Gallic acid-loaded microemulsion and microemulsion gel: Development, characterization, and evaluation of antioxidant effectiveness

In this study, it was aimed to develop, characterize, and improve the antioxidant activity of gallic acid (GA) by formulating it into microemulsion (ME) and microemulsion gel (MEg). Blank MEs were prepared using different proportions of oil/water/surfactant, which provide stable and transparent ME production. Their droplet sizes, zeta potentials and stabilities after holding, centrifugation, and freeze-thawing processes were determined. F2 and F5 coded MEs were selected among the blank MEs and GA was loaded into these formulations. Besides the characterization studies, pH and viscosity measurement, in vitro release, cytotoxicity test, cell permeation, and antioxidant activity studies were performed. In vitro released amount of GA was enhanced by formulating it into ME and MEg at the end of six hours and it showed a scavenging effect of DPPH center dot and ABTS(center dot+) radicals. In conclusion, increased efficacy, reduced toxicity, and prolonged antioxidant activity have been achieved with the use of new, non-toxic, and stable ME and MEg loaded with GA and it is thought that these formulations create the potential for topical application.