Control of human filarial vector, Culex quinquefasciatus Say 1823 (Diptera:Culicidae) through bioactive fraction of Cayratia trifolia leaf

Objective:To investigate the mosquito larvicidal activity of Cayratia trifolia (L.) Domin (Vitaceae:Vitales) (C. trifolia) which is distributed in many parts of India with medicinal properties as vector control is facing threat due to the emergence of resistance to synthetic insecticides. Methods:Young and mature leaves of C. trifolia were investigated for larvicidal activity against 3rd instars larvae of Culex quinquefasciatus in different seasons throughout the year. The active fractions were extracted using six different solvents in a non-polar to polar fashion viz petroleum-ether, benzene, chloroform:methanol (1:1 v/v), acetone, absolute alcohol and distilled water. Dose dependent mortality was recorded against each solvent extract. Determination of LD50 and LD90 were executed through log-probit analysis using the most bioactive fraction. The fluctuations in mortality were statistically co-related through ANOVA analyses concerning different seasons and types of leaves as random variables. Justification of larvicidal activity was established through student’s t-test. Costing effects were evaluated on the non-target water fauna under laboratory conditions. Thin layer chromatographic techniques were performed for phytochemical analysis and categorization of chemical personality of the active fractions using the most effective solvent extract following standard methods. Results:Significant variations in mortality rate were noted with respect to the type of leaves (mature and senescence), concentration of leaf extract and between seasons. The water extract among all the solvent extracts was found to induce cent percent mortality at 50 mg/L in test mosquito species within 24 h with a LD50 and LD90 value of 10.70 mg/L and 27.64 mg/L respectively. No significant mortality was recorded in non-target water population. Chromatographic analyses of the water extract revealed the presence of steroids, triterpene glycosides, essential oil, phenolics and diterpenes as secondary phytochemicals. Conclusions:Water extract of C. trifolia leaf promised as a cost effective and potent larvicidal agent against Culex quinquefasciatus.

Smoke repellency and mosquito larvicidal potentiality of Mesua ferra L. leaf extract against filarial vector Culex quinquefasciatus Say

Objective: Present study was made to evaluate the smoke repellent potentiality and mosquito larvicidal activity of Mesua ferra (M. ferra) leaves against filarial vector Culex quinquefasciatus (Cx.quinquefasciatus ). Methods: Crude, petroleum-ether, chloroform: methanol (1:1 v/v) and ethyl acetate extracts of mature plant leaves were investigated to establish its biocontrol potentiality under laboratory condition against larvae of Cx. quinquefasciatus at different concentrations i.e. 25 ppm, 50 ppm and 75 ppm. Mosquito coil prepared from M. ferra leaves powder were tested for smoke toxicity effect against Cx. quinquefasciatus adult mosquitoes. Results: The mortality rates of crude extract at 0.5% concentration were higher than all other concentrations tested against the first, second, third and fourth instars larvae at 24 h, 48 h and 72 h of exposure. Larval mortality rate in chloroform: methanol (1:1 v/v) extract was significantly higher (P<0.05) than other extracts. LC50 value of petroleum ether, chloroform: methanol (1:1 v/v) and ethyl acetate extracts were 195.33 ppm, 27.28 ppm and 74.19 ppm respectively, after 48 h of exposure. Smoke exposed gravid females oviposited fewer eggs when compared to non exposed female mosquitoes. Conclusions:In conclusion M. ferra crude and chloroform: methanol (1:1) extract can be used effectively against mosquito control programmes. Smoke from M. ferra can play an important role in the interruption of transmission of those diseases where mosquitoes act as vector at the individual level.

Efficacy of Limonia acidissima L. (Rutaceae) leaf extract on larval immatures of Culex quinquefasciatus Say 1823

OBJECTIVE@#To investigate the role of leaf extract of Limonia acidissima L. (Rutaceae) as a biocontrol agent against the larval form of Culex quinquefasciatus, and characterization of bioactive component responsible for larvicidal activity.@*METHODS@#Larval mortality of mosquito species was observed after 24, 48 and 72 hours of exposure to different concentrations of aqueous extract, solvent extract and subsequently bioactive compound. The bioactive compound was subjected to IR and GC-MS analysis.@*RESULTS@#Mortality rate at 3% concentration of crude extract were highest (90%) amongst all concentrations tested and subsequently highest (95%) mortality was achieved in chloroform: methanol extract at 100 ppm concentrations. IR and GC-MS analysis of bioactive compound revealed the presence of steroid compound which may act as larvicide.@*CONCLUSIONS@#The chloroform: methanol extract of mature leaves of Limonia acidissima was found to exhibit considerable mosquito larvicidal activity against Culex quinquefasciatus.

Mosquito larvicidal activity of some common spices and vegetable waste on Culex quinquefasciatus and Anopheles stephensi

OBJECTIVE@#To investigate the larvicidal activities of crude and chloroform: methanol (1:1 v/v) extracts of some common spices (Cuminum cyminum, Allium sativum, Zingiber offinale, Curcuma longa) and vegetable waste (Solanum tuberosum germinated tuber) against Anopheles stephensi and Culex quinquefasciatus mosquito larvae.@*METHODS@#Larval mortality of above mosquito species were observed after 24, 48 and 72 h of exposure to five concentrations of aqueous extract (0.1%, 0.2%, 0.3%, 0.4% and 0.5%) and four concentrations (25, 50, 75 ppm) of chloroform: methanol (1:1 v/v) extract. The lethal concentration of individual spices or vegetable waste was determined by log-probit analysis (at 95% confidence level) and effect of crude and chloroform: methanol (1:1 v/v) extracts were recorded on non target organisms.@*RESULTS@#Relative mortality rate of both larval mosquito species were recorded in the following sequences: Cuminum cyminum >Allium sativum >Zingiber offinale, Curcuma longa >Solanum tuberosum germinated tuber for crude extract, and efficacy of chloroform: methanol (1:1 v/v) extract were as follows: Curcuma longa >Zingiber offinale >Solanum tuberosum germinated tuber >Cuminum cyminum >Allium sativum.@*CONCLUSIONS@#Crude and chloroform: methanol (1:1 v/v) extract of Cuminum cyminum, Allium sativum, Zingiber offinale, Curcuma longa and Solanum tuberosum germinated tuber can be recommended effectively in mosquito control programmes at very low concentrations. No mortality and other abnormalities were noticed on non target organisms and further studies are needed to investigate the chemical structure of active principal which are responsible for larvicidal activity.

Synergistic effect of Croton caudatus (fruits) and Tiliacora acuminata (flowers) extracts against filarial vector Culex quinquefasciatus

Objective:To investigate the synergistic effect of crude and solvent extract of Croton caudatus (C. caudatus ) (fruits) and Tiliacora acuminata (T. acuminata) (flowers) against the larval form of Culex quinquefasciatus (Cx. quinquefasciatus). Methods: Crude and solvent [chloroform:methanol (1:1 v/v), benzene and ethyl acetate] extracts of two plants, C. caudatus (fruits) and T. acuminata (flowers) were examined separately against filarial vector Cx. quinquefasciatus larvae with gradually increasing concentration i.e. from 0.1%to 0.5%of crude extract and 25 ppm to 75 ppm of solvent extracts. To observe the synergistic effect, if any, extracts of these two plant parts were mixed at different concentrations and treated against mosquito larvae. Phytochemical analyses of extracts of both the plant parts were carried out. Results: In a 72-h bioassay experiment with plant extracts, highest mortalities were recorded at 0.5% (crude) and 75 ppm (solvent) concentration for fruits of C. caudatus and flowers of T. acuminata individually. For synergistic effect, only 0.2%of the mixture of these two crude extracts and 75 ppm concentration of chloroform:methanol (1:1 v/v) and ethyl acetate extracts showed 100%mortality after 24 h and 48 h of exposure respectively. Conclusions:In the field of mosquito control, insecticides of plant origin may serve as suitable alternative to the toxic chemicals. Some secondary metabolites in combination may be responsible for better larvicidal activity.