INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 2, ISSUE 10, OCTOBER 2013
The Effect Of Combination Of Octadecanoic Acid, Methyl Ester And Ribavirin Against Measles Virus
Reagan Entigu Ak Linton @ Jerah, Samuel Lihan, Ismail bin Ahmad
Abstract: Ribavirin is a broad spectrum antiviral drug and has been used to treat various diseases. It has been used as a treatment for subacute sclerosis panencephalitis (SSPE) caused by measles virus infection. However, there were several adverse effects when receiving ribavirin treatment. Other than ribavirin and vaccine, there is no cure for the disease thus medicinal plants being studied for their potential active compounds to be used as either mono or combined treatment with drugs. The objective of this study was to test antiviral activity of octadecanoic acid, methyl ester (OA), extracted from Cymbopogon nardus (sweet lemon grass) against measles virus in both mono and combination with ribavirin. The cytotoxicity and antiviral activity were tested at low concentration for the compound (25, 12.5 and 2.5 µg/ml) and ribavirin (0.1, 0.05 and 0.01 CC50). The cytotoxicity result showed that the low concentrations of both compounds have low cytotoxicity on Vero cell although there was slight increment of toxicity when they were combined. However, the combined treatment showed higher antiviral activity (p <0.05) compared to single treatment of both compounds (OA12.5 µg/ml + RBV0.05CC50: 94.38 ± 1.5%, OA12.5 µg/ml: 67.09 ± 0.2%, RBV0.05CC50: 51.12 ± 2.1%). The result has also shown that decreasing of the concentration of the combination could still maintained the antiviral activity comparable to single treatment and less cytotoxicity toward Vero cell. This study has proven that OA can be combined with commercial drug such as ribavirin to produce higher antiviral activity at lower concentration for combination of both compounds. Index terms: Antiviral, Cymbopogon nardus,cytotoxicity, measles, octadecanoic acid, methyl ester, ribavirin
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1 Introduction
Although ribavirin showed antiviral activity against HCV,
Stearic acid, methyl ester or stearate is a saturated 19
there was adverse effect to recipients. SARS patient that
carbon-chained compound and it is also known as
was treated with ribavirin developed hypoxemia, a state of
octadecanoic acid methyl ester (OA). There are various
low healthy hemoglobin to carry oxygen [9]. The advantage
antiviral activities from fatty acids against viruses. Fatty acid
of synergistic effect between drugs in combination therapy
was able to inhibit the replication of HCV and synergistic
is the additive effect or diminished resistance of viral
effect with IFN-α was observed by Leu et al. [1]. Measles
infection. However, multiple therapies may incur higher
virus (MV) belongs to paramyxoviridae family along with the
cost, increase in toxicity and could lead to treatment failure
parainfluenza, mumps, Newcastle disease virus and
compared to monotherapy using single drug [10].
several other viruses. The MV replicates first in the
Combination of drug with herbs may increase or decrease
respiratory tract and moved to lymphoid tissue for further
the activity of either component [11] and the combination
viral processes [2]. The MV causes high death rates
could also cause various adverse effects such as bleeding
annually and has claimed as much as 13 million lives of
when patient mixed warfarin with Ginkgo biloba and mild
children less than 6 years of age [3]. Although introduction
serotonin syndrome when serotonin-reuptake inhibitors
of vaccine has been for 50 years, the disease is still could
mixed with Herpericum perforatum [12].
not be eradicated due to difficulty of vaccine distribution
especially in rural or undeveloped areas such as Africa [4].
2 Materials and Methods
Ribavirin is an antiviral drug used to treat respiratory
syncytial virus, RSV and strains of influenza A and B [5]. It
2.1 Octadecanoic acid, methyl ester preparation
has also shown antiviral activity against RNA viruses such
The octadecanoic acid, methyl ester (OA) was isolated from
as influenza A and B, measles and parainfluenza [6]. The
ribavirin has the ability to incorporate itself into viral RNA
chromatography mass spectrometry, GCMS. It was
and the reaction caused mutation that interferes with the
prepared at different concentrations (25, 12.5 and 2.5
normal viral replication processes [7],[8].
µg/ml) by diluting in Dulbecco‘s Modified Eagle Medium,
DMEM. The control drug, ribavirin was also prepared at 0.1,
2.2 Cell culture
The Vero cells were cultured and maintained in T-25 flask
with HyClone DMEM/ low glucose 5% FBS (HyClone)
added with penicillin streptomycin (AMRESCO tissue
Reagan Entigu Ak Linton @ Jerah, postgraduate
culture grade). The Vero cells were subcultured once it
student Virology laboratory, Department of Molecular
reached 80-90% confluent. The Vero cells were also given
geneticin to maintain the Signaling Lymphocyte Activating
Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia. 2.3 Vaccine
Samuel Lihan, Senior Lecturer of Department of
The vaccine used was the live attenuated Edmonston
Molecular Biology, Faculty of Resource Science and
Strain of the MMR vaccine (Serum Institute of India Ltd.).
Technology, Universiti Malaysia Sarawak, 94300 Kota
INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 2, ISSUE 10, OCTOBER 2013
2.4 Antiviral assay The Vero cells with the cell counts of 1.0 x 105 cells/ml were plated onto the 96-well plate with DMEM 2% FBS and incubated overnight until the cells are confluent. The medium were discarded and the plates were washed with DMEM twice and 10 µl of the measles vaccine was added into the designated wells of the plate and incubated for 30 minutes to allow the adsorption of virus to the cells. Then, 100 µl of groups of ribavirin and octadecanoic acid, methyl ester at different concentrations were added separately and combined to each well and left in the 37 ºC 5% CO2 incubator for 48 hours. 2.5 Plate processing
After 48 hours, the medium were discarded and the cells
Fig. 1: Cytotoxicity of octadecanoic acid, methyl ester
were fixed with 125 µl of cold TCA for each well which then
(OA) and ribavirin (RBV) against Vero cell. The graph
incubated for 1 hour at 40 ºC. The solution were removed
showed the percentage of cell viability after different
and washed 5 times with distilled water and left in 40 ºC for
1 hour. About 100 µl of eosin were added and left for 1 hour
at room temperature. The plates were washed 5 times with
300 µl of acetic acid to wash the excess dye and left for 1
In the individual treatment, both compounds showed low
day at room temperature. About 200 µl of 5mM NaOH were
cytoxicity. The ribavirin had cytotoxicity ranging from 90.03
added and left for 20 minutes at room temperature. The
± 1.1% to 96.88 ± 0.3% cell viability while octadecanoic
optical density, OD readings were taken with the Elisa
acid, methyl ester had cytotoxicity ranging from 91.01 ±
reader (Microplate reader Metertech Inc.) at 490nm
1.6% to 98.22 ± 1.7% cell viability. There was a slight
increase in cytotoxicity when 0.05CC50 ribavirin combined
with 12.5µg/ml octadecanoic acid, methyl ester compared
2.6 Statistical assay
to individual treatment (combined: 88.59 ± 1.5%, RBV
Each treatment of fractions/subfractions was carried out in
0.05CC50: 92.11 ± 2.1%, OA 12.5 µg/ml: 96.53 ± 2.6%).
5 replicates. The data were analyzed with one-way ANOVA
However the Vero cell viability increased slightly than
test to compare between groups of treatment and Student
individual treatment as the combined concentration became
T-test between the highest activity of treated group with
lower (combined: 98.60 ± 0.5%, RBV 0.01CC50: 96.88 ±
control group. The criteria for statistical significance were
3 Results The combination of octadecanoic acid, methyl ester (OA) and ribavirin (RBV) would determine whether the combination treatment could exhibit higher antiviral activity. It was also vital that the combination used lower cytotoxitcity and lower concentrations compared to individual treatment. In this study, both compounds (octadecanoic acid, methyl ester and ribavirin) were tested for their cytotoxicity against Vero cell prior to antiviral assay both individual and combined treatment (Fig. 1). Fig. 2: Antiviral activity of octadecanoic acid, methyl
ester and ribavirin against measles disease virus. The
graph was based on the viability of treated infected-Vero
In this study, the inhibition of ribavirin ranged from 68.67 ± 0.4% to 40.59 ± 1.9% while the octadecanoic acid, methyl ester had inhibition activity ranging from 82.33 ± 1.0% to 58.79 ± 2.4% (Fig. 2). When OA combined with RBV at concentration of 12.5 µg/ml and 0.05CC50 respectively, there was an increase of inhibition activity observed. The individual treatment had lower activity (OA 12.5 µg/ml: 67.09 ± 0.2% and RBV 0.05CC50: 51.12 ± 2.1%) compared to combined treatment of the same concentration, 94.38 ± 1.5%. The combined treatment had higher (p <0.05) inhibition activity even when compared to individual treatments at double the concentrations (OA 25 µg/ml:
INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 2, ISSUE 10, OCTOBER 2013
82.33 ± 1.0% while RBV 0.1CC50: 68.67 ± 0.4%). By
and cancer cells together with testing for other bioactivities
alternating the concentration of ribavirin and octadecanoic
such antimicrobial, antioxidant and antifungus. OA might
acid, methyl ester, there was an influenced on the inhibition
possess various bioactivities that are yet to be fully studied
activity. When the OA concentration was decreased from
and could also provide based-structure for other derivatives
12.5 to 2.5 µg/ml while maintaining RBV concentration at
0.05CC50, there was 16.06% decrease of activity. Whereas
when the RBV concentration was decreased from 0.05 to
Acknowledgement
0.01CC50 with fixed concentration of OA at 12.5 µg/ml,
The research was funded under the grant E-science Vot no:
4 Discussions References
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