The coronavirus disease 2019 (COVID-19) pandemic is an ongoing global health concern, and effective antiviral reagents are urgently needed. Traditional Chinese medicine theory-driven natural drug research and development (TCMT-NDRD) is a feasible method to address this issue as the traditional Chinese medicine formulae have been shown effective in the treatment of COVID-19. Huashi Baidu decoction (Q-14) is a clinically approved formula for COVID-19 therapy with antiviral and anti-inflammatory effects. Here, an integrative pharmacological strategy was applied to identify the antiviral and anti-inflammatory bioactive compounds from Q-14. Overall, a total of 343 chemical compounds were initially characterized, and 60 prototype compounds in Q-14 were subsequently traced in plasma using ultrahigh-performance liquid chromatography with quadrupole time-of-flight mass spectrometry. Among the 60 compounds, six compounds (magnolol, glycyrrhisoflavone, licoisoflavone A, emodin, echinatin, and quercetin) were identified showing a dose-dependent inhibition effect on the SARS-CoV-2 infection, including two inhibitors (echinatin and quercetin) of the main protease (Mpro), as well as two inhibitors (glycyrrhisoflavone and licoisoflavone A) of the RNA-dependent RNA polymerase (RdRp). Meanwhile, three anti-inflammatory components, including licochalcone B, echinatin, and glycyrrhisoflavone, were identified in a SARS-CoV-2-infected inflammatory cell model. In addition, glycyrrhisoflavone and licoisoflavone A also displayed strong inhibitory activities against cAMP-specific 3',5'-cyclic phosphodiesterase 4 (PDE4). Crystal structures of PDE4 in complex with glycyrrhisoflavone or licoisoflavone A were determined at resolutions of 1.54 Å and 1.65 Å, respectively, and both compounds bind in the active site of PDE4 with similar interactions. These findings will greatly stimulate the study of TCMT-NDRD against COVID-19.
In this work, polyaniline (PANI) film was synthesized by the two-step electrochemical polymerization method from sulfonic acid solution on the spectrographic pure graphite (SPG) surface. Scanning electron microscope (SEM) characterization shows that the resulting PANI film had porous morphology and loosely textured structure, which is composed of uniform 1D nanowires with an average diameter of about 100-200 nm. The electroreduction of Cr(VI) to the much less toxic trivalent state (Cr(III)) was then studied on the PANI/SPG electrode. The effects of various parameters such as cathode potential, solution pH, PANI film thickness and electrolyte temperature on the Cr(VI) removal rate were investigated in detail. It was found that the negative cathod potential, low solution pH and appropriate PANI film thickness are benefit for the removal of Cr(VI). While the electrolyte temperature had no evident effect on the Cr(VI) electroreduction reaction. The electrochemical stability of the PANI film after use in Cr(VI) reduction process was also investigated using cyclic voltammetry and Fourier transfer infrared spectroscopy technologies.
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