-Epicatechin (EC) is a flavanol that has shown numerous biological effects such as: decrease risk of cardiovascular dysfunction, metabolism regulation, skeletal muscle (SkM) performance improvement and SkM cells differentiation induction, among others. The described EC acceptor/receptor molecules do not explain the EC's effect on SkM. We hypothesize that the pregnane X receptor (PXR) can fulfill those characteristics, based on structural similitude between EC and steroidal backbone and that PXR activation leads to similar effects as those induced by EC. In order to demonstrate our hypothesis, we: 1) analyzed the possible EC and mouse PXR interaction through in silico strategies, 2) developed an EC's affinity column to isolate PXR, 3) evaluated, in mouse myoblast (C2C12 cells) the inhibition of EC-induced PXR's nucleus translocation by ketoconazole, a specific blocker of PXR and 4) analyzed the effect of EC as an activator of mouse PXR, evaluating the expression modulation of cytochrome 3a11 (Cyp3a11) gen and myogenin protein. (-)-Epicatechin interacts and activates PXR, promoting this protein translocation to the nucleus, increasing the expression of Cyp3a11, and promoting C2C12 cell differentiation through increasing myogenin expression. These results can be the base of further studies to analyze the possible participation of PXR in the skeletal muscle effects shown by EC.