Laboratory Evaluation of the Aqueous Extract ofAzadirachta indica(Neem) Wood Chippings onAnopheles gambiaes.s. (Diptera: Culicidae) Mosquitoes

Abstract

Azadirachta indica A. Juss (the neem tree), a source of limonoid insect growth regulatory (IGRs), grows well in many places in sub-Saharan Africa. We explored the potential of neem wood and bark chippings in malaria vector control by evaluating their aqueous extracts as a larvicide and growth disruptor of Anopheles gambiae s.s. (Diptera: Culicidae) under laboratory conditions. Immature stages of the mosquito were tested using WHO guidelines. Fifty percent inhibition of adult emergence (IE50) of all larval instars was obtained with <0.4 g of neem chippings in 1 liter of distilled water. For pupae, significant mortality occurred at 5 g/liter. Inhibition of pupation was seen with some larvae staying as LIVs for 9 d before dying. In addition to growth retardation, reduced reaction by larvae to visual and mechanical stimuli observed at higher neem concentrations may make them more susceptible to natural predators. There were no significant differences in the sex ratio of emerged adults or wing length of females compared with the controls. High-performance liquid chromatography of aqueous extracts showed a series of constituents of varying polarity, including the limonoids nimbin and salannin, which were quantified. Azadirachtin was not detected and the observed activities are attributed to other constituents of the chippings. Such larvicides can be particularly effective where larval habitats are relatively large and readily identifiable. Aqueous extracts of neem wood chippings can be produced locally and their use has the potential to be a low-tech component of integrated malaria vector control schemes in sub-Saharan Africa.

Neem Tree (Azadirachta indica A. Juss) as Source of Bioinsectides

“…These actions are based on multiactions against insects: toxicity, antimitotic effects, antifeedant activity, growth regulation, fecundity suppression, sterilization, oviposition repellency, including harmful effects on endocrinien system and damages of the cuticle of larvae preventing them from moulting . Also aqueous extracts of neem wood and bark chippings showed larvicidal activity against A. gambiae (Howard, 2009); in this extracts HPLC analysis showed the presence of a series of constituents of varying polarity, including nimbin and salannin, whereas AzA was not detected. Structure complexity of Az and other bioactive neem constituents precludes any large-scale chemical synthesis by the extremely high cost.…”

“…General cautions must be taken for the possible presence of aflatoxins, usually present in case of bad storage, as in other botanical raw materials. The results showed that neem products could act primarily as larvicides (Zebitz, 1986(Zebitz, , 1987Naqvi et al, 1991;Rao et al, 1992Rao et al, , 1995Amorose, 1995;Wandscheer et al, 2004;Okumu et al, 2007, Howard et al, 2009. Organic solvent extracts and oils from neem and Melia azedrach have displayed several bioactivities against insects governing chemical maturation of molt hormones, chitin biosynthesis and field deterrence.…”

Antimalarial and Anti-hypoglycemic Properties of Siamese Neem Tree (Azadirachta indica) in Plasmodium berghei Infected Mice

“…Hence, flavonoids and polyphenolic compounds in Siamese neem tree, and its potent antioxidant activity might play a role to inhibit PbANKA growth in vivo. In addition, it has been described that azadirachtin and nimbin, most active compounds in Siamese neem tree might also play a role in antimalarial activity [25][26][27]. Interestingly, oxidative damage in order to inhibit malaria parasite of artemisinin has been reported, and might related to antimalarial property of Siamese neem tree extract.…”

Biological Control of Dengue Vectors

“…Sodium anacardate from cashew nut shell liquid was evaluated against A. aegypti eggs, larvae and pupae and found to be highly toxic to all life stages, although the dose required to kill the pupae was much higher than that needed to kill larvae (Farias, et al 2009). This is not uncommon for botanical products (Howard, et al 2009). The authors also tested the effect against mice.…”

“…In the latter bracket, 14 Mexican medicinal plants were tested and a range of toxicity was found, with some being highly toxic and others showing very little larvicidal effect (Reyes-Villanueva, et al 2008). The neem tree (Azadirachta indica) is a well known medicinal plant that has been widely tested against mosquitoes (Howard, et al 2009;Fallatah and Khater, 2010). When tested against dengue vectors neem was found to be effective at relatively low doses (Wandscheer, et al 2004) but oviposition was inhibited (Coria, et al 2008).…”