Herbal warfare against dengue

Nichinda leaves can combat dengue and filariasis

By Biplab Das
Published: Saturday 15 October 2011

imageUSE of insecticides to get rid of mosquitoes is known to be detrimental to the environment and human health. A finding on how larvae of mosquitoes which cause dengue and filariasis can be killed in an eco-friendly way, therefore, holds significance.

Researchers at the Annamalai University in Tamil Nadu have found the secret in the leaves of Nichinda tree (Vitex trifolia), a coastal shrub. Extracts of its leaves attack the gut of the larvae’s epithelial cell. Methyl-para-hydroxybenzoate present in the leaves accomplish this task.

In 2007, researchers had exposed the larvae of dengue- and filariasis-causing mosquitoes to the leaf extracts of different species of Vitex. It was the leaf extract of Nichinda that killed the larvae of both mosquitoes.

In the recent study, researchers found the compound in the leaf responsible for the larvicidal activity. They used different organic solvents to separate chemicals in the leaf extract. The fraction that had the maximum larvicidal activity was found to contain methyl-para-hydroxybenzoate.

Researchers have also isolated the crystalised form of methyl-para-hydroxybenzoate. “The compound has been reported in many plant species but its crystal structure was never isolated,” says lead researcher V Venkatesalu. Knowing the crystal structure will help identify the exact structure of methyl-para-hydroxybenzoate responsible for the leaf extracts’ larvicidal property.

The compound belongs to a class of organic compounds known as phenols. It can be used after further toxicological evaluations on non-target organisms, he adds. The study was published in the October-November issue of the journal Acta Tropica.

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