Bioatividade de biflavonoide extraído de Luxemburgia nobilis (Eichl) (Ochnaceae) e do óleo essencial de Myrciaria floribunda Berg. (Myrtaceae) sobre o desenvolvimento de Rhodnius nasutus Stål, 1859 (Hemiptera: Reduviidae), vetor da Doença de Chagas

Abstract

The control of Chagas disease depends on the effective action against the vectors (bloodsucking insects such as Rhodnius nasutus). Chemical control has been widely used however; it creates risks to the environment and can be toxic to other animals. Therefore, it is necessary to search for alternative control methods, such as natural substances extracted from plants. This study aimed to investigate the effect of the biflavonoid (Lophirona B) extracted of Luxemburgia nobilis (Eichl) (Ochnaceae) and essential oil extracted of Myrciaria floribunda Berg. (Myrtaceae) on the development R. nasutus. Aiming to evaluate the effect of that substance, the parameters used were the period of development 5th instar nymphs to adults, adult longevity and morphological changes. In addition, we sought to determine toxicity, repellent activity, and inhibition of feeding. For this, we applied biflavonoid and essential oil topically to the ventral part of the nymphs, at concentrations of 10, 25 and 50%, 137.5 (1μL) and 275μg (2μL), respectively. Fifth instar nymphs of R. nasutus belonging to the third laboratory generation (F5) were used. These insects were divided into test and control groups containing 90 individuals per group (three replications of 10 individuals each) for the test with biflavonoid (Lophirona B) and 30 individuals for group (three replications of 30 individuals each) for the test with essential oil. After the application of the substance, they were separated individually in test tubes containing a filter paper which provided support for the movement of the insect and were covered with nylon fabric fastened with an elastic band. The nymphs were individually weighed on an analytical scale before and after the application of the substance at intervals of 24, 48 and 72 hours. After the first week, the nymphs were weighed before and after feeding in vivo, and fed weekly for approximately 30 minutes each. They were fed on mice (Mus musculus) in an artificial apparatus that was made of Styrofoam, that had on its underlying surface a basal concavity in which the mice were maintained, and top five holes where the test tubes containing the triatomines were inserted. The observations were made every two days, when we analyzed the number of ecdysis and mortality of the insects. From the observations, it was concluded that the Lophirona B and essential oil showed a decrease in the quantity of ingested blood and the development period of fifth instar nymphs to adult according to the concentration. In losing weight, Lophirona B (18.3, 19.8 and 8.4, respectively 10, 25 and 50%) and essential oil (6.6 and 23.1, respectively, MF1 and MF2) had a higher weight loss in accordance with the concentration increased. Since longevity in adult substances opposite results demonstrated where Lophirona B (25.4, 25.2 and 24.7, respectively, 10, 25 and 50%) and essential oil (19.6 and 19 days, respectively, MF1 and MF2) being approximately half of the control. Mortality of the nymphs Lophirona B had 35, 44, 60% (10, 25 and 50%, respectively) of the nymphs of the test group and the essential oil 57 and 83 % (MF1 and MF2, respectively) nymphs in less than 60 seconds. Only Lophirona B showed morphological alterations 34, 48 and 67% (10, 25 and 50%, respectively) in adults.