Ultrasound-Assisted Enzymatic Extraction of Polysaccharides from Waste Corn Bract: Process Optimization, Characterization, Antioxidant and Anti-Diabetic Potentials

Corn bract is the main agricultural waste of corn production and processing. Little information is focused on its value-added utilization. In the present study, the Ultrasound-Assisted Enzymatic Extraction (UAEE) was used for the first time to extract Corn Bract Polysaccharides (CBPs). The optimum conditions of UAEE for CBPs extraction were: Cellulase amount of 0.7%, enzymolysis for 58 min, and ultrasound treatment for 30 min at 729 W, under which the CBPs yield reached 1.17±0.06%, significantly higher than other methods. CBPs are composed of ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose, arabinose, and fructose at molar ratios of 3.82: 4.25: 3.54: 8.11: 32.89: 1.00: 27.96: 12.57: 13.25 and have a molecular weight of 215.7 kDa and a particle size of 255 nm. The surface of CBPs appears to be full of holes and bumps and the infrared spectroscopic analysis confirmed that CBPs possess the typical characteristics of polysaccharides and could be a kind of naturally occurring sulfated polysaccharides. CBPs extracted with the optimized UAEE preferentially scavenge reactive nitrogen species with IC50 of 1.76±0.14 mg.mL-1 for scavenging hydroxyl radical and have medium inhibitory effects on α-glucosidase with IC50 of 20.66±0.98% mg.mL-1. The present contribution provides an efficient UAEE method to obtain the CBPs with antioxidant and anti-diabetic potentials. It will give a useful clue for the comprehensive and value-added exploitation of waste corn bract.