Insecticidal activity of Limonium brasiliense (Plumbaginaceae) against Rhizopertha dominica (Coleoptera)”

BENZI, VERÓNICA; RODRIGUEZ, SILVANA; ANA PAULA MURRAY; SANCHEZ CHOPA, CAROLINA; ADRIANA FERRERO

Colonia del Sacramento

Congreso; 1st Meeting of ALAEQ; 2010

Latin America Association of Chemical Ecology

The lesser grain borer, Rhizopertha dominica F. is arguably the most important insect pest of stored grains worldwide. The conventional way to control this pest has been the use of synthetic insecticides. However, the persistence of them in grains and the resistance of insects have derivate in the research of natural products as an important source of botanical insecticides. Limonium brasiliense Kuntze (Plumbaginaceae) is a medicinal plant, known as “Guaycurú”. It is a shrub that grows in Argentina, Uruguay and south of Brazil. Infusions from the roots are used in the treatment of hemorrhage, menstrual disorders, rheumatism and it is believed to have cardioprotective properties [1]. In this work we report the insecticidal activity of the methanolic extract, aqueous subextract, and a fraction that derivates from this subextract. To determine the fumigant toxicity the protocol was follow as previously described by [2] with some modifications. Mortality was evaluated daily during 5 days. Probit analysis was used to estimate LC50 (lethal concentration) by Micro Probit 3.0.  Dried roots from L. brasiliense were milled and extracted with refluxing methanol. This extract was partitioned with water and hexane to obtain sub-extracts and then, these were fractionated by silica gel column chromatography, to obtain fractions and to isolate and identify active compounds [3]. The structure of the isolated compounds were determined by 1H and 13C NMR spectra and confirmed by comparison with literature data [4-5]. LC50 values are shown in table 1. The hexanic subextract was not toxic against R. dominica. However the fraction, the aqueous subextract and the methanolic extract showed an increment in the toxicity, respectively. That could be explained by a synergism between components that make the extract more toxic than the subextracts and fractions. Because of these results Limonium brasiliense should be considered as a resource of biological importance.