Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
Graduate PhD's Degree Program in Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
Parasit Vectors. 2018 Jul 13;11(1):417. doi: 10.1186/s13071-018-3001-7.
In a previous screening program for mosquitocides from local edible plants in Thailand, essential oils (EOs) of Cyperus rotundus, Alpinia galanga and Cinnamomum verum, were found to possess promising adulticidal activity against Aedes aegypti. With the aim of reducing usage of conventional insecticides and improving the management of resistant mosquito populations, this study was designed to determine the potential synergism in the adulticidal efficacy of EOs on permethrin toxicity against Ae. aegypti, both pyrethroid-resistant and -susceptible strains.
EOs extracted from rhizomes of C. rotundus and A. galanga as well as C. verum barks were evaluated for chemical compositions and adulticidal activity against Muang Chiang Mai-susceptible (MCM-S) and Pang Mai Dang-resistant (PMD-R) strains of Ae. aegypti. Adulticidal bioassays of EO-permethrin mixtures for synergistic activity were also performed on these Ae. aegypti strains.
Chemical characterization by the GC-MS analytical technique demonstrated that 48 compounds were identified from the EOs of C. rotundus, A. galanga and C. verum, representing 80.22%, 86.75% and 97.24%, respectively, of all compositions. Cyperene (14.04%), β-bisabolene (18.27%) and cinnamaldehyde (64.66%) were the main constituents of C. rotundus, A. galanga and C. verum oils, respectively. In adulticidal bioassays, EOs of C. rotundus, A. galanga and C. verum were effective in killing Ae. aegypti, both MCM-S and PMD-R strains, with LD values of 10.05 and 9.57 μg/mg female, 7.97 and 7.94 μg/mg female, and 3.30 and 3.22 μg/mg female, respectively. The adulticidal efficacy against MCM-S and PMD-R Ae. aegypti of these EOs was close to that of piperonyl butoxide (PBO, LD values = 6.30 and 4.79 μg/mg female, respectively) but less pronounced than that of permethrin (LD values = 0.44 and 3.70 ng/mg female, respectively). Nevertheless, combination-based bioassays discovered the accomplished synergism of EOs together with permethrin. Significant synergistic effects with permethrin against both the strains of Ae. aegypti were recorded in the EOs of C. rotundus and A. galanga. Addition of C. rotundus and A. galanga oils decreased the LD values of permethrin against MCM-S dramatically from 0.44 to 0.07 and 0.11 ng/mg female, respectively, with synergism ratio (SR) values of 6.28 and 4.00, respectively. Furthermore, EOs of C. rotundus and A. galanga also reduced the LD values of permethrin against PMD-R drastically from 3.70 to 0.42 and 0.003 ng/mg female, respectively, with SR values of 8.81 and 1233.33, respectively.
The synergy of enhanced adulticidal toxicity recorded from EO-permethrin combinations against both strains of Ae. aegypti presents a promising role of EOs as a synergist for improving mosquitocidal efficacy, particularly in situations where conventional compounds are ineffective or inappropriate.
在之前对泰国本地可食用植物进行的杀蚊剂筛选计划中，发现香附子、高良姜和肉桂的精油对埃及伊蚊具有有前景的杀成虫活性。为了减少对传统杀虫剂的使用并改善对抗药性蚊子种群的管理，本研究旨在确定精油对 permethrin 毒性的杀成虫功效的潜在协同作用，针对的是对 permethrin 具有抗药性和敏感性的埃及伊蚊。
从香附子和高良姜的根茎以及肉桂树皮中提取精油，并对其进行化学组成和对 Mae Chiang Mai 敏感（MCM-S）和 Pang Mai Dang 抗性（PMD-R）埃及伊蚊菌株的杀成虫活性进行评估。还对这些埃及伊蚊菌株进行了精油与 permethrin 混合物的杀成虫生物测定，以评估协同作用。
通过 GC-MS 分析技术对化学成分进行了表征，从香附子、高良姜和肉桂精油中鉴定出 48 种化合物，分别占所有成分的 80.22%、86.75%和 97.24%。香附子、高良姜和肉桂精油的主要成分分别为环癸烯（14.04%）、β-菖蒲烯（18.27%）和肉桂醛（64.66%）。在杀成虫生物测定中，香附子、高良姜和肉桂精油对 MCM-S 和 PMD-R 埃及伊蚊菌株均有效，LD 值分别为 10.05 和 9.57 μg/mg 雌蚊、7.97 和 7.94 μg/mg 雌蚊、3.30 和 3.22 μg/mg 雌蚊。这些精油对 MCM-S 和 PMD-R 埃及伊蚊的杀成虫功效与增效醚（PBO，LD 值分别为 6.30 和 4.79 μg/mg 雌蚊）相当，但不如 permethrin（LD 值分别为 0.44 和 3.70 ng/mg 雌蚊）明显。然而，基于组合的生物测定发现了精油与 permethrin 协同增效的效果。香附子和高良姜精油与 permethrin 对两种埃及伊蚊菌株均表现出显著的增效作用。香附子和高良姜精油的添加使 permethrin 对 MCM-S 的 LD 值分别显著降低至 0.07 和 0.11 ng/mg 雌蚊，增效比（SR）值分别为 6.28 和 4.00。此外，香附子和高良姜精油还使 permethrin 对 PMD-R 的 LD 值分别显著降低至 0.42 和 0.003 ng/mg 雌蚊，SR 值分别为 8.81 和 1233.33。
从精油与 permethrin 组合中记录到的增强的杀成虫毒性协同作用，对两种埃及伊蚊菌株均具有显著的效果，这表明精油作为增效剂在提高杀蚊效果方面具有广阔的前景，特别是在传统化合物无效或不适用的情况下。
