Fresh, dried or smoked? repellent properties of volatiles emitted from ethnomedicinal plant leaves against malaria and yellow fever vectors in Ethiopia

• Published in: Malaria Journal
• Main Authors: Dube Fitsum, Tadesse Kassahun, Birgersson Göran, Seyoum Emiru, Tekie Habte, Ignell Rickard, Hill Sharon R
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2011
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/1475-2875-10-375; https://doaj.org/article/0983e75c2a104898a61522d7ec2652c3

Abstract Background In the search for plant-based mosquito repellents, volatile emanations were investigated from five plant species, Corymbia citriodora , Ocimum suave , Ocimum lamiifolium, Olea europaea and Ostostegia integrifolia , traditionally used in Ethiopia as protection against mosquitoes. Methods The behaviour of two mosquitoes, the malaria vector Anopheles arabiensis and the arbovirus vector Aedes aegypti , was assessed towards volatiles collected from the headspace of fresh and dried leaves, and the smoke from burning the dried leaves in a two-choice landing bioassay and in the background of human odour. Results Volatile extracts from the smoke of burning dried leaves were found to be more repellent than those from fresh leaves, which in turn were more repellent to mosquitoes than volatiles from dried leaves. Of all smoke and fresh volatile extracts, those from Co. citriodora (52-76%) and Oc. suave (58-68%) were found to be the most repellent, Os. integrifolia (29-56%) to be intermediate while Ol. europaea (23-40%) and Os. integrifolia (19-37%) were the least repellent. One volatile present in each of the fresh leaf extracts of Co. citriodora , Oc. suave and Os. integrifolia was ß-ocimene. The levels of ß-ocimene reflected the mosquito repellent activity of these three fresh leaf extracts. Female host-seeking mosquitoes responded dose-dependently to ß-ocimene, both physiologically and behaviourally, with a maximal behavioural repulsion at 14% ß-ocimene. ß-ocimene (14%) repels mosquitoes in our 6-minute landing assays comparable to the synthetic insect repellent N,N-diethyl-m-toluamide (10% DEET). Conclusions Volatiles in the smoke of burning as well as fresh leaves of Co. citriodora and Oc. suave have significant repellent properties against host seeking An. arabiensis and Ae. aegypti mosquitoes. ß-ocimene, present in the fresh leaf headspace of Co. citriodora , Oc. suave and Os. integrifolia , is a significantly effective volatile mosquito repellent in the laboratory. In addition to its repellent ...