Tagetes erecta Linn.and its mosquitocidal potency against Culex quinquefasciatus

Objective:To investigate mosquitocidal effects of ethanolic extract of(lowers of Tagetes erecta(T.erecta) and its chloroform and petroleum ether soluble fractions against the larvae of Culex quinquefasciatus(Cx.quinquefasciatus).Methods:The fresh flowers of T.erecta were extracted in cold with ethanol(5.0 L) and after concentration,the ethanol extract was fractionated with chloroform and petroleum ether to afford a brownish syrupy suspension of ethanol extract(50.0 g),petroleum ether soluble fraction(18.6 g) and chloroform soluble fraction(23.8 g).The larvicidal effect of ethanol extract and their solvent fractions were determined by the standard procedure of WHO against different instars of Cx.quinquefasciatus.Results:Among the tested samples the chloroform soluble fractions showed the highest toxicity and consequently,the lowest LC_(50) values(14.14 μ g/mL,17.06 μ g/mL.36.88 μ g/mL and 75.48 μ g/mL) for all the instars larvae of Cx.quinquefasciatus.The larvae showed comparative tolerance in the course of increasing age and time.Conclusions:It can be concluded that the flowers of T.erecta are very effective natural larvicide and could be useful against Cx.quinquefasciatus.

Pouteria campechiana leaf extract and its bioactive compound myricitrin are mosquitocidal against Aedes aegypti and Culex quinquefasciatus

Objective: To test the mosquitocidal potential of leaf extracts of Pouteria campechiana prepared with different solvents and elucidate the structure of an isolated mosquitocidal compound. Methods: The leaf extracts of Pouteria campechiana prepared with three solvents(petroleum benzene, ethyl acetate and acetone) and potential bioactive fractions were tested against various stages of Aedes aegypti and Culex quinquefasciatus by using the WHO protocols, and the chemical profile and its functional groups were identified by GC-MS and Fourier transmissioninfrared spectroscopy(FT-IR). The structure of bioactive compound was characterized by nuclear magnetic resonance(NMR) spectral technique. Results: The preliminary phytochemical results revealed the presence of alkaloids, amino acids, flavonoids, quinones, saponins, steroids, tannins, and terpenoids in the acetone extract. A significant toxic potential was observed in the acetone extract against both Aedes aegypti and Culex quinquefasciatus mosquitoes. The acetone extract exhibits remarkable larvicidal(LC50: 12.232 μg/mL and LC90: 63.970 μg/mL), pupicidal(LC50: 18.949 μg/mL and LC90: 167.669 μg/m L) and adulticidal(LC50: 20.689 μg/mL and LC90: 72.881 μg/mL) effects against Aedes aegypti. Furthermore, the same extract was subjected to isolation of bioactive compound by GCMS and FT-IR analysis. GC-MS results showed the presence of 5 major compounds, and octacosane(18.440%) was detected as the predominant compound. The FT-IR result of acetone extract demonstrated the presence of various functional groups like alkanes/alkynes, ester, aromatic and amides. The NMR spectrum results of isolated compound were well matched to glycoside linked flavonoids. Based on the chromatography and spectral techniques the isolate molecule was identified as myricitrin by FT-IR and nuclear magnetic resonance spectral data. Conclusion: The isolated compound myricitrin possesses a significant toxic effect in all stages of Aedes aegypti and Culex quinquefasciatus mosquito’s with lowest LC50 and LC90 values.

Phytochemical profiling and biological activity of Plectranthus amboinicus(Lour.) mediated by various solvent extracts against Aedes aegypti larvae and toxicity evaluation

Objective:To analyze the phytochemical compounds and to investigate the bio-toxic efficacy of various solvent extracts of Plectranthus amboinicus against mosquito larvae activity and lethality on non-targeting organisms.Methods:The methanol,ethyl acetate,hexane,and aqueous extracts of Plectranthus amboinicus were subjected to analyze the mosquitocidal activity against the dengue vector,Aedes aegypti and toxicity assays on zebra fish and brine shrimp.Three replications were performed,and negative control was also maintained.Amongst,ethyl acetate extract of Plectranthus amboinicus was chosen for the determination of bio-active compounds.Results:The mosquitocidal assays of methanol and ethyl acetate extracts of Plectranthus amboinicus showed the maximal activity with minimal concentration against the 4 th instar mosquito-larvae of Aedes aegypti through the following lethal concentration(LC50 and LC90)values:53.36&92.51μg/m L and 13.64&86.09μg/mL,respectively.In addition,the plant extracts showed no toxicity on zebra fish embryo and brine shrimp assays.The gas-chromatography analysis of the ethyl acetate extract of Plectranthus amboinicus revealed the presence of seven different compounds.Among them,PAEA-fraction 60 contained a major active bioactive compound,hexadecanoic acid,methyl ester(270.0).Conclusions:Plectranthus amboinicus possesses mosquitocidal properties and could be used as a potential alternative source for preparing the mosquitocidal agents.