ABSTRACT
The unusual biological properties of the neem tree, well described elsewhere in this volume, have been known in the Indian subcontinent for many centuries but only attracted the attention of scientists in the past 50 years or less. The impetus towards the investigation of triterpenoids of neem was given by the first isolation of a substance with insect feeding-deterrent properties. Azadirachtin, from a commercial and biological point of view is the most interesting of the tetranortriterpenoids from neem. There can be no other plant as the neem tree for which such a wide range of triterpenoid-derived substances is known, and certainly none that has been shown to produce such highly oxidized products. The amount of water used with the methanol can vary from 5% up to 35%, when a third insoluble phase begins to form, in order to control the amount of less polar substances extracted from the oil.
