Isolation of 4-nerolidylcatechol from leaves of Piper peltatum L., and evaluation of larvicidal activity in mosquito vectors, with emphasis on Aedes aegypti (Diptera: Culicidae)

ABSTRACT

ABSTRACT Synthetic chemical insecticides are widely used in population control of pests. Aedes aegypti is the primary vector of dengue, Zika, chikungunya and yellow fever to humans, and has proven resistance to chemical insecticides. As an alternative vector control method, the ethanolic extract of the leaves of Piper peltatum L. (Piperaceae) showed larvicidal activity against Ae. aegypti. Despite the wide medicinal use of this plant, the biological activity of its isolated constituents remains unexplored. In this sense, we isolated, identified and evaluated the larvicidal activity of 4-nerolidylcatechol (4-NC) from P. peltatum against Ae. aegypti, Culex quinquefasciatus and Anopheles darlingi, focusing on the larvicidal, adulticidal and genotoxic potential of 4-NC on Ae. aegypti. Larvae were captured in the city of Manaus, Amazonas state, Brazil. 4-NC was isolated from the extract of the leaves of P. peltatum via silica gel chromatography. This was identified using nuclear magnetic resonance spectroscopy and tested in Artemia franciscana (6.25, 12.5, 25, 50, 100 and 200 µg/mL). In the toxicity bioassay, Ae. aegypti larvae were exposed to 30, 50, 70, 90, and 110 µg/mL of 4-NC, while Cx. quinquefasciatus and An. darlingi were exposed to 6.25, 12.5, 25, 50 and 100 µg/mL. Ae. aegypti larvae were also subjected to 40 and 60 µg/mL of 4-NC (genotoxicity bioassay), and adult females to 62.5 to 1,000 µg/mL (adulticidal bioassay). The results of the 4-NC toxicity assays showed that there was 100% mortality in larvae of Ar. franciscana at the concentration of 200 µg/mL, with an LC50 of 8.0 μg/mL. In the larvae of Ae. aegypti, mortality was 100%, with an LC50 of 62 μg/mL. In larvae of Cx. quinquefasciatus, 97% mortality occurred, with an LC50 of 52.3 μg/mL, and in An. darlingi larvae there was an 83% mortality rate, with an LC50 of 55.8 μg/mL. In adults of Ae. aegypti, however, there was no adulticidal activity. In the larvae of Ae. aegypti, the genotoxic effect of 4-NC (40 and 60 µg/mL) showed significant frequency (p < 0.05) of cellular abnormalities (micronuclei, budding and nuclear bridges) of interphasic nuclei of neuroblasts and oocytes in relation to the negative control. This result may be associated with a decrease in oviposition of females, which was observed in two generations. We can confirm that 4-NC has larvicidal activity against Ae. aegypti, Cx. quinquefasciatus and An. darlingi. Although it does not present adulticidal activity in Ae. aegypti, it reduced the oviposition of females. Therefore, 4-NC seems to be a strong candidate for the development of an alternative method for the control of these mosquitoes in the immature phase.