Formulation and physicochemical characterization of hydrogels with 18β-glycyrrhetinic acid/phospholipid complex phytosomes

Abstract

Carbomer based hydrogels with 1% of 18β-glycyrrhetinic acid complex in the form of phytosomes (18β-GAP) were formulated by using Carbopol®980 and Carbopol®Ultrez 10 as gelling agents (1%), sodium hydroxide (neutralizing agent) (0.4%), glycerol (humectant) (10%), Sepicide® HB (preservative) (1%), and water (up to 100%). In order to prepare the hydrogels, 18β-GAP was dispersed into the water phase prior the carbomer neutralization or the 18β-GAP aqueous dispersion was added into the previously neutralized carbomer dispersion. The pH values (6.71 ± 0.16–7.09 ± 0.06), soft semisolid consistency and spreadability (25.7 ± 1.5 mm–33.7 ± 0.6 mm) of the hydrogels were acceptable for application on the skin. The influence of the preparation procedure, the carbomer type, and addition of a humectant (glycerol 10%) on physicochemical properties was evaluated using light microscopy, DSC analysis and rheological behavior characterization. The preparation procedure, the carbomer type, and the addition of the humectant did not affect significantly organoleptic and morphological characteristics and spreadability of the hydrogels. The Carbopol®980 based hydrogels were more sensitive than hydrogels based on Carbopol®Ultrez 10 upon thermal variations regarding the water evaporation loss. Physical stability of the investigated hydrogels was satisfactory for minimum 30 days of storage at a temperature range from +4 °C up to +40 °C.