Optimization of Essential Oil Extraction from Agastache Mexicana subsp. Xolocotziana through Surfactant-assisted Hydrodistillation: A Response Surface Approach and Pareto Front Analysis for Enhancing Antioxidant Activity and Yield

Agastache mexicana subsp. mexicana and Agastache mexicana subsp. xolocotziana are endemic plants of Mexico known as red and white toronjil, respectively. These plants are popular in Mexico due to their ornamental and medicinal value. With the aim of obtaining the essential oil of Agastache mexicana subsp. xolocotziana with the highest quality, the extraction method known as surfactant-assisted hydrodistillation was employed. Subsequently, an evaluation of the extraction yield and antioxidant activity of the oil was conducted. Given that various variables influence the quality of the essential oil, it was necessary to employ the response surface methodology. Parameters such as the concentration of Tween 20, liquid-solid ratio, and extraction time were varied. The response variables included the extraction yield and antioxidant activity expressed through the IC50 value, determined using the DPPH method (IC50 DPPH). In this context, the IC50 value represents the concentration of essential oil required to neutralize 50% of free radicals in a solution, serving as an inverse indicator of antioxidant activity: the lower the IC50, the higher the antioxidant activity. As a result, the criterion for optimizing the extraction process, i.e., finding the overall optimal solution, is based on maximizing the extraction yield and minimizing the IC50 DPPH value (equivalent to maximizing antioxidant activity). The task of performing this optimization is challenging, and a method supported by the theory of order was employed to identify non-dominated solutions. This led to the identification of a set of non-dominated and non-comparable solution pairs, forming the non-dominated set used to construct the Pareto front. The obtained results reveal that the extracted essential oils exhibit the best antioxidant activity (represented by the lower IC50 DPPH value) and the highest extraction yield (%w/w).