Anti-SARS-CoV-2, antioxidant and immunomodulatory potential of dietary flavonol quercetin: Focus on molecular targets and clinical efficacy

The current coronavirus disease 2019 (COVID-19) outbreak, caused by the infection of SARS-CoV-2, seems to be a tough global challenge because of its highly contagious nature and rapid evolution of the virus strain. As no effective clinical drugs are available for the treatment of this disease in the early phase till to date, scientists are hunting for drugs from natural sources for its treatment. Quercetin, a dietary polyphenolic flavonoid found in fruits and vegetables, has been reported to exhibit various health-benefit pharmacological properties including antioxidant, anti-inflammatory, antimicrobial, antiviral and anticancer properties. In silico and in vitro studies demonstrated that quercetin potently inhibits the infections of SARS-CoV-2 and other coronaviruses by interfering with viral entry and replication via inhibiting the activity of host ACE2 receptor, and viral S-, 3CL-, PL-, RdRp- and Nsp13 - proteases. Moreover, quercetin is able to suppress oxidative stress, cytokine storm, thrombosis, sepsis and lung fibrosis, and thereby very likely is able to mitigate COVID-19 infection. In this review article, we elaborately discussed the antiviral, immunomodulatory, antioxidant properties of quercetin against viral infections and other diseases, as well as on its nanoformulations for enhancement of oral bioavailability and clinical efficacy in COVID-19 infection for its development as clinical drug for COVID-19

Therapeutic potential of natural alkaloid emetine against emerging COVID-19 and future viral pandemics

The outbreak of COVID-19 pandemic caused by the infection of SARS-CoV-2, has become a global crisis, threatening public health and disrupting global economy. Until now, effective therapeutics against COVID-19 and other coronavirus diseases are in high demand. Several antiviral strategies of drug discovery have identified many small molecules with potent anti-COVID-19 activity. Emetine, one of the main alkaloids of Carapichea ipecacuanha, has been found to exhibit potent antiviral activity against SARS-CoV-2, and other human coronaviruses, multiple RNA and DNA viruses at low nanomolar concentrations in different cell lines. In silico analysis reveals that emetine directly disrupts the activities of SARS-CoV-2 S-protein with host ACE2, and of RdRp-, 3CL-, PL-,and N- proteins. Moreover, emetine shows potent anti-inflammatory and anti-pulmonary arterial hypertensive properties by down-regulating the p38, ERK1/2, NF-κB and RhoA/Rho-kinase/CyPA/Bsg signaling pathways. At low doses, emetine is effective for treatment of COVID-19 patients and other viral infections in rodents. This review discusses the current findings on the antiviral efficacy of emetine against the emerging SARS-CoV-2 and other corona, RNA and DNA viruses, as well as its immunoregulatory pathways and clinical potential in COVID-19 infection for its development as antiviral prodrugs to treat current COVID-19 and future viral pandemics

Synthesis and structure of iron (III) and iron (II) complexes in S₄P₂ environment created by diethyldithiocarbamate and 1,2-bis(diphenylphosphino)ethane chelation: Investigation of the electronic structure of the complexes by Mössbauer and magnetic studies

Iron (II) and iron (III) complexes, [FeII(DEDTC)2(dppe)] · CH2Cl2 (1), [FeII(ETXANT)2(dppe)] (2) (DEDTC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [FeIII(DEDTC)2(dppe)] [FeIIICl4] (3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCl4− by a non-magnetic BPh4− ion producing [FeIII(DEDTC)2(dppe)]BPh4 (4) for the sake of unequivocal understanding of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCl4− ion, the counter anion of 3, is trapped as PPh4[FeIIICl4] (5) and its magnetic property from 298 to 2 K has been studied. Besides the spectroscopic (IR, UV–Vis, NMR, EPR, Mass and XPS) characterization of the appropriate compounds, especially 2, others viz. 1, 3 and 4 have been structurally characterized by X-ray crystallography. While FeII complexes, 1 and 2, are diamagnetic, the FeIII systems, namely the cations of 3, and 4 behave as low-spin (S = 1/2) paramagnetic species from 298 to 50 K. Below 50 K 3 shows gradual increase of χMT up to 2 K suggesting ferromagnetic behavior while 4 exhibits gradual decrease of magnetic moment from 60 to 2 K, indicating the occurrence of weak antiferromagnetic interaction. These conclusions are supported by the Mössbauer studies of 3 and 4. The Mössbauer pattern of 1 exhibits a doublet site for diamagnetic (2–400 K) FeII. The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving FeII, FeIII and FeIV