Bioactivity of sea grass against the malarial fever mosquito Culex quinquefasciatus

ObjectiveTo identify the larvicidal activity of the seagrass extracts against Culex quinquefasciatus (Cx. quinquefasciatus)MethodsSeagrass extracts, Halodule pinifolia (H. pinifolia), Cymodocea serrulata (C. serrulata) and Thalasia testudinum (T. testudinum) were dissolved in dimethylsulfoxide to prepare a graded series of concentration. Batches of 25 early 4th instars larvae of Cx. quinquefasciatus 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)]×100. Each experiment was conducted with three replicates and a concurrent control group. A control group consisted of 1 mL of dimethylsulfoxide and 199 mL of distilled water only.ResultsThe root extract of H. pinifolia showed maximum larvicidal activity with minimum concentration of extract of LC50 value of (0.614±0.006) μg/mL with lower confidence limit-upper confidence limit value of (0.052–0.072) and LC90 value of 0.9120 μg/mL followed by leaf extract of C. serrulata LC50 value of (0.074±0.008) μg/mL and LC90 value of 0.1487 μg/mL. T. testudinum leaf extract showed LC50 value of (0.082±0.006) μg/mL. The regression equation of root and leaf extract of H. pinifolia for 4 th instar larvae of Cx. quinquefasciatus were Y=5.229+1.36x (R2=0.993) and Y=2.369+1.21x (R2=0.878) respectively and analysis of variation was significant at P<0.05 level. The result of the preliminary phytochemical constituents showed the presence of saponin, steroids, terpenoid, phenols, protein and sugars.ConclusionsFrom the present study the ethanolic extracts of seagrass of H. pinifolia possess lead compound for development of larvicidal activity.