Mosquito larvicidal activities of Solanum villosum berry extract against the dengue vector Stegomyia aegypti

<p>Abstract</p> <p>Background</p> <p>Vector control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. Although several plants have been reported for mosquitocidal activity, only a few botanicals have moved from the laboratory to field use, because they are poorly characterized, in most cases active principals are not determined and most of the works are restricted to preliminary screening. <it>Solanum villosum </it>is a common weed distributed in many parts of India with medicinal properties, but the larvicidal activity of this plant has not been reported so far.</p> <p>Methods</p> <p>Aqueous and polar/non-polar solvent extract of fresh, mature, green berries of <it>S. villosum </it>was tested against <it>Stegomyia aegypti</it>, a common vector of dengue fever. A phytochemical analysis of chloroform:methanol extract was performed to search for the active toxic ingredient. The lethal concentration was determined (log probit analysis) and compared with Malathion. The chemical nature of the active substance was also evaluated following ultraviolet-visual (UV-Vis) and infrared (IR) analysis.</p> <p>Results</p> <p>In a 72 hour bioassay experiment with the aqueous extract, the highest mortality was recorded in 0.5% extract. When the mortality of different solvent extracts was compared, the maximum (<it>p </it>< 0.05) mortality was recorded at a concentration of 50 ppm of chloroform:methanol extract (1:1, v/v). The larvicidal activity was lower when compared with the chemical insecticide, Malathion (<it>p </it>< 0.05). Results of regression analysis revealed that the mortality rate (<it>Y</it>) was positively correlated with the period of exposure (<it>X</it>) and the log probit analysis (95% confidence level) recorded lowest value (5.97 ppm) at 72 hours of exposure. Phytochemical analysis of the chlororm:methanol extract reported the presence of many bioactive phytochemicals. Two toxic compounds were detected having <it>R</it>_f= 0.82 (70% and 73.33% mortality in 24 and 48 hours, respectively) and <it>R</it>_f= 0.95 (40% and 50% mortality in 24 and 48 hours, respectively). IR analysis provided preliminary information about the steroidal nature of the active ingredient.</p> <p>Conclusion</p> <p><it>S. villosum </it>offers promise as potential bio control agent against <it>S. aegypti </it>particularly in its markedly larvicidal effect. The extract or isolated bioactive phytochemical could be used in stagnant water bodies for the control of mosquitoes acting as vector for many communicable diseases.</p

NS3 protease from flavivirus as a target for designing antiviral inhibitors against dengue virus

The development of novel therapeutic agents is essential for combating the increasing number of cases of dengue fever in endemic countries and among a large number of travelers from non-endemic countries. The dengue virus has three structural proteins and seven non-structural (NS) proteins. NS3 is a multifunctional protein with an N-terminal protease domain (NS3pro) that is responsible for proteolytic processing of the viral polyprotein, and a C-terminal region that contains an RNA triphosphatase, RNA helicase and RNA-stimulated NTPase domain that are essential for RNA replication. The serine protease domain of NS3 plays a central role in the replicative cycle of dengue virus. This review discusses the recent structural and biological studies on the NS2B-NS3 protease-helicase and considers the prospects for the development of small molecules as antiviral drugs to target this fascinating, multifunctional protein