Ultrasound-assisted polysaccharide extraction from Hordei Fructus Germinatus and its stir-frying product: optimization, structural characterization and bioactivities

Hordei Fructus Germinatus (MY) is a food with therapeutic effects that mainly presented in two forms: unprocessed MY (Sheng MY) and stir-fried MY (Chao MY). Previous study indicated that polysaccharides were an important component in MY. However, the detailed physicochemical characteristics and structure-activity correlation were not explored. In this study, polysaccharides from Sheng MY and Chao MY were extracted using ultrasound-assisted extraction method. Subsequently, three neutral polysaccharides (SM-1, CM-1-1, and CM-1-2) were isolated, and their structural properties and hypoglycemic activity were comparatively studied. Our findings indicated that the optimum extraction conditions were: ultrasonic temperature 50 °C, liquid-to-solid ratio 50, ultrasonic time 60 min, and ultrasonic power of 350 W. Based on the ultrasonic conditions, the extraction rate could reach 27.24 ± 1.37%. After stir-frying, the molecular weight of polysaccharides had increased, the content of Ara, Xyl, and uronic acid had increased, and the main chain had undergone reaggregation. Additionally, the hypoglycemic activity decreased due to the polysaccharides formed after stir-frying had a high-molecular weight, thereby difficultly combining with enzymes. Conversely, the antioxidant activity increased with increase of average molecular weight. These results demonstrated that neutral polysaccharides might be the active substances that make the effectiveness of Sheng and Chao MY different. • Three novel polysaccharides are isolated from sheng and chao Mai-Ya • Three polysaccharides are xyloglucan • Compare the structural properties of polysaccharides from sheng and chao Mai-Ya • Structure-activity correlation of Mai-Ya polysaccharides is proposed