Antiviral effects of glycosylation and glucose trimming inhibitors on human parainfluenza virus type 3

Efficient synthesis for each of the eight stereoisomers of the iminosugars lentiginosine and 1,4-dideoxy-1,4-imino-D-arabinitol (DAB)

Herein, we describe the efficient, diastereoselective syntheses of the iminosugars 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) 1b, lentiginosine 3a, and the seven stereoisomers of each of these iminosugars starting from 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 with yields ranging from 38 % to 68 % for the DAB and isomers 1a-1h and from 44 % to 89 % for the lentiginosine and isomers 3a-3h. We also report the syntheses of the eight stereoisomers of the 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 from commercially available sugars. Key to the iminosugar syntheses is a single multistep reaction that converts the 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 to a vinyl pyrrolidine through a one-pot zinc mediated reductive elimination, followed by a reductive amination and finally an intramolecular nucleophilic substitution. Strategic selection of the amine utilized in the reductive amination and the functionalization of the intermediate carbon-carbon double bond provides access to a vast array of iminosugars.

The genus Oxytropis DC: application, phytochemistry, pharmacology, and toxicity

OBJECTIVES

Oxytropis DC is a perennial plant of Fabaceae family, which is widely distributed in the northern temperate zone. It is known as "locoweed" because of its toxic component swainsonine. However, it is widely used in Tibetan medicine and Mongolian medicine, mainly for the treatment of heat-clearing and detoxifying, pain-relieving, anti-inflammatory, hemostasis, and other diseases. To provide a basis for the further development and utilization of Oxytropis DC, the pieces of literature about the application, phytochemistry, pharmacological action, and toxicity of Oxytropis DC were reviewed and analyzed.

KEY FINDINGS

A total of 373 chemical constituents were found from Oxytropis DC, including flavonoids, alkaloids, steroids, terpenoids, and others. Pharmacological actions mainly include antitumor, antioxidation, anti-inflammatory, analgesic, antibacterial, antifibrosis, and other pharmacological actions, among them, the antitumor effect is particularly prominent.

SUMMARY

At present, studies on its pharmacological effects are mainly concentrated on the extracts, some flavonoids, and alkaloids. In the follow-up studies, research on the pharmacological activities of the other chemical constituents in Oxytropis should be strengthened. It has the potential to pave the way for research and development of novel Oxytropis medicines.

Research Progress of α-Glucosidase Inhibitors Produced by Microorganisms and Their Applications

Based on the easy cultivation of microorganisms and their short cycle time, research on α-glucosidase inhibitors (α-GIs) of microbial origin is receiving extensive attention. Raw materials used in food production, such as cereals, dairy products, fruits, and vegetables, contain various bioactive components, like flavonoids, polyphenols, and alkaloids. Fermentation with specific bacterial strains enhances the nutritional value of these raw materials and enables the creation of hypoglycemic products rich in diverse active ingredients. Additionally, conventional food processing often results in significant byproduct generation, causing resource wastage and environmental issues. However, using bacterial strains to ferment these byproducts into α-GIs presents an innovative solution. This review describes the microbial-derived α-GIs that have been identified. Moreover, the production of α-GIs using industrial food raw materials and processing byproducts as a medium in fermentation is summarized. It is worth analyzing the selection of strains and raw materials, the separation and identification of key compounds, and fermentation broth research methods. Notably, the innovative ideas in this field are described as well. This review will provide theoretical guidance for the development of microbial-derived hypoglycemic foods.

Metabolic Modifications by Common Respiratory Viruses and Their Potential as New Antiviral Targets

Respiratory viruses are known to be the most frequent causative mediators of lung infections in humans, bearing significant impact on the host cell signaling machinery due to their host-dependency for efficient replication. Certain cellular functions are actively induced by respiratory viruses for their own benefit. This includes metabolic pathways such as glycolysis, fatty acid synthesis (FAS) and the tricarboxylic acid (TCA) cycle, among others, which are modified during viral infections. Here, we summarize the current knowledge of metabolic pathway modifications mediated by the acute respiratory viruses respiratory syncytial virus (RSV), rhinovirus (RV), influenza virus (IV), parainfluenza virus (PIV), coronavirus (CoV) and adenovirus (AdV), and highlight potential targets and compounds for therapeutic approaches.

Selective Golgi α-mannosidase II inhibitors: N-alkyl substituted pyrrolidines with a basic functional group

Enzymatic assays, molecular modeling and NMR studies of novel 1,4-dideoxy-1,4-imino-l-lyxitols provided new information on the GH38 family enzyme inhibitors and their selectivity.

A ratiometric fluorescent probe for the detection of β-galactosidase and its application

Herein, a coumarin fluorescent probe (Probe 1) was developed for the ratiometric detection of β-galactosidase (β-gal) activity. The detection range was 0–0.1 U mL⁻¹ and 0.2–0.8 U mL⁻¹, and the limit of detection (LOD) was 0.0054 U mL⁻¹. Moreover, the luminous intensity of Probe 1 increased gradually with increase in β-gal activity. It could be observed under 254 nm UV irradiation by the naked eye. Furthermore, this method only required a small amount of sample (20 μL) and a short analytical time (30 min) for the detection of β-gal activity with a low LOD. Probe 1 was successfully used to detect β-gal activity in real fruit samples, and can be applied to the quantitative and qualitative detection of β-gal activity.

A ratiometric fluorescent probe was successfully used as a tool to determine β-galactosidase activity in fruits.

Natural Products Database Screening for the Discovery of Naturally Occurring SARS-Cov-2 Spike Glycoprotein Blockers

SARS-CoV-2 coronavirus has been recognized the causative agent of the recent and ongoing pandemic. Effective and specific antiviral agents or vaccines are still missing, despite a large plethora of compounds have been proposed and tested worldwide. New compounds are requested urgently and virtual screening can offer fast and robust predictions to investigate. Moreover, natural compounds were shown to exert antiviral effects and can be endowed with limited side effects and wide availability. Our approach consisted in the validation of a docking protocol able to refine the most suitable candidates, within the 31000 natural compounds of the natural product activity and species source (NPASS) library, interacting with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein. After the refinement process two natural compounds, castanospermine and karuquinone B, were shown to be the best-in-class derivatives in silico able to target an essential structure of the virus and to act in the early stage of infection.

1-Deoxynojirimycin: Occurrence, Extraction, Chemistry, Oral Pharmacokinetics, Biological Activities and In Silico Target Fishing

1-Deoxynojirimycin (DNJ, C₆H13NO₄, 163.17 g/mol), an alkaloid azasugar or iminosugar, is a biologically active natural compound that exists in mulberry leaves and Commelina communis (dayflower) as well as from several bacterial strains such as Bacillus and Streptomyces species. Deoxynojirimycin possesses antihyperglycemic, anti-obesity, and antiviral features. Therefore, the aim of this detailed review article is to summarize the existing knowledge on occurrence, extraction, purification, determination, chemistry, and bioactivities of DNJ, so that researchers may use it to explore future perspectives of research on DNJ. Moreover, possible molecular targets of DNJ will also be investigated using suitable in silico approach.

Simple Indolizidine and Quinolizidine Alkaloids

This review of simple indolizidine and quinolizidine alkaloids (i.e., those in which the parent bicyclic systems are in general not embedded in polycyclic arrays) is an update of the previous coverage in Volume 55 of this series (2001). The present survey covers the literature from mid-1999 to the end of 2013; and in addition to aspects of the isolation, characterization, and biological activity of the alkaloids, much emphasis is placed on their total synthesis. A brief introduction to the topic is followed by an overview of relevant alkaloids from fungal and microbial sources, among them slaframine, cyclizidine, Steptomyces metabolites, and the pantocins. The important iminosugar alkaloids lentiginosine, steviamine, swainsonine, castanospermine, and related hydroxyindolizidines are dealt with in the subsequent section. The fourth and fifth sections cover metabolites from terrestrial plants. Pertinent plant alkaloids bearing alkyl, functionalized alkyl or alkenyl substituents include dendroprimine, anibamine, simple alkaloids belonging to the genera Prosopis, Elaeocarpus, Lycopodium, and Poranthera, and bicyclic alkaloids of the lupin family. Plant alkaloids bearing aryl or heteroaryl substituents include ipalbidine and analogs, secophenanthroindolizidine and secophenanthroquinolizidine alkaloids (among them septicine, julandine, and analogs), ficuseptine, lasubines, and other simple quinolizidines of the Lythraceae, the simple furyl-substituted Nuphar alkaloids, and a mixed quinolizidine-quinazoline alkaloid. The penultimate section of the review deals with the sizable group of simple indolizidine and quinolizidine alkaloids isolated from, or detected in, ants, mites, and terrestrial amphibians, and includes an overview of the "dietary hypothesis" for the origin of the amphibian metabolites. The final section surveys relevant alkaloids from marine sources, and includes clathryimines and analogs, stellettamides, the clavepictines and pictamine, and bis(quinolizidine) alkaloids.

Antiviral drug discovery: broad-spectrum drugs from nature

Covering: up to April 2014. The development of drugs with broad-spectrum antiviral activities is a long pursued goal in drug discovery. It has been shown that blocking co-opted host-factors abrogates the replication of many viruses, yet the development of such host-targeting drugs has been met with scepticism mainly due to toxicity issues and poor translation to in vivo models. With the advent of new and more powerful screening assays and prediction tools, the idea of a drug that can efficiently treat a wide range of viral infections by blocking specific host functions has re-bloomed. Here we critically review the state-of-the-art in broad-spectrum antiviral drug discovery. We discuss putative targets and treatment strategies, with particular focus on natural products as promising starting points for antiviral lead development.

Deoxysugars as antituberculars and alpha-mannosidase inhibitors

A promising modified sugar molecule was identified which was active against multidrug-resistant (MDR) strains of Mycobacterium tuberculosis, suggesting involvement of a new target. The compound was demonstrated to be bactericidal, inhibited the growth of M. tuberculosis in mice, and targeted alpha-mannosidase as a competitive inhibitor with a Ki value of 353.9 μM.

Role of N-linked glycosylation of the human parainfluenza virus type 3 hemagglutinin-neuraminidase protein

Human parainfluenza virus type 3 (hPIV-3) is a major respiratory tract pathogen that affects infants and young children. The hPIV-3 hemagglutinin-neuraminidase (HN) protein is a multifunctional protein mediating hemadsorption (HAD), neuraminidase (NA), and fusion promotion activities, each of which affects the ability of HN to promote viral fusion and entry. The hPIV-3 HN protein contains four potential sites (N308, N351, N485 and N523) for N-linked glycosylation. Electrophoretic mobility analysis of mutated HN proteins indicated that N308, N351 and N523 sites, but not the N485 site in HN protein, were targeted for the addition of glycans in BHK-21 cells. These functional glycosylation sites were systematically eliminated in various combinations from HN to form a panel of mutants in which the roles of individual carbohydrate chains and groups of carbohydrate chains could be analyzed. Removal of individual or multiple N-glycans on the hPIV-3 HN protein had no effects on transport to the cell surface, expression and NA activity. Single glycosylation site mutants (G1, G2 and G4) not only impaired fusion promotion activity but also reduced HAD activity of HN protein, which was even more obvious for all three double mutants (G12, G14 and G24) and the triple mutant (G124). In addition, every mutant protein retained F-interactive capability that was equal to the wild-type protein capability. Interestingly, the F protein that could be co-immunoprecipitated with the G12 mutated protein or immunoprecipitated with anti-F antibody was not efficiently cleaved. For G14, G24 and G124, little cleaved F protein was detected in co-immuoprecipitation F protein assay and its total amounts where in the cell lysates. The mechanism underlying hPIV-3 HN and F protein remained associated before and after receptor engagement and the strength of the HN-receptor interaction modulated the activation of F the protein which could determine the extent of fusion. Finally, we demonstrated that single or multiple N-glycosylation site mutations inhibited fusion at the earliest stages. Taken together, these results indicated that N-glycosylation of hPIV-3 HN is critical to its receptor recognition activity, cleavage of the F protein, and fusion promotion activity, but had no influence on its interaction with the homologous F protein and NA activity.

Unexpected cure from cutaneous leukocytoclastic vasculitis in a patient treated with N-butyldeoxynojirimycin (miglustat) for Gaucher disease

Cutaneous leukocytoclastic vasculitis (CLV) is a necrotizing inflammation of the small vessels in the dermis. We report the case of a Swedish man with an untreated N370S/L444P Gaucher disease who developed CLV at the age of 79 years. The patient has been treated for CLV with topical and oral corticosteroids, moisturizing agents, and periodically with antibiotics for 3 years without improvement. Administration of miglustat (N-butyldeoxynojirimycin; Zavesca®) because of progress of Gaucher disease resulted in a prompt and durable cure of the CLV.

The endoplasmic reticulum protein folding factory and its chaperones: new targets for drug discovery?

Cytosolic heat shock proteins have received significant attention as emerging therapeutic targets. Much of this excitement has been triggered by the discovery that HSP90 plays a central role in the maintenance and stability of multifarious oncogenic membrane receptors and their resultant tyrosine kinase activity. Numerous studies have dealt with the effects of small molecules on chaperone- and stress-related pathways of the endoplasmic reticulum (ER). However, unlike cytosolic chaperones, relatively little emphasis has been placed upon translational avenues towards targeting of the ER for inhibition of folding/secretion of disease-promoting proteins. Here, we summarise existing small molecule inhibitors and potential future targets of ER chaperone-mediated inhibition. Client proteins of translational relevance in disease treatment are outlined, alongside putative future disease treatment modalities based on ER-centric targeted therapies. Particular attention is paid to cancer and autoimmune disorders via the effects of the GRP94 inhibitor geldanamycin and its population of client proteins, overloading of the unfolded protein response, and inhibition of members of the IL-12 family of cytokines by celecoxib and non-coxib analogues.

Diastereoselective nitrenium ion-mediated cyclofunctionalization: total synthesis of (+)-castanospermine

The asymmetric total synthesis of the α-glucosidase inhibitor (+)-castanospermine is reported. The central theme in our approach to this polyhydroxylated alkaloid is the simultaneous generation of the piperidine ring and the C-1/8a erythro stereodiad through the diastereoselective, oxamidation of an unsaturated O-alkyl hydroxamate. This process is believed to proceed sequentially via singlet acylnitrenium and aziridinium ion intermediates.

N-Butyldeoxynojirimycin is a broadly effective anti-HIV therapy significantly enhanced by targeted liposome delivery

OBJECTIVE

N-Butyldeoxynojirimycin (NB-DNJ), an inhibitor of HIV gp120 folding, was assessed as a broadly active therapy for the treatment of HIV/AIDS. Furthermore, to reduce the effective dose necessary for antiviral activity, NB-DNJ was encapsulated inside liposomes and targeted to HIV-infected cells.

METHODS

Thirty-one primary isolates of HIV (including drug-resistant isolates) were cultured in peripheral blood mononuclear cells to quantify the effect of NB-DNJ on viral infectivity. pH-sensitive liposomes capable of mediating the intracellular delivery of NB-DNJ inside peripheral blood mononuclear cells were used to increase drug efficacy.

RESULTS

NB-DNJ decreased viral infectivity with a single round of treatment by an average of 80% in HIV-1-infected and 95% in HIV-2-infected cultures. Two rounds of treatment reduced viral infectivity to below detectable levels for all isolates tested, with a calculated IC50 of 282 and 211 micromol/l for HIV-1 and HIV-2, respectively. When encapsulated inside liposomes, NB-DNJ inhibited HIV-1 with final concentrations in the nmol/l range (IC50 = 4 nmol/l), a 100 000-fold enhancement in IC50 relative to free NB-DNJ. Targeting liposomes to the gp120/gp41 complex with a CD4 molecule conjugated to the outer bilayer increased drug/liposome uptake five-fold in HIV-infected cells compared with uninfected cells. NB-DNJ CD4 liposomes demonstrated additional antiviral effects, reducing viral secretion by 81% and effectively neutralizing free viral particles to prevent further infections.

CONCLUSION

The use of targeted liposomes encapsulating NB-DNJ provides an attractive therapeutic option against all clades of HIV, including drug-resistant isolates, in an attempt to prevent disease progression to AIDS.

Pathobiology of virus glycosylation: implications to disease and prospects for treatment

Changes to the overall glycosylation profile of viral glycoproteins have been shown to be advantageous to virus survival and virulence. Many human viral pathogens rely on specific oligosaccharides to evade detection by the host immune system. Viruses such as HIV, Hendra, SARS-CoV, influenza, respiratory syncytial virus, hepatitis and West Nile virus rely on N-linked and O-Linked glycosylation for critical functions such as entry into host cells, proteolytic processing and protein trafficking. Recent findings demonstrate the importance of glycosylation to viral virulence, infectivity and immune evasion in several virus families impacting on human health. This review considers the role of glycosylation in viral infection and will detail several potential therapies for these important human pathogens and emerging infections.

Inhibition of human parainfluenza virus type 3 infection by novel small molecules

Human parainfluenza virus type 3 (HPIV3) is an important respiratory tract pathogen of infants and children. There are no vaccines or antivirals currently approved for prevention or treatment of HPIV3 infection. Towards developing an antiviral therapy to combat HPIV3 infection, we have established a green fluorescent protein (GFP)-tagged HPIV3 infected-cell assay and used it for screening of a small molecule library obtained from ChemBridge Diver. Two novel small molecules (C5 and C7) which shared structural similarities were identified and their inhibitory effects on HPIV3 were confirmed in CV-1 and human lung epithelium A549 cells by plaque assay, Western blot and Northern blot analyses. C5 and C7 effectively prevented the cytopathic effect in cells infected with HPIV3, achieving IC(50) values of 2.36 microM and 0.08 microM, respectively, for infectious virus production. The inhibition appears to be at the primary transcriptional level of HPIV3 life cycle based on sequential time course test, binding and internalization assays, and finally by a minigenome transcription assay in cells as well as measuring viral transcripts in cells in the presence of anisomycin. Interestingly, vesicular stomatitis virus (VSV), another member of mononegavirales order, was also inhibited by these compounds, whereas poliovirus-a picornavirus was not. Use of these inhibitors has a strong potential to develop novel antiviral agents against this important human pathogen.

Entry of hepatitis C virus and human immunodeficiency virus is selectively inhibited by carbohydrate-binding agents but not by polyanions

We studied the antiviral activity of carbohydrate-binding agents (CBAs), including several plant lectins and the non-peptidic small-molecular-weight antibiotic pradimicin A (PRM-A). These agents efficiently prevented hepatitis C virus (HCV) and human immunodeficiency virus type 1 (HIV-1) infection of target cells by inhibiting the viral entry. CBAs were also shown to prevent HIV and HCV capture by DC-SIGN-expressing cells. Surprisingly, infection by other enveloped viruses such as herpes simplex viruses, respiratory syncytial virus and parainfluenza-3 virus was not inhibited by these agents pointing to a high degree of specificity. Mannan reversed the antiviral activity of CBAs, confirming their association with viral envelope-associated glycans. In contrast, polyanions such as dextran sulfate-5000 and sulfated polyvinylalcohol inhibited HIV entry but were devoid of any activity against HCV infection, indicating that they act through a different mechanism. CBAs could be considered as prime drug leads for the treatment of chronic viral infections such as HCV by preventing viral entry into target cells. They may represent an attractive new option for therapy of HCV/HIV coinfections. CBAs may also have the potential to prevent HCV/HIV transmission.