Ultrasonic-enhanced subcritical water extraction of polysaccharides by two steps and its characterization from Lentinus edodes

Some studies have demonstrated that polysaccharides are the chief ingredient of Lentinus edodes. To extract the useful polysaccharides from Lentinus edodes, we used a novel extraction method, which was named ultrasonic enhanced subcritical water extraction by two steps (USWE). Four independent factors (extraction temperature, extraction time, liquid-to-solid ratio, and ultrasonic power) were studied. A Box-Behnken design (BBD) was applied to optimize the USWE condition based on the results of single-factor tests. The maximum extraction rate of polysaccharides was 17.34%. In addition, extracted polysaccharides at optimal condition were compared with subcritical water extraction (SWE), ultrasonic extraction (UE), and hot water extraction (HWE) samples. The antioxidant against 2,2 diphenyl 1 picryl hydrazyl (DPPH) and reducing power were also evaluated. The IC50 value for DPPH scavenging rate of HWE. SWE, UE, and USWE sample was 0.341, 0237, 0.280, and 0232 mg/mL, respectively. The USWE sample had the highest reducing power activity. The mole ratio of the monosaccharide composition of four samples was different. The results of AFM and SEM showed that the morphology of the four polysaccharides showed significant differences. These results revealed that USWE was an effective technique for extracting and separating polysaccharides from Lentinus edodes, which may be potentially applied in food, cosmetics, and medicines. (C) 2018 Elsevier B.V. All rights reserved.