Ultrasonic-Assisted Hot-Water Extraction Optimization, Preliminary Characterization and Antioxidant Activity of Polysaccharides from Zingiber striolatum

Polysaccharides serve as the main bioactive compounds of <i>Zingiber striolatum</i> (<i>Z. striolatum</i>). However, their structures and functions require further research. The present work used response surface methodology (RSM) for optimizing polysaccharide extraction conditions from <i>Z. striolatum</i> through ultrasonic-assisted hot-water extraction and evaluating the antioxidant properties of <i>Z. striolatum</i> polysaccharides. According to our findings, optimal <i>Z. striolatum</i> polysaccharide extraction conditions included ultrasonic power of 200 W, extraction temperature of 79 °C, extraction duration of 2.5 h, and ultrasonic time of 20 min, with the extraction yield reached 19.96% ± 0.18%. The molecular weight (MW) of the purified polysaccharide ZS-P1-1 isolated from <i>Z. striolatum</i> was 5.63 × 10⁴ kDa, mainly composed of galactose (Gal), galacturonic acid (GalA) and glucuronic acid (GlcA) in a 0.453:0.162:0.114 molar ratio. Typically, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) and hydroxyl radical (·OH) scavenging capacities and total reducing ability reached 30.49% ± 1.82%, 28.51% ± 1.40% and 0.64 ± 0.07 of ZS-P1-1 at 0.5 mg/mL, respectively. Moreover, ZS-P1-1 increased the reduced glutathione (GSH) level, enhanced the total superoxide dismutase (T-SOD), reduced the malondialdehyde (MDA) level, and alleviated the liver and kidney damage caused by oxidative stress in mice. Our results suggest that ZS-P1-1 shows excellent antioxidant properties and provides a certain theoretical foundation for developing and utilizing <i>Z. striolatum</i> polysaccharides.