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Mosquito repellent activity of essential oils and extracts from Chamomile flowers
Aedes aegypti L. is the major vector for dengue and yellow fever. In order to discover plant based mosquito repellents, the n-hexane, ethyl acetate extracts and essential oils from the flowers of German chamomile (Matricaria chamomilla L.), Roman chamomile (Chamaemelum nobile L.) and Juhua (Chrysanthemum morifolium Ramat.) were screened for the repellent activity against Ae. aegypti. In human based “cloth patch” repellent bioassays, German chamomile essential oils showed the highest activity. Thus, we determined chemical differences between these three chamomile essential oils using GC-FID and GC-MS. Two Roman chamomile oil samples were characterized by the isobutyl angelate, 2-butenyl angelate and 3-methyl pentyl angelate, whereas all four German chamomile essential oils were characterized by α-bisabolol oxide A and α-bisabolol oxide B, bisabolone oxide A, (E)-β-farnesene and chamazulene. Borneol, ar-curcumene and bornyl acetate were found as principle compounds in Juhua essential oil. In this study, the major compound α-bisabolol oxide A and some of polyacetylenes which have a history of insecticidal activity were investigated for their biting deterrent activity using in vitro K & D system against Ae. Aegypti.