Larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri Gagnep against Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles minimus mosquito vectors

Objective:To evaluate the larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri endocarp against Aedes aegypti,Aedes albopictus,Culex quinquefasciatus,and Anopheles minimus mosquitos.Methods:Larvicidal activity was tested according to World Health Organization standard protocol.The third-stage larvae of each mosquito species were exposed to various concentrations of Dracaena loureiri crude extract and six groups of Dracaena loureiri fractionated extracts(RC-DT 009-014).Larval mortality rates were observed after 24 h and48 h of exposure.Then,a computerized probit analysis of the mortality data was performed to determine lethal concentration 50(LC_(50))and lethal concentration 90 values.Results:Anopheles minimus larvae(24-h LC_(50)77.88 mg/L)had the highest susceptibility to crude extract,whereas others(Aedes aegypti,24-h LC_(50)224.73 mg/L;Aedes albopictus,24-h LC_(50)261.75 mg/L;and Culex quinquefasciatus,24-h LC_(50)282.86 mg/L)were significantly less susceptible.The most effective groups of fractionated extracts were RC-DT 012 and RC-DT 013.The mosquito species most susceptible to fractionated extracts was Culex quinquefasciatus,with 24-h LC_(50)values of 0.66 and 0.94 mg/L for RC-DT 012 and RC-DT 013,respectively.Conclusions:The larvicidal activity of fractionated extracts is more effective than that of crude extract against all tested mosquito species.For the most effective alternative larvicide,purification and a phytochemical constituent analysis must be performed.

Larvicidal activity of endocarp and seed crude extracts of Dracaena loureiri Gagnep against Aedes aegypti(L.) mosquito

Objective: To evaluate the larvicidal activity of the ethanolic and aqueous extracts of the endocarp and seeds of Dracaena loureiri(D. loureiri) against the dengue mosquito vector, Aedes aegypti.Methods: Bioassays were performed by exposing late third-stage to early fourth-stage larvae of Aedes aegypti to various concentrations of the extracts from D. loureiri. The larval mortality was observed after 24-and 48-h exposure.Results: The larvicidal bioassay in this study demonstrated that the ethanolic endocarp extract was the most effective with the LC50 value of 84.00 mg/L after 24 h exposure and< 50 mg/L after 48 h exposure. Extracts from the other parts of the plant were significantly less effective as a larvicide.Conclusions: The ethanolic endocarp extract of D. loureiri demonstrated effective larvicidal activity. It is an alternative source for developing a novel larvicide for controlling this mosquito species.

华南龙胆的化学成分研究

从华南龙胆(Gentiana loureirii Griseb.)全草中分离得到了8个化合物,通过光谱分析,分别鉴定为芹菜素(1),七叶内酯(2),(2′S)-2′,3′-dihydroxypropyl 1,6,8-trihydroxy-3-methylanthraquinone-2-carboxylate(3),木樨草素(4),槲皮素(5),槲皮素-3-O-β-D-葡萄糖苷(6),3,4-二羟基苯甲酸(7),胡萝卜苷(8)。以上8个化合物均为首次从华南龙胆中分离得到。