Azadirachtin insects

However, the acctimulated Information on azadirachtin, while promising, is presently much less than that needed for insecticidal product commercialization (41). The mode of action, structure-activity relationships (SAR s), formulation, and metabolism of azadirachtin are not yet well understood. Furthermore, formulation studies are required prior to product development and commercialization. Consequently, further investigations are needed before the full potential of azadirachtin as an insect control agent or insecticide can be realized. 

Azadirachtin has several effects on a number of economically important species of insect pests, including feeding deterrency. 

Many triterpenes also have anti herbivore activity. In general, those which are highly oxygenated seem to be more active in this regard M). The role of cardiac glycosides, insects and their predators has been reviewed (91-94). A number of metabolically altered triterpenes from the Rutaceae, Meliaceae and Simaroubaceae are antifeedants. Extracts of neem tree seeds (Azadirachta indica. Meliaceae) were shown to be repellent to a number of insects when applied to various crop plants at low concentrations. The probable active compound is tetranortriter-pene, azadirachtin (9 ). This compound from the leaves and fruits... 

A.J. Mordue, Actions of Azadirachtin, a Plant Allelochemical, against Insects , Pesticide Sci., 1997 (in press). 

Other benefits of large numbers of analogs to plants may include slower evolution of tolerance or lower rates of metabolism of mixtures compared with that of single compounds in herbivorous insects. Feng and Isman (1995) investigated the possibility of adaptation in herbivores by repeated selection of peach aphid colonies with either pure azadirachtin or neem seed extracts containing a large number of limonoids. The colonies treated with azadirachtin soon showed evidence of tolerance of this pure compound, whereas no evidence of tolerance was... 

HPLC H NMR spectroscopy using an isocratic separation with acetonitrile and D2O in the ratio 7 13 has also been used to study photo-isomerisation of the natural material azadirachtin extracted from the seeds of the neem tree and which is a powerful insect anti-feedant [34], This has a complex structure with an (ii)-2-methylbutyl-2-enoate fragment but which after exposure to UY iradiation is converted to the Z-isomer ... 

David Morgan is a member of the Chemical Ecology Group at Keele University. He was bom in Newfoundland and had his university education there, at Dalhousie University and University of King s College in Halifax, Nova Scotia, and at Oxford. His doctorate thesis was on the lipids of Mycobacterium tuberculosis. He later worked at the National Institute for Medical Research in London, and for Shell Chemical Company and Shell Research under the direction of Sir Robert Robinson, O.M., Nobel Laureate. From 1966 he has been at Keele in Staffordshire as lecturer, senior lecturer, reader, and professor. He discovered the natural pesticide azadirachtin and collaborated with S. V. Ley for its final structure elucidation. He is the author of over 300 papers and reviews, mostly on insect chemistry, editor, and contributor to several volumes and author of the book Biosynthesis in Insects. ... 

Limonoids are C2(, nortriterpenoids deriving from a C30 triterpene precursor. The best known limonoids are the Azadirachta indica (neem tree) antifeedant azadirachtin (C50L C40 C6 -C60(epoxide methylene cross-link) furan) and the Citrus species (Rutaceae) bitter antifeedant limonin (G50L G40 G6 G6 C50L(epoxide)-furan). Limonin gives a delayed bitter taste to Citrus fruit. The limonoids are typically bitter compounds with insect antifeedant activity... 

Azadirachtin Azadirachta indica (neem tree) V-K+CH (ECMOX) [insect... 

The third and final general protocol for the hydrolysis of 5 5-acetals exploits the very easy reaction of the sulfur atom of an S-acetal with alkylating agents such as iodomethane, trimethyl- or triethyl-oxonium tetrafluoroborate, and methyl triHuoromethanesuLfonate to form the corresponding trialkylsulfonium salts. Ley s approach to the potent insect antifeedant Azadirachtin [Scheme 2 81]135,171,172 benefited from an easy S-alkylation-hydrolysis sequence. In a synthesis of Epiantillatoxin, a more difficult liberation of an aldehyde from its dithiane derivative was accomplished without rearrangement of a p,y-alkene into conjugation [Scheme 2,82].173... 

DMF without affecting ester functions.301 Scheme 4,161 illustrates a use of the reaction in a modification of the potent insect antifeedant Azadirachtin.302... 

Azadirachtin, which is a tetranortriterpenoid, is an active ingredient of neem Azadirachta indica) seed oil. The structure of azadirachtin is as follows. It controls 200 species of insects, including locusts, gypsy moths, cockroaches, and fall army worms. It has an oral LD50in rats of >5000 mg/kg, making it essentially nontoxic to mammals. 

Robertson, S.L., Ni, W., Dhadialla, T.S., Nisber, A.J., McCusker, C., Ley, S.V., Mordue, W., and Mordue (Luntz), A.J., Identification of a putative azadirachtin-binding complex from Drosophila Kcl67 cells, Arch. Insect Biochem. Physiol, 64, 200, 2007. 

Neem (also known as azadirachtin) is an insecticide extracted from the seeds of the neem tree (Azadirachta indica) common in most of Africa and India. It is closely related to the chinaberry tree (Melia azadarach), common in the southern and southeastern United States. Extracts of both trees have insecticidal properties. Neem is unique among pesticides since it has so many uses It acts as a broad-spectrum repellent, growth regulator, and insect poison. It discourages feeding by making plants unpalatable to insects if they still attack, it inhibits their ability to molt and lay eggs. 

Some of the metabolites of higher plants inhibit the feeding activity of insects. Poisons and antifeedants are the defense substances of higher plants against insects. Insect antifeedants have been studied as a part of our efforts to protect our crops against pest insects. A triterpene named azadirachtin (Figure 3.12) is practically used in several countries as a pesticide of natural origin. 

Numerous other insect antifeedants have been isolated from a variety of sources. One way to search for these is to look for a plant that would appear to be good food for nearby insects, but that is not eaten. Two compounds that are about as effective as azadirachtin are shown in 11.23.138 Mycotoxins can be as effective as azadirachtin in some cases, as in the following example (11.24).139 It would be instructive to try this technique on some of the highly invasive exotic weeds found in the eastern United States. It is possible that weeds such as kudzu, Lonicera japonica, Alliaria petiolata, and Celastrus orbiculatus, contain antifeedants that might be used on crops in the area where they are pests. Their harvest for this purpose... 

Repellents such as azadirachtin and the repellent in 11.52 can be used to keep insects out of stored grain.195... 

The neem tree, Azadirachta indica, is native to tropical Asia but has been planted widely in the warmer parts of Africa, Central and South America, and Asia. Extracts from neem seed kernels act as repellents, antifeedants, and growth disruptants. The main active principle in kernels is azadirachtin (AZ), a limonoid with a very complicated structure. A range of other compounds is also present. These neem substances can repel insects, prevent... 

The transformation of a series of norbomanone derivatives (Fig. 16.5-34) was studied by Roberts and coworkers who determined that both the MOl complement of NADH dependent BVMOs from Pseudomonas putida ATCC 17453 and the NADPH dependent fraction M02 were successful in the resolution of hydroxy, acetoxy and benzyloxy norbomanones11231. Interestingly 25DKCMO and 36DKCMO when separate, displayed notably different reactivity toward the hydroxy and acetoxy derivative, again emphasizing their complementary nature as potential individual biocatalysts. The benzyloxy lactone is an intermediate in the synthesis of the insect antifeedant azadirachtin. 

The three metabolites assayed produced the same effect on the insect used that the control (a commercial extract of the neem tree, containing 2% of azadirachtin), although at higher concentrations. 20a-hydroxy-tingenone was the most active compound among the three assayed. Pristimerin shows also a high antifeedant activity together with molt effect suppression. 

---