Polysaccharides from Nitraria retusa Fruit: Extraction, Purification, Structural Characterization, and Antioxidant Activities

Polysaccharides are important bioactive components of Nitraria retusa fruit (NRF). In this study, the ultrasonic-assisted extraction (UAE) conditions of polysaccharides from Nitraria retusa fruit (NRFPs) were optimized by response surface methodology (RSM). The structural characteristics and antioxidant activity were investigated. The maximum NRFPs yield of 3.35% was obtained under the following optimal conditions: temperature of 59.5 degrees C, time of 30.5 min, liquid-to-solid ratio of 19.5 mL/g. Three polysaccharide fractions, NRFP-1 (20.01 kDa), NRFP-2 (28.96 kDa), and NRFP-3 (67.45 kDa), were isolated. Glucose, galactose, and arabinose in different percentages were identified as the primary monosaccharide units. The Fourier transform infrared spectrometer (FT-IR) and nuclear magnetic resonance (NMR) analysis indicated the presence of alpha- and beta-glycosidic bonds in NRFPs. The NRFP-3 exhibited the highest scavenging activities against DPPH, ABTS, -OH free radicals, and Fe+3-reducing activity.

Automated summary

In this study, the ultrasonic-assisted extraction conditions of polysaccharides from Nitraria retusa fruit were optimized, and their structural characteristics and antioxidant activity were investigated. The maximum yield of polysaccharides was obtained under the optimal conditions of temperature, time, and liquid-to-solid ratio. Three polysaccharide fractions with different molecular weights were isolated, and glucose, galactose, and arabinose were identified as the primary monosaccharide units.