Bioactivity of sea grass against the malarial fever mosquito Culex quinquefasciatus

Objective: To identify the larvicidal activity of the seagrass extracts against Culex\udquinquefasciatus (Cx. quinquefasciatus)\udMethods: Seagrass extracts, Halodule pinifolia (H. pinifolia), Cymodocea serrulata (C. serrulata)\udand Thalasia testudinum (T. testudinum) were dissolved in dimethylsulfoxide to prepare a\udgraded series of concentration. Batches of 25 early 4th instars larvae of Cx. quinquefasciatus\udwere transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant\udextracts (0.01 mg-0.1 mg). After 24 h the mortality rate was identified with the formulae [(% of\udtest mortality - % of control mortality)/(100 - % of control mortality)]伊100. Each experiment was\udconducted with three replicates and a concurrent control group. A control group consisted of 1 mL\udof dimethylsulfoxide and 199 mL of distilled water only.\udResults: The root extract of H. pinifolia showed maximum larvicidal activity with minimum\udconcentration of extract of LC\ud50 value of (0.614依0.006) µg/mL with lower confidence limit-upper\udconfidence limit value of (0.052-0.072) and LC90 value of 0.9120 µg/mL followed by leaf extract of\udC. serrulata LC\ud50 value of (0.074依0.008) µg/mL and LC90 value of 0.1487 µg/mL. T. testudinum leaf\udextract showed LC\ud50 value of (0.082依0.006) µg/mL. The regression equation of root and leaf extract\udof H. pinifolia for 4 th instar larvae of Cx. quinquefasciatus were Y=5.229+1.36x (R2=0.993) and\udY=2.369+1.21x (R2=0.878) respectively and analysis of variation was significant at P<0.05 level. The\udresult of the preliminary phytochemical constituents showed the presence of saponin, steroids,\udterpenoid, phenols, protein and sugars.\udConclusions: From the present study the ethanolic extracts of seagrass of H. pinifolia possess\udlead compound for development of larvicidal activity