Isolation and Structure Elucidation of Potential Anti-Dengue Metabolites from Tawa-tawa (Euphorbia hirta Linn.)

Many natural products found in plants exhibit a variety of biological activities including antibiotic, antitumor, and antiviral activities that have been utilized in the medicinal field to cure millions of people from serious diseases. Euphorbia hirta Linn. herb, a folkloric medicinal plant in the Philippines against dengue is reportedly effective against the dengue virus. This deadly and painful mosquito-born disease continuously affects millions of people worldwide for there are no commercially developed drugs or vaccines available. From the viewpoint of overcoming the dengue disease, the authors investigated the chemical components of Euphorbia hirta Linn. Preliminary anti-dengue assay by Plaque Reduction Neutralization Test (PRNT) revealed that the ethyl acetate layer was the most active fraction and significantly reduced the plaque forming capacity of the dengue virus serotypes 1 and 2 relative to the control. Further purification of the active ethyl acetate fraction afforded 6 known triterpene and 3 flavonoid compounds. The planar structures of these molecules were established by ESIMS and NMR spectroscopic analyses