Laboratory evaluation of a phytosteroid compound of mature leaves of Day Jasmine (Solanaceae: Solanales) against larvae of Culex quinquefasciatus (Diptera: Culicidae) and nontarget organisms.

Crude mature leaves extract of Day Jasmine, Cestrum diurnum (Solanaceae: Solanales), was investigated for larvicidal activities against Culex quinquefasciatus, the vector of human filariasis. All the graded concentrations (0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% v/v) showed significant (P < 0.05) larval mortality, and results of regression equations revealed that the mortality rates were positively correlated with the concentrations of the extract (R (2) close to 1). LC(50), LC(95), and LC(99) values were calculated at different time intervals, and the lowest value was recorded at the 72-h bioassay for third-instar larvae. Significant changes in the larval mortality (F < 0.05) was also recorded between the periods of exposure and between instars during t test and single analysis of variance analysis. No mortality was noticed for nontarget organisms, such as Oreochromis niloticus niloticus and Chironomid larvae within 72 h of postexposure to 1%, 2%, and 3% crude plant extract under the laboratory condition. Qualitative and chromatographic analysis of the crude extract of C. diurnum revealed the presence of many bioactive phytochemicals. The bioassay experiment with the third-instar larval form established that the presence of a steroid compound (R (f), 0.67) was responsible for mosquitocidal activity.