Experimental design for the determination of the antioxidant activity of the essential oil of "Toronjil blanco" (Agastache mexicana subsp. xolocotziana)

Agastache mexicana subsp. xolocotziana is a Mexican endemic plant known in traditional medicine as “toronjil blanco” (Mexican giant hyssop). The aim of this study was to evaluate the effect of selected processing variables on essential oil (EO) extraction via surfactant-assisted hydrodistillation (SAH). The factors studied were the concentration of Tween 20 (0.001–0.007 g/mL), the solid--liquid ratio (15.8–45.8 g/L), and the extraction time (0.5–3.0 h). This analysis showed that of the three linear independent variables tested (as well as their interactions and quadratic effects), only the extraction time factor had a significant effect on the removal capacity of the ABTS• radical. Also, the antioxidant activity of the essential oil obtained via hydrodistillation was determined. The IC₅₀ obtained via the ABTS method for the essential oil was found to be between 19.7 and 53.8 (mg/mL). A comparison was made with three synthetic antioxidants widely used in the food industry (BHT, Trolox, and ascorbic acid). The GC–MS analysis of the essential oil showed that nerol was the main component. The study concluded that the Agastache mexicana subsp. xolocotziana EO showed significant antioxidant activity. It is important to know the chemical properties of the essential oil of Agastache mexicana subsp. xolocotziana since they have not been reported so far and because it is consumed as tea in certain regions of Mexico and is a plant of commercial importance.