Mosquito larvicidal efficacy of seaweed extracts against dengue vector of Aedes aegypti

Objective To identify the larvicidal activity of the seaweed extracts. Methods Seaweed extracts of Enteromorpha intestinalis ( E.intestinalis ), Dictyota dichotoma ( D.dichotoma ) and Acanthopora spicifera ( A. spicifera ) were dissolved in dimethylsulfoxide (DMSO) to prepare a graded series of concentration. Batches of 25 early 4 th instars larvae of Aedes aegypti were transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant extracts (0.01–0.1 mg). Each experiment was conducted in three replicates. A control group consisted of 1 mL of DMSO and 99 mL of distilled water only. After 24 h, the percentage of mortality was identified with the formula: % of mortality=[(% of test mortality - % of control mortality) / (100 - % of control mortality )]×100. Results The extract of D. dichotoma showed minimum level of LC 50 value (0.0683±0.0084 μg/mL) and LC 90 value was 0.140 1. The regression equations of D. dichotoma and E. intestinalis for 4 th instar larvae were Y=0.333 + 0.684x ( R 2 =0.946) and Y=0.600 + 0.781x ( R 2 =0.812), respectively. The results of the preliminary phytochemical constituents showed the presence of saponin, steroids, terpenoid, phenols, protein and sugars. Conclusions It can be concluded from the present study that, the ethanolic extracts of seaweed of D. dichotoma possess active compounds for development of larvicidal ativity.