Study on physicochemical properties of polysaccharides and glycosides from Rehmannia glutinosa under different processing conditions

AIM: The physicochemical properties of polysaccharides and changes in the glycoside composition under different processing conditions of Rehmannia glutinosa were studied. METHODS: High-pressure processing temperature, processing time, processing frequency, and thickness of fresh Rehmannia glutinosa slices were taken as factors, and the contents of polysaccharides, catalpol, and rehmannioside D were taken as evaluation indexes. The physicochemical properties and the inhibition of α-glucosidase were characterized via ion chromatography, Fourier transform infrared spectroscopy, and environmental scanning electron microscopy. RESULTS: The parameter values for the highest polysaccharide content were as follows: processing temperature of 110 ℃, processing time of 4 h, processing frequency of 2 times, and slice thickness of 1.0–1.5 cm. The parameter values for the highest α-glucosidase inhibition rate were as follows: processing temperature of 120 ℃ and processing time of 2 h. The surface morphology of polysaccharides from Rehmannia glutinosa showed irregular fragments, and glucose and galactose were dominant. The α-glucosidase inhibitory activity of polysaccharides from processed Rehmannia glutinosa reached 60% at a low concentration of 0.05 mg/mL.