Stability of azadirachtin: A tetranortriterpenoid from Neem tree

Abstract

Azadirachtin-A is the most active secondary metabolite possessing various pesticidal properties among a number of liminoids isolated from Neem (Azadirachta indica) seeds. It has a complex molecular structure and possesses reactive functional groups susceptible to oxidative degradation. Owing to the presence of acid sensitive groups like tertiary hydroxyls and a dihydrofuran ring it is highly unstable under acidic conditions, while the presence of four ester groups makes it equally unstable under alkaline conditions. Various physical parameters such as, temperature, moisture and light effect differently on most vulnerable sites of the molecule which, lead to its degradation under these conditions. In addition, interaction of solvent molecules with active functionalities also results in chemical changes in the molecule. The stability of Azadirachtin-A also varies in different storage environments due to one or several factors described above. An understanding of its degradation mechanism and effect of various factors influencing stability of Azadirachtin will be of great help for development of stable formulations and effective utilization of Neem products. The chemistry of active sites of Azadirachtin, possible molecular changes under mild conditions, degradation kinetics and mechanisms has been reviewed in this publication.