Optimizing the ultrasound-assisted phenolic extraction from Equisetum arvense L. and its antioxidant activity using response surface methodology

Common horsetail (Equisetum arvense L.) is a rhizomatous and herbaceous perennial medicinal plant belonging to the Equisetaceae family, which is known as a rich source of phenolics and flavonoids. The previous studies have reported the anticancer, anti-inflammatory, antidiabetic, antioxidant, wound-healing, and hair- and nail-strengthening properties of the plant. The present study evaluated the effect of sonication time (6, 10, and 14 min), sonication temperature (20, 40, and 60 degrees C), and solvent concentration (0, 50, and 100% ethanol) on the total phenolic content (TPC), isoquercitroside amount, and antioxidant activity of the hydroalcoholic extract of E. arvense. In this regard, the shoots of E. arvense were extracted based on ultrasound-assisted hydroalcoholic extraction using response surface methodology (RSM). Additionally, the ferric-reducing antioxidant power (FRAP) assay was used to evaluate TPC, isoquercitroside quantity, and antioxidant activity under optimal conditions. The results suggested the sonication time of 6.91 min, sonication temperature of 27.88 degrees C, and solvent concentration of 56.62% ethanol (relative to water) as the best treatment. In general, the high R-2, adjusted R-2 (adj-R-2), and P-values in the model fitting indicated the ideality of the delineated RSM models, as well as a suitable correlation between observed and predicted data.