Bioactivity of seagrass against the dengue fever mosquito Aedes aegypti larvae

摘要

Objective: To identify the larvicidal activity of the seagrass extracts. Methods: Seagrass extracts, Syringodium isoetifolium (S. isoetifolium), Cymodocea serrulata and Halophila beccarii, were dissolved in DMSO to prepare a graded series of concentration. Batches of 25 early 4th instars larvae of Aedes aegypti (Ae. aegypti) were transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant extracts (0.01 mg–0.1 mg). After 24 h the mortality rate was identified with the formulae [(%of test mortality- %of control mortality)/(100- %of control mortality)]í100. Each experiment was conducted with three replicates and a concurrent control group. A control group consisted of 1 mL of DMSO and 199 mL of distilled water only. Results:The root extract of S. isoetifolium showed maximum larvicidal activity with minimum concentration of extract of LC50= 0.0 604± 0.0 040)μg/mL with lower confidence limit (LCL)-upper confidence limit (UCL)=(0.051-0.071) and LC90=0.0 972μg/mL followed by leaf extract of S. isoetifolium showed LC50= (0.062± 0.005)μg/mL. The regression equation of root and leaf extract of S. isoetifolium for 4th instar larvae were Y=4.909+1.32x (R2=0.909) and Y=2.066+1.21x (R2=0.897) respectively. The results of the preliminary phytochemical constituents shows the presence of saponin, steroids, terpenoid, phenols, protein and sugars. Conclusions: From the present study the ethanolic extracts of seagrass of S. isoetifolium possesses lead compound for development of larvicidal activity.