Neuraminidase Inhibitory Activity Research Articles

Naturally Occurring Xanthones: Chemistry and Biology

Xanthones are one of the biggest classes of compounds in natural product chemistry. A number of xanthones have been isolated from natural sources of higher plants, fungi, ferns, and lichens. They have gradually risen to great importance because of their medicinal properties. This review focuses on the types, isolation, characterization, biological applications, and biosynthesis of naturally occurring xanthones isolated so far. Different physicochemical and instrumental methods such as liquid-solid and liquid-liquid extraction, TLC, flash chromatography, column chromatography, IR, 1H NMR and 13C NMR spectroscopy, GLC, HPLC, GC, and LCMS have been widely used for isolation and structural elucidation of xanthones. Hepatoprotective, anticarcinogenic, antileprosy, antimalarial, antioxidant, anticholinergic, mutagenicity, radioprotective, immunomodulatory, antibone resorption, antiparasitic, neuraminidase inhibitory, anticomplement, antibacterial, antifungal, algicidal, anti-HIV, cardioprotective, antitumoral, antidiabetes, antihyperlipidemic, antiatherogenic, anti-inflammatory, antiulcer, antidiabetic, hypolipidemic, analgesic, antiasthmatic, antihistaminic, antiamoebic, diuretic, antidiarrheal, larvicidal, and ovicidal activities have been reported for natural occurring xanthones. To a certain extent, this review provides necessary foundation for further research and development of new medicines.

Bacterial neuraminidase inhibitory effects of prenylated isoflavones from roots of Flemingia philippinensis

Bacterial neuraminidase (NA) is one of the key enzymes involved in pathogenesis of inflammation during infection. The organic extract of the roots of Flemingia philippinensis showed high bacterial NA inhibitory activity with an IC50 of around 5μg/mL. Activity-guided separation of the methanol extract yielded nine prenylated isoflavones together with the novel species isoflavone (2) which was given the name flemingsin. Isolated prenylated isoflavones (1–9) were evaluated for NA inhibition and their IC50 values were determined to range between 0.30 and 56.8μM. The most potent inhibitor 4 (IC50=300nM, Ki=130nM) features a catechol motif in the B-ring and a furan in the A-ring. Structure–activity analysis also showed a 4-hydroxyl group within the B-ring was essential for NA inhibitory activity, because isoflavone (9) having protected 4-hydroxyl group was much less potent than its hydroxylated counterpart. All neuraminidase compounds screened were found to be reversible noncompetitive inhibitors. Furthermore, the most active NA inhibitors (1–9) were proven to be present in the native roots in high quantities by HPLC and LC-DAD-ESI/MS.

288: Identification of an anti-viral compound with inhibitory effects on influenza replication

In light of the recent novel H1N1 virus epidemic, virus resistance to currently approved antiviral medications has become a global health concern. Since almost all circulating strains of influenza A viruses are resistant to either adamantanes or neuraminidase inhibitors, new therapeutic approaches and means to discover new antiviral agents are critical to address the issue of recurring drug resistance. We postulate that computational molecular docking provides an efficient and innovative approach to examine small molecules against influenza viruses. We have identified a potent inhibitor of the H5N1 neuraminidase protein from a library of 23,000 compounds. This compound demonstrated anti-viral activity efficacy in vitro across a number of cell-lines assays in H5N1, H1N1, H9N2/G1, H3N2 and the oseltamivir-resistant H1N1 virus while the compound itself did not show any cytotoxicity. The underlying mechanisms including immunoregulation, upstream signalling pathways and neuraminidase inhibitory activity were also studied. It was found that the compound inhibit the viral titers via inhibiting the neuraminidase activity. Upon successful demonstration of the effectiveness of the compound in the cell culture model, we further validated the anti-influenza effect of the compound in a mouse model. BALB/c mice were administrated once daily with the compound or diluent control (DMSO). They were then intranasally infected with A/PR/8/34 influenza virus. The mice were treated with the compound or DMSO through oral gavage for five more days starting from 8 h post-infection. Our results showed that the compound prolonged the life span and increased the survival rate of the mice. These results demonstrated that the compound screened from molecular docking is a new potential drug candidate for inhibiting viral replications of different influenza viruses.

Design and Synthesis of 4‐Alkyl‐2‐amino(acetamino)‐6‐aryl‐1,3‐thiazine Derivatives as Influenza Neuraminidase Inhibitors

With a convenient and economical method, two series of 1,3-thiazine derivatives 1 and 2 were synthesized, and their neuraminidase (NA) inhibitory activities were evaluated. The pharmacological results showed that most of the compounds have potent NA inhibitory activity. Especially, 1g exhibited the best activity against influenza virus A (H1N1) NA (IC50=29.06 µg/mL), and its crystal structure was determined by single-crystal X-ray diffraction. The preliminary biological assay indicated that 1,3-thiazine could be used as a core structure to design novel influenza NA inhibitors.

Dry extract BNO 1011 inhibits human influenza a replication and neuraminidase activity in oseltamivir‐resistant and ‐sensitive viral strains

Virus infection is the main triggering event for the development of acute rhinosinusitis and human influenza A virus ranks among the most frequent viral causes of infection. Influenza neuraminidase, a key enzyme in viral replication, spread, and pathogenesis, is the primary target in prevention and treatment of influenza infection. Sinupret®, a herbal medicinal product composed of Gentianae radix, Primulae flos, Sambuci flos, Rumicis herba, and Verbenae herba, is frequently used for the treatment of acute rhinosinusitis. To investigate the anti-viral activity of the Sinupret® dry extract BNO 1011 in vitro and its potential to inhibit neuraminidase in oseltamivir-resistant and -sensitive human influenza A H1N1 strains of clinical relevance. In vitro, BNO 1011 was tested for its interference with human influenza A infection using a plaque reduction assay in MDCK cells. The impact on two clinically relevant human influenza A H1N1 strains displaying divergent sensitivity against the well-known neuraminidase inhibitor oseltamivir (OS) was studied (OS-sensitive: human influenza A/California/07/2009; OS-resistant: human influenza A/Maryland/04/2011). In addition, BNO 1011 was studied for its inhibitory activity on neuraminidase of the same influenza A strains in a highly sensitive chemiluminescence assay. The in vitro experiments were paralleled by monitoring viability of MDCK cells in the presence of BNO 1011. BNO 1011 efficiently blocked the infectivity of both influenza A H1N1 strains studied in a plaque reduction assay [EC50: 8.3 µg/mL (A/California/07/2009), 8.2 µg/mL (A/Maryland/04/2011)] but did not affect cell viability (CC50>1 mg/mL), yielding a therapeutic index (CC50/EC50) of 121 and 122, respectively. BNO 1011 also inhibited neuraminidase activity in both viral strains with comparable efficiency [IC50: 59.3 µg/mL (A/California/07/2009), 99.7 µg/mL (A/Maryland/04/2011)], irrespective of the strains' oseltamivir sensitivity. Taken together, Sinupret® dry extract BNO 1011 inhibits the replication of clinically relevant influenza A isolates. As underlying mechanism, the inhibition of viral neuraminidase was identified. Our results support the application of Sinupret® dry extract BNO 1011 in the treatment of acute, viral rhinosinusitis.

Neuraminidase Inhibitors from marine-derived actinomycete Streptomyces seoulensis

This work was performed to characterize new secondary metabolites with neuraminidase (NA) inhibitory activity from marine actinomycete strains. An actinomycete strain IFB-A01, capable of producing new NA inhibitors, was isolated from the gut of shrimp Penasus orientalis and identified as Streptomyces seoulensis according to its 16S rRNA sequence (over 99% homology with that of the standard strain). Repeated chromatography of the methanol extract of the solid-substrate culture of S. seoulensis IFB-A01 led to the isolation of streptoseolactone (1), and limazepines G (2) and H (3). The structures of 1-3 were determined by a combination of IR, ESI-MS, 1D ((1) H and (13) C NMR, and DEPT) and 2D NMR experiments (HMQC, HMBC, (1) H-(1) H COSY and NOESY). Compounds 1-3 showed significant inhibition on NA in a dose-dependent manner with IC50 values of 3.92, 7.50 and 7.37 μmol l(-1), respectively. This is the first report of two new (1 and 2) and known (3, recovered as a natural product for the first time in the work) NA inhibitors from the marine-derived actinomycete S. seoulensis IFB-A01. The three natural NA inhibitors maybe of value for the development of drug(s) necessitated for the treatment of viral infections.

Classification Prediction of Inhibitors of H1N1 Neuraminidase by Machine Learning Methods

Influenza is a major respiratory infection associated with significant morbidity in the general population and mortality in elderly and high-risk patients.Research has shown that inhibiting neuraminidase (NA) prevents RNA replication,so NA is an important drug target in the treatment of H1N1 influenza virus.It is becoming increasingly important to screen and predict molecules that have NA inhibitory activity by computational methods.In this work,we explored several machine learning methods (support vector machine (SVM),k-nearest neighbor (k-NN),and C4.5 decision tree (C4.5 DT)) for predicting NA inhibitors (NAIs).These predictive systems were tested using 227 compounds (72 NAIs and 155 non-NAIs),which were significantly more diverse in chemical structure than those used in other studies.A feature selection method was used to improve the accuracy of the predictions and the selection of molecular descriptors responsible for distinguishing between NAIs and non-NAIs.The prediction accuracies were 75.9%-92.6% for all the compounds,64.3%-78.6% for NAIs,and 77.5%-97.5% for non-NAIs.The SVM method gave the best total accuracy of 92.6% for all of methods.This work suggests that machine learning methods can be useful to predict potential NAIs from unknown sets of compounds and to determine molecular descriptors associated with NAIs.

Active Peptide from Acetes Chinensis with Inhibitory Activity on Neuraminidase of Influenza Virus

Low-valued Acetes Chinensis was chosen to prepare the enzymatic hydrolysate with neuraminidase(NA) inhibitory activity by controlled hydrolysis. A novel NA inhibitory peptide was purified by gel chromatography and reversed phase high performance liquid chromatography. The IC50value of the peptide was only96. 1 μmol / L and it could also significantly inhibit influenza A virus replication in MDCK cells. The amino acid sequence of this peptide was EISYIHAEAYRRGELK which identified by LC-MS / MS and its binding with NA protein was proved by UV spectrum analysis. The accurate sites of NA protein that the peptide bind to were determined using the computer assisted software SYBYL. The largest non-toxic concentration( TC0)was1. 26 mg / mL which assayed by cell cytotoxicity experiments. The hemagglutination essay showed that this pepetide could obviously decrease the agglutination titer influenza virus in a dose-dependent manner which suggested that the antiviral activity of this peptide might be attributed to its action on multiple targets.

155 3D QSAR and protein–protein interaction studies on neuraminidase against Clostridium perfringens: An approach toward target identification using structure-based drug designing

The rapid onset of resistance to new drugs and emergence of antibiotic resistant bacteria has led to resurgence in life-threatening bacterial infections. These problems have revitalized interest in antibiotics and lead to new research. To gain further insight between structural and biological activity of Clostridium perfringens, a gram-positive anaerobe responsible for food poisoning, mynecrosis in wound infections, and enterotoxemia in humans. We have considered various in silico approaches for developing new drug leads, based on small ligand structure. The importance of neuraminidases in the virulence of C. perfringens makes it a potent target for the studies of drug designing against this microbe. Natural products or their direct derivatives play crucial roles in many diseases. In the present study, 3D QSAR analysis using kNN-MFA method was performed on a series of pterocarpan derivatives as Clostridial neuraminidase inhibitors. Twenty-five compounds using random selection and sphere exclusion method for the division of dataset into training and test set were chosen. kNN-MFA methodology with stepwise, simulated annealing and genetic algorithm was used for model building and four predictive models have been generated. The most significant model has a high internal predictivity of 64.80% (q 2 = 0.6480) and an external predictivity of 95.46% (r 2 = 0.9546). Model showed that electrostatic and steric interactions play important role in determining neuraminidase inhibitory activity. The kNN-MFA plots provide further understanding of the relationship between structural features of substituted pterocarpan derivatives and their activities which were applied for designing new compounds as inhibitors. The drug likeliness of these compounds was checked through ADME property prediction and their interaction with the neuraminidase was checked by molecular docking studies. Moreover, analysis of protein–protein interaction network of NanI in C. perfringens was done.

Oseltamivir Pharmacokinetics in Critically Ill Adults Receiving Extracorporeal Membrane Oxygenation Support

Extracorporeal membrane oxygenation (ECMO) is known to affect pharmacokinetics and hence optimum dosing. The aim of this open label, prospective study was to investigate the pharmacokinetics of oseltamivir (prodrug) and oseltamivir carboxylate (active metabolite) during ECMO. Fourteen adult patients with suspected or confirmed H1N1 influenza were enrolled in the study. Oseltamivir 75 mg was enterally administered twice daily and blood samples for pharmacokinetic assessment were taken on day 1 and 5. A multi-compartmental model to describe the pharmacokinetics of oseltamivir and oseltamivir carboxylate was developed using a non-linear mixed effects modelling approach. The median (range) clearance of oseltamivir carboxylate was 15.8 (4.8-36.6) l/hour, lower than the reported mean value of 21.5 l/hour in healthy adults. The median (range) steady state volume of distribution of oseltamivir carboxylate was 179 (61-436) litres, much greater than healthy adults but similar to previous reports in critically ill patients. Substantial 'between subject' variability in systemic exposure to oseltamivir carboxylate was revealed; median (range) area under the curve and Cmax were 4346 (644-13660) ng/hour/ml and 509 (54-1277) ng/ml, respectively. Both area under the curve and Cmax were significantly correlated with serum creatinine (r2=0.37, P=0.02 and r2=0.29, P=0.02, respectively). Systemic exposure to oseltamivir carboxylate following the administration of enteral oseltamivir 75 mg twice daily in adult ECMO patients is comparable to those in ambulatory patients and far in excess of concentrations required to maximally inhibit neuraminidase activity of the H1N1 virus. Dosage adjustment for ECMO, per se, appears not to be necessary; however, doses should be reduced in patients with renal dysfunction.

Influenza virus neuraminidase contributes to the dextran sulfate-dependent suppressive replication of some influenza A virus strains

Dextran sulfate (DS), a negatively charged, sulfated polysaccharide, suppresses the replication of an influenza A virus strain, and this suppression is associated with inhibition of the hemagglutinin (HA)-dependent fusion activity. However, it remains unknown whether the replication of all or just some influenza A virus strains is suppressed by DS, or whether HA is the only target for the replication suppression. In the present study, we found that DS inhibited the replication of some, but not all influenza A virus strains. The suppression in the DS-sensitive strains was dose-dependent and neutralized by diethylaminoethyl-dextran (DD), which has a positive charge. The suppression by DS was observed not only at the initial stage of viral infection, which includes viral attachment and entry, but also at the late stage, which includes virus assembly and release from infected cells. Electron microscopy revealed that the DS induced viral aggregation at the cell surface. The neuraminidase (NA) activity of the strains whose viral replication was inhibited at the late stage was also more suppressed by DS than that of the strains whose replication was not inhibited, and this inhibition of NA activity was also neutralized by adding positively charged DD. Furthermore, we found that replacing the NA gene of a strain in which viral replication was inhibited by DS at the late stage with the NA gene from a strain in which viral replication was not inhibited, eliminated the DS-dependent suppression. These results suggest that the influenza virus NA contributes to the DS-suppressible virus release from infected cells at the late stage, and the suppression may involve the inhibition of NA activity by DS's negative charge.

In silico design of cyclic peptides as influenza virus, a subtype H1N1 neuraminidase inhibitor

Nowadays, influenza has become a global public health concern because it is responsible for significant morbidity and mortality due to annual epidemics and unpredictable pandemics. There are only limited options to control this respiratory disease. Vaccine treatment is useless for controlling this disease because of the occurrence of mutation in the influenza virus. Influenza virus is also resistant to some antiviral drugs like oseltamivir and zanamivir, which inhibit neuraminidase. Another solution for controlling this virus is to find new design for antiviral drugs. Cyclic peptides can be used to make new antiviral drug design especially to inhibit neuraminidase activity by using ’structure-based design’ method. Based on molecular docking, new antiviral drug designs have been found. They are DNY, NNY, DDY, DYY, RRR, RPR, RRP and LRL. These cyclic peptides showed better activity and affinity than standard ligand to inhibit neuraminidase activity. From drug scan, DNY, NNY and LRL ligands have low toxicity and were predicted to have at least 59% possibility that it could be synthesized in wet laboratory experiment. Key words : Influenza virus A, neuraminidase, cyclic peptide, structure based design, molecular docking.

Influenza M1 VLPs containing neuraminidase induce heterosubtypic cross-protection

Influenza virus like particles (VLPs) containing hemagglutinin were previously demonstrated to induce protection against the homologous strains. However, little information is available on the protective role of neuraminidase (NA), the second major glycoprotein. In this study, we developed VLPs (NA VLPs) containing NA and M1 derived from A/PR/8/34 (H1N1) influenza virus, and investigated their ability to induce protective immunity. Intranasal immunization with NA VLPs induced serum antibody responses to H1N1 and H3N2 influenza A viruses as well as significant neuraminidase inhibition activity. Importantly, mice immunized with NA VLPs were 100% protected against lethal infection by the homologous A/PR/8/34 (H1N1) as well as heterosubtypic A/Philippines/82 (H3N2) virus, although body weight loss was observed after lethal challenge with heterosubtypic H3N2 virus. The present study therefore provides evidence that influenza VLPs containing M1 and NA are capable of inducing immunity to homologous as well as antigenically distinct influenza A virus strains.

In vitro neuraminidase inhibitory activities of four neuraminidase inhibitors against influenza viruses isolated in the 2010-2011 and 2011-2012 influenza seasons in Japan

In vitro neuraminidase inhibitory activities of four neuraminidase inhibitors against influenza viruses isolated in the 2010-2011 and 2011-2012 influenza seasons in Japan

Pyrrolidinobenzoic acid inhibitors of influenza virus neuraminidase: The hydrophobic side chain influences type A subtype selectivity

Neuraminidase (NA) plays a critical role in the life cycle of influenza virus and is a target for new therapeutic agents. A series of influenza neuraminidase inhibitors with the pyrrolidinobenzoic acid scaffold containing lipophilic side chains at the C3 position have been synthesized and evaluated for influenza neuraminidase inhibitory activity. The size and geometry of the C3 side chains have been modified in order to investigate structure–activity relationships. The results indicated that size and geometry of the C3-side chain are important for selectivity of inhibition against N1 versus N2 NA, important type A influenza variants that infect man, including the highly lethal avian influenza.

In vitro neuraminidase inhibitory activity of four neuraminidase inhibitors against influenza virus isolates in the 2011–2012 season in Japan

The neuraminidase inhibitors oseltamivir phosphate (Tamiflu®), zanamivir (Relenza®), laninamivir octanoate (Inavir®), and peramivir (Rapiacta®) have been available for the treatment of influenza in Japan since 2010. To assess the extent of viral resistance, we measured the 50% inhibitory concentration (IC₅₀) of each drug for influenza virus isolates from the 2011-2012 influenza season. Specimens were obtained from patients prior to treatment. Viral isolation was done using Madine-Darby canine kidney cells, and the type and subtype of influenza A(H1N1)pdm09, A(H3N2), or influenza B were determined by RT-PCR using type- and subtype-specific primers. The IC₅₀ was determined by a neuraminidase inhibition assay using a fluorescent substrate. The lineage of influenza B virus was determined by direct sequencing of the hemagglutinin gene. Influenza A(H3N2) and influenza B viruses were isolated in 283 and 42 patients, respectively, while no influenza A(H1N1)pdm09 virus was isolated. No isolate showed an IC₅₀ value exceeding 50 nM for any of the neuraminidase inhibitors. IC50 values for A(H3N2) were similar between the 2010-2011 and 2011-2012 seasons. In contrast, the IC₅₀ values for influenza B viruses in the 2011-2012 season to the four drugs were significantly lower than those found in the 2010-2011 season. These results indicate that the currently epidemic influenza viruses are susceptible to all four neuraminidase inhibitors, with no trend for IC₅₀ values to increase in Japan at present.

ChemInform Abstract: Potent Inhibition of Bacterial Neuraminidase Activity by Pterocarpans Isolated from the Roots of Lespedeza bicolor.

AbstractSix pterocarpans, including the three new pterocarpans bicolosin A—C (I), displaying significant levels of neuraminidase inhibitory activity are isolated and characterized.

In vitro neuraminidase inhibitory activities of four neuraminidase inhibitors against influenza viruses isolated in the 2010–2011 season in Japan

The half maximal inhibitory concentration (IC(50)) of four neuraminidase inhibitors (NAIs), oseltamivir, zanamivir, laninamivir, and peramivir; was measured using influenza viruses isolated in the 2010-2011 influenza season in Japan. Clinical samples for viral isolation were obtained from nasal aspiration, nasopharyngeal swab, or self-blown nasal discharge and cultured with Madin-Darby canine kidney cells. The type and subtype of H3N2 or B were determined by reverse transcriptase polymerase chain reaction (RT-PCR). For the A(H1N1)pdm09 virus, the subtype was determined by real-time RT-PCR. IC(50)s to oseltamivir carboxylate, zanamivir, laninamivir, and peramivir were determined by a fluorescence-based neuraminidase inhibition assay. Influenza viruses were isolated from 269 patients. A(H1N1)pdm09, H3N2, and B were isolated from 185, 54, and 30 patients, respectively. The geometric means of IC(50) for oseltamivir were 0.86 and 0.73 nM to A (H1N1) pdm09, except for the two outlier viruses described below and H3N2, respectively, and 33.12 nM for B. The geometric means of IC(50) for the other three NAIs were lowest to A(H1N1)pdm09 and highest to B. Two A(H1N1)pdm09 isolates showed very high IC(50) values for oseltamivir (840 and 600 nM) and peramivir (19 and 24 nM). No isolate showed significantly high IC(50) values for zanamivir or laninamivir. Continuous surveillance against the emergence or spread of influenza virus with high IC(50) values for anti-influenza drugs is important.

P-Terphenyl and Diterpenoid Metabolites from Endophytic Aspergillus sp. YXf3

Six new p-terphenyl derivatives, named 4″-deoxy-3-hydroxyterphenyllin (1), 4″-deoxy-5'-desmethyl-terphenyllin (2), 5'-desmethylterphenyllin (3), 4″-deoxycandidusin A (4), 4,5-dimethoxycandidusin A (5), and terphenolide (6), four new diterpenoids with norcleistanthane (aspergiloid A (12) and aspergiloid B (13)), cleistanthane (aspergiloid C (14)), and isopimarane (aspergiloid D (15)) type skeletons, and five known p-terphenyl compounds (7-11) were isolated from the fermentation broth of the plant endophytic fungus Aspergillus sp. Their structures were elucidated on the basis of detailed spectroscopic analysis and by comparison of their NMR data with those reported in the literature. Compounds 4, 6, 7, and 9 displayed moderate neuraminidase inhibitory activity with IC(50) values ranging from 4.34 to 9.17 μM.

Synthesis and biological evaluation of sialic acid derivatives containing a long hydrophobic chain at the anomeric position and their C-5 linked polymers as potent influenza virus inhibitors

Conversions of the C-5 acetamide group in sialic acid into two kinds of CC double bond substituents were accomplished under Shotten–Baumann conditions. The polymerizable glycomonomers also contain a hydrophobic chain or hydroxyl group at the anomeric position. Radical polymerizations of the fully protected glycomonomers were carried out with acryl amide in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED), followed by deprotection to furnish water-soluble glycopolymers. The activities of the deprotected glycopolymers and glycomonomers against human influenza viruses (H1N1 and H3N2) and avian influenza virus (H5N3) were evaluated. Biological evaluations showed that the glycomonomers containing a long hydrophobic chain at the anomeric position had both hemagglutination and neuraminidase inhibitory activities.