Neem A Tree for Solving Global Problems (1992) / Chapter Skim
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4 What's in a Neem
4 What's in a Neem
Pages 31-38
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From page 31... ...
In the main, these compounds belong to a general class of natural products called "triterpenes"; more specifically, "limonoids." LIMONOIDS So far, at least nine neem limonoids have demonstrated an ability to block insect growth, affecting a range of species that includes some of the most deadly pests of agriculture and human health. New limonoids are still being discovered in neem, but azadirachtin, salannin, meliantriol, and nimbin are the best known and, for now at least, seem to be the most significant.
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From page 32... ...
Leuschner, a German graduate student working at the Coffee Research Station in Upper Kiambu, observed that a methanolic neemleaf extract controlled the coffee bug (Antestiopsis orbitalis bechuana) by growth-regulating effects.
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From page 33... ...
The migratory locust, California red scale, striped cucumber beetle, houseflies, and the Japanese beetle have been strongly deterred in both laboratory and field tests. Nimbin and Nimbidin Two more neem components, nimbin and nimbidin, have been found to have antiviral activity.
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From page 34... ...
The complexity of these compounds demonstrates that nature is still the greatest chemist. Of the numerous pesticidal agents isolated so far from neem kernels, azadirachtin is the most active against insects.
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From page 35... ...
WHAT'S IN A NEEM 35 o O H H O - _/ O H _ ., '-~N ll HO'' be., ~ meliantrio' CO2M em ~\o it' .
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From page 36... ...
They are obtained by making various extracts of the kernels and, to a lesser extent, of the press cake. Although the active ingredients are only slightly soluble in water, they are freely soluble in organic solvents such as hydrocarbons, alcohols, ketones, or ethers.
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From page 37... ...
The residue left after the hexane extraction still contains the main active limonoid ingredients, and subsequent extractions with water or alcohol produce them in large amounts, clean and uncontaminated by oil. Pentane Extraction Pentane extracts of seed kernels are effective against spider mites.
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From page 38... ...
For example, neem leaves and seeds and dry neem cake are ingredients in some mosquito coils. SYSTEMIC EFFECT The fact that the extracts can be taken up by plants (and thereby confer protection from within)
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