Houttuynia cordata Thunb. is a medicinal plant widely used in folk medicine in several Asian countries. It
has been reported that a water extract of H. cordata exhibits activity against herpes simplex virus (HSV)
and the virus of severe acute respiratory syndrome (SARS), although the mechanisms are not fully understood
yet. Previous studies have demonstrated absolute requirement of NF-jB activation for efficient replication
of HSV-1 and HSV-2 and inhibition of NF-jB activation has been shown to suppress HSV
infection. Here we show that a hot water extract of H. cordata (HCWE) inhibits HSV-2 infection through
inhibition of NF-jB activation. The IC50 was estimated at 50 lg/ml of lyophilized HCWE powder. At 150
and 450 lg/ml, HCWE blocked infectious HSV-2 production by more than 3 and 4 logs, respectively. The
inhibitory activity was concomitant with an inhibition of NF-jB activation by HSV-2 infection. Although
activation of NF-jB and Erk MAPK has been implicated for HSV replication and growth, HCWE showed no
effect on HSV-2-induced Erk activation. Furthermore, we show that treatment with quercetin, quercitrin
or isoquercitrin, major water extractable flavonoids from H. cordata, significantly blocked HSV-2 infection.
These results together demonstrated that H. cordata blocks HSV-2 infection through inhibition of
NF-jB activation.
Houttuynia cordata Thunb. is a medicinal plant widely used in folk medicine in several Asian countries. It
has been reported that a water extract of H. cordata exhibits activity against herpes simplex virus (HSV)
and the virus of severe acute respiratory syndrome (SARS), although the mechanisms are not fully understood
yet. Previous studies have demonstrated absolute requirement of NF-jB activation for efficient replication
of HSV-1 and HSV-2 and inhibition of NF-jB activation has been shown to suppress HSV
infection. Here we show that a hot water extract of H. cordata (HCWE) inhibits HSV-2 infection through
inhibition of NF-jB activation. The IC50 was estimated at 50 lg/ml of lyophilized HCWE powder. At 150
and 450 lg/ml, HCWE blocked infectious HSV-2 production by more than 3 and 4 logs, respectively. The
inhibitory activity was concomitant with an inhibition of NF-jB activation by HSV-2 infection. Although
activation of NF-jB and Erk MAPK has been implicated for HSV replication and growth, HCWE showed no
effect on HSV-2-induced Erk activation. Furthermore, we show that treatment with quercetin, quercitrin
or isoquercitrin, major water extractable flavonoids from H. cordata, significantly blocked HSV-2 infection.
These results together demonstrated that H. cordata blocks HSV-2 infection through inhibition of
NF-jB activation.
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