Larvicididal Activity of Natural Repellents Against the Dengue Vector, Aedes aegypti.

The present research aimed to evaluate the larvicidal activity of several recently discovered natural repellents formulated in lotions against larvae of Aedes aegypti. We used a modified larval bioassay method by the World Health Organization standards in evaluating larval mortality at 24-, 48-, and 72-h exposure. Among the test repellents, 2-undecanone showed 100% mortality of Ae. aegypti larvae, followed by catnip oil, capric acid, coconut oil fatty acids, methyl caprate, methyl laurate, and coconut oil methyl esters. The repellent, 2-undecanone showed median lethal concentration (LC50) values of 73.07, 26.45, and 15.68 ppm at 24-, 48-, and 72-h exposure, respectively. Larvicidal activity varied among the other repellents tested.

Pharmacological effect of deoxypodophyllotoxin: a medicinal agent of plant origin, on mammalian neurons.

Deoxypodophyllotoxin (DOP) is a natural product that can be isolated from a variety of medicinal herb plants. It is well known for its antitumor, antiviral, and anti-inflammatory activities. However, there are few investigations that address neurotoxic effect of DOP in animal nervous system. In this study, whole-cell patch clamp and calcium imaging techniques were employed to investigate effects of DOP on electrophysiological properties and calcium regulation of rat dorsal root ganglion (DRG) neurons. DOP inhibited both TTX-S (tetrodotoxin-sensitive) and TTX-R (tetrodotoxin-resistant) sodium currents in voltage clamp recording and caused a decrease in the number of action potentials (APs) in current clamp experiment. Suppressive and unfavorable effects of DOP on the kinetics of sodium currents in terms of excitability of DRG neurons may greatly contribute to its antitumor and anti-inflammatory activities. Moreover, DOP evoked increase of intracellular Ca(2+) concentrations ([Ca(2+)](i)) in DRG neurons, and this effect may lead to neuronal cytotoxicity.