As a tetracyclo-quinolizidine alkaloid, matrine is one of the bioactive components extracted from Sophora flavescens, a traditional Chinese medicinal herb that is used as the main ingredient in a number of Chinese bio-pesticidal products. While it has known activity against agricultural pests, its insecticidal potency against mosquitoes and mechanism of action have not been well documented. Accordingly, we examined the mosquitocidal activity to adults and larvae of Aedes aegypti, as well as its mode of action in various physiological preparations. Matrine caused flaccid paralysis in headless fourth instar Ae. aegypti larvae (50% paralysis in 5 hours at 8 ppm) and is toxic to adult females by contact (topical LD50 was 258 ng/mg), all with little or no expression of hyperactivity or hyperexcitability. Matrine (ca. 1 mM) suppresses firing of Drosophila melanogaster larval central nervous system and reduces EPSP amplitude at the Musca domestica neuromuscular junction, without any evidence of neuroexcitation or membrane depolarization. On homomultimeric Anopheles gambiae GABA receptors expressed in Xenopus laevis oocytes, matrine acts as a positive allosteric modulator, increasing the potency and maximal effectiveness of applied GABA, effects similar to those of the natural product, thymol. These physiological actions are sufficient to explain the whole animal intoxication by matrine, but require relatively high concentrations to manifest themselves.

Mosquitocidal activity and physiological actions of matrine, a plant natural product insecticide

254th National Meeting (2017)

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