Abstract
Purpose : To formulate the water in oil (W/O) emulsion of corn silk (CS) extract and to evaluate its stability at various storage conditions. Methods : Ethanol CS extract was prepared using maceration (cold) technique. A 4 % CS emulsion was prepared using varying concentrations of liquid paraffin, ABIL EM90 and water. The formulations were kept at 25 o C for 28 days and to screen out the less stable formulations. The remaining formulations were further stressed at 40 o C to choose the most stable formulation. The optimized formulation was evaluated for physical characteristics including phase separation, rheology and mean droplet size. The physical stability of the formulation was evaluated by monitoring these parameters over a period of 12 weeks at 8, 25, 40 and 40 o C, and 75 % RH. Results : The chosen formulation showed good resistance to phase separation on centrifugation under all storage conditions. Rheological behavior followed non-Newtonian pseudoplastic pattern at various storage conditions. Mean droplet size of freshly prepared formulation was 2.98 ± 1.32 μm and did not show significant (p < 0.05) changes at normal storage conditions (8 and 25 o C). Conclusion : The findings indicate that the developed CS extract W/O emulsion is stable and therefore may be suitable for topical use on skin as an antioxidant preparation. Keywords : Corn silk, Emulsion, Nonionic surfactant, Rheology, Flow index, Droplet size, Non-Newtonian pseudoplastic
Highlights
Emulsions are widely used in the pharmaceutical, cosmetic, food, petroleum and agriculture industry
The % DPPH activity plateaued at 81.5 ± 0.93 and 75.06 ± 1.27 for corn silk (CS) extract and CS emulsion, respectively
The mean droplet size of emulsion was found to be within macroemulsion range (1 - 100 μm) for 12 weeks of study when kept at different temperature and humidity conditions (Figure 3)
Summary
Emulsions are widely used in the pharmaceutical, cosmetic, food, petroleum and agriculture industry. Emulsion is a two phase system of immiscible liquids where one phase is distributed throughout the other in the form of small globules and the dispersion being stabilized by emulsifying agent. It is challenge for the scientists to design formulations that are sufficiently stable against these phenomena during the period of use In this quest various methods have been established to predict the stability and to evaluate the influence of various factors involved during storage. Formulation was stored for a period of 12 weeks and physical stability was evaluated by observing phase separation, rheology and droplet size of formulations under observation. The stable formulations after the initial stress test were further stored at 40 oC to obtain the most stable W/O emulsion (CS extract 4 %, ABIL EM90 2.5 %, liquid paraffin 10 %, and distilled water 83.5 %). The level of significance adopted was p < 0.05
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