Conversion of Complex Sialooligosaccharides into Polymeric Conjugates and their Anti-Influenza Virus Inhibitory Potency

ABSTRACT

To investigate the specificity of various influenza virus strains we have prepared polyacrylic type conjugates of undecasaccharide (Neu5Acα2-6Galβ1-4GlcNAcβ1-2Manα1)₂-3,6Manβ1-4GlcNAcβ1-4GlcNAc (YDS), and trisaccharides 6‵-sialyl-N-acetyllactosamine (6‵SLN), 6‵-sialyllactose (6‵SL), and 3‵-sialyllactose (3‵SL). Free oligosaccharides were transformed to glycosylamine-1-N-glycyl derivatives by sequential action of NH₄HCO₃, chloroacetic anhydride, and aqueous NH₃. The known derivatization protocol has been optimized for these sialooligosaccharides. Coupling of obtained amino-spacered derivatives with poly(4-nitrophenyl acrylate) gave rise to two types of conjugates, namely with polyacrylic acid and polyacrylamide backbones; the conversion proceeded quantitatively and without destruction of the oligosaccharides. The content of oligosaccharides in the conjugates was 10, 20, and 30% mol for 3‵SL, 6‵SL, 6‵SLN, and 2, 5 and 10% mol for YDS. Free oligosaccharides and the glycoconjugates were tested as inhibitors of influenza virus adhesion, and also as blockers of virus infectivity in MDCK cell culture. Biantennary YDS demonstrated similar activity to trisaccharide 6‵SLN both as the free form and neoglycoconjugate.     

Investigation on DNA Binding and Photo-Cleavage Properties of Water-Soluble Porphyrin and Metalloporphyrins

A water-soluble porphyrin, tetrakis[4-(trimethylammonium)phenyl]porphyrin (TAPP), and its metal complexes with Zn(II), (ZnTAPP), have been synthesized and characterized by elemental analyses and u.v.-vis. spectra. The binding of the two complexes with calf thymus DNA has been investigated by absorption spectra, luminescence titrations, and viscosity measurements. The changes of the u.v.-vis. absorption spectra during the titration of these porphyrins with calf thymus DNA revealed a large bathochromic shift (upto 8–12 nm) and a hypochromicity of the porphyrins soret bands. The intensity of the fluorescence spectra of these porphyrins was enhanced. The cytotoxicity of the series of porphyrins TAPP and MTAPP [M = Zn(II), Cu(II), Fe(III), Co(III), Ni(II), Mn(III)] complexes was determined for Madin–Darby Canine Kindney (MDCK) cells and Vero cells with the method of cell culture, and were evaluated as anti-virus activity for influenza virus type A (H3N2), B and Herpes simplex virus type-1 (HSV-1, strain SM44), type-2 (HSV-2, strain 333) in vitro. Among the complexes evaluated, inhibited viral cytopathogenicity at lower concentrations that were found cytotoxic for the MDCK cells. Differences were observed in the 50% effective doses (based on inhibition of viral cytopathogenicity) of these complexes for a number of influenza viruses type A, B, and HSV-1, HSV-2 strains. It was found that CoTAPP displayed good inhibitory action against the virus in vitro.     

Synthesis and Antiviral Activity of N-Adamantyl-2-amino(or 2-phenoxy)-acylamides

New N-adamantyl-2-amino-acylamides(3a―3f) and N-adamantyl-2-phenoxy-acetamides(6a―6d) were designed and synthesized by the modification of the amino group of amantadine 1 and the structures were confirmed by mass spectra(MS) and ¹H NMR spectra. The antiviral potencies of the synthesized compounds were evaluated against the replication of influenza virus A/H₃N₂ subtype in Madin-Darby canine kidney(MDCK) cells. Among the amantadine derivatives, compound 3a had the strongest antiviral potency and showed activity similar to that of amantadine. Interestingly, the bulky and extended lipophilic moieties on the α-position of the carbonyl group resulted in decreases in potency.     

Synthesis and Antiviral Evaluation of Nucleoside Analogues Bearing One Pyrimidine Moiety and Two D-Ribofuranosyl Residues

A series of 1,2,3-triazolyl nucleoside analogues in which 1,2,3-triazol-4-yl-β-d-ribofuranosyl fragments are attached via polymethylene linkers to both nitrogen atoms of the heterocycle moiety (uracil, 6-methyluracil, thymine, quinazoline-2,4-dione, alloxazine) or to the C-5 and N-3 atoms of the 6-methyluracil moiety was synthesized. All compounds synthesized were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1) and coxsackievirus B3. Antiviral assays revealed three compounds, 2i, 5i, 11c, which showed moderate activity against influenza virus A H1N1 with IC₅₀ values of 57.5 µM, 24.3 µM, and 29.2 µM, respectively. In the first two nucleoside analogues, 1,2,3-triazol-4-yl-β-d-ribofuranosyl fragments are attached via butylene linkers to N-1 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine, respectively). In nucleoside analogue 11c, two 1,2,3-triazol-4-yl-2′,3′,5′-tri-O-acetyl-β-d-ribofuranose fragments are attached via propylene linkers to the C-5 and N-3 atoms of the 6-methyluracil moiety. Almost all synthesized 1,2,3-triazolyl nucleoside analogues showed no antiviral activity against the coxsackie B3 virus. Two exceptions are 1,2,3-triazolyl nucleoside analogs 2f and 5f, in which 1,2,3-triazol-4-yl-2′,3′,5′-tri-O-acetyl-β-d-ribofuranose fragments are attached to the C-5 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine respectively). These compounds exhibited high antiviral potency against the coxsackie B3 virus with IC₅₀ values of 12.4 and 11.3 µM, respectively, although both were inactive against influenza virus A H1N1. According to theoretical calculations, the antiviral activity of the 1,2,3-triazolyl nucleoside analogues 2i, 5i, and 11c against the H1N1 (A/PR/8/34) influenza virus can be explained by their influence on the functioning of the polymerase acidic protein (PA) of RNA-dependent RNA polymerase (RdRp). As to the antiviral activity of nucleoside analogs 2f and 5f against coxsackievirus B3, it can be explained by their interaction with the coat proteins VP1 and VP2.     

Synthesis and antiviral activity of novel imidazo[2,1-b]thiazoles coupled with morpholine and thiomorpholines

Herein described the synthesis and antiviral evaluation of a novel series of morpholine and thio-morpholine coupled imidazo[2,1-b]thiazoles. The three-step reaction sequence involving the condensation of 1,3-dichloroacetone with thiourea followed by coupling with morpholine and thiomorpholine and finally cyclization with substituted α-bromoacetophenones yielded the desired imidazothiazoles 7(a–l) . Screening of all the new compounds for their in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells, resulted in two potent analogs, 7d (IC₅₀: 1.1 μM, C₅₀: >300 μM, SI = 273) and 7e (IC₅₀: 2.0 μM, C₅₀: >300 μM, SI = 150), with a favorable toxicity profile and are the best anti-influenza hit analogs for further structural optimization.     

Development and Effects of Influenza Antiviral Drugs

Influenza virus is a highly contagious zoonotic respiratory disease that causes seasonal outbreaks each year and unpredictable pandemics occasionally with high morbidity and mortality rates, posing a great threat to public health worldwide. Besides the limited effect of vaccines, the problem is exacerbated by the lack of drugs with strong antiviral activity against all flu strains. Currently, there are two classes of antiviral drugs available that are chemosynthetic and approved against influenza A virus for prophylactic and therapeutic treatment, but the appearance of drug-resistant virus strains is a serious issue that strikes at the core of influenza control. There is therefore an urgent need to develop new antiviral drugs. Many reports have shown that the development of novel bioactive plant extracts and microbial extracts has significant advantages in influenza treatment. This paper comprehensively reviews the development and effects of chemosynthetic drugs, plant extracts, and microbial extracts with influenza antiviral activity, hoping to provide some references for novel antiviral drug design and promising alternative candidates for further anti-influenza drug development.     

Synthesis and antiviral activities of N-mono- and/or N,N'-di-carbamoyl and acyl derivatives of symmetrical diamines

N-carbamoyl and N-acyl diamine derivatives were synthesized from symmetrical diamines by their addition to iso(thio)cyanates, cleavage reaction of acid anhydride, or N-acylation by acyl chloride. (1R,2R)-1,2-Diaminocyclohexane [(1R,2R)-1], meso-1,2-diaminocyclohexane (meso-1), (1R,2R)-1,2-diphenylethylenediamine [(1R,2R)-3], or meso-1,2-diphenylethylenediamine (meso-3) were used as the starting symmetrical diamines. The target compounds synthesized herein were evaluated for antiviral activity with herpes simplex virus type 1 (HSV-1). A few derivatives of 1,2-diaminocyclohexane [(1R,2R)-7aa and cis-7b] with adamantyl group(s) showed significant antiviral activity (EC(50)=16.0, 27.0 microg/ml).     

Synthesis of adamantyl-containing cidofovir analogs as potential antiviral prodrugs with high bioavailability parameters

We report on preparation of potential nucleoside phosphonate prodrugs: 1-{3-hydroxy-2-[O-(adamantylalkyl)phosphorylmethoxy]propyl}cytosines containing two structural fragments providing antiviral activity, nucleoside phosphonate and adamantyl sites.

     

Synthesis and antiviral activities of synthetic glutarimide derivatives

A series of novel glutarimide compounds were synthesized and their antiviral activities were evaluated. The compounds displaying the strongest antiviral activities included 5, 6f, 7e and 9 against coxsackievirus B3 (Cox B3), 10 and 6f against influenza virus A (influenza A) and 7a against herpes simplex virus 2 (HSV-2). However, most of the synthetic glutarimides showed comparatively much weaker activity against influenza A, Cox B3 and HSV-2 than the natural glutarimide compounds tested. Based on the results, it seemed likely that a conjugated system at the β-substituted moiety provides stronger antiviral activity.     

中国毛虾流感病毒神经氨酸酶抑制活性肽的研究

以中国毛虾为原料, 以抑制流感病毒神经氨酸酶(NA)活性为初筛指标, 通过控制酶切位点制备了具有抑制NA活性的酶解液. 利用凝胶层析和高效液相色谱等技术分离纯化出高活性的抑制肽, 其IC₅₀ 值为96.1 μmol/L.经串联质谱测定该抑制肽序列为EISYIHAEAYRRGELK, 紫外光谱分析结果证明该抑制肽能与NA结合.基于反向对接, 应用SYBYL软件模拟抑制肽与NA活性区域结合, 确定了抑制肽与NA的结合位点. 细胞毒性实验测得该抑制肽对细胞的最大无毒浓度(TC₀)为1.26 mg/mL.在红细胞凝集实验中, 随着抑制肽浓度增大, 病毒的凝集价显著降低, 证明抑制肽的抗病毒作用具有多靶点.     

Facial Synthesis and Bioevaluation of Well-Defined OEGylated Betulinic Acid-Cyclodextrin Conjugates for Inhibition of Influenza Infection

Betulinic acid (BA) and its derivatives exhibit a variety of biological activities, especially their anti-HIV-1 activity, but generally have only modest inhibitory potency against influenza virus. The entry of influenza virus into host cells can be competitively inhibited by multivalent derivatives targeting hemagglutinin. In this study, a series of hexa-, hepta- and octavalent BA derivatives based on α-, β- and γ-cyclodextrin scaffolds, respectively, with varying lengths of flexible oligo(ethylene glycol) linkers was designed and synthesized using a microwave-assisted copper-catalyzed 1,3-dipolar cycloaddition reaction. The generated BA-cyclodextrin conjugates were tested for their in vitro activity against influenza A/WSN/33 (H1N1) virus and cytotoxicity. Among the tested compounds, 58, 80 and 82 showed slight cytotoxicity to Madin-Darby canine kidney cells with viabilities ranging from 64 to 68% at a high concentration of 100 μM. Four conjugates 51 and 69–71 showed significant inhibitory effects on influenza infection with half maximal inhibitory concentration values of 5.20, 9.82, 7.48 and 7.59 μM, respectively. The structure-activity relationships of multivalent BA-cyclodextrin conjugates were discussed, highlighting that multivalent BA derivatives may be potential antiviral agents against influenza infection.     

Synthesis and Antiviral Activity of Camphene Derivatives against Different Types of Viruses

To date, the ‘one bug-one drug’ approach to antiviral drug development cannot effectively respond to the constant threat posed by an increasing diversity of viruses causing outbreaks of viral infections that turn out to be pathogenic for humans. Evidently, there is an urgent need for new strategies to develop efficient antiviral agents with broad-spectrum activities. In this paper, we identified camphene derivatives that showed broad antiviral activities in vitro against a panel of enveloped pathogenic viruses, including influenza virus A/PR/8/34 (H1N1), Ebola virus (EBOV), and the Hantaan virus. The lead-compound 2a, with pyrrolidine cycle in its structure, displayed antiviral activity against influenza virus (IC₅₀ = 45.3 µM), Ebola pseudotype viruses (IC₅₀ = 0.12 µM), and authentic EBOV (IC₅₀ = 18.3 µM), as well as against pseudoviruses with Hantaan virus Gn-Gc glycoprotein (IC₅₀ = 9.1 µM). The results of antiviral activity studies using pseudotype viruses and molecular modeling suggest that surface proteins of the viruses required for the fusion process between viral and cellular membranes are the likely target of compound 2a. The key structural fragments responsible for efficient binding are the bicyclic natural framework and the nitrogen atom. These data encourage us to conduct further investigations using bicyclic monoterpenoids as a scaffold for the rational design of membrane-fusion targeting inhibitors.     

Pharmacophore Mode lingand Virtual Screening to Design the Potential Influenza Virus Endonuclease Inhibitors

Influenza virus endonuclease is an attractive target for antiviral therapy in the treatment of influenza infection. The purpos e of this study is to design a novel antiviral agent with improved biological activities against the influenza virus endonuclease. In this study, chemical feature‐based 3D pharmacophore models were developed from 41 known influenza virus endonuclease inhibitors. The best quantitative pharmacohore model (Hypo 1), which consists of two hydrogen‐bond acceptors and two hydrophobic features, yields the highest correlation coefficient (R = 0.886). Hypo 1 was further validated by the cross validation method and the test set compounds. The application of this model for predicting the activities of 11 known influenza virus endonuclease inhibitors in the test set shows great success. The correlation coefficient of 0.942 and a cross validation of 95;% confidence level prove that this model is reliable in identifying structurally diverse compounds for influenza virus endonuclease inhibition. The most active compound (compound 1) from the training set was docked into the active site of the influenza virus endonuclease as an additional verification that the pharmacophore model is accurate. The docked conformation showed important hydrogen bond interactions between the compound and two amino acids, Lys 134 and Lys 137. After validation, this model was used to screen the NCI chemical database to identify new influenza virus endonuclease inhibitors. Our study shows that the to pranking compound out of the 10 newly identified compounds using fit value ranking has an estimated activity of 0.049 μM. These newly identified lead compounds can be further experimentally validated using in vitro techniques.     

In vitro evaluation of secoiridoid glucosides from the fruits of Ligustrum lucidum as antiviral agents.

Six secoiridoid glucosides, lucidumoside C (1), oleoside dimethylester (2), neonuezhenide (3), oleuropein (4), ligustroside (5) and lucidumoside A (6), isolated from the fruits of Ligustrum lucidum (Oleaceae), were examined in vitro for their activities against four strains of pathogenic viruses, namely herpes simplex type I virus (HSV-1), influenza type A virus (Flu A), respiratory syncytial virus (RSV) and parainfluenza type 3 virus (Para 3). Antiviral activities were evaluated by the cytopathic effect (CPE) inhibitory assay. The purpose was to check if the antioxidative potency of these glucosides correlated with their antiviral potency. Results showed that none of the glucosides had any significant activity against HSV-1 and Flu A. Oleuropein, however, showed significant antiviral activities against RSV and Para 3 with IC50 value of 23.4 and 11.7 microg/ml, respectively. Lucidumoside C, oleoside dimethylester and ligustroside showed potent or moderate antiviral activities against Para 3 with IC50 values of 15.6-20.8 microg/ml. These results also documented that the anti-oxidative potency of these secoiriodoid glucosides was not directly related to their antiviral effects.     

Flavonoids as Promising Antiviral Agents against SARS-CoV-2 Infection: A Mechanistic Review

A newly diagnosed coronavirus in 2019 (COVID-19) has affected all human activities since its discovery. Flavonoids commonly found in the human diet have attracted a lot of attention due to their remarkable biological activities. This paper provides a comprehensive review of the benefits of flavonoids in COVID-19 disease. Previously-reported effects of flavonoids on five RNA viruses with similar clinical manifestations and/or pharmacological treatments, including influenza, human immunodeficiency virus (HIV), severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and Ebola, were considered. Flavonoids act via direct antiviral properties, where they inhibit different stages of the virus infective cycle and indirect effects when they modulate host responses to viral infection and subsequent complications. Flavonoids have shown antiviral activity via inhibition of viral protease, RNA polymerase, and mRNA, virus replication, and infectivity. The compounds were also effective for the regulation of interferons, pro-inflammatory cytokines, and sub-cellular inflammatory pathways such as nuclear factor-κB and Jun N-terminal kinases. Baicalin, quercetin and its derivatives, hesperidin, and catechins are the most studied flavonoids in this regard. In conclusion, dietary flavonoids are promising treatment options against COVID-19 infection; however, future investigations are recommended to assess the antiviral properties of these compounds on this disease.     

Chemical analysis and antiviral activity evaluation of Baccharis anomala

The chemical composition and antiviral activity of aqueous extract from Baccharis anomala was studied by bioactivity-guided fractionation. Ethanol precipitation and fractionation by molecular permeation allowed the separation of the anti-herpes simplex virus 1 (HSV-1) active fraction from aqueous extract (Fraction B). Natural Product Reagent A, FeCl₃ and thin-layer chromatography indicated the presence of phenolic compounds in the aqueous extract. Fraction B showed pronounced antiviral activity when tested with HSV-1 strains VR733/ATCC and Acyclovir-resistant 29-R, displaying virucidal but not virustatic activity.     

Synthesis and antiviral activity of new substituted pyrimidine glycosides

A number of N‐substituted pyrimidine glycosides were synthesized by coupling reaction of the pyrimidine base with acetobromosugars followed by deprotection. The synthesized compounds were tested for their antiviral activity against Hepatitis B Virus (HBV). Plaque reduction infectivity assay was used to determine virus count reduction as a result of treatment with tested compounds which showed moderate to high anti viral activities. J. Heterocyclic Chem., (2011).     

Anti-NDV activity of 9-oxo10,11-dehydroageraphorone extracted from Eupatorium adenophorum Spreng in vitro

The purpose of this study was to investigate the anti-Newcastle disease virus (NDV) activities of 9-oxo-10,11-dehydroageraphorone (euptox A) from Eupatorium adenophorum Spreng (E. adenophorum) in vitro. NDV infection of chicken embryo fibroblasts (CEFs) was performed. Cytotoxicities and antiviral activities of euptox A was assessed by the MTT method. The interaction of NDV with cell membrane protein was detected by virus overlay protein binding assay (VOPBA). The expression levels of NDV genes in CEFs was tested by RTFQ PCR. The results showed that the maximal safe concentrations of euptox A to CEFs was 10 μg/mL. Euptox A could directly neutralise NDV, inhibit the infectivity of NDV to CEFs and block intracellular NDV treat NDV infection. And euptox A brings competitiveness inhibition for NDV binding to its receptors and then prevent NDV infection. These results indicated that euptox A possessed anti-NDV activity has potential use as components of a natural antiviral drug.     

Antiviral properties of cage compounds. New prospects

The published data of the last 15 years on the antiviral activity and the mechanism of action of cage compounds are integrated and described systematically. The considerable interest in the cage compounds as antiviral agents is related to the specific features of the spatial structure of this class of derivatives and high lipophilicity and rigidity of the carbon cage, which allows these molecules to easily penetrate through the lipid layer of biological membranes. Data on the ion channel structure of influenza A and hepatitis C viruses and docking data for some cage structures to these channels are presented. Data on the antiviral properties of cage compounds against RNA genome viruses, the influenza A virus and its mutant strains, hepatitis C virus, human immunodeficiency viruses, and other RNA-containing viruses, are presented. The efficiency of cage compounds against the DNA-genome viruses, herpes virus, cytomegalovirus and orthopoxviruses, is demonstrated. The proven participation of aminoadamantanes in the suppression of early stages of the influenza virus life cycle suggests that efficient inhibitors of not only the influenza virus but also other RNA- and DNA-containing viruses could be found among the cage molecules.     

Identification of potential influenza virus endonuclease inhibitors through virtual screening based on the 3D-QSAR model

Influenza endonucleases have appeared as an attractive target of antiviral therapy for influenza infection. With the purpose of designing a novel antiviral agent with enhanced biological activities against influenza endonuclease, a three-dimensional quantitative structure-activity relationships (3D-QSAR) model was generated based on 34 influenza endonuclease inhibitors. The comparative molecular similarity index analysis (CoMSIA) with a steric, electrostatic and hydrophobic (SEH) model showed the best correlative and predictive capability (q ² = 0.763, r ² = 0.969 and F = 174.785), which provided a pharmacophore composed of the electronegative moiety as well as the bulky hydrophobic group. The CoMSIA model was used as a pharmacophore query in the UNITY search of the ChemDiv compound library to give virtual active compounds. The 3D-QSAR model was then used to predict the activity of the selected compounds, which identified three compounds as the most likely inhibitor candidates.