Comparison of litchi polysaccharides extracted by four methods: composition, structure and in vitro antioxidant activity

Water‐soluble polysaccharides (LCPs) were extracted from litchi, wherein LPS, LPH, LPP and LPM were extracted by ultrasound, hot water, ultra‐high pressure and microwave methods, respectively. The physicochemical properties, components, structures and in vitro antioxidant activities of four LCPs were investigated. LPP was the highest in yield and purity, and most physicochemical properties of four LCPs were similar. FTIR showed that LPP, LPS and LPH had ɑ‐dominating configuration in pyranose rings. SEM showed that four LCPs were different, and LPH and LPP had relatively smooth and compact surfaces. The Mw of LPS, LPH, LPP and LPM were 79 538, 320 213, 192 891 and 200 198 Da, respectively. All four LCPs consisted of fucose, galactose, glucose and rhamnose. Except for LPS, the other three LCPs contained mannose. Based on the results of in vitro antioxidant activity, 5 mg mL⁻¹ LPP presented the highest in DPPH and hydroxyl scavenging activity, while it ranked secondly in reducing power.