Effect of Thai Medicinal Plant Extracts against Dengue Virus in vitro N. Klawikkan, V. Nukoolkarn, N. Jirakanjanakit, S. Yoksan, C. Wiwat1 and K. Thirapanmethee*
Dengue hemorrhagic fever is one of the major public health problems in Thailand. The disease caused by the mosquito-borne dengue virus (DENV). DENV is the member of the Flavivirus genus, Flaviviridae family. There are four genetically related but distinct serotypes DENV 1, 2, 3, and 4. It is transmitted to people through the bite of mosquitoes Aedes aegypti and Aedes albopictus. It has been reported that dengue virus infects 50 to 100 million people annually. However, there is neither vaccine nor effective antiviral drugs to treat dengue virus infection. Consequently, the development of antiviral drugs licensed for treatment of patients remains an urgent need to prevent dengue fatalities. Many studies have been conducted for exploring the antiviral activity of chemical compounds against DENV. Among these compounds, some are small molecules that can inhibit specific steps of viral intracellular replication or effect at viral proteins. But none of these compounds have been approved to be used in human. Thailand has many traditional medicinal plants that have been reported on strong antiviral activity and some of them have already been used to treat people who were infected with viruses. Therefore, the aim of this study is to investigate the in vitro anti-dengue activity from Thai medicinal plants. In this present study, ten medicinal plants were collected from Siri Ruckhachati Natural Park, Salaya campus, Mahidol University. These plants were extracted with dichloromethane ethanol and subsequently tested for their anti-dengue type 2 activities in Vero cell by MTT method. The results showed that the ethanol extracts of Rhizophora apiculata Blume., Flagellaria indica Linn. and Cladogynos orientalis Zipp. at a concentration of 12.5 ?g/ml exhibited inhibitory activity on DENV-2 with 56.14%, 45.52% and 34.85%, respectively. Moreover, Houttuynia cordata Thunb. exhibited inhibitory activity against DENV-2 with 35.99% at a concentration of 1.56 ?g/ml. In addition, Cladogynos orientals Zipp., Piper retrofractum Vahl. and Rhizophora apiculata Blume. exhibited an inactivated viral particle activity with 52.9%, 84.93% and 41.5% at a concentration of 100 ?g/ml. This study indicated that Rhizophora apiculata Blume., Flagellaria indica Linn., Cladogynos orientalis Zipp. and Houttuynia cordata Thunb. have a significant potential effect on the dengue virus in vitro. These medicinal plants could potentially be sources for developing the anti-DENV drug.
Dengue virus type 2, Thai medicinal plants, Anti-dengue activity
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