Bioactivity of seagrass against the dengue fever mosquito Aedes aegypti larvae.

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)] × 100. 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 (R(2)= 0.909) and Y= 2.066 + 1.21x (R(2) =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.