Azadirachtin is the main
substance which can be extracted from neem seeds (Azadiractha Indica), the tree
belongs to the species of Meliaceae, it is native to the Indian continent, but it
is also widespread in tropical and subtropical areas, like Africa, America and Australia.
The main characteristic is the presence in many parts of the tree (leaves, seeds,
fruits, wood and bark) of some active ingredients belonging to the class of limonoids.
This is of great importance, because among the hundred substances present the most
important from a biological point of view is limonoid tetranotriterpenes, commonly
called azadirachtin. Even if these organic molecules are isolated by all the parts
of the tree, those which are active against insects are concentrated in the seeds
and in the oil obtained from their pressing.
In general, the contents of azadirachtin
are very variable (0.1 – 1 %) and that depends mainly on the place of origin and
on the season trend.
Limonoid tetranotriterpenes
acts as growth
control, it alters the development of insects in the pre-immaginal stages because
it prevents the creation and distribution of ecdysone, the main hormone employed
during insect moult. This interference on hormonal level, is usually accompanied
by morphogenetic alterations and it creates the so called “ permanent larva”, i.e.
grubs which cannot moult due to the destruction of the cuticle. Moreover, limonoid
tetranotriterpenes has an antifeedant effect, in fact it reduces the adult’s fertility.
Azadirachtin is effective against
200 insect types, like orthopteran, homopteran, aphid, leafhopper, hymenopter, heteropteran,
thysanopteran, lepidopter, dipteran and coleopteran.