Optimization of Extraction Process for Total Flavonoids and Crude Polysaccharides from Nephrolepis cordifolia and Assessment of Their In Vitro Antioxidant Properties

This study systematically optimized the extraction processes of two bioactive constituents, total flavonoids and crude polysaccharides, from the dried underground tubers of Nephrolepis cordifolia (L.) C. Presl, and further comprehensively characterized their in vitro antioxidant activities. For total flavonoid extraction, an ethanol–ammonium sulfate aqueous two-phase system (ATPS) was integrated with ultrasonic-assisted aqueous two-phase extraction (UATPE), and the process parameters were optimized via Box–Behnken design-based response surface methodology (RSM) using total flavonoid content (TFC) as the primary response indicator. The validated optimal conditions were determined as follows: extraction time of 40.67 min, solid-to-liquid ratio of 1:30.71 (g/mL), ammonium sulfate mass fraction of 24.03%, and ethanol concentration of 35% (v/v). Under these optimized conditions, the TFC reached (54.83 <!-- MathType@Translator@5@5@MathML2 (no namespace).tdl@MathML 2.0 (no namespace)@ -->