Nowadays, dengue fever, a mosquito-borne tropical disease, has become widely distributed in Brazil. In order to prevent such disease, the population of Aedes aegypti mosquito has to be controlled. Then, the aim of this study is to assess the toxicological effects of phenolic compounds against dengue mosquitos. Hence, the larvicidal activity and toxicity of phenolic compounds against Ae. aegypti larvae and A. salina, are evaluated, respectively. The phenolic compounds 2,6-diiodophenol and 4-chloro-2,6-diiodophenol have different toxicity and larvicidal activity. The compound 4-chloro-2,6-diiodophenol shows the highest toxicity for larvae of Ae. aegypti, exhibiting higher toxicity than 2,6-diiodophenol. Although less toxic than Temephos ® (organophosphate), the phenolic compounds evaluated by this research, are proved to be effective against Ae. aegypti larvae. This study demonstrates the importance of controlling the dengue mosquito, considering toxicological aspects of phenolic compounds to prevent environmental impacts.
A total of 36 ethanol extracts from different anatomical parts of 27 plant species
(18 families), native to the Pantanal and Cerrado biomes in Midwest Brazil, was
assessed for their effect against Aedes aegypti larvae, the vector
of dengue, hemorrhagic dengue, Zika and chikungunya fevers. Only the extract obtained
from seeds of Guarea kunthiana (Meliaceae) proved active (LC50 =
169.93 μg/mL). A bioassay-guided investigation of this extract led to the isolation
and identification of melianodiol, a protolimonoid, as the active constituent (LC50 =
14.44 mg/mL). Meliantriol, which was also obtained from the
bioactive fraction, was nevertheless devoid of any larval toxicity, even at the
highest concentration tested (LC50 > 100.0 mg/mL). These results
indicate that the larvicidal activity of melianodiol stems from the presence of the
carbonyl moiety at C-3 in the 21,23-epoxy-21,24,25-trihydroxy-tirucall-7-ene-type
skeleton. The structures of both protolimonoids were established on the basis of
spectral methods (1H and 13C NMR and MS). This is the first
report on the toxicity of melianodiol against Ae. aegypti larvae.
Based on the results, melianodiol can be regarded as a potential candidate for use as
an ecologically sound biocontrol agent for reducing the larval population of this
vector.
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