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Effects of polyphenol compounds on influenza A virus replication
and definition of their mechanism of action
Rossella Fioravanti
, Ignacio Celestino
, Roberta Costi
, Giuliana Cuzzucoli Crucitti
, Luca Pescatori
Leonardo Mattiello
, Ettore Novellino
, Paola Checconi
, Anna Teresa Palamara
, Lucia Nencioni
Roberto Di Santo
Istituto Pasteur Cenci Bolognetti - Dip. Chimica e Tecnologie del Farmaco, ‘‘Sapienza’’ University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
Istituto Pasteur Cenci Bolognetti - Dip. Sanità Pubblica e Malattie Infettive, ‘‘Sapienza’’ University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
Dipartimento di Dip. di Scienze di Base e Applicate per l’Ingegneria, ‘‘Sapienza’’ University of Rome, Via del Castro Laurenziano 7, 00161 Rome, Italy
Dipartimento di Chimica Farmaceutica e Tossicologica, Università di Napoli ‘‘Federico II’’, Via D. Montesano 49, 80131 Napoli, Italy
San Raffaele Pisana Istituto Scientifico di Ricerca e Cura, Via della Pisana 235, 00166 Rome, Italy
article info
Article history:
Received 21 March 2012
Revised 16 May 2012
Accepted 25 May 2012
Available online 4 June 2012
A set of polyphenol compounds was synthesized and assayed for their ability in inhibiting influenza A
virus replication. A sub-set of them showed low toxicity. The best compounds within this sub-set were
4and 6g, which inhibited the viral replication in a dose-dependent manner. The antiviral activity of these
molecules was demonstrated to be caused by their interference with intracellular pathways exploited for
viral replication: (1) MAP kinases controlling nuclear-cytoplasmic traffic of viral ribonucleoprotein com-
plex; (2) redox-sensitive pathways, involved in maturation of viral hemagglutinin protein.
Ó2012 Elsevier Ltd. All rights reserved.
1. Introduction
Each year influenza A viruses (IAV) cause thousands of deaths
and hospitalizations. The pandemic caused by the 2009 influenza
A (H1N1) virus—the first of the 21st century—was characterized
mainly by mild-moderate infections similar to those seen with
seasonal influenza,
but several cases of acute respiratory distress
syndrome and pneumonia in previously healthy persons were also
Influenza A viruses are enveloped, negative strand RNA
viruses belonging to the Orthomyxoviridae family. Their genome
consists of eight single-stranded RNA segments encoding 11 pro-
teins including hemagglutinin (HA), one of the main surface glyco-
The receptor binding site of HA is necessary for the virus
to bind galactose-bound sialic acid on the surface of host-cells, and
16 different subtypes have been isolated thus far from different
Influenza virus replication has been studied in depth, and
several antiviral agents all targeting viral structures, have been
Among them, amantadine and rimantadine have a spe-
cific inhibitory effect on type A but not on type B influenza viruses.
These agents block the ion-channel activity of the viral matrix (M2)
protein, which is mainly required for virus uncoating.
the viral neuraminidase (NA) inhibitors such as oseltamivir, zanam-
ivir, and peramivir are the mainstay of pharmacological protocols to
fight global influenza pandemics.
However, the long-term efficacy
of these inhibitors is often limited by their toxicity and by the high
incidence in the selection of drug-resistant viral mutants that is al-
most certain.
Actually, the main effort of the preclinical research
is addressed to block the viral replication by interfering with path-
ogen-exploited host-cell machinery.
This approach could give
important advantages, including the broad-spectrum efficacy, the
antigenic properties, and the reduced probability to select drug-
resistant viral strains.
In particular, a very promising and innova-
tive strategy to develop new antiviral agents could be based on the
inhibition of intracellular pathways that are specifically activated
by influenza virus to ensure its replication.
Interestingly, many
of these pathways are highly sensitive to changes in the intracellu-
lar redox state,
and as a matter of fact their activation is induced
by the oxidative stress caused by infections by DNA or RNA virus,
including influenza.
Dietary polyphenols, such as resveratrol (RV) [5-[(1E)-2-(4-
hydroxyphenyl)ethenyl]-1,3-benzenediol (found in red wine) and
curcumin [diferuloyl methane; 1,7-bis-(4-hydroxy-3-methoxy-
0968-0896/$ - see front matter Ó2012 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.:+39 6 49693247.
E-mail address: (R. Costi).
Authors to indicate that they contributed equally to the work.
Bioorganic & Medicinal Chemistry 20 (2012) 5046–5052
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
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phenyl)-1,6-heptadiene-3,5-dione] (found in curry powder), were
reported to posses anticancer,
antiviral properties.
Curcumin is a colouring compound present in the rhizome of Cur-
cuma longa L. It has been used for thousands of years in Southeast
Asia and Indian folk medicine to treat various diseases and eradicate
health problems.
It shows many pharmacological properties
including anti-inflammatory,
antioxidant, iron-chelating, and
some other activities.
For example, the antioxidant activity of cur-
cumin is responsible for its ability to decrease the incidence of colon
cancer, and for its anti-atherogenic property.
It has cytoprotective
effect on PC12 cells against 1-methyl-4-phenylpridinium ions-in-
duced neurotoxicity through the anti-apoptotic and anti-oxidative
properties of the Bcl-2-mitochondria-ROS-iNOS pathway.
cently, curcumin has been proven to exert anti-influenza activity
by inhibition of the virus-cell attachment. These studies demon-
strated that treatment of cells with curcumin greatly reduced the
yield of IAV at sub-cytotoxic doses. Pre-incubation of virus with cur-
cumin pronouncedly inhibited influenza virus plaque formation.
Unfortunately, curcumin is water insoluble, poorly dissolves in
organic phase, and shows low bioavailability in vivo after oral
It is unstable at neutral-basic pH values and
in serum-free medium degrading to vanillin, ferulic acid, feruloyl
methane and trans-6-(40-hydroxy-30-methoxy-phenyl)-2,4-di-
RV is a very interesting polyphenol belonging to the stilbene
family. It is found in several fruits, vegetables and beverages
including red wine. It is one of the most important plant polyphe-
nols with proven salutary activity on animal health. The most
important source of polyphenols and in particular RV for human
diet is grape (Vitis vinifera).
In the last two decades the potential protective effects of RV
against cardiovascular
and neurodegenerative diseases,
as well
as the chemo-preventive properties against cancer,
have been
largely investigated. RV appears to be capable of interfering with
several intracellular signaling pathways, including those activated
by protein kinase C (PKC) and by mitogen-activated protein kinases
RV has been also reported to exert an antiviral activity in differ-
ent experimental systems.
A few years ago, we showed that
RV inhibits influenza virus replication in vitro and it is also effec-
tive in increasing the survival of influenza virus-infected mice.
Surprisingly, these effects are not related to its well-known antiox-
idant activity. They are rather related to the inhibition of intracel-
lular pathways JNK (c-Jun N-terminal kinase) and p38MAPK
involved in regulation of viral ribonucleoprotein (vRNP) complex
traffic across the nuclear membrane, a key step of viral replication
cycle that precedes viral assembly and release.
The biological activity of RV is limited by its low bioavailability
and metabolic instability. In fact, stilbene double bond is readily
oxidized by cytochrome P450 monooxygenases into highly reac-
tive epoxides, that may act as carcinogenic metabolites.
ther, under UV irradiation, RV converts to the (Z)-isomer
this was claimed as one of the reason for the presence of small
amounts of (Z)-resveratrol in wines. The conversion from (E)- to
(Z)-configuration makes resveratrol less stable
and consequently
decreases its biological activity.
Therefore, pursuing our studies on compounds active against
influenza and taking advantage of our experience in the synthesis
of polyhydroxylated analogues,
we decided to synthesize a num-
ber of curcumin and resveratrol analogues with the aim of obtain-
ing compounds with improved ability in interfering with the cell
pathways exploited by the virus for its replication, such as kinase
pathways and intracellular redox state. These compounds were
evaluated for their antiviral activity and their structures are
reported in Figure 1.
2. Chemistry
All derivatives tested except 6b, were prepared as reported in
Method of synthesis of compound 6b, chemical
and physical data are reported in Supplementary data.
3. Result
In a first set of experiments the cytotoxicity of the compounds
has been evaluated in a test on confluent monolayers of MDCK cells.
Cells were plated at concentration of 2 10
/ml, treated after 24 h
with various concentrations (range 5–40
g/ml) of the synthesized
compounds ( 1, 2, 3, 4, 5, 6a–m), and incubated for the following
24 h. Microscopical examination, Trypan blue exclusion and cells
counts demonstrated that the compounds 1, 2, 3, 5, 6a, 6b, 6d,
6e, 6h, 6i, 6l and 6m, produced a dose-dependent toxic effect.
Indeed, morphological alterations, loss of cells viability and modifi-
cation of cell multiplication rate in treated cells were observed
(data not shown). These substances have been excluded for the fol-
lowing experiments. On the contrary, the treatment with the other
compounds did not induce any toxicity on cell monolayer, even if
the compound 6g caused a slight alteration of cell morphology
starting from 20
g/ml and the compounds 4, 6c, and 6f starting
from 40
g/ml. These results were further confirmed using the
Comp. X
2 CH2
4 O
5 N-(CH2)2-CH3
Comp. R R1 R
2 R
3 R
4 R
5 R
6a H H H H OH OH H
6e H NH2 H H OH OH H
6f OH H H H H Cl H
6i OH H OH H H CH3 H
6m OH H OCH3 H H F H
Figure 1. Structures of curcumin and resveratrol analogues.
R. Fioravanti et al./ Bioorg. Med. Chem. 20 (2012) 5046–5052 5047
3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide (MTT)
proliferation assay (data not shown).
3.1. Compounds 4 and 6g inhibit late phases of influenza virus
First, to assess whether the compounds that did not cause toxic
effect on cells, could exert an antiviral effect on influenza virus rep-
lication, confluent monolayers of MDCK cells highly permissive to
influenza virus replication, were infected with influenza A/Puerto
Rico/8/34 H1N1 (PR8) virus at low multiplicity of infection (0.01
M.O.I.) to allow multi-cycle replication. One hr after adsorption
the cells were washed and different concentrations of compounds
or DMSO (control infected CI cells) were added to MDCK and main-
tained for the duration of the experiment. As shown in Figure 2A,
24 h post infection (p.i.) virus titer, measured as the amount of virus
released into the cell supernatant by means of hemagglutinating
unit (HAU) assay, was dose-dependently (range 5–20
inhibited by compounds 4and 6g. In particular, viral replication
was markedly reduced by 10
g/ml of 6g (75% vs CI cells) and
by 20
g/ml of 4(75% vs CI cells) while the concentration of
g/ml of 6g was able to completely inhibit viral replication.
However, since it induced some alteration of the monolayer, we
chose to not use it for the following experiments. The compounds
6c and 6f were able to inhibit influenza virus in a dose-dependent
manner (data not shown), however the molecular mechanisms
underlying their anti-influenza activity are still under investigation.
Next, to identify the step(s) of the influenza virus life-cycle that
were affected by compounds 4and 6g, we first evaluated the effect
of these compounds on the PR8 virus alone. No significant antiviral
effect was detected when a stock solution of PR8 virus was incu-
bated for 1 h with 4or 6g and then used for infection. Similarly,
virus production was not affected when compounds were present
in cell culture medium only during the 1 h phase of viral adsorp-
tion or when MDCK cells underwent a overnight pre-infection
treatment with two compounds, with drugs washout right before
viral challenge (data not shown). Then, 4and 6g were added to
MDCK cells immediately after virus challenge and afterwards re-
moved at different time points (Fig. 2B). Post-infection treatment
with both compounds for 2 or 4 h produced no significant antiviral
effect, which confirmed that they did not act by preventing virus
entry into the cells. In MDCK exposed to 4or 6g for the first 6 h
after infection, slight decreases (about 30%) in viral replication
were noted 24 h p.i. More substantial inhibition was observed
when exposure was extended to the first 8 h (55%) or 24 h (75%)
p.i. In other experiments, the treatment was started at different
times after PR8 infection, and the compounds remained in the cell
culture medium through 24 h after infection (Fig. 2C).
The highest inhibition (about 79%) of viral replication was
achieved when treatment began 2 and 4 h after viral challenge.
When treatment was delayed until 6 h after infection, effects were
more limited but still observable and finally, when two compounds
were added 8 h p.i., no significant inhibition was noted. These data
indicate that the antiviral activity of the compounds is largely re-
lated to their inhibition of virus life-cycle steps occurring 2-8 h
p.i., and possibly related to post-transcriptional events.
3.2. Compound 4 inhibits expression of late viral proteins
Nucleoprotein (NP) is the most abundant influenza A viral pro-
tein that is synthesized immediately after infection, whereas the
major external glycoprotein hemagglutinin (HA), neuraminidase
(NA) and matrix protein 1 (M1) are late gene products.
In order
to determine whether the inhibition of viral replication was related
to the modulation of viral protein synthesis, the cells were infected
with PR8, and compounds 6g (10
g/ml) or 4(20
g/ml) were
immediately added after PR8 adsorption. Twenty-four hours after
infection, protein from cell lysates were separated by sodium
dodecyl sulfate-polyacrylammide gel electrophoresis in reducing
conditions and immunoblotted with anti-influenza Abs. As shown
in Figure 3 (left panel), while the treatment with 6g did not cause
any effect on the expression on viral proteins, except for NA
Figure 2. Compounds 4and 6g inhibit specific steps of influenza virus life-cycle. (A) Different concentrations of each compound were added to PR8-infected (M.O.I = 0.01)
MDCK cells. Viral yields 24 h p.i. are expressed as percentages of those recorded for control infected (CI) cells treated with 0.02% dimethyl sulfoxide (DMSO; the concentration
present in culture medium containing the highest dose of compounds). Values shown are means of four experiments, each run in duplicate.
vs CI. Viral yields 24 h p.i. for CI cells and cells infected/treated as follows: (B) 4and 6g (20 and 10
g/ml, respectively) were added to cell cultures immediately after PR8
challenge and removed at different time points (2, 4, 6, 8 or 24 h) after infection; (C) 4and 6g were added 2, 4, 6, or 8 h p.i., and maintained in the culture medium for 24 h
after infection. Values shown are means of two experiments, each run in duplicate.
P<0.01 vs CI.
5048 R. Fioravanti et al./ Bioorg. Med. Chem. 20 (2012) 5046–5052
protein (by 42% vs untreated cells), a significant inhibition of some
viral proteins was observable after treatment with 4.
In particular, densitometric analysis (Fig. 3, right panel) re-
vealed decreased expression of HA (by 25% vs untreated), NA (by
56% vs untreated) and M1 (by 62% vs untreated), even if the
expression of NP protein was slight inhibited. These results suggest
that the antiviral activity exerted by 4could be due to an interfer-
ence with viral protein synthesis, while the effect of 6g to the inhi-
bition of other steps of virus life-cycle.
3.3. Compounds 6g and 4 retain viral NP in the nucleus of
infected cells
During influenza virus replication, viral RNAs are packaged into
helical ribonucleoprotein (RNP) complexes with polymerase and
NP in the host-cell nucleus and are subsequently exported into
the cytosol to be assembled with the other structural proteins.
Our previous studies demonstrated that RV blocks the nuclear-
cytoplasmic translocation of RNP complexes.
To determine
whether the same mechanism was involved in 4and 6g inhibition
of influenza virus replication, immunofluorescence analysis of
vRNP trafficking was performed. MDCK cells were infected with
PR8 at a high M.O.I. to allow single-cycle replication. Eight hours
after infection, cells were fixed, permeabilized and stained with
-diamidino-2-phenylindole hydrochloride (DAPI), and then
incubated in turn with primary anti-NP antibody and with fluores-
cein isothiocyanate-conjugated secondary antibody. As shown in
Figure 4 in the untreated cells, NP was located predominantly in
the cytosol, and addition of compounds 4and 6g led to the inhibi-
tion of viral RNP export from nucleus to cytoplasm. In particular,
the treatment with 6g caused a strong inhibition of nuclear-cyto-
plasmic traffic of NP, suggesting that this compound could inter-
fere with some pathways that regulate this important step of
influenza virus replication. These results were confirmed by wes-
tern blot analysis of NP localization in the nuclear and cytoplasmic
extracts after 8 h p.i. As shown in Figure 5 the treatment with the
compounds, especially with 6g, caused an inhibition of NP levels in
the cytosol, while the protein was mainly expressed in the nucleus
of the cells. Several kinase cascades, such as PKC and MAPKs are
activated during influenza virus infection.
Pleschka et al.
onstrated that ERK (extracellular signal-regulated kinase) phos-
phorylation promotes vRNP traffic and virus production. Our
previous studies demonstrated the role of p38MAPK activity in nu-
clear export of RNP complexes of influenza virus. In particular, the
inhibition of this kinase decreased vRNP traffic, phosphorylation of
viral NP (a key event for the export in the cytoplasm), and viral
titers in cells supernatants.
Moreover, it is known that RV inter-
feres with several intracellular pathways including those activated
by PKC and MAPKs.
Therefore to determine the underlying mechanism for the
inhibitory effect of 4and 6g on nuclear translocation of vRNP com-
plexes, the possible involvement of the PKC pathway in the antivi-
ral activity of the compounds was investigated in human NCI-H292
infected cells. As shown in Figure 6, the phosphorylation of PKD,
the PKC downstream effector,
was observed in infected cells
6 h p.i., and this event was markedly reduced by compounds 4
and 6g. Then, the phosphorylation of p38MAPK, JNK, and ERK path-
ways was analyzed. As shown in Figure 6, the compound 6g
strongly diminished p38MAPK and JNK phosphorylation, but had
no effect on that of ERK 1 and 2. Similar results were obtained in
cells treated with 4, although the inhibition of p38MAPK phos-
phorylation was less pronounced. These results indicate that the
strong inhibition of p38MAPK phosphorylation by 6g leads to vRNP
retaining in the nucleus of infected cells.
3.4. Compound 4 restores the intracellular redox balance during
viral infection and affects viral HA localization
Influenza virus infection is associated with redox changes char-
acteristic of oxidative stress, including depletion of GSH levels and
a general oxidative stress in both in vivo and in vitro experimental
Our recent studies have demonstrated a key role of GSH
levels in the regulation of viral HA maturation. Indeed, the addition
of a GSH derivative was able to restore the reduced environment in
infected cells and, as a consequence, to interfere with intracellular
redox-regulated pathways responsible for the folding of viral pro-
teins. The final effect on viral replication was an impairment of vir-
al propagation by impeding HA plasma-membrane insertion.
Therefore we evaluated the potential antioxidant activity of these
compounds. Twenty-four hours after infection, as expected influ-
enza virus-induced a significant depletion of intracellular GSH con-
tent (Fig. 7A). On the contrary, in infected cells treated with 4, GSH
levels did not diminish during viral infection, and GSH content was
similar to that measured in control (mock-infected) cells. The
treatment with 6g was also able to restore the intracellular GSH
content, even if in less extent. A confirmation of this difference
was obtained by measuring the redox potentials of 4and 6g. Com-
pound 4showed Epa1 = 0.75 V compared to Epa1 = 1,35 V found
for 6g. It is evident the higher reducing property of 4 compared
to that of 6g.
Next, we evaluated whether these compounds could interfere
with HA maturation, especially with HA localization on the plas-
ma-membrane. Immunofluorescence studies of HA localization
were performed 8 h after PR8 infection with high M.O.I. Cells were
fixed and stained with anti-HA antibody and with secondary anti-
body conjugated with phycoerythrin. As shown in Figure 7B, viral
protein HA was highly expressed, diffused into the cells and local-
ized predominantly on the plasma-membrane of infected cells.
Figure 3. Compound 4inhibits expression of late viral proteins. (Left panel) expression of viral proteins in influenza A/PR8/34 H1N1 infected cells untreated or treated with
6g or 4, respectively. After 24 h, cells were lysed and cell homogenates were separated in reducing conditions by 12% gel, transferred to nitrocellulose membrane and
immunostained with goat polyclonal anti-influenza Abs. PR8 virus protein molecular weights are indicated to the right of the figure. HA, hemagglutinin; NP, nucleoprotein;
NA, neuraminidase; M1, matrix protein 1. Results are shown for one representative experiment of three performed. (Right panel) densitometric analysis of viral proteins
expression shown in (left panel). Results are expressed as ratio of each viral protein to actin.
R. Fioravanti et al./ Bioorg. Med. Chem. 20 (2012) 5046–5052 5049
On the contrary, the treatment with the compounds, especially
with 4, inhibited HA expression, and viral protein localization on
the plasma-membrane was impaired. In particular, in these latter
cells HA was localized on the peri-nuclear zone (see white arrows,
Fig. 7B). These results suggest that 4could exert its antiviral activ-
ity through regulation of some redox-sensitive pathways involved
in HA maturation. Further studies are in progress to better charac-
terize the molecular mechanism involved in this inhibition.
4. Discussion
In the present study we have demonstrated the antiviral activ-
ity of compounds 4and 6g. These compounds inhibited the influ-
enza A virus replication in a dose-dependent manner without
inducing any cytotoxic effect. The antiviral activity of these mole-
cules is due to inhibition of two key steps of influenza virus life-
cycle: (1) nuclear-cytoplasmic traffic of vRNP; (2) maturation of
viral HA protein.
These fundamental steps are finely regulated by redox-sensitive
intracellular pathways that are activated during viral infection. In
particular, vRNP traffic is regulated by several intracellular kinases,
including PKC and MAPKs.
In our previous paper we have dem-
onstrated that influenza virus-activated p38MAPK phosphorylated
viral NP, an event needed for vRNP nuclear export. Inhibition of
p38MAP led to retention of NP in the nucleus of infected cells.
Here, we demonstrate that the two compounds were able to inhibit
p38MAPK and, as consequence, to impede the export of vRNP from
the nucleus to the cytoplasm, confirming the role of p38MAPK in
the regulation of this step of viral replication.
Viral infection is often associated with redox changes character-
istic of oxidative stress, and these alterations are mainly due to
virus-induced depletion of intracellular GSH levels.
A decrease
in GSH content and general oxidative stress have been also demon-
strated during influenza virus infection in both in vivo and in vitro
experimental models.
We have recently demonstrated a key
role of GSH levels in the regulation of viral HA maturation. Indeed
the addition of a GSH derivative impairs viral propagation by
Figure 4. Compounds 6g and 4block the nuclear-cytoplasmic vRNP traffic. MDCK cells were infected with 1 M.O.I. to allow single-cycle replication. Cells were fixed,
permeabilized and stained with monoclonal anti-NP Ab and analyzed by fluorescence microscopy. Nuclei were stained with DAPI. Merged images are shown in the third
Figure 5. Compounds 6g and 4retain the NP in the nucleus of infected cells.
Cytosolic and nuclear extracts from 4or 6g treated and untreated cells were
subjected to SDS-PAGE and immunoblotted with anti-NP Abs. The same nitrocel-
lulose filters were then stripped and restained with anti-
-tubulin or anti-lamin A/
C. Above each blot, densitometric analysis expressed as the ratio of viral NP/tubulin
or lamin is reported. Results are shown for one representative experiment of three
Figure 6. Compounds 4and 6g interfere with PKC pathway. NCI-H292 cells were
mock- or PR8-infected (1 M.O.I.), treated with 4or 6g and lysed 6 h p.i. Proteins
were separated by 10% SDS–PAGE and gels were blotted onto nitrocellulose
membranes and immunostained with rabbit anti-phospho-PKD, anti-phospho-ERK
1/2, anti-phospho-p38MAPK or anti-phospho-JNK Abs. The same nitrocellulose
filters were then stripped and restained with anti-PKD, anti-ERK1/2, anti-p38MAPK,
or anti-JNK Abs, respectively. Results are shown for one representative experiment
of three performed.
5050 R. Fioravanti et al./ Bioorg. Med. Chem. 20 (2012) 5046–5052
impeding HA plasma-membrane insertion.
The antioxidant activ-
ity of RV has been well demonstrated in numerous studies.
ever, in our previous paper, RV was not able to restore intracellular
levels of GSH in influenza virus-infected cells.
Here, the addition
of the new compounds, in particular of 4, to infected cells was able
to restore virus-induced depletion of GSH. Moreover, we have ob-
served that the compounds, especially 4, were able to interfere
with HA localization on plasma-membrane, an event that occurs
when HA redox-regulated maturation process is completed.
These results suggest that the compounds could interfere with
some redox-sensitive intracellular pathways involved in matura-
tion of viral HA. Further studies are in progress to evaluate the
molecular mechanisms underlying this process.
5. Conclusion
Overall the data demonstrated that the compounds 4and 6g
exert their anti-influenza activity by inhibiting intracellular meta-
bolic pathways rather than viral proteins. Inactivation of host-cell
functions that are essential for the virus replication offers two
important advantages: not only it is more difficult for the virus
to adapt to, but it can also expected to affect viral replication
independently from virus type or strain.
This work was partially supported by the Italian Ministry of
Instruction, Universities, and Research (Progetto PON), and PRIN
n°2008 CE75SA the Italian Ministry of Health, and Fondazione
Roma Grants.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at
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5052 R. Fioravanti et al./ Bioorg. Med. Chem. 20 (2012) 5046–5052
... As shown in Figure 4, both compounds were effective at specific phases: compound 1 was mainly effective when added PRE or POST (** p < 0.001); for compound 3, although quite effective at all the phases, the most inhibition (46% compared to untreated cells) was reached during viral challenge (DUR). On the basis of these results, we hypothesize that compound 1 might act before infection by interfering with some cell factors on the plasma membrane or, due to the antioxidant activity of furanodienone [16], it may maintain reduced conditions into the cells making them more resistant to virus infection [17][18][19]. With regard to compound 3, since it mainly acts during viral adsorption, it might interfere with the viral attachment or entry into the cells. ...
... Virus production was evaluated in the supernatants of infected cells recovered 24 h after infection, by measuring the hemagglutinin units (HAU), using human type 0 Rh+ erythrocytes [19]. Stock solutions of compounds dissolved in DMSO were diluted in RPMI medium to final concentrations of 2.5-500 µg/mL. ...
... The ICW assay was performed using the Odyssey Imaging System (LI-COR, Lincoln, NE, USA) [19]. Briefly, A549 cells grown in 96-well plates (2 × 104 cells/well), either infected or mock-infected (Ctr) with PR8, were fixed with 4% formaldehyde, washed, permeabilized with 0.1% Triton X-100 and incubated with PBS containing Odyssey Blocking buffer (LI-COR Biosciences, Lincoln, NE, USA). ...
Full-text available
The resinous exudate produced by Commiphora myrrha (Nees) Engl. is commonly known as true myrrh and has been used since antiquity for several medicinal applications. Hundreds of metabolites have been identified in the volatile component of myrrh so far, mainly sesquiterpenes. Although several efforts have been devoted to identifying these sesquiterpenes, the phytochemical analyses have been performed by gas-chromatography/mass spectrometry (GC–MS) where the high temperature employed can promote degradation of the components. In this work, we report the extraction of C. myrrha by supercritical CO2, an extraction method known for the mild extraction conditions that allow avoiding undesired chemical reactions during the process. In addition, the analyses of myrrh oil and of its metabolites were performed by HPLC and GC–MS. Moreover, we evaluated the antiviral activity against influenza A virus of the myrrh extracts, that was possible to appreciate after the addition of vitamin E acetate (α-tocopheryl acetate) to the extract. Further, the single main bioactive components of the oil of C. myrrha commercially available were tested. Interestingly, we found that both furanodienone and curzerene affect viral replication by acting on different steps of the virus life cycle.
... Polyphenolic natural products are a family of naturally occurring secondary metabolites that exhibit a wide spectrum of biological activities ranging from antioxidant, anti-inflammatory, antitumor, and antibacterial properties [14][15][16][17]. More significantly, they exhibit antiviral properties on a diverse range of pathogenic viruses such as influenza virus [18,19], hepatitis C virus [20,21], Herpes simplex virus [22,23], flavivirus [24,25], enterovirus [26], and human immunodeficiency virus [27,28]. As such, polyphenolic compounds are an attractive group of potential drug candidates against SARS-CoV-2. ...
... Epigallocatechin-3-gallate (22), papyriflavonol A (71), theaflavin-3,3'-digallate (27), catechin (24), astragalin (17), quercetin-3-O-glucoside (18), and (−)-epicatechin-3-Ogallate (23) have been reported to exhibit high binding propensities onto the catalytic site of PL pro . Among the compounds, 27 showed the most number of interacting residues via hydrogen bonding: Gln269, Asn109, Leu162, Thr158, Glu161, and Val159. ...
The ongoing Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has been proven to be more severe than the previous coronavirus outbreaks due to the virus’ high transmissibility. With the emergence of new variants, this global phenomenon took on a more dramatic turn with many countries recently experiencing higher surges of confirmed cases and deaths. On top of this, the inadequacy of effective treatment options for COVID-19 aggravated the problem. As a way to address the unavailability of target-specific viral therapeutics, computational strategies have been employed to hasten and systematize the search. The objective of this review is to provide initial data highlighting the utility of polyphenols as potential prophylaxis or treatment for COVID-19. In particular, presented here are virtually screened polyphenolic compounds which showed potential as either antagonists to viral entry and host cell recognition through binding with various receptor-binding regions of SARS-CoV-2 spike protein or as inhibitors of viral replication and post-translational modifications through binding with essential SARS-CoV-2 non-structural proteins.
... Several pieces of evidence reported the antiviral efficacy of polyphenols, included resveratrol and its derivatives [26]. Our group demonstrated their ability to interfere with specific steps during the replicative cycle [8,27]. Based on this observation, we evaluated the potential anti-influenza virus activity of polydatin and A5+. ...
Full-text available
Polyphenols have been widely studied for their antiviral effect against respiratory virus infections. Among these, resveratrol (RV) has been demonstrated to inhibit influenza virus replication and more recently, it has been tested together with pterostilbene against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In the present work, we evaluated the antiviral activity of polydatin, an RV precursor, and a mixture of polyphenols and other micronutrients, named A5+, against influenza virus and SARS-CoV-2 infections. To this end, we infected Vero E6 cells and analyzed the replication of both respiratory viruses in terms of viral proteins synthesis and viral titration. We demonstrated that A5+ showed a higher efficacy in inhibiting both influenza virus and SARS-CoV-2 infections compared to polydatin treatment alone. Indeed, post infection treatment significantly decreased viral proteins expression and viral release, probably by interfering with any step of virus replicative cycle. Intriguingly, A5+ treatment strongly reduced IL-6 cytokine production in influenza virus-infected cells, suggesting its potential anti-inflammatory properties during the infection. Overall, these results demonstrate the synergic and innovative antiviral efficacy of A5+ mixture, although further studies are needed to clarify the mechanisms underlying its inhibitory effect.
... Compounds 12, 14, and 16-19 are propionic acid derivatives, while 13 and 15 possess an ethylamine side chain in which the nitrogen is either acetylated (13) or included in a piperidin-4-one ring (15). The library also includes compounds possessing small alkyl side chains (20,21), heteroaromatic groups (22,23), as well as aryl moieties variously functionalised at ortho, meta, and mainly para position (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42). Finally, compounds 43-45 are analogues of 1 in which the sulphur in position 4 is oxidised to sulphinyl (43), sulphonyl (44) or replaced by an amino group (45) 27 . ...
Full-text available
Influenza viruses represent a major threat to human health and are responsible for seasonal epidemics, along with pandemics. Currently, few therapeutic options are available, with most drugs being at risk of the insurgence of resistant strains. Hence, novel approaches targeting less explored pathways are urgently needed. In this work, we assayed a library of nitrobenzoxadiazole derivatives against the influenza virus A/Puerto Rico/8/34 H1N1 (PR8) strain. We identified three promising 4-thioether substituted nitrobenzoxadiazoles (12, 17, and 25) that were able to inhibit viral replication at low micromolar concentrations in two different infected cell lines using a haemagglutination assay. We further assessed these molecules using an In-Cell Western assay, which confirmed their potency in the low micromolar range. Among the three molecules, 12 and 25 displayed the most favourable profile of activity and selectivity and were selected as hit compounds for future optimisation studies.
... Accordingly, resveratrol and catechin 3-O-gallate showed an inhibitory effect against NAs activity, with IC 50 values of 129.8 and 21.3 µM, respectively (Chen et al., 2012a). Considering the results of a docking study, resveratrol and its derivatives (as natural polyphenol) can inhibit the replication of influenza A virus, as well as inhibited intracellular pathways c-Jun N-terminal kinase (JNK) and p38MAPK in the regulation of viral ribonucleoprotein complex (Fioravanti et al., 2012;Li et al., 2015). Evidence has shown that resveratrol and other derivatives have antiviral and antioxidant activities with different mechanisms, such as the inhibition of viral protein synthesis or transcription and modulating viral-related gene expressions or signaling pathways in host cells as it could be useful for the treatment of DENV (Han et al., 2017). ...
Full-text available
Growing studies are revealing the critical manifestations of Influenza, Dengue virus infection, Zika virus disease, and Ebola, as emerging infectious diseases. However, their corresponding mechanisms of major complications headed for neuronal dysfunction are not completely understood. From the mechanistic point of view, during emerging infectious diseases, inflammatory/oxidative mediators are activated towards a less cell migration, neurogenesis impairment, and neuronal death. Accordingly, the virus life cycle and associated enzymes, as well as host receptors, cytokine storm, and multiple signaling mediators are the main players of emerging infectious diseases. Consequently, chemokines, interleukins, interferons, carbohydrate molecules, toll-like receptors, and tyrosine kinases (e.g., TAM), are leading orchestrates of peripheral and central complications which are in a near interconnection. Of resulted neuronal manifestations, inflammatory polyneuropathy, encephalopathy, meningitis, myelitis, stroke, Guillain-Barré syndrome, radiculomyelitis, meningoencephalitis, memory loss, headaches, cranial nerve abnormalities, tremor, and seizure have attracted much attention. The complex pathophysiological mechanism behind the aforementioned complications urges the need for finding multi-target agents with higher efficacy and lower side effects. In recent decades, the natural kingdom has been highlighted as promising neuroprotective natural products through modulating several dysregulated signaling pathways/mediators. In the present study, neuronal manifestations of some emerging infectious diseases, and underlying pathophysiological mechanisms are provided. Besides, a mechanistic-based strategy is developed to introduce candidate natural products as promising multi-target agents in combating major dysregulated pathways towards neuroprotection in Influenza, Dengue virus infection, Zika virus disease, and Ebola.
... [170] viral proteases. The antiviral activity of polyphenol compounds occurred due to their interference with the following intracellular pathways exploited for viral replication: (1) MAP kinases controlling nuclear-cytoplasmic traffic of viral ribonucleoprotein complex, (2) redox-sensitive pathways, involved in the maturation of viral hemagglutinin protein [232]. Byler et al. [233] reported that no antiviral agents are available for Zika virus infections. ...
In this mini-review article, we have mentioned the key roles of some of the most important herbal plants medicines containing flavonoids and phytochemicals with antiviral activities. All relevant information was searched for terms of influenza, phytochemicals, SARS, SARS-Cov-2, flavonoids, and traditional medicinal plants uses from reliable databases, such as PubMed, Science Direct, and Google Scholar. The most important medicinal herbs which contain flavonoids with antiviral activities are Limonium densiflorum, Oroxylum indicum, Tribulus terrestris L., Paulownia tomentosa Steud., Allophylus africanus, Houttuynia cordata, Moslea Herba, Mosla scabra, Scutellaria baicalensis, Berries, Genus Psoralea, Sophora tonkinensis, Trollius chinensis, Tilia cordata, Hippophae rhamnoides L. (Seabuckthorn), Paulownia tomentosa steud, and C. swietenia. Phytochemicals are chemicals of plant origin produced by plants through primary or secondary metabolism. The most important medicinal plants which contain phytochemicals with antiviral activities are Blue honeysuckle (Lonicera caerulea L.), Forsythia suspense, Ligustrum lucidum, Radix Paeoniae Alba (Bai Shao), Banlangen (Radix Isatidis), Lysiphyllum strychnifolium, Phellinus baumii, Mesona chinensis, Sanguinaria Canadensis, Dodonaea viscosa, Isatis indigotica, Pelargonium sidoides, Entada Africana Guill., Pomegranate (Punica granatum), Goldenseal (Hydrastis canadensis), Lychee fruit extract, Lycoris radiate, Cistus incanus, Chaenomeles sinensis Koehne (Chinese quince), Geranium sanguineum L., and Tea polyphenols. Natural products from traditional herbal medicines, especially traditional Chinese and Persian medicines, have been found to exert antiviral impacts against influenza and human coronaviruses. The natural plant-derived compounds that have been used for treating various diseases are flavonoids and phytochemicals.
... publicaciones han emergido en donde se han reportado efectos inmunomoduladores (potenciadores) del consumo de polifenoles específicos o extractos ricos en estos compuestos 13 . Por lo tanto, la evidencia existente indica que principalmente polifenoles (y también matrices alimentarias ricas en estos compuestos), tienen un alto potencial para ser considerados en profilaxis o tratamiento para atenuar incidencia o gravedad de enfermedad respiratoria. ...
Full-text available
Obesity has been identified as a risk factor for the severity of respiratory infections. The support of the immune response in obese subjects is of interest. The present work evaluated the effect of the consumption of a Calafate extract on markers of the immune response in lean and obese mice. Male C57BL/6J mice were exposed for 82 days to a standard, and a high-fat (HF) diet. A subgroup of both groups was given 50 and 100 mg [total polyphenols] / kg body weight / day of extract in the last two weeks. Gene expression and secretion of immune response markers were evaluated in lung tissue and plasma. An effect of extract treatment on IFN expression was observed. Effects induced by the HF diet and treatment with extract were observed independently in the expression of IL-12. An overall effect of the HF diet on plasma IFN was observed, specifically a decrease in animals fed the HF diet. An interaction between diet and extract treatment was observed over plasma IL-12. The treatment used modulates markers that activate the immune response to respiratory infections, mainly of viral origin, in lean and obese animals.
... Биология. медицина [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. В табл.2 приведен перечень полифенолов-антиоксидантов, для которых подтверждены их антивирусное действие, их структура и пищевые источники [34][35][36][37][38][39][40][41][42][43][44][45][46][47]. ...
Inflenza A viruses (IAVs) are highly transmissible and pathogenic Orthomyxoviruses, which have led to worldwide outbreaks and seasonal pandemics of acute respiratory diseases, causing serious threats to public health. Currently used anti-influenza drugs may cause neurological side effects, and they are increasingly less effective against mutant strains. To help prevent the spread of IAVs, in this work, we have developed quercetin-derived carbonized nanogels (CNGsQur) that display potent viral inhibitory, antioxidative, and anti-inflammatory activities. The antiviral CNGsQur were synthesized by mild carbonization of quercetin (Qur), which successfully preserved their antioxidative and anti-inflammatory properties while also contributed enhanced properties, such as water solubility, viral binding, and biocompatibility. Antiviral assays of co-treatment, pre-treatment, and post-treatment indicate that CNGsQur interacts with the virion, revealing that the major antiviral mechanism resulting in the inhibition of the virus is by their attachment on the cell surface. Among them, the selectivity index (SI) of CNGsQur270 (> 857.1) clearly indicated its great potential for clinical application in IAVs inhibition, which was much higher than that of pristine quercetin (63.7) and other clinical drugs (4−81). Compared with quercetin at the same dose, the combined effects of viral inhibition, antioxidative and anti-inflammatory activities impart the superior therapeutic effects of CNGsQur270 aerosol inhalation in the treatment of IAVs infection, as evidenced by a mouse model. These CNGsQur effectively prevent the spread of IAVs and suppress virus-induced inflammation while also exhibiting good in vivo biocompatibility. CNGsQur shows much promise as a clinical therapeutic agent against infection by IVAs.
Influenza and ARVIs are the most common forms of infectious respiratory diseases in humans. In this regard, the search and development of means for the prevention and treatment of viral infections is a high priority task. The aim of this study was to assess the mechanisms of the antiviral activity of sage-leaved rock-rose extract (Cistus salviifolius) against the causative agents of influenza and ARVIs in humans. In the course of the study, it was shown that C.salviifolius extract inhibits reproduction of influenza viruses A(H1N1), A (H1N1)pdm09, A(H3N2), A(H5N2), A(H7N9) and influenza B virus. The extract showed maximum virus-inhibiting activity at the early stages of the viral cycle (0–2 hours after infection). C.salviifolius extract significantly reduced the hemagglutinating activity of the virus, and at the same time did not affect the fusogenic properties of viral hemagglutinin. Transmission electron microscopy was used to demonstrate that the cistus extract prevents the absorption of influenza virions on the surface of cells in culture. The inhibitory activity of the extract against other human respiratory viruses, parainfluenza virus and adenovirus, was also shown. The protective activity of C.salviifolius extract was demonstrated when applied intranasally during the experiments on a model of influenza pneumonia in mice. The degree of this activity was in inverse proportion to the time window between the application of the extract and the infection of the animals. The virus, pre-incubated with C.salviifolius extract, did not cause death in the animals. The data obtained indicate that C.salviifolius extract serves as an effective and broad-range means of preventing respiratory viral infections in humans.
Full-text available
Resveratrol has attracted interest as a wine constituent that may reduce heart disease. Published data on the molar absorptivity and chemical stability of cis- and trans-resveratrol have varied greatly. Accurate values for UV absorbance for trans-resveratrol [UV λmax (EtOH) nm (ε) 308 (30 000)] and cis-resveratrol [UV λmax (EtOH) nm (ε) 288 (12 600)] were determined and are used to improve chromatographic quantitation methods. Trials conducted under a variety of commonly encountered laboratory conditions show that trans-resveratrol is stable for months, except in high-pH buffers, when protected from light. cis-Resveratrol was stable only near pH neutrality when completely protected from light. Keywords: Antioxidant; phenolic; wine; grape; stilbene; isomer; UV spectroscopy; absorptivity
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Curcumin (diferuloylmethane) is a widely used spice and colouring agent in food. Accumulated evidence indicates that curcumin is associated with a great variety of pharmacological activities, including an anti-microbial effect. In this study, the anti-influenza activity of curcumin was evaluated. Our results demonstrated that treatment with 30 μM curcumin reduced the yield of virus by over 90% in cell culture. The EC50 determined using plaque reduction assays was approximately 0.47 μM (with a selective index of 92.5). Time of drug addition experiments demonstrated curcumin had a direct effect on viral particle infectivity that was reflected by the inhibition of haemagglutination; this effect was observed in H1N1 as well as in H6N1 subtype. In contrast to amantadine, viruses did not develop resistance to curcumin. Furthermore, by comparison of the antiviral activity of structural analogues, the methoxyl groups of curcumin do not play a significant role in the haemagglutinin interaction.
A series of hydroxy- and hydroxy-methoxychalcones was synthesized and the inhibitory activity and selectivity of the compounds towards bovine lens aldose reductase (AR) were tested. All the compounds display affinity for AR. The most active proved to be 1-(2,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)propen-1-one (isoliquiritigenin, IC50= 7.60 μM). The selectivity of this compound was also tested, its inhibitory activity being assayed against glutathione reductase and sorbitol dehydrogenase.
The (E)- and (Z)-diastereomers of resveratrol were investigated with respect to their photochemical and thermal diastereomerization reactions. The free enthalpy difference between the two diastereomers was estimated to be in the order of common stilbenes, with the (E)-diastereomer more stable by about 11–14 kJ mol−1. The Arrhenius activation barrier of about 280 kJ mol−1 was found to be quite high and implies that thermal equilibration cannot account for the (Z)-diastereomer found in nature. A preparative access to the (Z)-diastereomer by photodiastereomerization is described. The 1H and 13C NMR spectra of the two diastereomers were assigned and their absorption spectra and fluorescence quantum yields of the neutral and monodeprotonated species were determined.
Various cinnammoyl-based structures were synthesized and tested in enzyme assays as inhibitors of the HIV-1 integrase (IN). The majority of compounds were designed as geometrically or conformationally constrained analogues of caffeic acid phenethyl ester (CAPE) and were characterized by a syn disposition of the carbonyl group with respect to the vinylic double bond. Since the cinnamoyl moiety present in flavones such as quercetin (inactive on HIV-1-infected cells) is frozen in an anti arrangement, it was hoped that fixing our compounds in a syn disposition could favor anti-HIV-1 activity in cell-based assays. Geometrical and conformational properties of the designed compounds were taken into account through analysis of X-ray structures available from the Cambridge Structural Database. The polyhydroxylated analogues were prepared by reacting 3,4-bis(tetrahydropyran-2-yloxy)benzaldehyde with various compounds having active methylene groups such as 2-propanone, cyclopentanone, cyclohexanone, 1,3-diacetylbenzene, 2,4-dihydroxyacetophenone, 2,3-dihydro-1-indanone, 2,3-dihydro-1,3-indandione, and others. While active against both 3‘-processing and strand-transfer reactions, the new compounds, curcumin included, failed to inhibit the HIV-1 multiplication in acutely infected MT-4 cells. Nevertheless, they specifically inhibited the enzymatic reactions associated with IN, being totally inactive against other viral (HIV-1 reverse transcriptase) and cellular (RNA polymerase II) nucleic acid-processing enzymes. On the other hand, title compounds were endowed with remarkable antiproliferative activity, whose potency correlated neither with the presence of catechols (possible source of reactive quinones) nor with inhibition of topoisomerases. The SARs developed for our compounds led to novel findings concerning the molecular determinants of IN inhibitory activity within the class of cinnamoyl-based structures. We hypothesize that these compounds bind to IN featuring the cinnamoyl residue CC−CO in a syn disposition, differently from flavone derivatives characterized by an anti arrangement about the same fragment. Certain inhibitors, lacking one of the two pharmacophoric catechol hydroxyls, retain moderate potency thanks to nonpharmacophoric fragments (i.e., a m-methoxy group in curcumin) which favorably interact with an “accessory” region of IN. This region is supposed to be located adjacent to the binding site accommodating the pharmacophoric dihydroxycinnamoyl moiety. Disruption of coplanarity in the inhibitor structure abolishes activity owing to poor shape complementarity with the target or an exceedingly high strain energy of the coplanar conformation.
The ternary phase diagram of a curcumin-encapsulated O/W microemulsion system using food-acceptable components, lecithin and Tween 80 as the surfactants and ethyl oleate as the oil phase, was constructed. The stability and characterisation of curcumin in microemulsion were investigated. The results indicated that a composition of curcumin microemulsion (DI water: surfactants (the mole ratio of lecithin/Tween 80 was 0.3): EO = 10:1.7:0.4 in wt ratio) was stable for 2 months with an average diameter of 71.8 ± 2.45 nm, as detected by UV–Vis spectra and diameter distributions. The microemulsion possesses an ability to be diluted with aqueous buffer without destroying its structure for 48 h. A skin permeation study for testing the penetration effect of various curcumin loading in the microemulsions with different particle diameters was also performed and discussed in this contribution.
Conference Paper
It is impractical to use traditional access control mechanisms to design a digital content access control mechanism for an organization since even a role-based access control mechanism only guarantees that it can be flexibly applied to the determined access policy for various roles in an organization. It cannot allow users to flexibly define various access rights for different digital contents for diverse applications. To make sure these requirements can be satisfied and also combine the hierarchy structure of organization to the access control and thus protect digital content from being illegally duplicated, printed, deleted, noted, modified and stored, in this paper, we apply a digital certificate to record each user's role(s) and the corresponding access rights inherited from the access policies defined by the administration department in the organization.