Pierre Danga Yinyang Simon, Okechukwu Esimone Charles, Nchiwan Nukenine Elias
Department of Biological Sciences, Faculty of Science, University of Ngaoundere, Ngaoundere, Cameroon.
J Vector Borne Dis. 2014 Sep;51(3):216-23.
BACKGROUND & OBJECTIVES: Due to ever-growing insecticide resistance in mosquito vectors and environmental contamination by synthetic insecticides, plants may be a source of alternative agents for mosquito control. Therefore, the present investigation involved the determination of larvicidal and phytochemical properties of Callistemon rigidus leaf extracts against Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus.
The standard protocol of WHO was used for larval tests. Twenty five IV instar larvae were exposed to various concentrations from 125-1000 ppm for methanol crude extract (MCE), hexane (HF), chloroform (CF), ethyl acetate (EAF) and methanol (MF) fractions, from 250-2000 ppm for aqueous extract (AE) and 2500 ppm for Diclorvos. The mortality was observed 24 h post-exposure. The LC50 and LC90 values were determined by Probit analysis.
The phytochemical analysis revealed that the presence of alkaloids, steroids, saponins, terpenoids, tannins and phenolic compounds, lipids, fats and fixed oils in MCE; terpenoids, steroids, lipids, fats and fixed oils in HF; terpenoids in CF; tannins and phenolic compounds in EAF and alkaloids, tannins, saponins and phenolic compounds in MF. Against Ae. aegypti, HF was the most active fraction with LC50 of 56.25 ppm. Against An. gambiae, HF demonstrated its potential mosquito larvicide killing relatively all exposed larvae at all concentrations with LC50 of 17.11 ppm. Against Cx. quinquefasciatus, only MCE and HF exhibited larvicidal activity with LC50 of 447.38 and 721.95 ppm, respectively.
INTERPRETATION & CONCLUSION: Callistemon rigidus exhibited some promising larvicidal activity against medically important vector mosquitoes. Studies are indicated to identify the active compounds from this plant for developing mosquito larvicides.
由于蚊媒对杀虫剂的抗性不断增强以及合成杀虫剂对环境污染，植物可能成为控制蚊虫的替代药剂来源。因此，本研究旨在测定红千层叶提取物对冈比亚按蚊、埃及伊蚊和致倦库蚊的杀幼虫活性及植物化学特性。
采用世界卫生组织的标准方案进行幼虫试验。将25只四龄幼虫暴露于甲醇粗提物（MCE）、己烷（HF）、氯仿（CF）、乙酸乙酯（EAF）和甲醇（MF）馏分的125 - 1000 ppm不同浓度、水提取物（AE）的250 - 2000 ppm浓度以及敌敌畏的2500 ppm浓度下。暴露24小时后观察死亡率。通过概率分析确定LC50和LC90值。
植物化学分析表明，MCE中存在生物碱、甾体、皂苷、萜类、单宁和酚类化合物、脂质、脂肪和固定油；HF中存在萜类、甾体、脂质、脂肪和固定油；CF中存在萜类；EAF中存在单宁和酚类化合物；MF中存在生物碱、单宁、皂苷和酚类化合物。对埃及伊蚊而言，HF是活性最强的馏分，LC50为56.25 ppm。对冈比亚按蚊而言，HF在所有浓度下对所有暴露幼虫均显示出潜在的杀蚊幼虫活性，LC50为17.11 ppm。对致倦库蚊而言，只有MCE和HF表现出杀幼虫活性，LC50分别为447.38和721.95 ppm。
红千层对重要的医学病媒蚊虫表现出一些有前景的杀幼虫活性。建议开展研究以鉴定该植物中的活性化合物用于开发杀蚊幼虫剂。
