Degradation and Bioactivity of Azadirachtin-A and Dihydroazadirachtin-A based Neem (Azadirachta indica A. Juss) Formulations

Stability of azadirachtin-A (Aza-A) and 22, 23-dihydroazadirachtin-A (dihydro Aza-A) was studied in different media at (5±1°C) and (54±1°C) storage for 14 days. The effect was also observed in emulsifiable concentrates employing ceenine solvent and 5% of 1:1 mixture of Tween - 20 (PEO 20 sorbitan monolaurate) and IGSURF-6000, (a proprietary blend of anionic and non ionic surfactants) as surfactant. The dihydro derivative was significantly more stable than Aza-A with half life in different recipes ranging from 22.65 to 103.79 d as compared to 3.50 to 65.13 d in case of Aza-A. The insect growth inhibitary and antifeedant activities of Aza-A against Spodoptera litura larvae were reduced significantly after heat storage as compared to the refrigerated storage. In contrast, the bioactivity of dihydro Aza-A was not affected significantly, except the IG inhibitory activity in neem oil and antifeedent activity in emulsifiable concentrate employing neem oil.