Larvicidal activity of Artemisia annua L. callus culture against Anopheles stephensi larvae.

The emergence of resistance by both Plasmodium falciparum and Anopheles stephensi made the search for an alternative environmentally safe plant based insecticide inevitable. Artemisia annua is a well known antimalarial. Present study is an attempt to induce callus production from young leaves of Artemisia annua plant and study its larvicidal activity against larvae of Anopheles stephensi. Callus was initiated by using different concentrations of auxins and cytokinins. A suitable culture media was standardized for optimal growth of callus. Healthy callus cultures were obtained in the slightly modified Murashige and Skoog’s medium + NAA and BAP (0.03 and 0.2 mg l-1 respectively) + Sucrose 20 gm l-1 + Agar 8 gm l-1 within 28 days of inoculation. Callus was successively extracted in order of increasing polarity of solvents. Larvicidal activity, in terms of lethal concentration (LC50) of the callus extract in chloroform was calculated to be 18.45 ± 0.75 ppm after 72 hr against third instar larvae of A. stephensi.

Larvicidal activity of an indigenous plant, Centratherum anthelminticum.

Crude extracts of fruits and leaves of Centratherum anthelminticum in different solvents were tested for larvicidal activity against Anopheles stephensi, the vector of malaria. The petroleum ether crude extract of both fruits and leaves exhibited significant larvicidal activity against III instar larvae with LC50 values of 162.60 ppm and 522.94 ppm, respectively after 24 hr. The petroleum ether extract of fruit was 11.66, 2.15 and 1.32 times more toxic than that of leaf extract after 24, 48 and 72 hr, respectively at LC90 level. However at LC50 level the corresponding values were 3.22, 1.83 and 1.19, respectively. The petroleum ether extract of C. anthelminticum fruits is a promising source for the control of Anopheles larvae.

Effective method for extraction of larvicidal component from leaves of Azadirachta indica and Artemisia annua Linn.

Leaves of Artemisia annua linn. and Azadirachta indica were extracted in petroleum ether and hexane respectively by different methods of extraction i.e. cold extraction, reflux extraction and soxhlet extraction. The crude extract obtained was tested against third instar larvae of Anopheles stephensi. On comparison of larval mortality of crude extract obtained by these three methods, both soxhlet and reflux extraction method showed 100% mortality at 200 ppm after 48 hr in case of A. annua. However LC50 (20 ppm) value of crude extract obtained by soxhlet extraction showed better results than reflux extraction (35 ppm) method after 72 hr. In case of A. indica, crude obtained by soxhlet showed 100% mortality (after 48 hr) at 250 ppm and LC50 of 69 ppm at 72 hr. Reflux extraction does not show any appreciable mortality even at 250 ppm concentration.