Formulation, stability evaluation and characterization of Tween 80® consisting of Neem oil-based emulsion

The pharmaceutical properties of an emulsion ranges from lotion to cream instead of the consistency of the content and the particle size. Neem oil is widely used in Ayurveda medicine due to the presence variety of bioactive compounds which is used in various cosmetic preparations. Due to having considerable Sun Protection Factor value in Neem oil and leaves extract, Neem is used in development of a sunscreen formulation. The objective of this study was to formulation, optimization, stability evaluation and characterization of Tween 80® consisting of Neem oil-based emulsion. Primary emulsions were prepared using Neem oil, distilled water, and Tween 80® according to randomly selected ratios and secondary emulsions were obtained by high shear homogenization of respective primary emulsions. The short term, long term and accelerated stability were visually observed. Creaming, sedimentation, flocculation, coalescence, phase separation and phase inversion were considered as unstable conditions to evaluate stability. The microscopic analysis, pH, viscosity, creaming index and colour change were used to characterize the emulsions. All optimized primary and secondary emulsions were stable throughout the short-term stability evaluation period. All optimized secondary emulsions were stable throughout the accelerated stability evaluation period. Creaming was observed as the major unstable condition in long term stability evaluation. The formula consisted of 30% Neem oil, 40% water and 30% Tween 80® in Oil-in-Water type secondary emulsion was the best formula obtained with the viscosity of 2750 Redwood seconds which is within the non-skin irritating range of pH 4-7.