Development and Optimization of a Topical Formulation with Castanea sativa Shells Extract Based on the Concept “Quality by Design”

The proposed study aims to develop and optimize a topical formulation with Castanea sativa shells extract considering the concept of Quality by Design, focusing on a planned development that consider the vulnerabilities of the entire process through risk analysis tools and design of experiments (DoE). A Box–Behnken design with three factors and three levels was used as a statistical tool for the execution of the DoE and the analysis of the response surface methodology responses. The independent variables studied were the quantity of sodium lauryl sulfate (%) (X1), beeswax (%) (X2) and macadamia oil (%) (X3); the dependent variables were pH (Y1), viscosity (Y2) and adhesiveness (Y3). According to the mathematical model, the optimal formulation contains 0.93% of sodium lauryl sulfate, 5.00% of beeswax and 10.00% of macadamia oil. The optimal formulation with the extract was prepared and characterized over the time, regarding organoleptic and technological characteristics, allowing conclusions to be reached regarding its stability. The formulation presented a pleasant odor and was light brown in color, it also demonstrated pseudoplastic-thixotropic behavior and a small reduction in the formulation consistency after 30 days of storage. This study demonstrated the efficiency of the Quality by Design methodology to understand the product variability, supporting that this approach favors a better understanding of the whole process and enables to design a robust development stage, reducing costs and generating high-quality products.