Flavonoids from the roots and rhizomes of Sophoratonkinensis and their in vitro anti-SARS-CoV-2 activity.

Acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had caused a global pandemic since 2019, and posed a serious threat to global health security. Traditional Chinese medicine (TCM) has played an indispensable role in the battle against the epidemic. Many components originated from TCMs were found to inhibit the production of SARS-CoV-2 3C-like protease (3CLpro) and papain-like protease (PLpro), which are two promising therapeutic targets to inhibit SARS-CoV-2. This study describes a systematic investigation of the roots and rhizomes of Sophora tonkinensis, which results in the characterization of 12 new flavonoids, including seven prenylated flavanones (1-7), one prenylated flavonol (8), two prenylated chalcones (9-10), one isoflavanone (11), and one isoflavan dimer (12), together with 43 known compounds (13-55). Their structures including the absolute configurations were elucidated by comprehensive analysis of MS, 1D and 2D NMR data, and time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculations. Compounds 12 and 51 exhibited inhibitory effects against SARS-CoV-2 3CLpro with IC50 values of 34.89 and 19.88 µmol·L-1, repectively while compounds 9, 43 and 47 exhibited inhibitory effects against PLpro with IC50 values of 32.67, 79.38, and 16.74 µmol·L-1, respectively.

Ginkgolic acids inhibit SARS-CoV-2 and its variants by blocking the spike protein/ACE2 interplay.

Targeting the interaction between the spike protein receptor binding domain (S-RBD) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and angiotensin-converting enzyme 2 (ACE2) is a potential therapeutic strategy for treating coronavirus disease 2019 (COVID-19). However, we still lack small-molecule drug candidates for this target due to the missing knowledge in the hot spots for the protein-protein interaction. Here, we used NanoBiT technology to identify three Ginkgolic acids from an in-house traditional Chinese medicine (TCM) library, and they interfere with the S-RBD/ACE2 interplay. Our pseudovirus assay showed that one of the compounds, Ginkgolic acid C17:1 (GA171), significantly inhibits the entry of original SARS-CoV-2 and its variants into the ACE2-overexpressed HEK293T cells. We investigated and proposed the binding sites of GA171 on S-RBD by combining molecular docking and molecular dynamics simulations. Site-directed mutagenesis and surface plasmon resonance revealed that GA171 specifically binds to the pocket near R403 and Y505, critical residues of S-RBD for S-RBD interacting with ACE2. Thus, we provide structural insights into developing new small-molecule inhibitors and vaccines against the proposed S-RBD binding site.

Discovery of novel inhibitors against main protease (Mpro) of SARS-CoV-2 via virtual screening and biochemical evaluation.

SARS-CoV-2 is the pathogen that caused the global COVID-19 outbreak in 2020. Promising progress has been made in developing vaccines and antiviral drugs. Antivirals medicines are necessary complements of vaccines for post-infection treatment. The main protease (Mpro) is an extremely important protease in the reproduction process of coronaviruses which cleaves pp1ab over more than 11 cleavage sites. In this work, two active main protease inhibitors were found via docking-based virtual screening and bioassay. The IC50 of compound VS10 was 0.20 µM, and the IC50 of compound VS12 was 1.89 µM. The finding in this work can be helpful to understand the interactions of main protease and inhibitors. The active candidates could be potential lead compounds for future drug design.

Anti-SARS-CoV-2 activities in vitro of Shuanghuanglian preparations and bioactive ingredients.

Human infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) and there is no cure currently. The 3CL protease (3CLpro) is a highly conserved protease which is indispensable for CoVs replication, and is a promising target for development of broad-spectrum antiviral drugs. In this study we investigated the anti-SARS-CoV-2 potential of Shuanghuanglian preparation, a Chinese traditional patent medicine with a long history for treating respiratory tract infection in China. We showed that either the oral liquid of Shuanghuanglian, the lyophilized powder of Shuanghuanglian for injection or their bioactive components dose-dependently inhibited SARS-CoV-2 3CLpro as well as the replication of SARS-CoV-2 in Vero E6 cells. Baicalin and baicalein, two ingredients of Shuanghuanglian, were characterized as the first noncovalent, nonpeptidomimetic inhibitors of SARS-CoV-2 3CLpro and exhibited potent antiviral activities in a cell-based system. Remarkably, the binding mode of baicalein with SARS-CoV-2 3CLpro determined by X-ray protein crystallography was distinctly different from those of known 3CLpro inhibitors. Baicalein was productively ensconced in the core of the substrate-binding pocket by interacting with two catalytic residues, the crucial S1/S2 subsites and the oxyanion loop, acting as a "shield" in front of the catalytic dyad to effectively prevent substrate access to the catalytic dyad within the active site. Overall, this study provides an example for exploring the in vitro potency of Chinese traditional patent medicines and effectively identifying bioactive ingredients toward a specific target, and gains evidence supporting the in vivo studies of Shuanghuanglian oral liquid as well as two natural products for COVID-19 treatment.

Iron overload by Superparamagnetic Iron Oxide Nanoparticles is a High Risk Factor in Cirrhosis by a Systems Toxicology Assessment.

Superparamagnetic iron oxide nanoparticles (SPIONs) as a contrast agent have been widely used in magnetic resonance imaging for tumor diagnosis and theranostics. However, there has been safety concern of SPIONs with cirrhosis related to excess iron-induced oxidative stress. In this study, the impact of iron overload by SPIONs was assessed on a mouse cirrhosis model. A single dose of SPION injection at 0.5 or 5 mg Fe/kg in the cirrhosis group induced a septic shock response at 24 h with elevated serum levels of liver and kidney function markers and extended impacts over 14 days including high levels of serum cholesterols and persistent low serum iron level. In contrast, full restoration of liver functions was found in the normal group with the same dosages over time. Analysis with PCR array of the toxicity pathways revealed the high dose of SPIONs induced significant expression changes of a distinct subset of genes in the cirrhosis liver. All these results suggested that excess iron of the high dose of SPIONs might be a risk factor for cirrhosis because of the marked impacts of elevated lipid metabolism, disruption of iron homeostasis and possibly, aggravated loss of liver functions.

CpG-induced immunomodulation and intracellular bacterial killing in a chicken macrophage cell line.

The immunostimulatory properties of synthetic CpG oligodeoxynucleotides (ODNs) have been studied in various mammalian models including humans and mice. However, little was known about effects of CpG ODNs on immune responses of chickens, a common avian species with important economical value in the poultry industry. In the present study, two CpG ODNs, 2006 and 1826, which show immunomodulating properties for humans and mice were tested using a chicken macrophage cell line (HD11). ODN 2006, which has been reported to be an optimal stimulatory sequence for humans, showed strong immunomodulatory effects on HD11 cells, whereas ODN 1826, a CpG sequence with optimal immunostimulatory effects on mice, had weak influences on HD11 cells. ODN 2006 also induced strong IL-6 and nitric oxide secretion by HD11 cells in both dose- and time-dependent manners. Intracellular killing of Salmonella enteritidis (SE) was also increased in ODN 2006-activated HD11 cells. Furthermore, HD11 cells had reduced proliferation and underwent apoptosis, which is contradictory to the effects of ODN 2006 on human and murine cells. N(G)-monomethyl L-arginine (L-NMMA), an iNOS inhibitor, inhibited apoptosis of HD11 cells induced by ODN 2006, suggesting that this effect was likely mediated through an iNOS-dependent pathway. These results indicate that the differences in the responses of chicken HD11 macrophage cells to CpG ODNs compared to those of mammalian macrophages are species-related, and the potential of CpG ODNs as immunomodulators in poultry needs to be further explored.