Azadirachtin extraction

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 ... 

Azadirachtin extracted from Azadirachta indicta (neem tree)... 

The seeds from the Indian neem tree, Azadirachta indica, are the source of two types of neem-derived botanical insecticides neem oil and medium polarity extracts. Neem seeds contain numerous azadirachtin (Fig. 9) analogs, but the major form is azadirachtin and the remaining minor analogs are likely to contribute little to the overall efficacy of the extracts. Typically, solvent partitions or other chemical processes are required to concentrate this active ingredient to the level of 10% to 50% seen in the technical grade material used to produce commercial products. 

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... 

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... 

Neem extracts, pure constituents (i.e. azadirachtin) and formulated products showed positive results against Tetranichus mites [279-283]. Less polar extracts were considerably more toxic than polar ones or cold-pressed neem oil or commercial neem oil, and reduced the fecundity of the mites on treated plants and the survival of nymphs hatched from treated eggs application of pentane extract or neem oil in sublethal concentrations, caused growth disrupting effects on the nymphal stages and ovicidal effects. Quantification of the insecticidal substance azadirachtin in the extracts revealed that this compound was not the most active principle against the mites [284]. 

Dr. Govindachari has an indefatigable interest in the study of Natural Products and has elucidated the structures of many novel oxygen heterocyclics and terpenoids like polyalthic acid and azadirachtins from the neem kernel extracts. 

Investigation of the contents of the acetone extract of T. tomentosum yielded in total six clerodanes. Although there were some slight differences, all six clerodanes 127—132 were active antifeedants against both S. litura and Plutella xylostella with feeding inhibition values between 60 and 85% at lOpgcm-2 and 55-75% at 5 pgcm-2. Teuflin (128) was the most effective. However, compared with azadirachtin, the effectiveness is still about 10 times less.74... 

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. 

The neem products currently sold for pest control contain a seed extract known as azadirachtin, and not neem oil, so they do not have any fungicidal activity. But it s possible that neem oil products tor controlling both pests and diseases may be available in the future. 

Table I. Azadirachtin determined by high-performance liquid chromatography (HPLC) in neem kernel extracts prepared with various solvents.

Birds eat the neem fruit in large quantity with impunity but spit out the seed, which has a strongly bitter taste (2). An ethanol extract of the seed instilled into the rabbit eye caused no irritation and no significant skin-sensitizing reaction resulted from injection into the shaved skin of a guinea pig. The standard Ames test with azadirachtin showed no mutagenic activity on four strains of Salmonella typhimurium (127). The acute oral toxicity of the extract in mice was extremely low (13 g/kg) (121). 

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 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. 

Azadirachta indica Refined extract of seeds Azadirachtin (31%),... 

Azadirachta excelsa Crude MeOH extract of Azadirachtin analogues ... 

Use N. can be used in plant protection as a natural antifeedant and insecticide. These uses are due to azadirachtin. The oil is superior in action to the pure active principle this is due to the stabilizing effect of the oil and to its content of other active substances. Aqueous seed extracts or emulsions of the oil have traditional uses in India as insecticides and represent an important alternative to the use of synthetic neurotoxins (for mechanism of action, see azadirachtin(s)). In India the yearly production of the oil amounts to ca. 80000 t/a N. however, the larger part is used for the production of soaps. 

Extracts and exudates of neem trees, Azadirachta indica (Meliaceae), have biological activity against a variety of different nematodes. For example, a neem seed extract applied to tomato plants as a root drench at 125 fxg/ml inhibited reproduction of the root-rot nematode Meloidogyne javanica (Chitwood, 1992). Azadirachtin (33), at 10 xg/ml, inhibits microfilarial release in the animal-parasitic nematode, Brugia pahangi. A similar mode of action may be involved in phytoparasitic nematodes (Chitwood, 1992). 

Certain other meliaceous seed extracts were equally active to azadirachtin in bioassays (Mikolajczak and Reed, 1987). TTiose of Aglaia cordata were more potent than extracts of neem toward larvae of Spodoptera frugiperda (Mikolajczak et al., 1989). A limonoid compound from Carapa procera had antifeedant activity comparable to that of azadirachtin, but much weaker insecticidal properties. This compound, methyl 3 3-isobutyryloxy-l-oxomeliac-8(30)-enate (42), also was found in Khaya senegalensis and K. nyasica (Mikolajczak et al., 1988). 

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