Optimization of a surfactant-free antioxidant formulation using response surface methodology

Area of Science:

• Dermatology and Pharmaceutical Sciences
• Natural Product Chemistry
• Formulation Science

Background:

• Topical natural antioxidants protect skin from UV-induced oxidative damage.
• Castanea sativa leaf extract shows potent antioxidant activity against reactive oxygen species.
• Glycerine enhances extract stability, leading to a glycerine-based formulation with Carbopol 940 and liquid paraffin (LP).

Purpose of the Study:

• To evaluate the influence of glycerine and LP content on topical formulation texture and antioxidant activity.
• To optimize a semisolid base for Castanea sativa extract using response surface methodology.
• To assess formulation stability after 30 days of storage at 20°C and 40°C.

Main Methods:

• Response surface methodology was employed to study ingredient effects.
• Textural properties were analyzed using a texturometer's spreadability test.
• DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity was measured to assess antioxidant capacity.

Main Results:

• Both glycerine and LP content significantly affected formulation textural properties (p < 0.05), with LP having a greater impact.
• Antioxidant activity (DPPH scavenging) was not correlated with glycerine or LP content.
• These findings remained consistent across storage temperatures of 20°C and 40°C.

Conclusions:

• Formulation ingredient selection for this topical base can be driven solely by desired textural properties.
• The study provides crucial data for developing stable and effective semisolid topical formulations containing Castanea sativa extract.
• Optimized textural properties are key for successful topical delivery systems, independent of antioxidant activity modulation by base ingredients.