Abstract:
Due to newly emerging viral diseases and the building of rapid resistance among targeted
viruses, the continuous search for useful and novel antiviral compounds has become
important. Hence, a study was carried to develop a method for the preliminary screening
of antiviral drugs and identification of their targeted stage of the viral replication cycle.
A model system of bacteriophage and susceptible Escherichia coli, isolated together from
a sewage effluent was used for the screening process. Two plant extracts, each from Carica
papaya leaves and Psidium guajava leaves and two plant based products each
“Sudarshana Churnaya”, an aurvedic drug and black tea produced from Camellia sinensis
leaves were screened using two approaches developed based on plaque reduction assay
to detect their effect on different stages of the phage replication cycle. In the first approach,
the purified virus suspensions pre-incubated with filter sterilized herbal extracts were used
to detect the antiviral effects of herbal extracts on adsorption and penetration steps. For
the second approach, the host bacterium pre-incubated in filter sterilized herbal extracts
were used as the indicator host to detect the effects of herbal extracts on intracellular
replication steps of the virus replication cycle.
Screening revealed that black tea has the ability to inhibit viral propagation by preventing
phage attachment to their host and Carica papaya leaf extract showed an ability to inhibit
intracellular stage(s) of the bacteriophage’s replicative cycle. The study provides evidence
for the availability of antiviral compounds in plant extracts and plant based products which
are used in routine life and traditional healing methods. The results also indicate that
different herbal extracts apply different modes of action to prevent the propagation of the
targeted virus.
