Stability studies and characterization of nanoemulgel containing gallic acid

Gallic acid is a natural phenolic compound with excellent antioxidant, antimicrobial and anti-inflammatory activity and good skin penetration. Gallic acid demonstrates both stability and solubility problems in topical formulations. A nanoemulgel combines an emulsion for enhanced solubility with a gel base for improved physical stability.

The main objective of this study is to characterize and assess the stability of a gallic acid-containing nanoemulgel.

Various gallic acid nanoemulsions (GNE) were prepared using optimized ratios of oil, surfactants, gallic acid and water and evaluated for stability. Finally, stable GNE-19 was characterized for particle size and converted to nanoemulgel (GNEG-19). Nanoemulgel was subjected to short-term and accelerated stability studies and characterized for pH, viscosity, spreadability, occlusion effect, FTIR, in-vitro drug release and in-vitro pharmacological activities.

The results showed that formulation GNEG-19 showed optimum thermodynamic stability, having no phase separation and color change. The droplet size of freshly prepared GNE and after 28 days was 175.43nm and 183.23nm, respectively. The pH was slightly acidic but still within the human skin range (3.9-4.5). No interaction was found between the gallic acid and other components of nanoemulgel following FTIR analysis. The viscosity of freshly prepared GNEG-19 was 2127.1 cP and after 90 days, it was 2102.3 cP, which showed its stability. The percent drug release of gallic acid from nanoemulgel after 24 hrs was 93.12%. GNEG-19 also showed effective occlusion properties when compared with gel base and petroleum jelly. In-vitro pharmacological activities showed that GNEG-19 had antioxidant activity of 63.77% and a zone of inhibition (ZOI) of 11.4 mm compared to pure gallic acid (9.5 mm).

In conclusion, nanoemulgel containing gallic acid showed good physical and chemical stability and was pharmacologically active.