Larvicidal activity of Dalbergia brasiliensis (Fabaceae - Papilionoideae) on Aedes aegypti

Dengue is a viral infectious disease, transmitted by mosquito of the genus Aedes. This work describes the in vivo toxicity analysis of the crude EtOH extract (EEC), hexanic (HF), chlorophormic (CF), ethyl acetate (EAF) fractions, of bark and leaves, and isoflavonoids, from Dalbergia brasiliensis, an arboreal species with wide distribution in Brazilian territory. When considering the issue of controlling the vector Aedes aegypti, the investigation of natural products shows as an important field once natural products can demonstrate fast and effective activity and less environmental impact than synthetic compounds. In this context, we evaluated the activity of the crude extract and fractions of Dalbergia brasiliensis in larvae on the third developmental stage. Five concentrations (0; 125; 250; 500 and 1000 μg/ml) were used on the assays, with 4 repetitions for each treatment, using fifteen 24 h exposed larvae for each repetition. The assays showed that all extracts, fractions and isoflavonoids induced mortality, indicating a larvicidal effect. However, when comparing the results, it becomes evident that the chlorophormic fraction of the bark (BCF) and ethyl acetate fraction of the leaves (LEAF) were the most active, with DL 50 barely 25 and 24 μg/ml, respectively. External morphological alterations were verified in all larvae exposed to D. brasiliensis, after a 24 h exposure. The main alterations observed for the extracts were rigid but easily breakable exoskeleton and elongation of the anterior portion to the thorax. The results observed in this work shows that Dalbergia brasiliensis has an important larvicidal potential.