Design, synthesis, and biological evaluation of a series of new anthraquinone derivatives as anti-ZIKV agents

A Marine Natural Product, Harzianopyridone, as an Anti-ZIKV Agent by Targeting RNA-Dependent RNA Polymerase

The Zika virus (ZIKV) is a mosquito-borne virus that already poses a danger to worldwide human health. Patients infected with ZIKV generally have mild symptoms like a low-grade fever and joint pain. However, severe symptoms can also occur, such as Guillain-Barré syndrome, neuropathy, and myelitis. Pregnant women infected with ZIKV may also cause microcephaly in newborns. To date, we still lack conventional antiviral drugs to treat ZIKV infections. Marine natural products have novel structures and diverse biological activities. They have been discovered to have antibacterial, antiviral, anticancer, and other therapeutic effects. Therefore, marine products are important resources for compounds for innovative medicines. In this study, we identified a marine natural product, harzianopyridone (HAR), that could inhibit ZIKV replication with EC50 values from 0.46 to 2.63 µM while not showing obvious cytotoxicity in multiple cellular models (CC50 > 45 µM). Further, it also reduced the expression of viral proteins and protected cells from viral infection. More importantly, we found that HAR directly bound to the ZIKV RNA-dependent RNA polymerase (RdRp) and suppressed its polymerase activity. Collectively, our findings provide HAR as an option for the development of anti-ZIKV drugs.

In Silico and In Vitro Identification of 1,8-Dihydroxy-4,5-dinitroanthraquinone as a New Antibacterial Agent against Staphylococcus aureus and Enterococcus faecalis

Increasing rates of bacterial resistance to antibiotics are a growing concern worldwide. The search for potential new antibiotics has included several natural products such as anthraquinones. However, comparatively less attention has been given to anthraquinones that exhibit functional groups that are uncommon in nature. In this work, 114 anthraquinones were evaluated using in silico methods to identify inhibitors of the enzyme phosphopantetheine adenylyltransferase (PPAT) of Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli. Virtual screenings based on molecular docking and the pharmacophore model, molecular dynamics simulations, and free energy calculations pointed to 1,8-dihydroxy-4,5-dinitroanthraquinone (DHDNA) as the most promising inhibitor. In addition, these analyses highlighted the contribution of the nitro group to the affinity of this anthraquinone for the nucleotide-binding site of PPAT. Furthermore, DHDNA was active in vitro towards Gram-positive bacteria with minimum inhibitory concentration (MIC) values of 31.25 µg/mL for S. aureus and 62.5 µg/mL for E. faecalis against both antibiotic-resistant isolates and reference strains but was ineffective against E. coli. Experiments on kill-time kinetics indicated that, at the tested concentrations, DHDNA produced bacteriostatic effects on both Gram-positive bacteria. Overall, our results present DHDNA as a potential PPAT inhibitor, showing antibacterial activity against antibiotic-resistant isolates of S. aureus and E. faecalis, findings that point to nitro groups as key to explaining these results.

Dapoxetine, a Selective Serotonin Reuptake Inhibitor, Suppresses Zika Virus Infection In Vitro

Zika virus (ZIKV) belongs to the Flavivirus genus of the Flaviviridae family, and is a pathogen posing a significant threat to human health. Currently, there is a lack of internationally approved antiviral drugs for the treatment of ZIKV infection, and symptomatic management remains the primary clinical approach. Consequently, the exploration of safe and effective anti-ZIKV drugs has emerged as a paramount imperative in ZIKV control efforts. In this study, we performed a screening of a compound library consisting of 1789 FDA-approved drugs to identify potential agents with anti-ZIKV activity. We have identified dapoxetine, an orally administered selective serotonin reuptake inhibitor (SSRI) commonly employed for the clinical management of premature ejaculation (PE), as a potential inhibitor of ZIKV RNA-dependent RNA polymerase (RdRp). Consequently, we conducted surface plasmon resonance (SPR) analysis to validate the specific binding of dapoxetine to ZIKV RdRp, and further evaluated its inhibitory effect on ZIKV RdRp synthesis using the ZIKV Gluc reporter gene assay. Furthermore, we substantiated the efficacy of dapoxetine in suppressing intracellular replication of ZIKV, thereby demonstrating a concentration-dependent antiviral effect (EC50 values ranging from 4.20 μM to 12.6 μM) and negligible cytotoxicity (CC50 > 50 μM) across diverse cell lines. Moreover, cell fluorescence staining and Western blotting assays revealed that dapoxetine effectively reduced the expression of ZIKV proteins. Collectively, our findings suggest that dapoxetine exhibits anti-ZIKV effects by inhibiting ZIKV RdRp activity, positioning it as a potential candidate for clinical therapeutic intervention against ZIKV infection.

Ascomylactam C Induces an Immunogenic Cell Death Signature via Mitochondria-Associated ER Stress in Lung Cancer and Melanoma

Ascomylactam C (AsC) is a new 13-membered-ring macrocyclic alkaloid, which was first isolated and identified in 2019 from the secondary metabolites of the mangrove endophytic fungus Didymella sp. CYSK-4 in the South China Sea. AsC has been found to have a broad-spectrum cytotoxic activity. However, the antitumor effects in vivo and mechanisms of AsC remain unclear. The aim of this study was to describe the effects of AsC on lung cancer and melanoma cells and to explore the antitumor molecular mechanism of AsC. In vitro, we used plate colony formation experiments and demonstrated the ability of AsC to inhibit low-density tumor growth. An Annexin V/PI cell apoptosis detection experiment revealed that AsC induced tumor cell apoptosis. In vivo, AsC suppressed the tumor growth of LLC and B16F10 allograft significantly in mice, and promoted the infiltration of CD4+ T and CD8+ T cells in tumor tissues. Mechanistically, by analyses of Western blotting, immunofluorescence and ELISA analysis, we found that AsC increased ROS formation, induced endoplasmic reticulum (ER) stress, activated the protein kinase RNA-like ER kinase (PERK)/eukaryotic translation initiation factor (eIF2α)/activating transcription factor 4 (ATF4)/C/EBP homologous protein (CHOP) signaling pathway, and induced immunogenic cell death (ICD) of tumor cells. Our results suggest that AsC may be a potentially promising antitumor drug candidate.