Optimization of preparation process and preliminary structure characterization of polysaccharides from lemon peel with high hypoglycemic activity

Abstract

Objective: This study aimed to optimize the preparation process of polysaccharides from lemon peel and screen out the components with high hypoglycemic activity. Methods: Ultrasonic assisted enzymatic extraction of lemon peel polysaccharide, combined with response surface test to explore the best extraction process, through DEAE-52 anion chromatography and Sephadex G-100 gel column chromatography separation and purification to obtain a homogeneous polysaccharide fraction (named as LPs-1a). The effective hypoglycemic components of lemon peel polysaccharides were screened by α-glucosidase and their relative molecular weight, monosaccharide composition and characteristic groups were analyzed. Results: The optimal extraction process of lemon peel polysaccharide was ultrasonic treatment for at 55 ℃ for 44 min with solid-liquid ratio 1∶20 (g/mL) and cellulase addition rate 1.1%. Under the control of these conditions, the yield of lemon peel polysaccharide was 6.83%, which was close to the predicted value. The LPs-1a fraction significantly inhibited the activity of α-glucosidase with （1.22±0.04） mg/mL of IC50(P＜0.05). The relative molecular weight of this component was 195 260, and it was connected by α-glycosidic bonds and β-glycosidic bonds with a pyranose ring. The morphology of the polysaccharide was fibrous, and it was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose Conclusion: Ultrasound-assisted enzymatic method is helpful in screening the highly hypoglycemic active components of lemon peel polysaccharides.

Keywords

• lemon peel
• polysaccharide
• preparation
• high hypoglycaemic activity
• structural characterization