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Journal of Microbiology and Antimicrobials Vol. 2(3), pp. 23-29, May 2010
Available online http://www.academicjournals.org/JMA
ISSN 1996-0875 © 2010 Academic Journals
Full Length Research Paper
Antiviral activity and mode of action of Dianthus
caryophyllus L. and Lupinus termes L. seed extracts
against in vitro herpes simplex and hepatitis A viruses
infection
Ahmed B. Barakat1*, Sahar A. Shoman1, N. Dina2 and Omar R. Alfarouk1
1Department of Microbiology, Faculty of Science, Ain Shams University, Cairo, Egypt.
2Department of water pollution, National Research Center, Dokki, Egypt.
Accepted 28 January, 2010
Crude extracts of sixteen seeds belonging to different plant species were tested for their antiviral
activity against herpes simplex virus-1 (HSV-1) and hepatitis A virus-27 (HAV-27). Non-toxic
concentration (20 µg/ml) of Dianthus caryophyllus and Lupinus termes seed extracts to both Vero and
HepG2 cells showed potent antiviral activity against HSV-1 and HAV-27 using plaque infectivity count
assay. The mechanism of action D. caryophyllus revealed its virucidal activity against HSV-1 and HAV-
27 as 92.3 and 92.6%, respectively, while, the virucidal activity of L. termes was observed only against
HAV-27 giving 93.7% of inhibition. No effect was detected for both extracts on adsorption or on the
stages of virus replication. A comparison has been done between the antiviral activity of two
therapeutic drugs (Acyclovir and Amentadine used as controls for HSV-1 and HAV-MBB, respectively)
and the two tested seed extracts. The results revealed that these seed extracts were more efficient in
their inhibitory activity than synthetic chemical drugs against the same viruses. This may open the way
to give more attention to use the natural botanical origin in treatmenting viral infection with or without
therapeutic agents to obtain better recovery with least side effects.
Key words: Antiviral seed extract, herpes virus infection, hepatitis virus infection, amantadine, acyclovir.
INTRODUCTION
There is currently a large and ever-expanding global
population base that prefers the use of natural products
in treating and preventing medical problems. This has
influenced many pharmaceutical companies to produce
new antimicrobial formulations extracted from plants or
herbs. At present, plant and herb resources are unlimited,
have provided mankind remedies for many infectious
diseases and continue to play a major role in primary
health care as therapeutic remedies in developing
countries (Sokmen et al., 1999). The search for biological
active extracts based traditionally used plants is still
relevant due to induction of resistance of pathogens to
chemical drugs and the prevalence of the fatal different
infections (Rabindran et al., 2003). Human herpes
viruses are found worldwide and are among the most
*Corresponding author. E-mail: karimbahaa2004@yahoo.com.
frequent causes of viral infections in immunocompetent
as well as in immunocompromised patients. During the
past two decade a better understanding of the replication
and disease causing state of herpes simplex virus type 1
and 2 (HSV-1 and HSV-2), has been achieved due the
development of potent antiviral compounds that target
these viruses. While some of the antiviral therapies are
considered safe and efficacious (acyclovir, pencyclovir),
others have toxicities associated with them (gancyclovir
and foscarnet). In addition, the increased and prolonged
use of these compounds in clinical setting, especially for
the treatment of immunocompromised patients, has led to
the emergence of viral resistance against most of these
drugs (Villarreal, 2001).
Fulminant hepatitis is a severe complication of hepatitis
A virus infection (HAV). Its mechanism is unknown but
spontaneous recovery is frequent. There are no data on
the level of viral replication according to the clinical form
of HAV (Rezende et al., 2003). A high fatality rate among
24 J. Microbiol. Antimicrob.
chronic hepatitis B or C patients with HAV super-infection
was observed (Lee, 2003). Although there are no
commercial antiviral drugs specifically licensed for
treating HAV infection, ribavirin, amentadine, and 2-
deoxy-D-glucose are among several antiviral substances
known to interfere with HAV replication (Hollinger and
Emerson, 2001).
Although a significant number of studies have used
known purified plant chemicals as antiviral drugs (Binnus
et al., 2002; Guarino and Sciarrillo, 2003; Jassim and
Naji, 2003), very few screening programmes have been
initiated on crude plant materials. Crude extracts of plant
seeds are also a promising source of systemic broad-
spectrum antiviral that may cause less damage to host
cells than do pharmaceuticals. Topical antiviral
substances are also important areas of study for the
treatment of viral lesions such as in HSV, and plant-
based substances offer promise as virucidal alternates
(Hudson, 1990). The seed extracts of Phyllanthus
amarus (Euphorbiaceae) species are known to reduce or
eliminate detectable hepatitis B virus surface antigen in
humans and show in vitro inhibition of viral DNA
polymerase (DNAp) (Unander and Blumberg, 1991). The
repeated oral administration of extracts of Strychnos
potatrum seeds appreciably suppressed the development
of skin lesions induced by HSV-1 in mice (Hattori et al.,
1995). The Pinus nigra seed cones extract has anti-HIV
activity (Eberhardt and Young, 1996). Incubation of
acyclovir-resistant HSV-1 (ACVr-HSV-1), during infection
of the HEp-2 cell culture, with an extract prepared from
the seeds of Licania tomentosa species impaired the
productive replication of this virus in a concentration-
dependent manner. The extract was able to inhibit
extracellular virus (virucidal effect) and also interfered
with a very early event of cell infection at a non-cytotoxic
concentration (Miranda et al., 2002).
The current investigation was undertaken to test the
extracts of 16 plant seeds for their antiviral activity
against herpes simples virus -1 (HSV-1, a DNA virus) and
hepatitis A virus (HAV, a RNA virus). The mode of action
of the most promising extracts was also studied.
MATERIALS AND METHODS
Plant material
Sixteen species of seeds belonging to different families were
collected from seed bank of botanical garden, Ain Shams
University; Ministry of Agriculture and land reclamation, Giza,
Egypt; Orman botanical garden, Giza, Egypt and Flora and
phytotaxonomy research department, Agriculture museum, Giza,
Egypt.
Preparation of seed extracts for bioassay
10 mg of each crushed seed was resuspended in 1 ml solvent (10%
Dimethyl sulfoxide (DMSO) in deionized water). Decontamination
was carried out by adding 1% antibiotic-antimycotic mixture (10,000
IU Penicillin G sodium, 10,000 µg Streptomycin sulfate and
250 µg Amphotericin B) and the extracts were incubated at 37°C for
30 min then stored at -20°C. Sterility test was performed to ensure
the sterility of the prepared extracts.
Cells
Both Vero and HepG2 cells were propagated in minimum essential
medium (MEM) and RPMI 1640 medium respectively. They were
supplemented with 10% foetal bovine serum, 1% antibiotic-
antimycotic mixture. The cell culture was kindly provided by faculty
of medicine, El-azhar University as confluent monolayer in 25 cm2
tissues culture flasks.
Cytotoxicity assays
The cell culture safety doses of the dissolved seed extracts were
performed by cell morphology technique (Aquino et al., 1989). Seed
extracts were inoculated (100 µL each) into both cell lines with
concentration, 5, 10, 20, 30, 40, 50 µg /100 µL and observed
microscopically for any morphological changes after 24 h incubation
at 37o C in a humidified incubator with 5% CO2 .
Viruses
Egyptian isolate of Herpes simplex virus type 1, was provided by
Virology Lab., Department of water pollution, NRC. Hepatitis A
virus-MBB strain was kindly provided by Prof. Dr. Verena gauss-
Muller, Molecular virology Institute, Luebeck University for
Medicine, Germany.
Antiviral bioassay
Plaque infectivity count assay is the most widely accepted method
for determining the % inhibition of virus as a result of being
subjected to a given material (Tebas et al., 1995). A 6 well plate
was cultivated with the specific cell type (105cell/mL) and incubated
for 1 - 2 days at 37°C. Virus was diluted to final concentration of 107
PFU/mL and mixed with the safe concentrations of each seed
extract as mentioned previously and incubated for 1 h at 37°C.
Growth medium was removed from the multi-well plate and virus-
extract mixture was inoculated (100 µl/ well). After 1 h contact time
for virus adsorption, the inoculum was aspirated and 3 ml of cell-
specific 2× medium 2% agarose was overlaid the cell sheet. The
plates were left to solidify and incubated at 37°C until the
development of the viral plaques. Formalin was added for two hours
then plates were stained with crystal violet staining solution. Control
virus and cells were treated identically without seed extract. Viral
plaques were counted and the percentage of virus reduction was
calculated.
Mechanism of virus inhibition
Virus inhibition mechanism for the most potent crude seed extracts
was studied in three categories:
A) Virucidal; tested by subjecting virus to extract directly
(Schuhmacher et al., 2003).
B) Viral Adsorption; tested by subjecting cells to extract for 2 h
before virus inoculation (Zhang et al., 1995).
C) Viral replication; tested by post inoculation of extract after virus
application to cells (Amoros et al., 1994).
Barakat et al. 25
Table 1. Cytotoxicity of the sixteen seed extracts on Vero and HepG2 cells.
Seed extracts / Cell culture
Conc. of extracts (µ
µµ
µg)
5 10 20 30 40 50
Vero/HepG2
A. precatorius
L. +/+ +/+ +/+ +/+ +/+ +/+
A. cepa L. -/- -/- -/- -/- -/- -/-
A. nobilis L. -/- -/- -/- -/- -/- -/-
C. frutescens L. -/- -/- -/- -/- -/- -/-
D. caryophyllus L. -/- -/- -/- +/- +/+ +/+
E. sativa Mill. -/- -/- -/- +/+ +/+ +/+
G. hispida L. -/- -/- -/- +/+ +/+ +/+
L. usitatissimum L. -/- -/- -/- +/+ +/+ +/+
L. termes L. -/- -/- -/- -/- +/+ +/+
N. sativa L. -/- -/- -/- +/+ +/+ +/+
P. harmala L. -/- -/- -/- +/+ +/+ +/+
P. vulgaris L. -/- -/- -/- +/+ +/+ +/+
P. sativum L. -/- -/- -/- -/+ +/+ +/+
P. armeniaca Marshall -/- -/- -/- +/- +/+ +/+
S. alba L. -/- -/- -/- +/+ +/+ +/+
T. f. graecum L. -/- -/- -/- -/- -/- -/-
(-): means safe to cells / (+): means toxic to cells.
RESULTS AND DISCUSSION
Cytotoxicity of tested seed extracts on VERO and
HepG2 cells
Results as shown in Table (1) indicate that the accepted
safe concentrations on both Vero and HepG2 cells were
less than 30 µg/100 µl. The results also showed that the
rate of cell death increased with increasing the
concentration of the tested seed extract. However, 4 out
of 16 tested seed extracts (Allium cepa, Capsicum
frutescens, Anthemis nobilis and Trigonella foenum
graceum) had no toxic effect on both Vero and HepG2
cells even when applied at high concentrations. On the
other hand, Abrus precatorius showed high toxicity on
both Vero and HepG2 cells even when applied at low
concentrations.
The antiviral activity of seed extracts against HSV-1
and HAV-27
To evaluate the antiviral activities of 16 plant seeds, the
inhibitory effects on the plaque formation were examined.
The results in Table 2 show that out of sixteen seed
extracts, D. caryophyllus has strong inhibitory activity
against both HSV-1 and HAV-27 giving 92.3 and 92.6%
inhibition at 20 µg, respectively. L. termes extract showed
strong inhibitory activity against HAV-27 only giving
93.7% inhibition at 20 µg (Table 2). Except for these two
seed species, all other tested seed extracts showed
moderate or negligible inhibitory activity, giving us a
green light to put both seeds under focus as promising
natural extracts to be used for therapeutic purposes.
The effectiveness of seed extracts inhibiting several
human viruses has been demonstrated. For examples,
the hot water extract from seeds of Arachis hypogaea
blocked HSV infection while, the hot water extract from
seeds of Pisum sativum blocked adenoviruses (ADV)
infection (Chiang et al., 2003). The hot-water extract of
black soyabean showed significant antiviral activity
against human adenovirus type 1 and coxsackievirus B1
(Yamai et al., 2003). The crude seed extract of Quercus
lusitanica plant also has a good inhibitory effect on the
replication of dengue virus type 2 (Muliawan et al., 2006).
The purified Egyptian pea (Pisum sativum) lectin which
was isolated from its seed showed a high inhibitory effect
on HCV replication (Al-Sohaimy et al., 2007). In addition,
the black cumin seed (Nigella sativa) exhibited antiviral
activity against infectious Laryngotracheitis virus (Zaher
et al., 2008).
Inhibitory action of D. caryophyllus L. and L. termes L.
extracts comparing with Antiviral drugs (Acyclovir and
Amentadine) against HSV-1 and HAV-MBB viruses.
Effectness of D. caryophyllus extract and anti HSV-1
therapeutic agent (Acyclovir) was compared. Using
similar concentrations of acyclovir and extract starting
from 10 to 50 µg /100 µL were tested against the same
virus (HSV-1). In similar manner, L. termes extract and
anti HAV-MBB control (Amentadine) was also compared.
Similar concentrations of amentadine and each extract
(10 to 50 µg /100 µl) were individually tested against the
26 J. Microbiol. Antimicrob.
Table 2. Inhibitory activity of seed extracts (n = 16) using plaque reduction assay against HSV-1 and HAV-27.
Antiviral effect
Conc.
(µg)
Seed extract
HAV- 27 HSV- 1
% of
virucidal
effect
Viral count
(PFU/ml) × 107
Initial viral
count ×107
% of
virucidal
effect
Viral count
(PFU/ml) × 107
Initial viral
count ×107
0 High toxicity 3.5 0 High toxicity 2.6 10
A. precatorius L. 0 1.6 3.5 0 2 2.6 20
49.7 1.76 3.5 0 2.6 2.6 10
A. cepa L. 54.3 1.6 3.5 0 2.8 2.6 20
20 2.8 3.5 0 3 2.6 10
A. nobilis L. 25.7 2.6 3.5 2.3 2.54 2.6 20
20 2.8
2
3.5 0 2.8
2.88
2.6 10
C. frutescens L. 42.9 3.5 0 2.6 20
88 0.42 3.5 88.5 0.3 2.6 10
D. caryophyllus L. 92.6 0.26 3.5 92.3 0.2 2.6 20
5.7 3.3 3.5 7.7 2.4 2.6 10
E. sativa Mill.
20 2.8 3.5 24.6 1.96 2.6 20
25.7 2.6 3.5 0 2.7 2.6 10
G. hispida L. 42.9 2 3.5 0 2.65 2.6 20
51.4 1.7 3.5 0 3.2 2.6 10
L. usitatissimum L. 65.7 1.2 3.5 34.6 1.7 2.6 20
92 0.28 3.5 0 2.6 2.6 10
L. termes L. 93.7 0.22 3.5 0 2.64 2.6 20
31.43 2.4 3.5 0 2.6 2.6 10
N. sativa L. 42.6 2 3.5 30.77 1.8 2.6 20
45.7 1.9 3.5 3.9 2.5 2.6 10
P.
harmala L. 65.7 1.2 3.5 7.7 2.4 2.6 20
65.7 1.2 3.5 0 3.2 2.6 10
P. vulgaris L. 71.4 1 3.5 3.1 2.52 2.6 20
48.6 1.8 3.5 30.77 1.8 2.6 10
P. sativum L. 51.4 1.7 3.5 46.15 1.4 2.6 20
42.6 2 3.5 0 2.7 2.6 10
P. armenia Marshell 48.6 1.8 3.5 0 2.8 2.6 20
31.4 2.4 3.5 11.5 2.3 2.6 10
Sinapis alba L. 54.3 1.6 3.5 23 2 2.6 20
0 3.6 3.5 0 2.8 2.6 10
Trigonella f. graecum 25.7 2.6 3.5 11.5 2.3 2.6 20
Barakat et al. 27
same virus (HAV-27). The results in Figures 1 and 2
show that the inhibitory activity of all applied
concentrations of the natural seed extracts were higher
than that shown by Acyclovir and Amentadine at the
same concentrations. Treatment of viral infection either
using herbal extracts or combination between natural
extracts and therapeutic agents has been reported in
many investigations. Soybean oil showed significantly
higher activity in vitro against both Herpes simplex virus
and Para-influenza–3 virus as compared to acyclovir and
Oseltamivir (Orhan et al., 2007). The synergistic effect of
betulin, a pentacyclic triterpenoid, isolated from the bark
of Betula papyrifera with acyclovir against herpes simplex
viruses (Yunhao et al., 2004). A combined application of
flowers of Verbascum thapsiforme and three amentadine
derivatives resulted in a marked enhancement of the
inhibitory effect of the natural extract on the reproduction
of influenza virus (Serkedjieva, 2000).
Corina et al. (1999) examined the effect of extracts of
Romanian medicinal plants in combination with acyclovir
in the treatment of 52 patients suffering herpetic keratitis.
Better results and faster healing of ulceration were
obtained using Actium lappa, Calendula officinalis and
Geranium robertianum extracts than with the usual
acyclovir treatment only. These herbal extracts may have
different mechanisms of anti-HSV-1 action from Acyclovir
thus the combination of Acyclovir with herbal extracts
might have worked synergistically. It is also observed that
patients in the Far East are incorporating orthodox
medical drugs into herbal medicinal preparations for
alleviating their illnesses (Chan and Cheung, 2000). The
rationale for doing so is to reduce the side effects of
orthodox medical drugs, and to produce synergistic
effects for better treatment outcome.
Mechanism of action of D. caryophyllus and L.
termes extracts against HSV-1 and HAV-MBB
The results obtained by plaque infectivity count assay
when the seed extracts A and B (D. caryophyllus) and C
(L. termes) (Figure 3) were applied with pre and post viral
treatment revealed that both seed extracts have strong
virucidal activity (97.1, 88.7 and 96.9% at 60 g) either
by their effect on the virus or forming a complex with the
virus preventing it from being adsorbed to its binding sites
on Vero or HepG2 cells. However, no effects were shown
either on the early adsorption or on the replication of
HSV-1 and HAV-27. These results agreed with the study
on Peppermint oil which has antiviral activity against an
acyclovir resistant strain of HSV-1 (HSV-1-Acv). This
essential oil is capable to exert a direct virucidal effect on
HSV (Schuhmacher et al., 2003). While, the mannose-
specific plant lectins showed strong antiviral activity in
vitro against the two corona viruses severe acute
respiratory syndrome (SARS) and the feline infectious
peritonitis virus (FIPV) at 50 - 100 µg/mL by interfering
with two targets in the viral replication cycle. The first
0
10
20
30
40
50
60
70
80
90
100
10
20
30
40
50
Extract conc. in microgram
% of Inhibition
Dianthus
caryophyllus
Acyclovir
Figure 1. Comparison between Dianthus caryophyllus seed
extract and Acyclovir for HSV-1 inhibition.
0
10
20
30
40
50
60
70
80
90
100
10
20
30
40
50
Extract conc. in microgram
% of Inhibition
Dianthus
caryophyllus
Amentadine
Lupinus termes
Figure 2. Comparison between Dianthus caryophyllu,
Lupinus termes seed extracts and Amentadine for
HAV-27 inhibition.
target is located early in the replication cycle, most
probably viral attachment, and the second target is
located at the end of the infectious virus cycle (Keyaerts
et al., 2007).Generally, there are many antiviral
compounds can be found in botanical sources which
have the ability to inhibit human DNA and RNA viruses
which causing serious diseases to humans without
damaging or affecting the host cells. From this
investigation, we hope to open the way for several
studies in this field on these promising effectiveness
natural seed extracts to be used with or without
commercial therapeutic agents against human viral
infections.
28 J. Microbiol. Antimicrob
A B C
Virucidal effect of Dianthus
caryophyllus extract on HSV-1
(60 µg gives 97.1 % viral
inhibition)
Virucidal effect of Dianthus
caryophyllus extract on HAV-27
(60 µg gives 88.7 % viral
inhibition)
Virucidal effect of Lupinus
termes extract on HAV-27
(60 µg gives 96.9 % viral
inhibition)
Effect of pre-treatment of Vero
cells with Dianthus
caryophyllus extract before its
inoculation with HSV-1
(60 µg gives 2.9 % viral
inhibition)
Effect of pre-treatment of HepG2
cells with Dianthus caryophyllus
extract before its inoculation with
HAV-27
(60 µg gives 6 % viral inhibition)
Effect of pre-treatment of
HepG2 cells with Lupinus
termes extract before its
inoculation with HAV-27
(60 µg gives 36.8 % viral
inhibition)
Effect of post-treatment of
Vero cells with Dianthus
caryophyllus extract after its
inoculation with HSV-1
(60 µg gives 47.4 % viral
inhibition)
Effect of post-treatment of
HepG2 cells with Dianthus
caryophyllus extract after its
inoculation with HAV-27
(60 µg gives 65 % viral inhibition)
Effect of post-treatment of
HepG2 cells with Lupinus
termes extract after its
inoculation with HAV-27
(60 µg gives 25 % viral
inhibition)
Figure 3. Studying the mechanism of action of Dianthus caryophyllus L. and Lupinus termes L.
seed extracts against human viruses (HSV-1 and HAV-27).
C: Cell control; V: Virus control; 30, 40, 50, and 60: concentration / µg of seed extract used in
treating each well. Color wells: no viral growth; dotted wells: obvious virus growth.
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