Effects of extract of soapnut Sapindus emarginatus on esterases and phosphatases of the vector mosquito, Aedes aegypti (Diptera: Culicidae)

• Published in: Acta tropica 2011-04, Vol.118 (1), p.27-36
• Main Authors: Koodalingam, Arunagirinathan, Mullainadhan, Periasamy, Arumugam, Munusamy
• Format: Article
• Language: English
• Subjects: Aedes - enzymology; Aedes aegypti; alkaline phosphatase; Animals; Anopheles stephensi; Antimosquito activity; aquatic insects; biochemical mechanisms; biocides; Biological and medical sciences; Botanical; Culex quinquefasciatus; Culicidae; Diptera; enzyme activity; Esterase; Esterases - antagonists & inhibitors; Esterases - isolation & purification; General aspects; Insect Proteins - antagonists & inhibitors; Insect Proteins - isolation & purification; Insecticides - pharmacology; instars; Larva - enzymology; larvae; Medical sciences; mortality; Phosphatase; Phosphoric Monoester Hydrolases - antagonists & inhibitors; Phosphoric Monoester Hydrolases - isolation & purification; Plant Extracts - pharmacology; polyacrylamide gel electrophoresis; proteins; Pupa - enzymology; pupae; Sapindus; Sapindus - chemistry; seeds; Soapnut; Toxicity
• ISSN: 0001-706X; 1873-6254
• DOI: 10.1016/j.actatropica.2011.01.003

The aqueous kernel extract of soapnut accomplishes its antimosquito activity by multiple modes of action as evident from adverse changes observed with three important metabolic enzymes, namely, acetylcholinesterase, β-carboxylesterase and acid phosphatase of the larvae of Aedes aegypti. [Display omitted] ► Total proteins, esterases, and phosphatases exhibited distinct patterns of variation during normal development of fourth instar larvae and pupae of Aedes aegypti. ► The aqueous extract of the soapnut Sapindus emarginatus exhibited a strong antimosquito activity against the larvae, and moderate effect on the pupae of A. aegypti. ► Upon exposure of the larvae to the extract, perceptible changes in quantitative and qualitative profiles were observed especially with β-carboxylesterase, acid and alkaline phosphatases. ► Only alkaline phosphatase was found to be sensitive in the extract-exposed pupae. ► The extract accomplishes its antimosquito activity by multiple modes of action. Our earlier investigations with kernels from the soapnut Sapindus emarginatus revealed it as a new source of botanical biocide with potent antimosquito activity, as evident from the proven unique ability of the aqueous kernel extract to kill all the developmental stages of three important vector mosquito species, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. This extract was also found to be safe for two non-target aquatic insects. As a sequel to these findings, we have further examined quantitative and qualitative changes in total proteins, esterases, and phosphatases in whole body homogenates of fourth instar larvae and pupae of A. aegypti exposed to this extract at an appropriate threshold time for its lethal effect to gain insights into the impact of the botanical biocide on biochemical characteristics of the target vector mosquito at two distinct developmental stages. The profiles of proteins, esterases (acetylcholinesterse, α- and β-carboxylesterases), and phosphatases (acid and alkaline) exhibited distinct patterns of variation during normal development of fourth instar larvae and pupae, indicating intrinsic difference in biochemical features between these two developmental stages of A. aegypti. Upon exposure of the larvae to the extract, significant reduction in the activities of acetylcholinesterse, β-carboxylesterase, and acid phosphatases were recorded, whereas the total proteins, α-carboxylesterase and alkaline phosphatase activities were unaffected. By