The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global crisis. There is no therapeutic treatment specific for COVID-19. It is highly desirable to identify potential antiviral agents against SARS-CoV-2 from existing drugs available for other diseases and thus repurpose them for treatment of COVID-19. In general, a drug repurposing effort for treatment of a new disease, such as COVID-19, usually starts from a virtual screening of existing drugs, followed by experimental validation, but the actual hit rate is generally rather low with traditional computational methods. Here we report a virtual screening approach with accelerated free energy perturbation-based absolute binding free energy (FEP-ABFE) predictions and its use in identifying drugs targeting SARS-CoV-2 main protease (Mpro). The accurate FEP-ABFE predictions were based on the use of a restraint energy distribution (RED) function, making the practical FEP-ABFE−based virtual screening of the existing drug library possible. As a result, out of 25 drugs predicted, 15 were confirmed as potent inhibitors of SARS-CoV-2 Mpro. The most potent one is dipyridamole (inhibitory constant Ki = 0.04 µM) which has shown promising therapeutic effects in subsequently conducted clinical studies for treatment of patients with COVID-19. Additionally, hydroxychloroquine (Ki = 0.36 µM) and chloroquine (Ki = 0.56 µM) were also found to potently inhibit SARS-CoV-2 Mpro. We anticipate that the FEP-ABFE prediction-based virtual screening approach will be useful in many other drug repurposing or discovery efforts.

Three new abyssomicin monomers designated neoabyssomicins D (1), E (2), and A2 (3) and the two dimeric neoabyssomicins F (4) and G (5) were discovered from the marine-derived Streptomyces koyangensis SCSIO 5802, and their structures rigorously elucidated. Neoabyssomicin D (1) possesses an unprecedented 8/5/5/7 ring skeleton, the biosynthesis of which (as well as 2) is proposed herein. Additionally, dimeric agents 4 and 5 were found to be active against methicillin-resistant Staphylococcus aureus and vesicular stomatitis virus, respectively.

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Two new antimicrobial bisabolane-type sesquiterpenoid derivatives, ent-aspergoterpenin C (compound 1) and 7-O-methylhydroxysydonic acid (2), and two new butyrolactone-type monoterpenoids, pestalotiolactones C (3) and D (4), along with a known monoterpenoid pestalotiolactone A (5) and four known bisabolane sesquiterpenoids (6−9), were isolated and identified from the deep-sea sediment-derived fungus Aspergillus versicolor SD-330. The structures of these compounds were elucidated on the basis of spectroscopic analysis, and the absolute configurations of the new compounds 1−4 were determined by the combination of NOESY and TDDFT-ECD calculations and X-ray crystallographic analysis. Additionally, we first determined and reported the absolute configuration of the known monoterpenoid pestalotiolactone A (5) through the X-ray crystallographic experiment. All of these isolated compounds were evaluated for antimicrobial activities against human and aquatic pathogenic bacteria. Compounds 1, 2, 6 and 9 exhibited selective inhibitory activities against zoonotic pathogenic bacteria such as Escherichia coli, Edwardsiella tarda, Vibrio anguillarum and V. harveyi, with MIC values ranging from 1.0 to 8.0 μg/mL.

The purpose of this investigation is to research the causal link between economic policy uncertainty (EPU) and the housing returns (HR)

An endophytic fungus Arthrinium arundinis TE-3 was isolated and purified from the fresh leaves of cultivated tobacco (Nicotiana tabacum L.). Chemical investigation on this fungal strain afforded three new prenylated diphenyl ethers (1–3) as well as three known analogues (4–6). Structure elucidation of the isolated compounds was carried out by analysis of 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) spectra, as well as by comparison of those data with literature data. The absolute configuration of the stereogenic center at C-8 in 1 was assigned by comparison of the experimental and calculated ECD spectra. Compounds 1 and 2 showed selective antifungal activity against Mucor hiemalis with minimum inhibitory concentration (MIC) values of 8 and 4 μg/mL, respectively. Compounds 5 and 6 exhibited inhibitory activity against Alteraria alternata with an MIC value of 8 μg/mL. In the cytotoxic assay, 2, 5, and 6 displayed moderate in vitro cytotoxicity against the human monocytic cell line (THP-1 cell line), with IC50 values of 40.2, 28.3, and 25.9 μM, respectively. This study indicated that endophytic fungi possess great potential for exploring new bioactive secondary metabolites.

0 -[3-(2-hydroxylethylammino)propyl]oxamide, dabt and dmbt are 2,2 0 -diamino-4,4 0 -bithiazole and 2,2 0 -dimethyl-4,4 0 -bithiazole, respectively, have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectral studies and single-crystal X-ray diffraction. The crystal structures reveal that both of the tetracopper(II) complexes are assembled by a pair of oxamido-bridged bicopper(II) units through carboxyl bridges, but the configuration of the m-oxamido-bridge is cis-in complex 1 while trans-in complex 2. All the copper(II) ions in the two tetranuclear complexes are located in a square-pyramidal environment. Through hydrogen bonds, the two tetracopper(II) complexes 1 and 2 are assembled into a three-dimensional supramolecular structure and a two-dimensional network structure, respectively. The reactivity towards DNA, cytotoxic and antibacterial studies show that both the tetracopper(II) complexes can bind to HS-DNA in the mode of intercalation, and the cytotoxic and antibacterial activities are consistent with their DNA-binding abilities, following the order of 1 o 2. The influence of the substituents on terminal ligands in the two tetracopper(II) complexes on the structure, reactivity towards DNA, cytotoxic and antibacterial activities is preliminarily discussed.

Proliferation and apoptotic pathways are tightly regulated in cells by the ubiquitin-proteasome system (UPS). Alterations in the UPS may result in cellular transformation or other pathological conditions. The proteasome is indeed often found to be overactive in cancer cells. It has been reported that 2,3-indolinedione (L), which exists in marine organisms, as well as in mammals, is a proteasome inhibitor. Studies have shown that metal-based complexes inhibit proteasome activity and induce apoptosis in certain human cancer cells. In the current study, we synthesized six novel metal-based complexes with derivatives of 2,3-indolinedione: [Cd (C15H11O3N2) (CH3COO)] (C1), [Cd (C15H11O2N2) (CH3COO)] (C2), [Co (C15H9O4N2) (CH3COO)] (C3), [Co (C15H11O2N2) (CH3COO)] (C4), [Zn (C19H14O3N3) (CH3COO)] (C5) and [Zn (C17H13O3N2) (CH3COO)] (C6). We sought to characterize and assess the proteasome inhibitory and anti-proliferative effects of these metal-based complexes in human breast (MDA-MB-231) and prostate (LNCaP and PC-3) cancer cells, in order to determine whether specific structures contribute to the inhibition of tumor proteasome activity and the induction of apoptosis. The results revealed that the complexes, C1, C3 and C5, but not their counterparts, C2, C4 and C6, inhibited the chymotrypsin-like activity of the human cancer cellular 26S proteasome; in addition, these complexes promoted the accumulation of the proteasome target protein, Bax, inhibited cell growth and induced apoptosis in a concentration- and time-dependent manner due to their unique structures. Our data suggest that the study of metal-based complexes, including aromatic ring structures with electron-attracting groups, may be an interesting research direction for the development of anticancer drugs.