USDA, Agricultural Research Service, NCAUR, Crop Bioprotection Research Unit, Peoria, IL, United States of America.
USDA, Agricultural Research Service, NCAUR, Plant Polymer Research Unit, Peoria, IL, United States of America.
PLoS One. 2020 Feb 20;15(2):e0229076. doi: 10.1371/journal.pone.0229076. eCollection 2020.
Synthetic pesticides are the cornerstone of vector-borne disease control, but alternatives are urgently needed to tackle the growing problem of insecticide resistance and concerns over environmental safety. Leptospermum scoparium J.R. Forst and G. Forst (manuka) essential oil and its four fractions were analyzed for chemical composition and toxicity against Aedes aegypti larvae. The use of bio-based amylose-N-1-hexadecylammonium chloride inclusion complexes (Hex-Am) as an emulsifier for L. scoparium essential oil was also investigated. Fraction 1 was inactive, fractions 2 (LC50 = 12.24 ppm) and 3 (LC50 = 20.58 ppm) were more toxic than the whole essential oil (LC50 = 47.97 ppm), and fraction 4 (LC50 = 35.87 ppm) had similar toxicity as the whole essential oil. Twenty-one chemical constituents were detected in L. scoparium essential oil compared to 16, 5, 19 and 25 chemical constituents in fractions, 1, 2, 3 and 4 respectively. The two most dominant chemical constituents were calamenene (17.78%) and leptospermone (11.86%) for L. scoparium essential oil, calamenene (37.73%) and ledene (10.37%) for fraction 1, leptospermone (56.6%) and isoleptospermone (19.73) for fraction 2, cubenol (24.30%) and caryophyllene oxide (12.38%) for fraction 3, and γ-gurjunene (21.62%) and isoleptospermone (7.88%) for fraction 4. Alpha-pinene, ledene, and aromandendrene were 2-7 times less toxic than the whole essential suggesting that the toxicity of L. scoparium essential oil was either due to other chemical constituents that were not tested or due synergist interactions among chemical constituents. Leptospermum scoparium essential oil-Hex-Am emulsion (LC50 = 29.62) was more toxic than the whole essential oil. These findings suggest that L. scoparium essential oil is a promising source of mosquito larvicide and that Hex-Am is an excellent emulsifier for L. scoparium essential oil for use as a larvicide.
合成农药是控制病媒传播疾病的基石，但迫切需要替代品来应对不断增长的杀虫剂耐药性问题和对环境安全的担忧。对 Leptospermum scoparium J.R. Forst 和 G. Forst（曼努卡）精油及其四个馏分进行了化学成分分析，并评估了它们对埃及伊蚊幼虫的毒性。还研究了使用生物基直链淀粉-N-1-十六烷基氯化铵包合物（Hex-Am）作为 Leptospermum scoparium 精油乳化剂的效果。馏分 1 无活性，馏分 2（LC50=12.24ppm）和馏分 3（LC50=20.58ppm）比全精油（LC50=47.97ppm）更有毒，馏分 4（LC50=35.87ppm）与全精油的毒性相似。与全精油相比，Leptospermum scoparium 精油中检测到 21 种化学成分，而馏分 1、2、3 和 4 中分别检测到 16、5、19 和 25 种化学成分。Leptospermum scoparium 精油中最主要的两种化学成分为石竹烯（17.78%）和石竹烯（11.86%），馏分 1 中最主要的两种化学成分为石竹烯（37.73%）和 Ledene（10.37%），馏分 2 中最主要的两种化学成分为石竹烯（56.6%）和异石竹烯（19.73%），馏分 3 中最主要的两种化学成分为β-古巴烯（24.30%）和氧化丁香烯（12.38%），馏分 4 中最主要的两种化学成分为γ-古巴烯（21.62%）和异石竹烯（7.88%）。α-蒎烯、Ledene 和安息香萜烯的毒性比全精油低 2-7 倍，这表明 Leptospermum scoparium 精油的毒性要么是由于其他未测试的化学物质所致，要么是由于化学物质之间的协同作用所致。Leptospermum scoparium 精油-Hex-Am 乳液（LC50=29.62）比全精油更有毒。这些发现表明，Leptospermum scoparium 精油是一种很有前途的蚊虫幼虫杀虫剂，而 Hex-Am 是一种极好的 Leptospermum scoparium 精油乳化剂，可用于制备幼虫杀虫剂。
