Malek Besbes Hlila, Habib Mosbah, Kaouther Majouli et al.152
3. RESULTS AND DISCUSSION
3.1. Cytotoxicity Test
Before conducting antiviral activity assays, the cytotoxicity of the extracts
on the Vero cells was studied. An antiviral drug should be active against the
virus inducing significant toxicity on the host cell. Therefore, the
concentration range in which the extracts will not induce significant toxicity to
the host cells was estimated and the 50% cytotoxic concentration (CC 50 ) was
determined for each extract. As shown in Table 1, the 50% cytotoxic
concentrations of the majority of the 16 extracts tested is between 500 μg/mL
and 4000 μg/mL. We can note that, the lowest cytotoxicity was observed with
the two water fractions of (stems and leaves) and fruits (CC 50 = 500 μg/mL).
Results revealed significant differences (P < 0.05). The cytotoxicity of our
studied extracts was very low (CC 50 > 20 μg/mL) [31].
The cytotoxicity of plants belonging to the dipsacaceae family was studied
for the first time in our work.
3.2. Antiviral Activity
All extracts tested were used at their non-cytotoxic concentrations (Table
1). To evaluate the activity of antiviral agents in vitro, the selectivity index
(SI = CC 50 /IC 50 ) was determined. The selectivity index describes the ratio
between the cytotoxic and the antiviral activity of a substance. The roots
EtOAc fraction showed the better antiviral activity (IC 50 = 722.22 ± 0.15
μg/mL and SI = 5.53) followed by the flowers butanol fraction which
presented also an interesting anti-coxsackie B 3 activity (IC 50 = 750 ± 0.12
μg/mL and SI = 2.66). While, the roots water fraction showed an IC 50 value
greater than the two previous extracts (IC 50 = 938.59 ± 0.1 μg/mL and SI =
2.13) (Table 1). We found that the selectivity index of the positive control,
Ribavirin, (SI = 7.03) was close to that of the roots EtOAc fraction. This
fraction showing the best anti-coxsackie B 3 activity was fractionated into 4
subfractions. The anti-coxsackie B 3 activity of the four subfractions was shown
in Table 1; the subfraction SR 1 showed the best result with IC 50 = 620 ± 0.05
μg/mL and selectivity index = 6.45 followed by the subfraction SR 4 with value
of IC 50 = 697.34 ± 0.04 μg/mL and selectivity index = 5.73.
These two subfractions demonstrated an anti-Coxsackie B 3 activity more
important than the crude extract (roots EtOAc) (IC 50 = 722.22 ± 0.15 μg/mL