Anti-picornavirus activity of synthetic flavon-3-yl esters

Synthesis and Anti-Rhinovirus Properties of Fluoro-Substituted Flavonoids

Fluoro-substituted flavones and 2-styrykhromones, related to natural and synthetic flavonoids previously described, were prepared, characterized and tested for anti-rhinovirus activity. Structural elucidation of the new compounds was performed by IR, NMR spectra and X-ray crystal structure analysis for 6-fluoro-3-hydroxy-2-styrylchromone. The antiviral potency was evaluated by a plaque reduction assay in HeLa cell cultures infected with rhinoviruses 1B and 14, selected as representative serotypes for viral groups B and A of human rhinoviruses, respectively. In comparison with results previously obtained, the introduction of the fluorine atom seems to exert a positive influence on the activity against serotype 14 while counteracting the effect against serotype 1B.

Synthesis and Evaluation of Antirhinovirus Activity of 3-Hydroxy and 3-Methoxy 2-Styrylchromones

Recently, we identified 2-styrylchromones as a new class of antirhinovirus flavonoids with moderate activity against both rhinovirus groups A and B. In order to improve the antiviral effect of the first series of tested 2-styrylchromones, a hydroxy or methoxy group was introduced in position 3 of the chromone ring. Cytotoxicity and antiviral activity of the new synthesized compounds were evaluated in HeLa cell cultures infected with rhinoviruses 1B and 14, selected as representative serotypes for viral groups B and A of human rhinoviruses (HRVs), respectively. These antiviral results compared to those obtained for 3-unsubstituted 2-styrylchromones indicate the greater potency of 3-hydroxy and 3-methoxy derivatives against both serotypes.

Recent developments in antiviral agents against enterovirus 71 infection

Enterovirus 71 (EV-71) is the main etiological agent of hand, foot and mouth disease (HFMD). Recent EV-71 outbreaks in Asia-Pacific were not limited to mild HFMD, but were associated with severe neurological complications such as aseptic meningitis and brainstem encephalitis, which may lead to cardiopulmonary failure and death. The absence of licensed therapeutics for clinical use has intensified research into anti-EV-71 development. This review highlights the potential antiviral agents targeting EV-71 attachment, entry, uncoating, translation, polyprotein processing, virus-induced formation of membranous RNA replication complexes, and RNA-dependent RNA polymerase. The strategies for antiviral development include target-based synthetic compounds, anti-rhinovirus and poliovirus libraries screening, and natural compound libraries screening. Growing knowledge of the EV-71 life cycle will lead to successful development of antivirals. The continued effort to develop antiviral agents for treatment is crucial in the absence of a vaccine. The coupling of antivirals with an effective vaccine will accelerate eradication of the disease.

Antiviral drug discovery for the treatment of enterovirus 71 infections

Enterovirus 71 (EV71) is a small, positive-sense, single-stranded RNA virus in the genus Enterovirus, family Picornavirus. It causes hand, foot and mouth disease in infants and children, which in a small percentage of cases progresses to central nervous system infection, ranging from aseptic meningitis to fatal encephalitis. Sporadic cases of EV71 infection occur throughout the world, but large epidemics have occurred recently in Southeast Asia and China. There are currently no approved vaccines or antiviral therapies for the prevention or treatment of EV71 infection. This paper reviews efforts to develop antiviral therapies against EV71.

Microplate assay for screening the antibacterial activity of Schiff bases derived from substituted benzopyran-4-one

Schiff bases (SB(1)-SB(3)) were synthesized from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one with 2-aminopyridine (SB(1)), p-phenylenediamine (SB(2)) and o-phenylenediamine (SB(3)), while Schiff bases (SB(4)-SB(6)) were synthesized by condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one with 2-aminopyridine (SB(4)), p-phenylenediamine (SB(5)) and o-phenylenediamine (SB(6)). Schiff bases were characterized using elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and mass spectroscopy. These compounds were screened for antibacterial activities by micro-plate assay technique. Escherichia coli and Staphylococcus capitis were exposed to different concentrations of the Schiff bases. Results showed that the antibacterial effect of these Schiff bases on Gram-negative bacteria were higher than that on Gram-positive bacteria moreover, the Schiff bases containing substituent OCH(3) on position five have higher antibacterial activity than that containing hydroxy group on the same position.

Selective inhibitors of picornavirus replication

Picornaviruses cover a large family of pathogens that have a major impact on human but also on veterinary health. Although most infections in man subside mildly or asymptomatically, picornaviruses can also be responsible for severe, potentially life-threatening disease. To date, no therapy has been approved for the treatment of picornavirus infections. However, efforts to develop an antiviral that is effective in treating picornavirus-associated diseases are ongoing. In 2007, Schering-Plough, under license of ViroPharma, completed a phase II clinical trial with Pleconaril, a drug that was originally rejected by the FDA after a New Drug Application in 2001. Rupintrivir, a rhinovirus protease inhibitor developed at Pfizer, reached clinical trials but was recently halted from further development. Finally, Biota's HRV drug BTA-798 is scheduled for phase II trials in 2008. Several key steps in the picornaviral replication cycle, involving structural as well as non-structural proteins, have been identified as valuable targets for inhibition. The current review aims to highlight the most important developments during the past decades in the search for antivirals against picornaviruses.

Effects of sea buckthorn berries on infections and inflammation: a double-blind, randomized, placebo-controlled trial

OBJECTIVE

To study the effect of sea buckthorn berries on the number and duration of common cold (CC) infections. As secondary objectives the effects on digestive and urinary tract infections (DTI, UTI), and serum C-reactive protein (CRP) concentrations were also investigated.

SUBJECTS

A total of 254 healthy volunteers were randomly assigned to receive sea buckthorn or placebo product during the study, which 233 of them completed.

RESULTS

There were no significant differences in the number or duration of CC or DTI between groups (CC: relative risks (sea buckthorn vs placebo) for the number and duration were 1.15 (95% CI 0.90-1.48) and 1.05 (95% CI 0.87-1.27), respectively). In the sea buckthorn group, as compared to the placebo, the serum CRP concentrations decreased significantly (difference in median change -0.059 mg/l, P=0.039). The number of UTI was too small to draw solid conclusions, but the results indicate the subject merits further investigation.

CONCLUSION

Sea buckthorn berries did not prevent CC or DTI. However, a reductive effect on CRP, a marker of inflammation, and a risk factor for cardiovascular diseases, was detected.

Antiviral activities of some Ethiopian medicinal plants used for the treatment of dermatological disorders

Acokanthera schimperi (Apocynaceae), Euclea schimperi (Ebenaceae), Inula confertiflora (Asteraceae), Melilotus elegans (Leguminosae), and Plumbago zeylanica (Plumbaginaceae), are some of the medicinal plants used in Ethiopia for treatment of various skin disorders. In this study, the antiviral activities of the 80% methanolic extracts of these plants have been examined against coxsackievirus B3 (CVB3), influenza A virus and herpes simplex virus type1 Kupka (HSV-1) using cytopathic effect (CPE) inhibitory assays in HeLa, MDCK, and GMK cells, respectively. In parallel, the cytotoxicity was quantified using a crystal violet uptake assay. The antiviral activity of the most active compound was confirmed with plaque reduction assays. The results revealed that the extracts of Acokanthera schimperi and Euclea schimperi showed antiviral activity against all three tested viruses albeit with unequal efficacy. Whereas the Acokanthera schimperi extract exhibited the strongest activity against CVB3, the extract of Euclea schimperi inhibited influenzavirus A replication most effectively. A weak anti-influenzavirus A activity was also exhibited by the other plant extracts tested. In addition, CVB3 was inhibited by the extracts of Plumbago zeylanica and HSV-1 by Inula confertiflora. Thus, the extracts of these plants, particularly those of Acokanthera schimperi, Euclea schimperi and Inula confertiflora which showed activity against CVB3 and HSV-1 support their traditional use in the treatment of skin diseases of viral origin.

Selective human enterovirus and rhinovirus inhibitors: An overview of capsid-binding and protease-inhibiting molecules

The absence of effective vaccines for most viral infections highlights an urgent necessity for the design and development of effective antiviral drugs. Due to the advancement in virology since the late 1980s, several key events in the viral life cycle have been well delineated and a number of molecular targets have been validated, culminating in the emergence of many new antiviral drugs in recent years. Inhibitors against enteroviruses and rhinoviruses, responsible for about half of the human common colds, are currently under active investigation. Agents targeted at either viral protein 1 (VP1), a relatively conserved capsid structure mediating viral adsorption/uncoating process, or 3C protease, which is highly conserved among different serotypes and essential for viral replication, are of great potential to become antipicornavirus drugs.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Synthesis and anti-rhinovirus activity of 2-styrylchromones

2-Styrylchromones were synthesized as vinylogues of 2-phenylchromones (flavones), a broad class of anti-rhinovirus compounds. The antiviral activity of 2-styrylchromones and 3-hydroxy-1-(2-hydroxyphenyl)-5-phenyl-2,4-pentadien-1-ones, which are intermediates in the synthesis, was evaluated against two selected serotypes of human rhinovirus, 1B and 14, by a plaque reduction assay in HeLa cell cultures. All of the compounds interfered with HRV 1B replication, with the exception of 3-hydroxy-1-(2-hydroxyphenyl)-5-(4-methoxyphenyl)-2,4-pentadien-1-one. The majority of derivatives were also found to be effective against serotype 14, often with a higher potency.