Development and Evaluation of Andrographis paniculata Root Extract Cream: Effects of Stearic Acid and Triethanolamine on Stability and Antioxidant Activity

Oxidative stress contributes to skin damage, highlighting the need for plant-derived topical antioxidants. This study aimed to evaluate antioxidant activity of Andrographis paniculata root extract and develop a stable antioxidant cream. Dried roots were macerated with 70% ethanol, and antioxidant activity was assessed using the DPPH scavenging assay with vitamin C as control. Three oil-in-water cream formulations containing 0.25% extract were prepared with different stearic acid and triethanolamine concentrations and evaluated after accelerated storage for organoleptic properties, pH, homogeneity, viscosity, spreadability, adhesion, emulsion type, and antioxidant activity. Extraction yielded 6.66% blackish-brown extract. The extract showed concentration-dependent antioxidant activity, with an IC50 of 16.55 ppm, while vitamin C showed activity with an IC50 of 4.72 ppm. All creams remained homogeneous, retained oil-in-water emulsion type, and showed no visible phase separation. Accelerated storage significantly increased pH in all formulations, significantly reduced viscosity only in Formula I, significantly increased spreadability only in Formula III, and did not significantly affect adhesion time. Higher stearic acid and triethanolamine concentrations increased viscosity and adhesion but reduced spreadability. The cream retained antioxidant activity, with an IC50 of 69.61 ppm. Overall, Formula II showed the most stable physical profile and is a promising candidate for herbal antioxidant development.