Development and stability enhancement of neem oil based microemulsion formulation using botanical synergist

The present study investigated the stability of neem oil based microemulsion (a water based formulation) by switching synthetic synergist with botanicals. Aqueous extract of Prosopis Juliflora was used as a botanical synergist. Microemulsion with different concentrations of neem oil i.e. 2%, 4%, 6%, 8%, 10% and 12% (w/w) were developed using a blend of ionic and anionic surfactant and 2-Butanol as a co-surfactant. Stability study has been done at first day and after 14 days of preparation at 54 degrees C by using HPLC, ATR-FHR and DLS. The phase diagram study was also done to observe the feasibility of the prepared formulation. The concentration of azadirachtin in microemulsion samples with and without botanical synergist range 95% and 40% of the initial concentration respectively. Particle size of all the microemulsion samples were range 14.47 nm-3236 nm with PI (polydisprsity index) value 0.19 to 0.74. This signifies that the formulated microemulsions are in one phase with homogeneous distribution of the molecules. Bioassay study with Spodoptera Litura also showed decrease in LD50 value from 40% to 10%. Thus the botanical synergist used in this study stabilize the azadirachtin content of neem oil in water based formulation. (C) 2019 Elsevier B.V. All rights reserved.