Isoflavonoids with insecticide and larvicide activities from Muellera frutescens Standl.

Many plants of the Fabaceae family, are used as fish poisoning and insecticides [1,2]. The genus Muellera in this family is represented by only seven species of climbers and trees and is distributed over south and central America. In 1984, Geesink proposed to consider Muellera as Lonchocarpus synonymous [3]. The Lonchocarpus genera is well known in French Guiana because of its traditional utilization as a fish poisoning [4]. However, one study only reported ethnobotanical use of M. frutescens as an ichtyotoxic plant. Furthermore, no ethnopharmacological use or biological activity data was ever reported in the literature for this plant. Many chemical studies dealing with Lonchocarpus genera have been published [5,6,7]. Phytochemical investigation of barks, stems and rarely leaves described isolation of active isoflavonoids named rotenoids. This study aims at conducting a phytochemical survey of Muellera frutescens in order to evaluate whether or not Muellera is closely related to Lonchocarpus and eventually isolate new bioactive secondary metabolites. Three different extracts (hexane, ethyl acetate and methanol) of bark, roots and leaves were prepared and tested on various biological assays. We discovered insecticide and larvicide activities for all extracts, and none of them exhibited cytotoxicity on human cells. The bioguided fractionation of the most active extract (bark hexane extract) allowed us to isolate eight isoflavonoids, the structures of which were elucidated by spectroscopic methods. It was found that Muellera is indeed closely related to Lonchocarpus, therefore corroborating Geesink's proposal.

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