A simple preparation method for dispersing glycyrrhizin solution into oil phase using an evaporation technique

We developed a simple method for preparing narrow-ranged polydispersity water-in-oil (w/o) emulsions containing the hydrophilic compound glycyrrhizin monoammonium (GZ). Firstly, soybean oil, condensed ricinoleic acid tetraglycerin ester (a hydrophobic emulsifier), and 400 mg/mL GZ solution (4.5:0.5:2.2-4.4, w/w/w) were homogenized using a polytron. Secondly, the water content was decreased using a rotary evaporator equipped with a vacuum controller at 40°C. After a short evaporation period, the emulsion phase behavior changed, becoming clear or slightly turbid. When the turbidity was minimized, the w/o emulsion formed. The average particle sizes and water content of w/o emulsions prepared by adding 2.2, 3.3, and 4.4 g GZ solutions were 225, 299, and 1105 nm and 7.8 ± 0.1, 9.4 ± 0.3, and 11.9 ± 0.3% (w/w), respectively. The w/o emulsions prepared by adding 2.2 and 3.3 g GZ solutions were extremely stable in terms of GZ dispersibility and dispersed particle size.