Mosquito repellent properties of essential oils from selected Tanzanian plant species

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University of Dar es Salaam,
The investigation whose results are reported in this study involve essential oil composition of four selected Tanzanian aromatic plant species namely Tagetes minuta, Ocimum basilicum, Satureja imbricata and Ethulia conyzoides. The oils content from whole plant of S. imbricata, ariel parts of O. basilicum, leaves of T. minuta and leaves of E. conyzoides were obtained by steam distillation using dean-stark distillation apparatus. The essential oils components were analysed using Gas Chromatograph-Mass Spectrometer (GC-MS) in which O. basilicum was found to contain the highest amount of oil content (0.48%) while E. conyzoides contained the lowest amount of oil content (0.006%). Essential oil from T. minuta was dominated by monoterpenes, that of E. conyzoides contained high amount of unsaturated sesquiterpenes while essential oils of S. imbricata and O. basilicum were dominated by oxygenated monoterpenes. Results from RC50 value indicated that T. minuta has stronger repellent activities (2.849x10-5 mg/cm2) against female Anopheles gambiae mosquitoe compared to O. basilicum, E. conyzoides and S. imbricata with RC50 value of 5.489x10-5 mg/cm2, 1.145x10-3 mg/cm2 and 3.21x10-3 mg/cm2 , respectively. The repellent results from number of mosquito bite and time before bite showed that O. basilicum is more repellent. Considering the repellency activities of four plants O. basilicum and T. minuta are more repellent against female Anopheles gambiae than E. conyzoides and S. imbricata. Although the two plants have promising repellency activities, they have higher RC50 value compared to standard citronellal, which has RC50 value of 4.431x10-7 mg/cm2. Furthermore, the repellency in number of mosquitoes bite and time before bite the standard citronellal showed to have high repellent activities compared to essential oils of those four plants species. Considering the results of previous study and the current study, it can be concluded that all essential oils from four plants repel mosquitoes, however, further studies on individual plants essential oil including isolation of pure components and characterization of the active principles.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF RA640.T34K542)
Integrated control, Plant species, Medicinal plants, Mosquitoes control
Kilatu, T K (2017), Mosquito repellent properties of essential oils from selected Tanzanian plant species,Master dissertation, University of Dar es Salaam. Dar es Salaam