Soapnut, a mosquito repellent

It inhibits growth of larvae and pupae of mosquitoes

By Biplab Das
Published: Thursday 31 March 2011

HAILED for being a vital ingredient in traditional medicines, cosmetics and detergents, soapnut can now combat mosquito-borne diseases and thus reduce indiscriminate use of harmful insecticides and mosquito repellents.

Kernel extracts of soapnut disrupt the activity of enzymes of larvae and pupae and inhibit the growth of Aedes aegypti, a mosquito that spreads viral diseases such as yellow fever, dengue and chikungunya. These diseases affect over 30 million people every year worldwide.

Findings of the study were published in the online edition of Acta Tropica on January 18, 2011.

imageIn an earlier study, when researchers exposed the larvae of A aegypti to 4 mg of soapnut extract mixed with one ml water, they died within 18 hours. At a concentration of 5 mg of soapnut per ml of water, the extract caused 100 per cent pupal mortality within 18 hours.

Researchers have now studied the impact of the extract on enzyme activity of the mosquito. “We found that soapnut extract significantly disrupts the metabolic activity of exposed larvae and pupae of A aegypti,” said lead researcher Periasamy Mullainadhan of Madras University’s of zoology department. Signs of this disruption were detected by way of reduced activities of metabolic enzymes of larvae and pupae of A aegypti.

Researchers specifically studied the proteins and marker enzymes esterases and phosphatases in the developmental stages of A aegypti. Esterases play a role in reproduction, digestion and metabolism of hormone in larvae. Phosphatases are important for diverse physiological processes such as cellular metabolism and activity of genes.

These enzymes have been used as accurate biomarkers to evaluate toxicity of insecticides.

There was significant reduction in the activity of acetylcholinestarase and betacarboxylestarase—enzymes in the larval stage of the mosquito. The outcome of this study also shows that the mosquito’s pupae are more tolerant to toxicants than the larvae.

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