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. 2022 Dec 2;27(23):8433.
doi: 10.3390/molecules27238433.

Larvicidal Effect of Hyptis suaveolens (L.) Poit. Essential Oil Nanoemulsion on Culex quinquefasciatus (Diptera: Culicidae)

Taires Peniche  1   2 , Jonatas L Duarte  3 , Ricardo M A Ferreira  2 , Igor A P Sidônio  3 , Rosângela S F R Sarquis  4 , Ícaro R Sarquis  3 , Anna E M F M Oliveira  3 , Rodrigo A S Cruz  3 , Irlon M Ferreira  5 , Alexandro C Florentino  6 , José C T Carvalho  4 , Raimundo N P Souto  2 , Caio P Fernandes  3
Affiliations

Larvicidal Effect of Hyptis suaveolens (L.) Poit. Essential Oil Nanoemulsion on Culex quinquefasciatus (Diptera: Culicidae)

Taires Peniche et al. Molecules. .

Abstract

Mosquitoes can be vectors of pathogens and transmit diseases to both animals and humans. Species of the genus Culex are part of the cycle of neglected diseases, especially Culex quinquefasciatus, which is an anthropophilic vector of lymphatic filariasis. Natural products can be an alternative to synthetic insecticides for vector control; however, the main issue is the poor water availability of some compounds from plant origin. In this context, nanoemulsions are kinetic stable delivery systems of great interest for lipophilic substances. The objective of this study was to investigate the larvicidal activity of the Hyptis suaveolens essential oil nanoemulsion on Cx. quinquefasciatus. The essential oil showed a predominance of monoterpenes with retention time (RT) lower than 15 min. The average size diameter of the emulsions (sorbitan monooleate/polysorbate 20) was ≤ 200 nm. The nanoemulsion showed high larvicidal activity in concentrations of 250 and 125 ppm. CL50 values were 102.41 (77.5253−149.14) ppm and 70.8105 (44.5282−109.811) ppm after 24 and 48 h, respectively. The mortality rate in the surfactant control was lower than 9%. Scanning micrograph images showed changes in the larvae’s integument. This study achieved an active nanoemulsion on Cx. quinquefasciatus through a low-energy-input technique and without using potentially toxic organic solvents. Therefore, it expands the scope of possible applications of H. suaveolens essential oil in the production of high-added-value nanosystems for tropical disease vector control.

Keywords: culicidae; filariasis; hydrodistillation; miniemulsion; nanostructured system.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chromatogram of Hyptis suaveolens essential oil obtained through gas chromatography and mass spectrometry analysis.
Figure 2
Figure 2
Set of emulsions prepared with H. suaveolens essential oil and the surfactants sorbitan trioleate/polysorbate 20 at different rates (from right to left: HLB of 10, 11, 12, 13, 14, 15, and 16.7). (A) Day 0 of preparation. (B) After 7 days of storage.
Figure 3
Figure 3
Set of emulsions prepared with H. suaveolens essential oil and the surfactants sorbitan monooleate/polysorbate 20 at different rates (from right to left: HLB of 10, 11, 12, 13, 14, 15, and 16.7). Highlighted is the rHLB of 15 since this is the HLB value of the mixture of surfactants that allowed the most stable nanoemulsion, with this being chosen for the bioassay. (A) Day 0 of preparation. (B) After 7 days of storage.
Figure 4
Figure 4
Size distribution graphs: (A) Day 0, (B) day 1, (C) day 2, and (D) day 7. Zeta potential (E) day 0, (F) day 1, (G) day 2, and (H) day 7 of the nanoemulsion prepared with H. suaveolens (rHLB = 15) and mixture of sorbitan monooleate/polysorbate 20 at HLB of 15.
Figure 5
Figure 5
Scanning electron micrographs of Culex quinquefasciatus larvae. Normal-looking larvae in the control group (A–C). Changes shown in larvae treated with H. suaveolens nanoemulsion (250 ppm) (D–F). Damage to the entire length of the cuticle, except for the siphon and the head. Head (H), thorax (TH), abdomen (AB), siphon (S), and anal papillae (AP).
See this image and copyright information in PMC

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