Target Discovery of Flavonoids from Elymus nutans Griseb Using Medium- and High-Pressure Liquid Chromatography Combined with Online High-Performance Liquid Chromatography–1,1-diphenyl-2-picrylhydrazyl Detection

Forage-based nutrients constitute the main forage value of forage grass. Elymus nutans Griseb possesses a wide ecological adaptability, enhanced crude protein content, good palatability, and excellent genes. Herein, employing medium- (MPLC) and high-pressure liquid chromatography (HPLC), along with online HPLC-DPPH (OHD)-based identification, two primary radical scavenging compounds were extracted and identified from the methanolic extract of Elymus nutans Griseb. With a starting material of 300 g of Elymus nutans Griseb, 5.95 g of the target DPPH suppressors fraction (Fr6) was separated following one cycle of MCI GEL® CHP20P medium pressure liquid chromatography. A Kromasil 100-5-Phenyl column was subsequently employed for further purification of the fraction, which yielded 432.16 mg of Fr62 (7.26% recovery) and 489.01 mg of Fr63 (8.22% recovery). The target compounds were then assessed based on their structure and purity, and two compounds (salcolin A and tricin) were extracted with > 95% purity. This newly designed procedure was highly effective for the targeted flavonoids, and high-purity radical scavenger extraction from forage extracts. This methodology can potentially provide a scientific basis for their quality evaluation.