Abstract

Objective: To identify the larvicidal activity of the seagrass extracts against Culex quinquefasciatus (Cx. quinquefasciatus) Methods: Seagrass 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)]伊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. Results: The root extract of H. pinifolia showed maximum larvicidal activity with minimum concentration of extract of LC 50 value of (0.614依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 LC 50 value of (0.074依0.008) µg/mL and LC90 value of 0.1487 µg/mL. T. testudinum leaf extract showed LC 50 value of (0.082依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. Conclusions: From the present study the ethanolic extracts of seagrass of H. pinifolia possess lead compound for development of larvicidal activity.

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