In vitro repellent efficacy of Pogostemon cablin (Blanco) Benth. [Lamiaceae] essential oil and its nanoemulsion against Haemaphysalis longicornis (Acari: Ixodidae)

ABSTRACT

This study was conducted to assess the repellent activity of Pogostemon cablin (Blanco) Benth. [Lamiaceae] essential oil (EO) and its nanoemulsion (NE) against Haemaphysalis longicornis nymphs. Pogostemon cablin EO nanoemulsion (PCNE) was prepared by ultrasonic emulsification using P. cablin EO and a surfactant, Tween 80. The results of gas chromatography–mass spectrometry analysis showed that the major component of P. cablin EO was patchouli alcohol (32.04%), followed by δ-guaiene (18.13%), α-guaiene (16.76%), seychellene (7.49%), and β-patchoulene (5.09%). The droplet sizes of PCNEs formulated using P. cablin EO and Tween 80 in ratios of 1:1, 1:2, and 1:3 were 23.8, 20.1 and 17.7 nm, respectively, indicating that the increase in the ratio of Tween 80 led to a decrease in droplet size. All essential oil preparations had an acceptable polydispersity index of 0.5 or less. The P. cablin EO and Tween 80 ratio of 1:3 was selected as the optimal formulation with the smallest droplet size; transmission electron microscopy indicated the formation of uniform spherical droplets. PCNE (84.0%) showed a higher repellent activity against H. longicornis nymphs than P. cablin EO (72.0%). The nanoemulsion is suitable for improving the repellent activity of P. cablin EO and is a potential repellent for H. longicornis.

KEYWORDS:

• Essential oil
• Pogostemon cablin
• Haemaphysalis longicornis nymphs
• repellent activity
• nanoemulsion

Author contributions

Conceptualisation, J.H.P.; methodology, J.H.P. and H.J.K.; investigation, J.H.P., H.J.K. and S.H.M.P.W.; data curation, J.H.P., H.J.K. and S.H.M.P.W.; writing—original draft preparation, J.H.P.; writing—review and editing, J.H.P. and G.W.S; supervision, G.W.S.; project administration, J.H.P.; funding acquisition, J.H.P. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are present in the main manuscript. Additional data related to this paper may be obtained from the corresponding author on reasonable request.

Additional information

Funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2021R1A6A3A01086605).