The methanol and dichloromethane extracts of Inula cappa (Ham. ex D. Don) DC. were evaluated for
inhibition of herpes simplex virus infection. Higher anti- herpes simplex virus (HSV) activity of I. cappa
methanol extract was observed comparing with I. cappa dichloromethane extract since more than 50%
of the virus was inhibited by I. cappa methanol extract and 50% effective doses of I. cappa methanol
extract on HSV-1and HSV-2 were 720.1±32.7 and 529.2±5.2 µg/ml respectively. However, when the virus
particles were treated with I. cappa dichloromethane and I. cappa methanol extracts, both HSV-1 and
HSV-2 particles were directly inactivated to negligible amount within 1 - 2 h. More than 50% interference
on blocking of HSV attachment and penetration was observed after treatment the virus with I. cappa
methanol extract. Moreover, within 30 h, the effective inhibitory activity of I. cappa methanol extract on
HSV replication was higher than that of the I. cappa dichloromethane extract. Both extracts had potent
activities in reducing viral deoxyribonucleic acid (DNA) synthesis since HSV DNA after treatment with
the extracts were 1.3-2 fold less than HSV DNA control after determination by real time polymerase
chain reaction and approximately 45 kilodalton viral proteins were clearly diminished after treatment
with I. cappa methanol extract. Therefore, methanol extract of I. cappa is a potent inhibitor of herpes
simplex virus infection in vitro.
Key words: Anti-viral activity, Inula cappa, plant extract, herpes simplex virus.