Semi-Synthesis and Biological Evaluation of 25(R)-26-Acetoxy-3ß,5α-Dihydroxycholest-6-One.

Previously, we identified a series of steroids (1-6) that showed potent anti-virus activities against respiratory syncytial virus (RSV), with IC50 values ranging from 3.23 to 0.19 µM. In this work, we first semi-synthesized and characterized the single isomer of 5, 25(R)-26-acetoxy-3ß,5α-dihydroxycholest-6-one, named as (25R)-5, in seven steps from a commercially available compound diosgenin (7), with a total yield of 2.8%. Unfortunately, compound (25R)-5 and the intermediates only showed slight inhibitions against RSV replication at the concentration of 10 µM, but they possessed potent cytotoxicity activities against human bladder cancer 5637 (HTB-9) and hepatic cancer HepG2, with IC50 values ranging from 3.0 to 15.5 µM without any impression of normal liver cell proliferation at 20 µM. Among them, the target compound (25R)-5 possessed cytotoxicity activities against 5637 (HTB-9) and HepG2 with IC50 values of 4.8 µM and 15.5 µM, respectively. Further studies indicated that compound (25R)-5 inhibited cancer cell proliferation through inducing early and late-stage apoptosis. Collectively, we have semi-synthesized, characterized and biologically evaluated the 25R-isomer of compound 5; the biological results suggested that compound (25R)-5 could be a good lead for further anti-cancer studies, especially for anti-human liver cancer.

One new sesquiterpene pyridine alkaloid from the stems and leaves of Euonymus fortunei.

A new sesquiterpene pyridine alkaloid (1), along with four known compounds (2-5), were isolated from the stems and leaves of Euonymus fortunei. The new structure was determined by extensive spectroscopic analyses (IR, UV, NMR, HRESIMS and ECD). In addition, compound 3 showed a stronger anti-respiratory syncytial virus (RSV) activity with an IC50 value of 1.20 ± 0.10 µM than the positive control ribavirin with an IC50 value of 5.62 ± 0.49 µM.[Formula: see text].

Inhibitory Effect of PIK-24 on Respiratory Syncytial Virus Entry by Blocking Phosphatidylinositol-3 Kinase Signaling.

Phosphoinositide-3 kinase signaling modulates many cellular processes, including cell survival, proliferation, differentiation, and apoptosis. Currently, it is known that the establishment of respiratory syncytial virus infection requires phosphoinositide-3 kinase signaling. However, the regulatory pattern of phosphoinositide-3 kinase signaling or its corresponding molecular mechanism during respiratory syncytial virus entry remains unclear. Here, the involvement of phosphoinositide-3 kinase signaling in respiratory syncytial virus entry was studied. PIK-24, a novel compound designed with phosphoinositide-3 kinase as a target, had potent anti-respiratory syncytial virus activity both in vitro and in vivo PIK-24 significantly reduced viral entry into the host cell through blocking the late stage of the fusion process. In a mouse model, PIK-24 effectively reduced the viral load and alleviated inflammation in lung tissue. Subsequent studies on the antiviral mechanism of PIK-24 revealed that viral entry was accompanied by phosphoinositide-3 kinase signaling activation, downstream RhoA and cofilin upregulation, and actin cytoskeleton rearrangement. PIK-24 treatment significantly reversed all these effects. The disruption of actin cytoskeleton dynamics or the modulation of phosphoinositide-3 kinase activity by knockdown also affected viral entry efficacy. Altogether, it is reasonable to conclude that the antiviral activity of PIK-24 depends on the phosphoinositide-3 kinase signaling and that the use of phosphoinositide-3 kinase signaling to regulate actin cytoskeleton rearrangement plays a key role in respiratory syncytial virus entry.

Synthesis and Biological Evaluation of Novel (thio)semicarbazone-Based Benzimidazoles as Antiviral Agents against Human Respiratory Viruses.

Respiratory RNA viruses are responsible for recurrent acute respiratory illnesses that still represent a major medical need. Previously we developed a large variety of benzimidazole derivatives able to inhibit these viruses. Herein, two series of (thio)semicarbazone- and hydrazone-based benzimidazoles have been explored, by derivatizing 5-acetyl benzimidazoles previously reported by us, thereby evaluating the influence of the modification on the antiviral activity. Compounds 6, 8, 16 and 17, bearing the 5-(thio)semicarbazone and 5-hydrazone functionalities in combination with the 2-benzyl ring on the benzimidazole core structure, acted as dual inhibitors of influenza A virus and human coronavirus. For respiratory syncytial virus (RSV), activity is limited to the 5-thiosemicarbazone (25) and 5-hydrazone (22) compounds carrying the 2-[(benzotriazol-1/2-yl)methyl]benzimidazole scaffold. These molecules proved to be the most effective antiviral agents, able to reach the potency profile of the licensed drug ribavirin. The molecular docking analysis explained the SAR of these compounds around their binding mode to the target RSV F protein, revealing the key contacts for further assessment. The herein-investigated benzimidazole-based derivatives may represent valuable hit compounds, deserving subsequent structural improvements towards more efficient antiviral agents for the treatment of pathologies caused by these human respiratory viruses.

N-((1,3-Diphenyl-1H-pyrazol-4-yl)methyl)anilines: A novel class of anti-RSV agents.

A series of N-((1,3-diphenyl-1H-pyrazol-4-yl)methyl)anilines were synthesized and evaluated in vitro for cytotoxicity and antiviral activity against a large panel of viruses. Most of the tested compounds interfered with RSV replication in the micromolar concentrations (EC50s ranging from 5 µM to 28 µM). SAR studies suggested that the presence of a trifluoromethyl group in R(1) abolished the anti-RSV activity and enhanced the cytotoxicity while the best results in term of both anti-RSV activity and selectivity were obtained by the introduction in R(1) of a chlorine or a bromine atom.

Two new compounds from the capitula of Chrysanthemum morifolium cv. Fubaiju.

A new germacrane-type sesquiterpenoid (1) and a new alkamide (2), as well as six known compounds (3-8) were isolated from the capitula of Chrysanthemum morifolium cv. Fubaiju. The new structures were elucidated by comprehensive spectroscopic analysis and quantum chemical calculations. The known structures were characterised via 1D NMR data compared with the already existing literature data. Among the isolates, compound 5 showed inhibitory activity against human lung cancer A549 cells and human hepatoma HepG2 cells with the IC50 values of 19.50 ± 1.23 and 23.24 ± 1.30 µM, respectively, and compound 8 exhibited inhibitory effect on RSV infection with IC50 value of 12.50 ± 1.02 µM.

Design, synthesis, and anti-respiratory syncytial virus potential of novel 3-(1,2,3-triazol-1-yl)furoxazine-fused benzimidazole derivatives.

Respiratory syncytial virus (RSV) is a major cause of serious lower respiratory tract infections in infants, children, and older persons. Currently, the only approved anti-viral chemotherapeutic drug for RSV treatment is ribavirin aerosol; however, its significant toxicity has led to restricted clinical use. In a previous study, we developed various benzimidazole derivatives against RSV. In this study, we synthesised 3-azide substituted furoxazine-fused benzimidazole derivatives by sulfonylation and azide substitution of the 3-hydroxyl group of the furoxazine-fused benzimidazole derivatives. Subsequently, a series of 3-(1,2,3-triazol-1-yl)-substituted furoxazine-fused benzimidazole derivatives were synthesised using the classical click reaction. Biological evaluations of the target compounds indicated that compound 4a-2 had higher activity against RSV (EC50 = 12.17 µM) and lower cytotoxicity (CC50 = 390.64 µM). Compound 4a-2 exerted anti-viral effects against the RSV Long strain by inhibiting apoptosis and the elevation of reactive oxygen species (ROS) and inflammatory factors caused by viral infection in vitro. Additionally, the clinical symptoms of the virus-infected mice were markedly relieved, and the viral load in the lung tissues was dramatically decreased. The biosafety profile of compound 4a-2 was also favourable, showing no detectable adverse effects on any of the major organs in vivo. These findings underscore the potential of compound 4a-2 as a valuable therapeutic option for combating RSV infections while also laying the foundation for further research and development in the field.

Design and synthesis of a new series of hybrids of functionalised N1-[(1H-1,2,3-triazol-4-yl)methyl]quinazoline-2,4-dione with antiviral activity against Respiratory Syncytial Virus.

In this study, a series of 48 hybrids of the functionalised 1-[(1H-1,2,3-triazole-4-yl)methyl]quinazoline-2,4-dione 17-22 were synthesised and evaluated for potential antiviral activity. The new hybrids were designed to contain a diethoxyphosphoryl group connected to the triazole moiety via ethylene or propylene linker, and in which the benzyl or benzoyl function is substituted at N3 in the quinazoline-2,4-dione moiety. The Cu(I)-catalyzed Hüisgen dipolar cycloaddition of azidophosphonates 23 and 24 with the respective N1-propargylquinazoline-2,4-diones 26aa-26ag, 26ba-26bg, 27aa-27ad and 27ba-27bd was applied for the syntheses of the designed compounds. All final hybrids 17-22 and N3-functionalised N1-propargylquinazoline-2,4-diones 26 and 27 were subsequently evaluated for their antiviral activity toward a broad range of DNA and RNA viruses. Importantly, hybrids 19be-19bg and 20be-20bg showed profound antiviral activities against Respiratory Syncytial Virus (RSV) with EC50 values in the lower micromolar range, with activity against viral strains of both subtypes (RSV A and B). In addition, several compounds also exerted some weak antiviral activity against varicella zoster virus. Finally, 19 ag was the only compound that showed antiviral potency against human cytomegalovirus, although with rather weak inhibitory activity. Notably, none of the tested compounds was cytotoxic toward uninfected cell lines used for the antiviral assays at a concentration up to 100 µM, returning interesting therapeutic indices for respiratory syncytial virus.

Three new bisflavonols from the seeds of Hovenia dulcis Thunb. and their anti-RSV activities.

Three novel bisflavonol derivatives, Hovenianins A-C, along with 12 known flavonoids were isolated and identified from the seeds of Hovenia dulcis Thunb. Their structures were established on the basis of spectroscopic methods (MS, UV, IR, 1D and 2D NMR) and electronic circular dichroism experiments. Hovenianin A (1) was the first dimer of flavonol linked dihydroflavonol via the B rings at C-2' and C-2″'positions to be found in nature. While Hovenianins BC (2-3) were a pair of diastereoisomeric bis-dihydroflavonols firstly reported in the Hovenia genus. The in vitro antiviral activity against respiratory syncytium virus (RSV) were evaluated by cytopathic effect (CPE) reduction assay. As a result, compounds 4, 5, and 10 displayed better antiviral effect against RSV A2 strains.

Caffeic acid oligomers from Mesona chinensis and their In Vitro antiviral activities.

The phytochemical study of the aerial part of Mesona chinensis led to the isolation of five new caffeic acid oligomers (1-5), as well as four known analogues (6-9). The structures of the new compounds including their absolute configurations were elucidated by comprehensive spectroscopic analysis, chemical method, and quantum-chemical electronic circular dichroism (ECD) calculation. Among the isolates, compound 7 showed significant in vitro antiviral activity on respiratory syncytial virus (RSV).

Terpenoids from the stems of Celastrus hindsii and their anti-RSV activities.

Two new oleanane-type triterpenoids (1-2), a new ursane-type triterpenoid (3), and a new podocarpane-type diterpenoid (4), together with 20 known compounds (5-24) were isolated from the stems of Celastrus hindsii Benth. Their structures were identified on the basis of the spectral data (HRESIMS, IR, UV, 1D, and 2D NMR) and the absolute configurations were determined by comparison of experimental and calculated ECD data. The structures of 1 and 4 were further confirmed by single crystal X-ray diffraction analysis. In addition, all compounds were evaluated for their in vitro antiviral activities against respiratory syncytium virus (RSV) using cytopathic effect (CPE) reduction assay. Compounds 7, 10, 11, 19 and 24 exhibited obvious anti-RSV activity with IC50 values from 1.55 to 6.25 µM.

Host dihydrofolate reductase (DHFR)-directed cycloguanil analogues endowed with activity against influenza virus and respiratory syncytial virus.

We have identified a series of 1-aryl-4,6-diamino-1,2-dihydrotriazines, structurally related to the antimalarial drug cycloguanil, as new inhibitors of influenza A and B virus and respiratory syncytial virus (RSV) via targeting of the host dihydrofolate reductase (DHFR) enzyme. Most analogues proved active against influenza B virus in the low micromolar range, and the best compounds (11, 13, 14 and 16) even reached the sub-micromolar potency of zanamivir (EC50 = 0.060 µM), and markedly exceeded (up to 327 times) the antiviral efficacy of ribavirin. Activity was also observed for two influenza A strains, including a virus with the S31N mutant form of M2 proton channel, which is the most prevalent resistance mutation for amantadine. Importantly, the compounds displayed nanomolar activity against RSV and a superior selectivity index, since the ratio of cytotoxic to antiviral concentration was >10,000 for the three most active compounds 11, 14 and 16 (EC50 ∼0.008 µM), far surpassing the potency and safety profile of the licensed drug ribavirin (EC50 = 5.8 µM, SI > 43).