Enzyme‐Ultrasound‐Assisted Extraction of Flavonoids From Asparagus Straw and Evaluation of Its Component Identification and Function

ABSTRACT The flavonoids from asparagus straw were extracted by sorbitol‐ethanol and ultrasonic assisted extraction with cellulase and pectinase. Through single factor experiment and Plackett–Burman experiment, the extraction conditions were optimized: the fixed sorbitol solution addition of 6%, the ethanol concentration of 70%, the enzymatic hydrolysis time of 1.5 h, the ultrasonic time of 30 min, liquid–solid ratio of 60 (mL/g), the composite enzyme addition with the ratio of cellulase to pectinase 2:1 of 1500 U/g, ultrasonic power of 200 W, enzymatic hydrolysis temperature of 50°C. Under the optimal settings, the extraction rate of flavonoids was 14.59%. A total of 68 flavonoids were identified, including 5 flavonoid‐C‐glycosides, 4 flavonoid‐O‐glycosides, 12 flavonoid‐O‐glycosides, 32 PMFs. The highest content was rutin, followed by Narcissin. The flavonoids in asparagus fern straw have excellent antioxidant activity, glucose‐lowering and uric acid‐lowering ability, and can be developed as natural antioxidants and potential substitutes for glucose and uric acid reduction. This provides certain theoretical support for the development of asparagus fern straw resources.