Division of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, 230 53 Alnarp, Sweden.
Malar J. 2011 Dec 19;10:375. doi: 10.1186/1475-2875-10-375.
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.
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.
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).
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 properties, ß-ocimene has long approved safe for use in food and cosmetics, making this volatile an intriguing compound to pursue in further tests in the laboratory and field to validate its mosquito repellent activity and potential for use in a commercial product. Also, the landing bioassay with humanised membranes is a potentially useful repellent screening technique that does not require the exposure of humans to the vectors, however further tests in parallel with conventional techniques are advised.
在寻找植物源驱蚊剂的过程中，研究了来自五种植物的挥发性散发物，即传统上用于埃塞俄比亚驱蚊的柠檬桉、甜罗勒、细叶罗勒、油橄榄和金纽扣。
使用两种蚊子，疟蚊（按蚊）和黄热病病毒载体埃及伊蚊（埃及伊蚊），在选择降落生物测定和人类气味背景下，评估了从新鲜和干燥叶子的头空间收集的挥发性物质以及干燥叶子燃烧产生的烟雾对两种蚊子的行为影响。
发现燃烧干燥叶子产生的烟雾的挥发性提取物比新鲜叶子的提取物更具驱避性，而新鲜叶子的提取物又比干燥叶子的挥发性提取物更具驱避性。在所有烟雾和新鲜挥发性提取物中，来自柠檬桉（52-76％）和甜罗勒（58-68％）的提取物被发现最具驱避性，金纽扣（29-56％）居中，而油橄榄（23-40％）和金纽扣（19-37％）的驱避性最低。柠檬桉、甜罗勒和金纽扣的新鲜叶子提取物中都存在一种挥发性物质β-罗勒烯。β-罗勒烯的水平反映了这三种新鲜叶子提取物的驱蚊活性。雌性宿主寻找蚊子对β-罗勒烯表现出生理和行为上的剂量依赖性反应，在 14％β-罗勒烯时表现出最大的行为排斥。β-罗勒烯（14％）在我们的 6 分钟降落测定中与合成驱虫剂 N，N-二乙基间甲苯酰胺（10％DEET）一样有效地驱蚊。
燃烧以及新鲜柠檬桉和甜罗勒叶子的烟雾中的挥发性物质对寻找宿主的按蚊和埃及伊蚊具有显著的驱避作用。β-罗勒烯存在于柠檬桉、甜罗勒和金纽扣的新鲜叶子的头空间中，是一种在实验室中非常有效的挥发性驱蚊剂。除了其驱避特性外，β-罗勒烯在食品和化妆品中已经被长期批准安全使用，这使得这种挥发性物质成为一种在实验室和实地进一步测试以验证其驱蚊活性和在商业产品中应用潜力的有趣化合物。此外，使用人类化膜的降落生物测定是一种潜在有用的驱蚊筛选技术，不需要将人类暴露于载体中，但是建议与传统技术平行进行进一步测试。
