Evaluation of Toxicity in Four Extract Types of Tuba Root against Dengue Vector, Aedes aegypti (Diptera: Culicidae) Larvae.

Background and objective Since the Dengue virus spreads rapidly and the vector becomes resistant to insecticides and larvicides, exploration of new compounds that overcome resistance problems, are easily degraded and do not lead to bioaccumulation, is needed. This study evaluated four extract types of Derris elliptica represented the polar, semi-polar and nonpolar extract against the 3rd-instar larvae of Ae. aegypti and determined the effective concentration among the extracts. Materials and methods The crude extract was obtained from the maceration of root powder of the plant with methanol and subsequently evaporated. The crude extract was diluted in distilled water and partitioned sequentially with ethyl-acetate, n-hexane and water to obtain their fractions. All the fractions were evaporated to obtain their extract types. Initial bioassay test of the extracts with concentration ranges of 50, 100, 500 and 1,000 mg L-1 against Ae. aegypti larvae and resulted in 86-100% larval mortality rates at concentrations of 50 and 100 mg L-1, except for water extract. The lower concentration range of 3, 5, 10, 25, 50 and 100 mg L-1 of three extract types were tested. Results Larval mortality rates of 18.4-100, 1.6-99.2 and 0.8-98.4% with LC50 of 4.088, 14.066 and 21.063 mg L-1, respectively for n-hexane, methanol and ethyl-acetate. FTIR analysis indicated nine lead compounds in which rotenone and ceramides were observed in all extract types. Conclusion The n-hexane extract showed the highest larvicidal toxicity and its specific compounds are necessarily isolated to obtain pure bioactive ingredients.