Comparison of the cytotoxicity and zebrafish embryo toxicity of insect repellent ingredients: p-Menthane-3,8-diol synthesized by green chemistry from Eucalyptus citriodora and N,N-diethyl-meta-toluamide

Abstract

Bio-sourced insect repellents are becoming more popular due to their safer applications. Known for its strong fly-repellent property, Cis, trans-para-menthane-3,8-diol (PMD) is the main component of the lemon eucalyptus essential oil and is synthesized from citronellal. In April 2005, US Centers for Disease Control approved two fly repellents that do not contain N,N-diethyl-meta-toluamide (DEET), including PMD. Due to the intentional and pervasive human exposure caused by DEET as insect repellent, concerns have been raised about its toxicological profile and potential harm to people. We hypothesized PMD would have a different toxicological profile than DEET. We synthesized PMD from Eucalyptus citriodora using green chemistry methods and analyzed its structures by ¹H-NMR,¹³C-NMR, and GC/MS spectral methods. We used MTS assay to determine the percentage inhibition of PMD and DEET on keratinocyte (human epidermal keratinocyte [HaCaT]) cells. The xCelligence system was used and followed at real time. Effects of PMD and DEET on zebrafish embryo development were monitored and levels of lipid peroxidation, glutathione-S-transferase (GST), superoxide dismutase (SOD), and acetylcholinesterase (AchE) were evaluated at 72 h post-fertilization using spectrophotometric methods. Our results showed that while DEET inhibited human keratinocyte cell growth, while imporved cell viability and proliferation was exposed in PMD exposed group. In zebrafish embryos, PMD was less toxic in terms of development, oxidant-antioxidant status, and AChE activities than DEET. Based on these results we suggest an efficient method using green chemistry for the synthesis of PMD, which is found to be less toxic in zebrafish embryos and human keratinocyte cells.

Graphical abstract

Keywords:

• p-Menthane-38-diol
• Eucalyptus citriodora
• NN-diethyl-meta-toluamide
• insect repellent
• zebrafish embryo toxicity
• cell proliferation

Author contribution statement: conception/design of study

Gökhan Özokan, Ebru Emekli-Alturfan; Data Acquisition: Gökhan Özokan, Abdulkerim Bilginer, Zülal Mızrak, Semanur Işıkoğlu, Merih Beler, İsmail Ünal, Derya Cansız; Data Analysis/Interpretation: Gökhan Özokan, A.Ata Alturfan; Ebru Emekli-Alturfan Drafting Manuscript:: Gökhan Özokan, Ebru Emekli-Alturfan; Critical Revision of Manuscript: A.Ata Alturfan, Ebru Emekli-Alturfan; Supervision: Ebru Emekli-Alturfan.

Disclosure statement

All authors declare that they have no competing interests.

Data availability statement

Data is available on reasonable request.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.