Chromatography-mass spectrometry and chemical characteristics of Thymus zygis and Cymbopogon winterianus essential oils: Possible insect repellents

Abstract

BackgroundPlant essential oils present a broad spectrum of activity against pests as possible insecticides, repellents, or deterrents. These oils also have a long tradition of use in the protection of stored products. Some chemical constituents of these oils interfere with the octopaminergic nervous system in insects. This target site is not shared with mammals; most essential oil chemicals are relatively non-toxic to mammals, including humans and domesticated animals, and meet the criteria for reduced-risk pesticides. Materials and methodsThe chemical composition of the two studied essential oils were analyzed using gas chromatography-mass spectrometry (GC-MS). Citronellal, α-Terpineol, 3,5,5-Trimethylhexanol, p-Thymol and p-Cymene were the main compounds focused on the study due to their known insect repellent properties. ResultsA total of 53 compounds were found in red thyme; p-Thymol (46.393%) and p-Cymene (22.154%) were the main constituents of the oil. Furthermore, Java citronella presented with 24 compounds, with 3,5,5-Trimethylhexanol (14.61%), Citronellal (15.94%), α-Terpineol (23.22%) being the major constituents of the oil. Red thyme had a much lower percentage of α-Terpineol of 0.290, which plays a role in how effectively the oil can act as an insect repellent. The difference in percentages shows that Java citronella is more potent as a possible repellent over red thyme. ConclusionThe study further provides evidence that plant essential oils can be explored as insect repellents for future pest management programmes as they comprise compounds that are known to be effective in preventing pest infestations.